Editing Cathode-ray tube (section)

==Types==
CRTs were produced in two major categories, picture tubes and display tubes.<ref name="auto27"/> Picture tubes were used in TVs while display tubes were used in computer monitors. Display tubes were of higher resolution and when used in computer monitors sometimes had adjustable [[overscan]],<ref>{{Cite book |last= |first= |url=https://books.google.com/books?id=kggOZ4-YEKUC&dq=display+tube+no+overscan&pg=PA224 |title=PC Mag |date=1989-02-14 |publisher=Ziff Davis, Inc. |language=en}}</ref><ref>{{cite web | url=https://books.google.com/books?id=DT8EAAAAMBAJ&dq=computer+monitor+overscan&pg=PA55 | title=InfoWorld | date=February 1988 }}</ref> or sometimes underscan.<ref>{{cite book | url=https://books.google.com/books?id=JcVEUNcHc0gC&q=computer%20monitor%20overscan | isbn=9780072264517 | title=Multimedia: Making it Work, Seventh Edition | date=2008 | publisher=McGraw Hill Professional }}</ref><ref>{{cite web | url=https://books.google.com/books?id=GNYH0lLwKgAC&dq=monitor+underscan&pg=PT199 | title=PC Mag | date=15 May 1990 }}</ref>
Picture tube CRTs have overscan, meaning the actual edges of the image are not shown; this is deliberate to allow for adjustment variations between CRT TVs, preventing the ragged edges (due to blooming) of the image from being shown on screen. The shadow mask may have grooves that reflect away the electrons that do not hit the screen due to [[overscan]].<ref>{{Cite web|url=https://patents.google.com/patent/US4191909A/en|title=Color CRT with shadow mask having peripherally grooved skirt|accessdate=18 December 2022}}</ref><ref name="auto4"/> Color picture tubes used in TVs were also known as CPTs.<ref>{{Cite web|url=https://patents.google.com/patent/KR830001536Y1/en|title=C.P.T. (colour picture tube) sockets with integral spark gaps|accessdate=18 December 2022}}</ref> CRTs are also sometimes called Braun tubes.<ref name="braun">{{Cite web|url=https://patents.google.com/patent/US6795131B1/en?q=braun+tube&oq=braun+tube|title=Structure for fastening flat braun tube to cabinet|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US6028392A/en?q=braun+tube&oq=braun+tube|title = Color braun tube}}</ref>

===Monochrome CRTs===
[[File:Mini Star 416 - cathode ray tube with deflection coils-2210.jpg|thumb|180px|An aluminized monochrome CRT. The black matte coating is aquadag.]]
[[File:Mini Star 416 - cathode ray tube, deflection coils-2146.jpg|thumb|180px|The deflection yoke over the neck of a monochrome CRT. It has two pairs of deflection coils.]]
If the CRT is in black and white (B&W or monochrome), there is a single electron gun in the neck and the funnel is [[aluminized screen|coated on the inside with aluminum]] that has been applied by evaporation; the aluminum is evaporated in a vacuum and allowed to condense on the inside of the CRT.<ref name="auto52"/> Aluminum eliminates the need for [[ion trap]]s, necessary to prevent ion burn on the phosphor, while also reflecting light generated by the phosphor towards the screen, managing heat and absorbing electrons providing a return path for them; previously funnels were coated on the inside with aquadag, used because it can be applied like paint;<ref name="auto29"/> the phosphors were left uncoated.<ref name="auto68"/> Aluminum started being applied to CRTs in the 1950s, coating the inside of the CRT including the phosphors, which also increased image brightness since the aluminum reflected light (that would otherwise be lost inside the CRT) towards the outside of the CRT.<ref name="auto68"/><ref>{{Cite web|url=https://patents.google.com/patent/US2819182A/en|title=Process of aluminizing cathode ray tube screen}}</ref><ref>{{cite journal |last1=Bowie |first1=R.M. |title=The Negative-Ion Blemish in a Cathode-Ray Tube and Its Elimination |journal=Proceedings of the IRE |date=December 1948 |volume=36 |issue=12 |pages=1482–1486 |doi=10.1109/JRPROC.1948.232950 |s2cid=51635920 }}</ref><ref>{{cite journal |last1=Dudding |first1=R.W. |title=Aluminium backed screens for cathode ray tubes |journal=Journal of the British Institution of Radio Engineers |volume=11 |issue=10 |year=1951 |pages=455–462 |doi=10.1049/jbire.1951.0057 }}</ref> In aluminized monochrome CRTs, Aquadag is used on the outside. There is a single aluminum coating covering the funnel and the screen.<ref name="auto52"/>

The screen, funnel and neck are fused together into a single envelope, possibly using lead enamel seals, a hole is made in the funnel onto which the anode cap is installed and the phosphor, aquadag and aluminum are applied afterwards.<ref name="auto37"/> Previously monochrome CRTs used ion traps that required magnets; the magnet was used to deflect the electrons away from the more difficult to deflect ions, letting the electrons through while letting the ions collide into a sheet of metal inside the electron gun.<ref>{{Cite magazine|title=Cathode-ray Tubes 1 <!--https://worldradiohistory.com/hd2/IDX-UK/Technology/Technology-All-Eras/Archive-Practical-Television-IDX/50s/Practical-Television-1959-01-OCR-Page-0029.pdf-->|date=January 1959|magazine=Practical Television}}</ref><ref name="auto53"/><ref name="auto28"/> Ion burn results in premature wear of the phosphor. Since ions are harder to deflect than electrons, ion burn leaves a black dot in the center of the screen.<ref name="auto53"/><ref name="auto28"/>

The interior aquadag or aluminum coating was the anode and served to accelerate the electrons towards the screen, collect them after hitting the screen while serving as a capacitor together with the outer aquadag coating. The screen has a single uniform phosphor coating and no shadow mask, technically having no resolution limit.<ref>{{Cite web|url=http://www.thg.ru/display/20011128/print.html|title=CRT Guide - A THG Primer - THG.RU|date=July 22, 2017|website=www.thg.ru}}</ref><ref name="auto79"/><ref name="auto91">{{cite web |url=https://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf |archive-url=https://web.archive.org/web/20150905122030/http://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf |archive-date=2015-09-05 |url-status=live |title=Manufacture of color picture tubes|website=www.earlytelevision.org |access-date=2020-12-11}}</ref>

Monochrome CRTs may use ring magnets to adjust the centering of the electron beam and magnets around the deflection yoke to adjust the geometry of the image.<ref name="auto19"/><ref>{{Cite web|url=https://www.repairfaq.org/REPAIR/F_monfaq4.html#MONFAQ_010|title=Sci.Electronics.Repair FAQ: Notes on the Troubleshooting and Repair of Computer and Video Monitors|website=www.repairfaq.org}}</ref>

When a monochrome CRT is shut off, the screen itself retracts to a small, white dot in the center, along with the phosphors shutting down, shot by the electron gun; it sometimes takes a while for it to go away.<ref>{{Cite web |last=Y |first=Roshni |date=2019-10-14 |title=What is Monochrome Picture Tube? Construction and Working of Monochrome Picture Tube |url=https://electronicsdesk.com/monochrome-picture-tube.html |access-date=2024-12-12 |website=Electronics Desk |language=en-US}}</ref>

<gallery mode="packed" heights="110px">
File:Osziroehre.jpg|Older monochrome CRT<ref>[http://www.earlytelevision.org/postwar_crts.html Early television] [https://www.crtsite.com/tv-crt.html The Cathode Ray Tube site] [http://www.earlytelevision.org/14ap4_construction.html Picture Tubes]</ref> without aluminum, only aquadag
File:Monochrome CRT electron gun close up.jpg|The electron gun of a monochrome CRT
</gallery>

===Color CRTs===
[[File:CRT screen. closeup.jpg|right|thumb|150px|Magnified view of a delta-gun [[shadow mask]] color CRT]]
[[File:CRT pixel array.jpg|thumb|On the left: Magnified view of In-line phosphor triads (a slot mask) CRT. On the right: Magnified view of Delta-gun phosphor triads.]]
[[File:CRT Phosphors.jpg|right|thumb|150px|Magnified view of a [[Trinitron]] (aperture grille) color CRT. A thin horizontal support wire is visible.]]
[[File:CRT mask types en-de.svg|thumb|CRT triad and mask types]]
[[File:CRT phosphors.png|thumb|right|Spectra of constituent blue, green and red phosphors in a common CRT]]
[[File:Electron gun.jpg|thumb|280px|The in-line electron guns of a color CRT TV]]
Color CRTs use three different phosphors which emit red, green, and blue light respectively. They are packed together in stripes (as in [[aperture grille]] designs) or clusters called [[Triad (monitors)|"triads"]] (as in shadow mask CRTs).<ref name=crtmonitorwork>{{cite web |url=http://www.bit-tech.net/hardware/2006/03/20/how_crt_and_lcd_monitors_work/1 |title=How CRT and LCD monitors work |access-date=4 October 2009 |work=bit-tech.net}}</ref><ref>{{Cite web|url=http://repairfaq.cis.upenn.edu/sam/icets/tvset.htm|title=The TV Set|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=12 November 2020|archive-url=https://web.archive.org/web/20201112014823/http://repairfaq.cis.upenn.edu/sam/icets/tvset.htm|url-status=dead}}</ref>

Color CRTs have three electron guns, one for each primary color, (red, green and blue) arranged either in a straight line (in-line) or in an [[equilateral triangle|equilateral triangular]] configuration (the guns are usually constructed as a single unit).<ref name="auto6"/><ref name="auto44"/><ref>{{Cite web|url=https://patents.google.com/patent/EP0281197A1/en|title=Colour cathode ray tube|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US4766344A/en|title=In-line electron gun structure for color cathode ray tube having oblong apertures|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/EP1536451A1/en|title=Cathode ray tube device with an in-line electron gun|accessdate=18 December 2022}}</ref> The triangular configuration is often called ''delta-gun'', based on its relation to the shape of the [[Greek letter]] [[Delta (letter)|delta]] (Δ). The arrangement of the phosphors is the same as that of the electron guns.<ref name="auto6"/><ref>{{Cite web|url=https://patents.google.com/patent/US20050001552A1/en|title=Cathode-ray tube}}</ref> A grille or mask absorbs the electrons that would otherwise hit the wrong phosphor.<ref name=maskgrill>{{cite web |url=http://www.pcguide.com/ref/crt/crtMask-c.html |title=The Shadow Mask and Aperture Grill |work=PC Guide |access-date=4 October 2009 |archive-url=https://web.archive.org/web/20100102114333/http://pcguide.com/ref/crt/crtMask-c.html |archive-date=2 January 2010 |url-status=dead }}</ref>

A [[shadow mask]] tube uses a metal plate with tiny holes, typically in a delta configuration, placed so that the electron beam only illuminates the correct phosphors on the face of the tube;<ref name=crtmonitorwork/> blocking all other electrons.<ref name="auto104"/> Shadow masks that use slots instead of holes are known as slot masks.<ref name="auto105"/> The holes or slots are tapered<ref>{{Cite web|url=https://patents.google.com/patent/US3973965A/en|title=Making shadow mask with slit-shaped apertures for CRT|accessdate=18 December 2022}}</ref><ref>{{cite web |url= http://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf |archive-url=https://web.archive.org/web/20150905122030/http://www.earlytelevision.org/pdf/manufacture_of_color_pic_tubes.pdf |archive-date=2015-09-05 |url-status=live|title=Manufacture of color picture tubes |website=www.earlytelevision.org |access-date=2020-12-11}}</ref> so that the electrons that strike the inside of any hole will be reflected back, if they are not absorbed (e.g. due to local charge accumulation), instead of bouncing through the hole to strike a random (wrong) spot on the screen. Another type of color CRT (Trinitron) uses an [[aperture grille]] of tensioned vertical wires to achieve the same result.<ref name=maskgrill/> The shadow mask has a single hole for each triad.<ref name="auto6"/> The shadow mask is usually {{Fraction|1|2}}&nbsp;inch behind the screen.<ref name="auto85"/>

Trinitron CRTs were different from other color CRTs in that they had a single electron gun with three cathodes, an aperture grille which lets more electrons through, increasing image brightness (since the aperture grille does not block as many electrons), and a vertically cylindrical screen, rather than a curved screen.<ref>{{Cite web|url=https://www.chicagotribune.com/news/ct-xpm-1991-10-18-9104040210-story.html|title=Several Companies Working on Flatter, Clearer TV Screens|first=Rich|last=Warren|website=chicagotribune.com|date=18 October 1991 }}</ref>

The three electron guns are in the neck (except for Trinitrons) and the red, green and blue phosphors on the screen may be separated by a black grid or matrix (called black stripe by Toshiba).<ref name="auto94"/>

The funnel is coated with aquadag on both sides while the screen has a separate aluminum coating applied in a vacuum,<ref name="auto6"/><ref name="auto38"/> deposited after the phosphor coating is applied, facing the electron gun.<ref>{{cite journal | url=https://ieeexplore.ieee.org/document/1451112 | doi=10.1109/PROC.1973.9182 | title=Cathode-ray-tube phosphors: Principles and applications | date=1973 | last1=Larach | first1=S. | last2=Hardy | first2=A.E. | journal=Proceedings of the IEEE | volume=61 | issue=7 | pages=915–926 }}</ref><ref>[https://pearl-hifi.com/06_Lit_Archive/02_PEARL_Arch/Vol_16/Sec_53/Philips_Tech_Review/PTechReview-44-1988_89-335.pdf Phosphor Screens in Cathode-Ray Tubes for Projection Television] pearl-hifi.com</ref> The aluminum coating protects the phosphor from ions, absorbs secondary electrons, providing them with a return path, preventing them from electrostatically charging the screen which would then repel electrons and reduce image brightness, reflects the light from the phosphors forwards and helps manage heat. It also serves as the anode of the CRT together with the inner aquadag coating. The inner coating is electrically connected to an electrode of the electron gun using springs, forming the final anode.<ref name="auto11"/><ref name="auto6"/> The outer aquadag coating is connected to [[Ground (electricity)|ground]], possibly using a series of springs or a harness that makes contact with the aquadag.<ref>{{Cite web|url=https://patents.google.com/patent/US3996491A/en|title=External connective means for a cathode ray tube|accessdate=18 December 2022}}</ref><ref name="auto96">{{Cite web|url=http://oldtellys.co.uk/otcolour.html|title=Colour Science|website=oldtellys.co.uk}}</ref>

====Shadow mask====
{{Main|Shadow mask}}
The shadow mask absorbs or reflects electrons that would otherwise strike the wrong phosphor dots,<ref name="auto91"/> causing color purity issues (discoloration of images); in other words, when set up correctly, the shadow mask helps ensure color purity.<ref name="auto6"/> When the electrons strike the shadow mask, they release their energy as heat and x-rays. If the electrons have too much energy due to an anode voltage that is too high for example, the shadow mask can warp due to the heat, which can also happen during the Lehr baking at ~435&nbsp;°C of the frit seal between the faceplate and the funnel of the CRT.<ref name="auto66"/><ref>{{Cite web|url=https://patents.google.com/patent/US4327307A/en|title=Shadow mask for color cathode ray tube|accessdate=18 December 2022}}</ref>

Shadow masks were replaced in TVs by slot masks in the 1970s, since slot masks let more electrons through, increasing image brightness. Shadow masks may be connected electrically to the anode of the CRT.<ref>{{Cite web|url=https://patents.google.com/patent/US3543072A/en|title=Color cathode ray tube with metallic contactor ribbon bonded on inside wall of tube between the high voltage terminal and the shadow mask frame|accessdate=18 December 2022}}</ref><ref name="auto40"/><ref>{{cite web |url=https://global.sharp/100th/pdf/gravure.pdf |archive-url=https://web.archive.org/web/20210126133217/https://global.sharp/100th/pdf/gravure.pdf |archive-date=2021-01-26 |url-status=live |title= Sharp radios over the years|website=global.sharp |access-date=2020-12-11}}</ref><ref name="auto14">{{Cite web|url=https://stweb.peelschools.org/pcsweb/pc_tut/06crtmon.htm|title=CRT Monitors|website=stweb.peelschools.org|access-date=8 December 2020|archive-date=16 April 2020|archive-url=https://web.archive.org/web/20200416205016/http://stweb.peelschools.org/pcsweb/pc_tut/06crtmon.htm|url-status=dead}}</ref> Trinitron used a single electron gun with three cathodes instead of three complete guns. CRT PC monitors usually use shadow masks, except for Sony's Trinitron, Mitsubishi's Diamondtron and NEC's [[Cromaclear]]; Trinitron and Diamondtron use aperture grilles while Cromaclear uses a slot mask. Some shadow mask CRTs have color phosphors that are smaller in diameter than the electron beams used to light them,<ref name="auto103">{{Cite web|url=https://patents.google.com/patent/US4251610A/en|title=Method of making multicolor CRT display screen with minimal phosphor contamination|accessdate=18 December 2022}}</ref> with the intention being to cover the entire phosphor, increasing image brightness.<ref name="auto55">{{Cite magazine|title=Mac's Service Shop: Zenith's 1973 Color Line<!--http://www.rfcafe.com/references/popular-electronics/macs-service-shop-zenith-1973-color-tv-popular-electronics-march-1973.htm -->|date=March 1973|magazine=Popular Electronics}}</ref> Shadow masks may be pressed into a curved shape.<ref>{{Cite web|url=https://patents.google.com/patent/US4482334A/en|title=Method for making CRT shadow masks|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://www.freepatentsonline.com/4859901.html|title=Color CRT shadow mask with wrinkle-free corners|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://books.google.com/books?id=jniJTaz6zDMC&q=shadow+mask+crt+tapered&pg=RA1-PA57|title = Official Gazette of the United States Patent and Trademark Office: Patents|year = 1990}}</ref>

====Screen manufacture====
Early color CRTs did not have a black matrix, which was introduced by Zenith in 1969, and Panasonic in 1970.<ref name="auto55"/><ref name="auto39">{{Cite web|url=https://patents.google.com/patent/US5081394A/en|title=Black matrix color picture tube|accessdate=18 December 2022}}</ref><ref name="auto95"/> The black matrix eliminates light leaking from one phosphor to another since the black matrix isolates the phosphor dots from one another, so part of the electron beam touches the black matrix. This is also made necessary by warping of the shadow mask.<ref name="auto94"/><ref name="auto103"/> Light bleeding may still occur due to stray electrons striking the wrong phosphor dots. At high resolutions and refresh rates, phosphors only receive a very small amount of energy, limiting image brightness.<ref name="auto97"/>

Several methods were used to create the black matrix. One method coated the screen in photoresist such as dichromate-sensitized polyvinyl alcohol photoresist which was then dried and exposed; the unexposed areas were removed and the entire screen was coated in colloidal graphite to create a carbon film, and then hydrogen peroxide was used to remove the remaining photoresist alongside the carbon that was on top of it, creating holes that in turn created the black matrix. The photoresist had to be of the correct thickness to ensure sufficient adhesion to the screen, while the exposure step had to be controlled to avoid holes that were too small or large with ragged edges caused by light diffraction, ultimately limiting the maximum resolution of large color CRTs.<ref name="auto103"/> The holes were then filled with phosphor using the method described above. Another method used phosphors suspended in an aromatic diazonium salt that adhered to the screen when exposed to light; the phosphors were applied, then exposed to cause them to adhere to the screen, repeating the process once for each color. Then carbon was applied to the remaining areas of the screen while exposing the entire screen to light to create the black matrix, and a fixing process using an aqueous polymer solution was applied to the screen to make the phosphors and black matrix resistant to water.<ref name="auto39"/> Black chromium may be used instead of carbon in the black matrix.<ref name="auto103"/> Other methods were also used.<ref>{{Cite web|url=https://patents.google.com/patent/KR100728490B1/en|title=photo-sensitive compound and photo-resist resin composition for forming black matrix of CPT containing effective amount thereof|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US5840450A/en|title=Method for forming a black matrix on a faceplate panel for a color CRT|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US6022651A/en|title=Black matrix and a phosphor screen for a color cathode-ray-tube and production thereof|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/DE19655045C2/en|title=Water-soluble photocurable resin compsn. useful in black matrix punch|accessdate=18 December 2022}}</ref>

The phosphors are applied using [[photolithography]]. The inner side of the screen is coated with phosphor particles suspended in PVA photoresist slurry,<ref>{{cite journal |last1=Lakatos |first1=Andras I. |title=Introduction |journal=Journal of the Society for Information Display |date=2000 |volume=8 |issue=1 |pages=1 |doi=10.1889/1.1985254 |s2cid=57611617 }}</ref><ref>{{Cite book|url=https://books.google.com/books?id=aAQBIuPrudQC&q=crt+phosphor+photolithography&pg=PA94|title = Cathodoluminescence and Photoluminescence: Theories and Practical Applications|isbn = 9781420052732|last1 = Ozawa|first1 = Lyuji|date = 3 October 2018| publisher=CRC Press }}</ref> which is then dried using infrared light,<ref>{{Cite magazine|title=Assembly line for lower-priced TV <!--http://www.earlytelevision.org/pdf/life_12-28-59.pdf-->|date=28 December 1959|magazine=Life Magazine}}</ref> exposed, and developed. The exposure is done using a "lighthouse" that uses an ultraviolet light source with a corrector lens to allow the CRT to achieve color purity. Removable shadow masks with spring-loaded clips are used as photomasks. The process is repeated with all colors. Usually the green phosphor is the first to be applied.<ref name="auto6"/><ref>{{cite web |url=http://www.earlytelevision.org/pdf/recent_improvements_in_the_21axp22_color_kinescope.pdf |archive-url=https://web.archive.org/web/20201101112452/http://www.earlytelevision.org/pdf/recent_improvements_in_the_21axp22_color_kinescope.pdf |archive-date=2020-11-01 |url-status=live |title= Recent Improvements in the 21AXP22 Color Kinescope|date=1956 |website=www.earlytelevision.org |access-date=2020-12-11}}</ref><ref name="auto47">{{Cite web|url=https://patents.google.com/patent/US6614160B1/en|title=Fluorescent screen of color CRT and fabricating method thereof|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US5256463A/en|title=Method for manufacturing color phosphor surface|accessdate=18 December 2022}}</ref> After phosphor application, the screen is baked to eliminate any organic chemicals (such as the PVA that was used to deposit the phosphor) that may remain on the screen.<ref name="auto39"/><ref>{{Cite web |url=https://patents.google.com/patent/US3515553A/en|title=Photolithographic deposition of phosphors on faceplate of crt using spraying of photosensitive pva-phosphor suspension in plural layers |website=Google Patents |date=26 September 1951}}</ref> Alternatively, the phosphors may be applied in a vacuum chamber by evaporating them and allowing them to condense on the screen, creating a very uniform coating.<ref name="auto26"/> Early color CRTs had their phosphors deposited using silkscreen printing.<ref name="auto90"/> Phosphors may have color filters over them (facing the viewer), contain pigment of the color emitted by the phosphor,<ref>{{cite journal |last1=Ohno |first1=K. |last2=Kusunoki |first2=T. |title=ChemInform Abstract: Effect of Ultrafine Pigment Color Filters on Cathode Ray Tube Brightness, Contrast, and Color Purity. |journal=ChemInform |date=5 August 2010 |volume=27 |issue=33 |pages=no |doi=10.1002/chin.199633002 }}</ref><ref name="auto8"/> or be encapsulated in color filters to improve color purity and reproduction while reducing glare.<ref name="auto47"/><ref name="auto14"/> Such technology was sold by Toshiba under the Microfilter brand name.<ref>{{cite web | url=https://books.google.com/books?id=QVZ3k_kTQ-oC&dq=toshiba+microfilter+tube&pg=PA30 | title=PC Mag | date=26 September 1995 }}</ref> Poor exposure due to insufficient light leads to poor phosphor adhesion to the screen, which limits the maximum resolution of a CRT, as the smaller phosphor dots required for higher resolutions cannot receive as much light due to their smaller size.<ref>{{Cite web|url=https://patents.google.com/patent/US6013978A/en|title=Method for producing phosphor screens, and color cathode ray tubes incorporating same|accessdate=18 December 2022}}</ref>

After the screen is coated with phosphor and aluminum and the shadow mask installed onto it the screen is bonded to the funnel using a glass frit that may contain 65–88% of lead oxide by weight. The lead oxide is necessary for the glass frit to have a low melting temperature. Boron oxide (III) may also present to stabilize the frit, with alumina powder as filler powder to control the thermal expansion of the frit.<ref>{{Cite web|url=https://patents.google.com/patent/US6583079B1/en|title=CRT frit capable of sealing a CRT bulb at a relatively low temperature and in a short time|accessdate=18 December 2022}}</ref><ref name="auto81"/><ref name="auto50"/> The frit may be applied as a paste consisting of frit particles suspended in [[amyl acetate]] or in a [[polymer]] with an alkyl methacrylate [[monomer]] together with an organic solvent to dissolve the polymer and monomer.<ref name="auto57">{{cite web |url=https://data.epo.org/publication-server/pdf-document?pn=0889010&ki=A1&cc=EP |title=Sealing glass paste for cathode ray tubes patent applicatrion|date=1999 |website= data.epo.org|format=PDF|access-date=2020-12-11}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US5281560A/en|title=Non-lead sealing glasses}}</ref> The CRT is then baked in an oven in what is called a Lehr bake, to cure the frit, sealing the funnel and screen together. The frit contains a large quantity of lead, causing color CRTs to contain more lead than their monochrome counterparts. Monochrome CRTs on the other hand do not require frit; the funnel can be fused directly to the glass<ref name="auto104"/> by melting and joining the edges of the funnel and screen using gas flames. Frit is used in color CRTs to prevent deformation of the shadow mask and screen during the fusing process. The edges of the screen and the edges of funnel of the CRT that mate with the screen, are never melted.<ref name="auto6"/> A primer may be applied on the edges of the funnel and screen before the frit paste is applied to improve adhesion.<ref>{{Cite web|url=http://scienceon.kisti.re.kr/srch/selectPORSrchPatent.do?cn=USP1988114788471|title=Sealing for CRT components|publisher=Zenith Electronics Corporation|date=November 21, 1986|website=ScienceON}}</ref> The Lehr bake consists of several successive steps that heat and then cool the CRT gradually until it reaches a temperature of 435–475&nbsp;°C<ref name="auto57"/> (other sources may state different temperatures, such as 440&nbsp;°C)<ref>{{cite web |url=https://patentimages.storage.googleapis.com/pdfs/US5355051.pdf |archive-url=https://web.archive.org/web/20201031225810/https://patentimages.storage.googleapis.com/pdfs/US5355051.pdf |archive-date=2020-10-31 |url-status=live |title=Patent data |website=patentimages.storage.googleapis.com |access-date=2020-12-11}}</ref> After the Lehr bake, the CRT is flushed with air or nitrogen to remove contaminants, the electron gun is inserted and sealed into the neck of the CRT, and a vacuum is formed on the CRT.<ref>{{Cite web|url=https://patents.google.com/patent/US3658401A/en|title=Method of manufacture of cathode ray tubes having frit-sealed envelope assemblies|accessdate=18 December 2022}}</ref><ref name="auto75"/>

====Convergence and purity in color CRTs====
Due to limitations in the dimensional precision with which CRTs can be manufactured economically, it has not been practically possible to build color CRTs in which three electron beams could be aligned to hit phosphors of respective color in acceptable coordination, solely on the basis of the geometric configuration of the electron gun axes and gun aperture positions, shadow mask apertures, etc. The shadow mask ensures that one beam will only hit spots of certain colors of phosphors, but minute variations in physical alignment of the internal parts among individual CRTs will cause variations in the exact alignment of the beams through the shadow mask, allowing some electrons from, for example, the red beam to hit, say, blue phosphors, unless some individual compensation is made for the variance among individual tubes.

Color convergence and color purity are two aspects of this single problem. Firstly, for correct color rendering it is necessary that regardless of where the beams are deflected on the screen, all three hit the same spot (and nominally pass through the same hole or slot) on the shadow mask.{{clarify|reason=See Talk page for apparent contradiction|date=August 2019}} This is called convergence.<ref>{{cite web |url=http://www.ultimateavmag.com/howto/305picture/|archive-url=https://web.archive.org/web/20091126054428/http://www.ultimateavmag.com/howto/305picture/|archive-date=26 November 2009|title=Picture This|date=March 2005|author=Norton, Thomas J. |work= UltimateAVmag.com}}</ref> More specifically, the convergence at the center of the screen (with no deflection field applied by the yoke) is called static convergence, and the convergence over the rest of the screen area (specially at the edges and corners) is called dynamic convergence.<ref name="auto48"/> The beams may converge at the center of the screen and yet stray from each other as they are deflected toward the edges; such a CRT would be said to have good static convergence but poor dynamic convergence. Secondly, each beam must only strike the phosphors of the color it is intended to strike and no others. This is called purity. Like convergence, there is static purity and dynamic purity, with the same meanings of "static" and "dynamic" as for convergence. Convergence and purity are distinct parameters; a CRT could have good purity but poor convergence, or vice versa. Poor convergence causes color "shadows" or "ghosts" along displayed edges and contours, as if the image on the screen were [[Intaglio (printmaking)|intaglio printed]] with poor registration. Poor purity causes objects on the screen to appear off-color while their edges remain sharp. Purity and convergence problems can occur at the same time, in the same or different areas of the screen or both over the whole screen, and either uniformly or to greater or lesser degrees over different parts of the screen.

[[File:Magnet on TV.webm|thumb|A magnet used on a CRT TV. Note the distortion of the image.]]
The solution to the static convergence and purity problems is a set of color alignment ring magnets installed around the neck of the CRT.<ref>{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvcrtpura.htm|title=SER FAQ: TVFAQ: CRT purity adjustment|website=www.repairfaq.org}}</ref> These movable weak permanent magnets are usually mounted on the back end of the deflection yoke assembly and are set at the factory to compensate for any static purity and convergence errors that are intrinsic to the unadjusted tube. Typically there are two or three pairs of two magnets in the form of rings made of plastic impregnated with a magnetic material, with their [[magnetic fields]] parallel to the planes of the magnets, which are perpendicular to the electron gun axes. Often, one pair of rings has 2 poles, another has 4, and the remaining ring has 6 poles.<ref>{{cite web |url= http://www.arcaderepairtips.com/wp-content/uploads/2016/01/guide_setup_adjust_arcade_monitors_v1.2.0.pdf |archive-url=https://web.archive.org/web/20170612054932/http://www.arcaderepairtips.com/wp-content/uploads/2016/01/guide_setup_adjust_arcade_monitors_v1.2.0.pdf |archive-date=2017-06-12 |url-status=live|title=A Guide to Setup and Adjust the CRT of an Arcade Color Monitor |last= Karlsson|first=Ingvar |website= www.arcaderepairtips.com|access-date=2020-12-11}}</ref> Each pair of magnetic rings forms a single effective magnet whose field [[vector field|vector]] can be fully and freely adjusted (in both direction and magnitude). By rotating a pair of magnets relative to each other, their relative field alignment can be varied, adjusting the effective field strength of the pair. (As they rotate relative to each other, each magnet's field can be considered to have two opposing components at right angles, and these four components [two each for two magnets] form two pairs, one pair reinforcing each other and the other pair opposing and canceling each other. Rotating away from alignment, the magnets' mutually reinforcing field components decrease as they are traded for increasing opposed, mutually cancelling components.) By rotating a pair of magnets together, preserving the relative angle between them, the direction of their collective magnetic field can be varied. Overall, adjusting all of the convergence/purity magnets allows a finely tuned slight electron beam deflection or lateral offset to be applied, which compensates for minor static convergence and purity errors intrinsic to the uncalibrated tube. Once set, these magnets are usually glued in place, but normally they can be freed and readjusted in the field (e.g. by a TV repair shop) if necessary.

On some CRTs, additional fixed adjustable magnets are added for dynamic convergence or dynamic purity at specific points on the screen, typically near the corners or edges. Further adjustment of dynamic convergence and purity typically cannot be done passively, but requires active compensation circuits, one to correct convergence horizontally and another to correct it vertically. In this case the deflection yoke contains convergence coils, a set of two per color, wound on the same core, to which the convergence signals are applied. That means 6 convergence coils in groups of 3, with 2 coils per group, with one coil for horizontal convergence correction and another for vertical convergence correction, with each group sharing a core. The groups are separated 120° from one another. Dynamic convergence is necessary because the front of the CRT and the shadow mask are not spherical, compensating for electron beam defocusing and astigmatism. The fact that the CRT screen is not spherical<ref>{{cite web |url=https://wiki.arcadeotaku.com/images/d/dc/Nanaoms2932.pdf |archive-url=https://web.archive.org/web/20170605081955/http://wiki.arcadeotaku.com/images/d/dc/Nanaoms2932.pdf |archive-date=2017-06-05 |url-status=live |title= General notice|website=wiki.arcadeotaku.com |access-date=2020-12-11}}</ref> leads to geometry problems which may be corrected using a circuit.<ref>{{Cite web|url=https://patents.google.com/patent/US3825796A/en|title=Crt geometry correction network|accessdate=18 December 2022}}</ref> The signals used for convergence are parabolic waveforms derived from three signals coming from a vertical output circuit. The parabolic signal is fed into the convergence coils, while the other two are sawtooth signals that, when mixed with the parabolic signals, create the necessary signal for convergence. A resistor and diode are used to lock the convergence signal to the center of the screen to prevent it from being affected by the static convergence. The horizontal and vertical convergence circuits are similar. Each circuit has two resonators, one usually tuned to 15,625&nbsp;Hz and the other to 31,250&nbsp;Hz, which set the frequency of the signal sent to the convergence coils.<ref>{{Cite book|url=https://books.google.com/books?id=53nnX4fnnNIC&q=crt+convergence&pg=PA110|title=Colour Television: Theory and Practice|date=March 1994|publisher=McGraw-Hill Education |isbn=9780074600245}}</ref> Dynamic convergence may be accomplished using electrostatic quadrupole fields in the electron gun.<ref>{{Cite web|url=https://patents.google.com/patent/EP0739028A2/en|title=Method and apparatus for controlling dynamic convergence of a plurality of electron beams of a color cathode ray tube|accessdate=18 December 2022}}</ref> Dynamic convergence means that the electron beam does not travel in a perfectly straight line between the deflection coils and the screen, since the convergence coils cause it to become curved to conform to the screen.

The convergence signal may instead be a sawtooth signal with a slight sine wave appearance, the sine wave part is created using a capacitor in series with each deflection coil. In this case, the convergence signal is used to drive the deflection coils. The sine wave part of the signal causes the electron beam to move more slowly near the edges of the screen. The capacitors used to create the convergence signal are known as the s-capacitors. This type of convergence is necessary due to the high deflection angles and flat screens of many CRT computer monitors. The value of the s-capacitors must be chosen based on the scan rate of the CRT, so multi-syncing monitors must have different sets of s-capacitors, one for each refresh rate.<ref name="auto4"/>

Dynamic convergence may instead be accomplished in some CRTs using only the ring magnets, magnets glued to the CRT, and by varying the position of the deflection yoke, whose position may be maintained using set screws, a clamp and rubber wedges.<ref name="auto48"/><ref>{{Cite web|url=https://patents.google.com/patent/CA1267682A/en|title=Deflection yoke for adhesive assembly and mounting|accessdate=18 December 2022}}</ref> 90° deflection angle CRTs may use "self-convergence" without dynamic convergence, which together with the in-line triad arrangement, eliminates the need for separate convergence coils and related circuitry, reducing costs. complexity and CRT depth by 10 millimeters. Self-convergence works by means of "nonuniform" magnetic fields. Dynamic convergence is necessary in 110° deflection angle CRTs, and quadrupole windings on the deflection yoke at a certain frequency may also be used for dynamic convergence.<ref>{{cite web |url=http://sbe.org/handbook/fundamentals/Video/Video-Electron_Optics.pdf |title= Video electron optics|website=sbe.org/handbook |access-date=2020-12-11}}</ref>

Dynamic color convergence and purity are one of the main reasons why until late in their history, CRTs were long-necked (deep) and had biaxially curved faces; these geometric design characteristics are necessary for intrinsic passive dynamic color convergence and purity. Only starting around the 1990s did sophisticated active dynamic convergence compensation circuits become available that made short-necked and flat-faced CRTs workable. These active compensation circuits use the deflection yoke to finely adjust beam deflection according to the beam target location. The same techniques (and major circuit components) also make possible the adjustment of display image rotation, skew, and other complex [[raster graphics|raster]] geometry parameters through electronics under user control.<ref name="auto4"/>

Alternatively, the guns can be aligned with one another (converged) using convergence rings placed right outside the neck; with one ring per gun. The rings can have north and south poles. There can be 4 sets of rings, one to adjust RGB convergence, a second to adjust Red and Blue convergence, a third to adjust vertical raster shift, and a fourth to adjust purity. The vertical raster shift adjusts the straightness of the scan line. CRTs may also employ dynamic convergence circuits, which ensure correct convergence at the edges of the CRT. Permalloy magnets may also be used to correct the convergence at the edges. Convergence is carried out with the help of a crosshatch (grid) pattern.<ref name=":98">{{cite web |url=http://educypedia.karadimov.info/library/DX2P.pdf |archive-url=https://web.archive.org/web/20160428122828/http://educypedia.karadimov.info/library/DX2P.pdf |archive-date=2016-04-28 |url-status=live |title=1DX2P Geometry, Convergence, and Purity Adjustments |website=educypedia.karadimov.info |access-date=2020-12-11}}</ref><ref name=":99">{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvcrtcona.htm|title=SER FAQ: TVFAQ: CRT convergence adjustment |website=www.repairfaq.org}}</ref> Other CRTs may instead use magnets that are pushed in and out instead of rings.<ref name="auto96"/> In early color CRTs, the holes in the shadow mask became progressively smaller as they extended outwards from the center of the screen, to aid in convergence.<ref name="auto55"/>

====Magnetic shielding and degaussing====
[[File:Degauss-in-progress at Dell-Trinitron-monitor.jpg|thumb|256px|A degaussing in progress]]
[[File:Mu metal CRT shields.jpg|thumb|[[Mu metal]] magnetic shields for oscilloscope CRTs]]
If the shadow mask or aperture grille becomes magnetized, its magnetic field alters the paths of the electron beams. This causes errors of "color purity" as the electrons no longer follow only their intended paths, and some will hit some phosphors of colors other than the one intended. For example, some electrons from the red beam may hit blue or green phosphors, imposing a magenta or yellow tint to parts of the image that are supposed to be pure red. (This effect is localized to a specific area of the screen if the magnetization is localized.) Therefore, it is important that the shadow mask or aperture grille not be magnetized. The earth's magnetic field may have an effect on the color purity of the CRT.<ref name=":98" /> Because of this, some CRTs have external magnetic shields over their funnels. The magnetic shield may be made of soft iron or mild steel and contain a degaussing coil.<ref>{{Cite web|url=https://www.freepatentsonline.com/4943755.html|title=Magnetic shielding with constant-current coils for CRT|accessdate=18 December 2022}}</ref> The magnetic shield and shadow mask may be permanently magnetized by the earth's magnetic field, adversely affecting color purity when the CRT is moved. This problem is solved with a built-in degaussing coil, found in many TVs and computer monitors. Degaussing may be automatic, occurring whenever the CRT is turned on.<ref>{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvdegacrt.htm|title=SER FAQ: TVFAQ: Degaussing (demagnetizing) a CRT|website=www.repairfaq.org}}</ref><ref name="auto6"/> The magnetic shield may also be internal, being on the inside of the funnel of the CRT.<ref>{{Cite web|url=https://patents.google.com/patent/US6768253B1/en|title=Inner magnetic shield and cathode-ray tube|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US6768252B2/en|title=Magnetic shield structure for color cathode ray tube|accessdate=18 December 2022}}</ref><ref name="auto4"/><ref>{{Cite web|url=https://books.google.com/books?id=35EbAQAAMAAJ&q=crt+internal+magnetic+shield&pg=RA1-PA501|title = Official Gazette of the United States Patent and Trademark Office: Patents|date = July 1994}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US6911769B2/en|title=Lateral magnetic shielding for color CRT|date=20 September 2001 |last1=Antonelli |first1=Goffredo |last2=Paolis |first2=Cesare De |last3=Giannantonio |first3=Giuseppe |last4=Ginesti |first4=Paolo }}</ref><ref>{{Cite web|url=https://patents.google.com/patent/US5804912A/en|title=Magnetic shielding CRT|accessdate=18 December 2022}}</ref>

Color CRT displays in TV sets and computer monitors often have a built-in [[degaussing]] (demagnetizing) coil mounted around the perimeter of the CRT face. Upon power-up of the CRT display, the degaussing circuit produces a brief, alternating current through the coil which fades to zero over a few seconds, producing a decaying alternating magnetic field from the coil. This degaussing field is strong enough to remove shadow mask magnetization in most cases, maintaining color purity.<ref>{{cite web |url=http://www.pcguide.com/ref/crt/crtGauss-c.html|title=Magnetization and Degaussing|access-date=4 October 2009}}</ref><ref>{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvcrtpca.htm|title=SER FAQ: TVFAQ: CRT purity and convergence problems|website=www.repairfaq.org}}</ref> In unusual cases of strong magnetization where the internal degaussing field is not sufficient, the shadow mask may be degaussed externally with a stronger portable degausser or demagnetizer. However, an excessively strong magnetic field, whether alternating or constant, may mechanically [[deformation (engineering)|deform]] (bend) the shadow mask, causing a permanent color distortion on the display which looks very similar to a magnetization effect.

====Resolution====
[[Dot pitch]] defines the maximum resolution of the display, assuming delta-gun CRTs. In these, as the scanned resolution approaches the dot pitch resolution, [[moiré]] appears, as the detail being displayed is finer than what the shadow mask can render.<ref>{{cite web |url=http://www.displaymate.com/moire.html |title= Moiré Interference Patterns |access-date=4 October 2006 |work=DisplayMate Technologies website}}</ref> Aperture grille monitors do not suffer from vertical moiré, however, because their phosphor stripes have no vertical detail. In smaller CRTs, these strips maintain position by themselves, but larger aperture-grille CRTs require one or two crosswise (horizontal) support strips; one for smaller CRTs, and two for larger ones. The support wires block electrons, causing the wires to be visible.<ref>{{cite web |url=http://computer.howstuffworks.com/question406.htm |title=What causes the faint horizontal lines on my monitor? |access-date=4 October 2009 |work=HowStuffWorks|date=21 June 2000 }}</ref> In aperture grille CRTs, dot pitch is replaced by stripe pitch. Hitachi developed the Enhanced Dot Pitch (EDP) shadow mask, which uses oval holes instead of circular ones, with respective oval phosphor dots.<ref name="auto14"/> Moiré is reduced in shadow mask CRTs by arranging the holes in the shadow mask in a honeycomb-like pattern.<ref name="auto4"/>

===Projection CRTs===
Projection CRTs were used in [[CRT projector]]s and CRT [[rear-projection TV]]s, and are usually small (being 7–9&nbsp;inches across);<ref name="auto92"/> have a phosphor that generates either red, green or blue light, thus making them monochrome CRTs;<ref>{{Cite web|url=http://www.curtpalme.com/CRTPrimer_3.shtm|title=CRT Projector Basics|website=www.curtpalme.com}}</ref> and are similar in construction to other monochrome CRTs. Larger projection CRTs in general lasted longer, and were able to provide higher brightness levels and resolution, but were also more expensive.<ref>{{Cite web|url=http://www.curtpalme.com/CRTPrimer_5.shtm|title=CRT Projector Tube Sizes|website=www.curtpalme.com}}</ref><ref>{{Cite web|url=http://www.curtpalme.com/CRTPrimer_11.shtm|title=CRT Projector Brightness|website=www.curtpalme.com}}</ref> Projection CRTs have an unusually high anode voltage for their size (such as 27 or 25&nbsp;kV for a 5 or 7-inch projection CRT respectively),<ref>{{cite web |url=http://www.earlytelevision.org/pdf/rca_projection_receiver.pdf |archive-url=https://web.archive.org/web/20130512163743/http://earlytelevision.org/pdf/rca_projection_receiver.pdf |archive-date=2013-05-12 |url-status=live |title= Broadcast News|website= www.earlytelevision.org|access-date=2020-12-11}}</ref><ref>{{Cite web|url=https://patents.google.com/patent/JP2002352749A/en|title=Projection-type cathode-ray tube having different diameter necks|accessdate=18 December 2022}}</ref> and a specially made tungsten/barium cathode (instead of the pure barium oxide normally used) that consists of barium atoms embedded in 20% porous tungsten or barium and calcium aluminates or of barium, calcium and aluminum oxides coated on porous tungsten; the barium diffuses through the tungsten to emit electrons.<ref name="auto18">{{Cite web|url=https://patents.google.com/patent/JP3135460B2/en|title=Aging method of cathode ray tube|accessdate=18 December 2022}}</ref> The special cathode can deliver 2&nbsp;mA of current instead of the 0.3mA of normal cathodes,<ref>{{Cite web|url=https://patents.google.com/patent/JPH10116566A/en|title=Electronic gun for cathode ray tube|accessdate=18 December 2022}}</ref><ref name="auto18"/><ref name=Gassler2016/><ref name="auto79"/> which makes them bright enough to be used as light sources for projection.  The high anode voltage and the specially made cathode increase the voltage and current, respectively, of the electron beam, which increases the light emitted by the phosphors, and also the amount of heat generated during operation; this means that projector CRTs need cooling.  The screen is usually cooled using a container (the screen forms part of the container) with glycol; the glycol may itself be dyed,<ref>{{Cite web|url=http://www.curtpalme.com/Tinting_Glycol1.shtm|title=Tinting Glycol|website=www.curtpalme.com}}</ref> or colorless glycol may be used inside a container which may be colored (forming a lens known as a c-element). Colored lenses or glycol are used for improving color reproduction at the cost of brightness, and are only used on red and green CRTs.<ref>{{Cite web|url=http://www.curtpalme.com/Sony_G90_C_Element_Change1.shtm|title=Sony G90 C-Element Change|website=www.curtpalme.com}}</ref><ref>{{Cite web|url=http://www.curtpalme.com/Changing_C_Elements1.shtm|title=Changing a C-Element (Marquee)|website=www.curtpalme.com}}</ref> Each CRT has its own glycol, which has access to an air bubble to allow the glycol to shrink and expand as it cools and warms. Projector CRTs may have adjustment rings just like color CRTs to adjust astigmatism,<ref>{{Cite web|url=http://www.curtpalme.com/Astig.shtm|title=CRT Projector Astigmatism Adjustments|website=www.curtpalme.com}}</ref> which is flaring of the electron beam (stray light similar to shadows).<ref>{{Cite web|url=http://www.curtpalme.com/Astig4.shtm|title=CRT Projector Astigmatism Adjustments|website=www.curtpalme.com}}</ref> They have three adjustment rings; one with two poles, one with four poles, and another with 6 poles. When correctly adjusted, the projector can display perfectly round dots without flaring.<ref>{{Cite web|url=http://www.curtpalme.com/CRT_Tube_Replacement.shtm|title=CRT Tube Replacement Procedure|website=www.curtpalme.com}}</ref> The screens used in projection CRTs were more transparent than usual, with 90% transmittance.<ref name="auto38"/> The first projection CRTs were made in 1933.<ref>{{Cite web|url=http://www.earlytelevision.org/prewar_crts.html|title=Prewar Picture Tubes|website=www.earlytelevision.org}}</ref>

Projector CRTs were available with electrostatic and electromagnetic focusing, the latter being more expensive. Electrostatic focusing used electronics to focus the electron beam, together with focusing magnets around the neck of the CRT for fine focusing adjustments. This type of focusing degraded over time. Electromagnetic focusing was introduced in the early 1990s and included an electromagnetic focusing coil in addition to the already existing focusing magnets. Electromagnetic focusing was much more stable over the lifetime of the CRT, retaining 95% of its sharpness by the end of life of the CRT.<ref>{{Cite web|url=http://www.curtpalme.com/CRTPrimer_12.shtm|title=CRT Projector Electrostatic (ES) vs Electromagnetic (EM) Focus|website=www.curtpalme.com}}</ref>

===Beam-index tube===
[[Beam-index tube]]s, also known as Uniray, Apple CRT or Indextron,<ref name="auto12">{{Cite web|url=https://visions4netjournal.com/indextron/|title=Indextron|date=December 29, 2016|website=Visions4 Magazine}}</ref> was an attempt in the 1950s by [[Philco]] to create a color CRT without a shadow mask, eliminating convergence and purity problems, and allowing for shallower CRTs with higher deflection angles.<ref>{{Cite web|url=http://www.earlytelevision.org/uniray.html|title=The Uniray Story|website=www.earlytelevision.org}}</ref> It also required a lower voltage power supply for the final anode since it did not use a shadow mask, which normally blocks around 80% of the electrons generated by the electron gun. The lack of a shadow mask also made it immune to the earth's magnetic field while also making degaussing unnecessary and increasing image brightness.<ref name="auto21">{{Cite magazine|title=UNIRAY-Amazing One-Gun <!--http://www.earlytelevision.org/pdf/pop_sci_2-72.pdf-->|date=February 1972|magazine=Popular Science}}</ref> It was constructed similarly to a monochrome CRT, with an aquadag outer coating, an aluminum inner coating, and a single electron gun but with a screen with an alternating pattern of red, green, blue and UV (index) phosphor stripes (similarly to a Trinitron) with a side mounted photomultiplier tube<ref>{{Cite web|url=https://patents.google.com/patent/US4894711A/en|title=Beam index display tube and display system including the beam index display tube|accessdate=18 December 2022}}</ref><ref name="auto21"/> or photodiode pointed towards the rear of the screen and mounted on the funnel of CRT, to track the electron beam to activate the phosphors separately from one another using the same electron beam. Only the index phosphor stripe was used for tracking, and it was the only phosphor that was not covered by an aluminum layer.<ref name="auto31"/> It was shelved because of the precision required to produce it.<ref>{{cite web |url= http://www.myvintagetv.com/Apple%20PDF%20files/Apple-Chatten_may1961.pdf|title=The "Apple" tube for colour television  |last=Chatten |first=John |website= www.myvintagetv.com|access-date=2020-12-11}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=p68XfA0MHpoC&q=beam+index+tube+expensive&pg=PA47|title=Handbook of Display Technology|first=Joseph A.|last=Castellano|date=June 17, 1992|publisher=Gulf Professional Publishing|isbn=9780121634209|via=Google Books}}</ref> It was revived by Sony in the 1980s as the Indextron but its adoption was limited, at least in part due to the development of LCD displays. Beam-index CRTs also suffered from poor contrast ratios of only around 50:1 since some light emission by the phosphors was required at all times by the photodiodes to track the electron beam. It allowed for single CRT color CRT projectors due to a lack of shadow mask; normally CRT projectors use three CRTs, one for each color,<ref>{{Cite web|url=https://www.broadcaststore.com/index.cfm|title=BroadcastStore.com − New and Used Professional Video, Audio, and Broadcast Equipment. Sony, JVC, Panasonic, Grass Valley, Tektronix, Avid, Applied Magic, and More...|website=www.broadcaststore.com}}</ref> since a lot of heat is generated due to the high anode voltage and beam current, making a shadow mask impractical and inefficient since it would warp under the heat produced (shadow masks absorb most of the electron beam, and, hence, most of the energy carried by the relativistic electrons); the three CRTs meant that an involved calibration and adjustment procedure<ref>{{Cite web|url=http://www.curtpalme.com/Advanced_Procedures.shtm|title=Advanced Procedures for CRT Projectors|website=www.curtpalme.com}}</ref> had to be carried out during installation of the projector, and moving the projector would require it to be recalibrated. A single CRT meant the need for calibration was eliminated, but brightness was decreased since the CRT screen had to be used for three colors instead of each color having its own CRT screen.<ref name="auto12"/> A stripe pattern also imposes a horizontal resolution limit; in contrast, three-screen CRT projectors have no theoretical resolution limit, due to them having single, uniform phosphor coatings.

===Flat CRTs===
[[File:SONY 03JM 2.5" Monochrome Flat Watchman CRT front.jpg|thumb|The front of a Sony Watchman monochrome CRT]]
[[File:SinclairFTV1frontPCB6.jpg|thumb|left|220px|A flat monochrome CRT assembly inside a 1984 Sinclair TV80 portable TV]]
Flat CRTs are those with a flat screen. Despite having a flat screen, they may not be completely flat, especially on the inside, instead having a greatly increased curvature. A notable exception is the LG Flatron (made by [[LG.Philips Displays]], later LP Displays) which is truly flat on the outside and inside, but has a bonded glass pane on the screen with a tensioned rim band to provide implosion protection. Such completely flat CRTs were first introduced by Zenith in 1986, and used flat tensioned shadow masks, where the shadow mask is held under tension, providing increased resistance to blooming.<ref>{{Cite web|url=https://patents.google.com/patent/US4779023A/en|title=Component mounting means for a tension mask color cathode ray tube|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://www.freepatentsonline.com/5059147.html|title=Method and apparatus for making flat tension mask color cathode ray tubes|accessdate=18 December 2022}}</ref><ref>{{Cite web|url=https://www.chicagotribune.com/news/ct-xpm-1986-06-08-8602110070-story.html|title=Zenith VDT Tube Gets Rid of Curve and Maybe the Headaches|first=Steven K.|last=Johnson|website=chicagotribune.com|date=8 June 1986 }}</ref><ref name="auto61"/><ref name="auto13"/><ref>{{Cite web|url=https://patents.google.com/patent/CN1264185C/en|title=Cathode-ray tube with tension shadow mask having reinforced support device|accessdate=18 December 2022}}</ref> LG's Flatron technology is based on this technology developed by Zenith,<ref>{{cite web | url=https://books.google.com/books?id=NjZKAQAAIAAJ&q=lg+flatron+zenith | title=Information Display | date=2000 }}</ref><ref>{{cite book | url=https://books.google.com/books?id=Wm15VzJU-EsC&q=lg+flatron+zenith | title=EuroDisplay '99: Proceedings / General chair Ernst Lüder | date=1999 | publisher=VDE-Verlag | isbn=978-3-8007-2478-9 }}</ref> now a subsidiary of LG. 
Flat CRTs have a number of challenges, like deflection. Vertical deflection boosters are required to increase the amount of current that is sent to the vertical deflection coils to compensate for the reduced curvature.<ref name="auto5"/> The CRTs used in the Sinclair [[TV80]], and in many [[Sony Watchman]]s were flat in that they were not deep and their front screens were flat, but their electron guns were put to a side of the screen.<ref>{{Cite web|url=https://www.experimental-engineering.co.uk/2016/08/22/sony-watchman-fd-20-flat-crt-tv-teardown/|title=Sony Watchman FD-20 Flat CRT TV Teardown – Experimental Engineering|date=22 August 2016 |accessdate=18 December 2022}}</ref><ref>{{Cite web|url=http://lampes-et-tubes.info/cr/cr037.php?l=e|title=SONY 03JM 2.5" Monochrome Flat Display Picture Tube for SONY Watchman pocket TV|website=lampes-et-tubes.info}}</ref> The TV80 used electrostatic deflection<ref>{{Cite web|url=http://www.r-type.org/exhib/aar0015.htm|title=FTV1 @ The Valve Museum|website=www.r-type.org}}</ref> while the Watchman used magnetic deflection with a phosphor screen that was curved inwards. Similar CRTs were used in video door bells.<ref>{{Cite web|url=http://lampes-et-tubes.info/cr/cr084.php?l=e|title=Samsung 4FNG45 4" Flat Display Picture Tube|website=lampes-et-tubes.info}}</ref>
<gallery mode="packed" heights="150px">
File:SONY 03JM 2.5" Monochrome Flat Watchman CRT side.jpg|The side of a Sony Watchman monochrome CRT. One of the pairs of deflection coils is easily noticeable.
</gallery>

===Radar CRTs===
[[Radar display|Radar CRTs]] such as the [[7JP4]] had a circular screen and scanned the beam from the center outwards. The deflection yoke rotated, causing the beam to rotate in a circular fashion.<ref>{{Cite web|url=https://www.earlytelevision.org/12_in_radar_tube.html|title=12 Inch WW2 Radar Tube|website=www.earlytelevision.org}}</ref> The screen often had two colors, often a bright short persistence color that only appeared as the beam scanned the display and a long persistence phosphor afterglow. When the beam strikes the phosphor, the phosphor brightly illuminates, and when the beam leaves, the dimmer long persistence afterglow would remain lit where the beam struck the phosphor, alongside the radar targets that were "written" by the beam, until the beam re-struck the phosphor.<ref>{{cite web | title=The Cathode Ray Tube site, Radar tubes. | website=The Cathode Ray Tube site, scientific glassware. | url=https://www.crtsite.com/radar-crt.html | access-date=2020-12-11}}</ref><ref>{{cite web | last=Diehl | first=Richard N. | title=LabGuy's World: 5FPn CRT Testing | website=LabGuy's World | date=2016-04-10 | url=https://labguysworld.com/5FPn_CRT_Tester.htm | access-date=2020-12-11}}</ref>

===Oscilloscope CRTs===
[[File:Lissajous-Figur 1 zu 3 (Oszilloskop).jpg|thumb|An oscilloscope showing a [[Lissajous curve]] ]]
[[File:Kathodestraalbuis2.jpg|thumb|The electron gun of an oscilloscope. A pair of deflection plates is visible on the left.]]
In [[oscilloscope]] CRTs, [[electrostatic deflection]] is used, rather than the magnetic deflection commonly used with TV and other large CRTs. The beam is deflected horizontally by applying an [[electric field]] between a pair of plates to its left and right, and vertically by applying an electric field to plates above and below. TVs use magnetic rather than electrostatic deflection because the deflection plates obstruct the beam when the deflection angle is as large as is required for tubes that are relatively short for their size. Some Oscilloscope CRTs incorporate post deflection anodes (PDAs) that are spiral-shaped to ensure even anode potential across the CRT and operate at up to 15&nbsp;kV. In PDA CRTs the electron beam is deflected before it is accelerated, improving sensitivity and legibility, specially when analyzing voltage pulses with short duty cycles.<ref>{{cite book | last=Trundle | first=E. | title=Newnes TV and Video Engineer's Pocket Book | publisher=Elsevier Science | series=Newnes Pocket Books | year=1999 | isbn=978-0-08-049749-5 | url=https://books.google.com/books?id=SSP06tjOO0QC | access-date=2020-12-11 }}</ref><ref name="auto69"/><ref>{{cite book | last=Boyes | first=W. | title=Instrumentation Reference Book | publisher=Elsevier Science | year=2002 | isbn=978-0-08-047853-1 | url=https://books.google.com/books?id=sarHIbCVOUAC&pg=PA697 | access-date=2020-12-11 | page=697}}</ref>

====Microchannel plate====
When displaying fast one-shot events, the electron beam must deflect very quickly, with few electrons impinging on the screen, leading to a faint or invisible image on the display. Oscilloscope CRTs designed for very fast signals can give a brighter display by passing the electron beam through a [[micro-channel plate]] just before it reaches the screen. Through the phenomenon of [[secondary emission]], this plate multiplies the number of electrons reaching the phosphor screen, giving a significant improvement in writing rate (brightness) and improved sensitivity and spot size as well.<ref>{{cite book |last= Williams |first= Jim |title= Analog circuit design: art, science, and personalities |publisher= Newnes |year= 1991 |pages= 115–116 |url= https://books.google.com/books?id=CFoEAP2lwLEC&pg=PA115 |isbn= 978-0-7506-9640-1}}</ref><ref>{{cite book |author1=Yen, William M. |author2=Shionoya, Shigeo |author3=Yamamoto, Hajime |title= Practical Applications of Phosphors |publisher= CRC Press |year= 2006 |page= 211 |url= https://books.google.com/books?id=cKMSf0iRVSgC&pg=PA211 |isbn=978-1-4200-4369-3}}</ref>

====Graticules====
Most oscilloscopes have a [[oscilloscope#Graticule|graticule]] as part of the visual display, to facilitate measurements. The graticule may be permanently marked inside the face of the CRT, or it may be a transparent external plate made of glass or [[acrylic glass|acrylic]] plastic. An internal graticule eliminates [[parallax error]], but cannot be changed to accommodate different types of measurements.<ref>{{cite book |author1= Bakshi, U. A. |author2= Godse, Atul P. |title= Electronic Devices And Circuits |publisher= Technical Publications |year= 2008 |page= 38 |url= https://books.google.com/books?id=uJaQML8-MggC&pg=PA38 |archive-url= https://web.archive.org/web/20201207015004/https://books.google.com/books?id=uJaQML8-MggC&pg=PA38 |url-status= dead |archive-date= 7 December 2020 |isbn= 978-81-8431-332-1 }}</ref> Oscilloscopes commonly provide a means for the graticule to be illuminated from the side, which improves its visibility.<ref>{{cite book |last= Hickman |first= Ian |title= Oscilloscopes: how to use them, how they work |publisher= Newnes |year= 2001 |page= 47 |url= https://books.google.com/books?id=O2oj04vbQqgC&pg=PA47 |isbn=978-0-7506-4757-1}}</ref>

====Image storage tubes====
{{Main|Storage tube}}
[[File:Tektronix 564 Analog Storage Oscilloscope.jpg|thumbnail|The Tektronix Type 564: first mass-produced analog phosphor storage oscilloscope]]
These are found in ''analog phosphor storage oscilloscopes''. These are distinct from ''[[digital storage oscilloscope]]s'' which rely on solid state digital memory to store the image.

Where a single brief event is monitored by an oscilloscope, such an event will be displayed by a conventional tube only while it actually occurs. The use of a long persistence phosphor may allow the image to be observed after the event, but only for a few seconds at best. This limitation can be overcome by the use of a direct view storage cathode-ray tube (storage tube). A storage tube will continue to display the event after it has occurred until such time as it is erased. A storage tube is similar to a conventional tube except that it is equipped with a metal grid coated with a [[dielectric]] layer located immediately behind the phosphor screen. An externally applied voltage to the mesh initially ensures that the whole mesh is at a constant potential. This mesh is constantly exposed to a low velocity electron beam from a 'flood gun' which operates independently of the main gun. This flood gun is not deflected like the main gun but constantly 'illuminates' the whole of the storage mesh. The initial charge on the storage mesh is such as to repel the electrons from the flood gun which are prevented from striking the phosphor screen.

When the main electron gun writes an image to the screen, the energy in the main beam is sufficient to create a 'potential relief' on the storage mesh. The areas where this relief is created no longer repel the electrons from the flood gun which now pass through the mesh and illuminate the phosphor screen. Consequently, the image that was briefly traced out by the main gun continues to be displayed after it has occurred. The image can be 'erased' by resupplying the external voltage to the mesh restoring its constant potential. The time for which the image can be displayed was limited because, in practice, the flood gun slowly neutralises the charge on the storage mesh. One way of allowing the image to be retained for longer is temporarily to turn off the flood gun. It is then possible for the image to be retained for several days. The majority of storage tubes allow for a lower voltage to be applied to the storage mesh which slowly restores the initial charge state. By varying this voltage a variable persistence is obtained. Turning off the flood gun and the voltage supply to the storage mesh allows such a tube to operate as a conventional oscilloscope tube.<ref>The [[Great Soviet Encyclopedia]], 3rd Edition (1970–1979)</ref>

===Vector monitors===
{{Main|Vector monitor}}
Vector monitors were used in early computer aided design systems<ref>{{cite journal |last1=Abend |first1=U. |last2=Kunz |first2=H. -J. |last3=Wandmacher |first3=J. |title=A vector graphic CRT display system |journal=Behavior Research Methods & Instrumentation |date=1 January 1981 |volume=13 |issue=1 |pages=46–50 |doi=10.3758/bf03201872 |s2cid=62692534 |doi-access=free }}</ref> and are in some late-1970s to mid-1980s arcade games such as ''[[Asteroids (video game)|Asteroids]]''.<ref>{{cite book |title= Supercade: A Visual History of the Videogame Age, 1971–1984 |author= Van Burnham |publisher= MIT Press |year= 2001 |isbn= 0-262-52420-1}}</ref>
They draw graphics point-to-point, rather than scanning a raster. Either monochrome or color CRTs can be used in vector displays, and the essential principles of CRT design and operation are the same for either type of display; the main difference is in the beam deflection patterns and circuits.

===Data storage tubes===
{{Main|Williams tube}}
The Williams tube or Williams-Kilburn tube was a cathode-ray tube used to electronically store binary data. It was used in computers of the 1940s as a random-access digital storage device. In contrast to other CRTs in this article, the Williams tube was not a display device, and in fact could not be viewed since a metal plate covered its screen.

===Cat's eye===
{{Main|Magic eye tube}}
In some [[vacuum tube]] radio sets, a [[Magic eye tube|"Magic Eye" or "Tuning Eye" tube]] was provided to assist in tuning the receiver. Tuning would be adjusted until the width of a radial shadow was minimized. This was used instead of a more expensive electromechanical meter, which later came to be used on higher-end tuners when transistor sets lacked the high voltage required to drive the device.<ref>{{cite web |url=http://www.vacuumtube.com/eyetubes.htm |title=Tuning-Eye Tubes |access-date=1 December 2009 |publisher=vacuumtube.com |url-status=dead |archive-url=https://web.archive.org/web/20090423055711/http://www.vacuumtube.com/eyetubes.htm |archive-date=23 April 2009}}</ref> The same type of device was used with tape recorders as a recording level meter, and for various other applications including electrical test equipment.

===Charactrons===
{{Main|Charactron}}
Some displays for early computers (those that needed to display more text than was practical using vectors, or that required high speed for photographic output) used Charactron CRTs. These incorporate a perforated metal character mask ([[stencil]]), which shapes a wide electron beam to form a character on the screen. The system selects a character on the mask using one set of deflection circuits, but that causes the extruded beam to be aimed off-axis, so a second set of deflection plates has to re-aim the beam so it is headed toward the center of the screen. A third set of plates places the character wherever required. The beam is unblanked (turned on) briefly to draw the character at that position. Graphics could be drawn by selecting the position on the mask corresponding to the code for a space (in practice, they were simply not drawn), which had a small round hole in the center; this effectively disabled the character mask, and the system reverted to regular vector behavior. Charactrons had exceptionally long necks, because of the need for three deflection systems.<ref>{{cite web |url=https://patents.google.com/patent/US2735956|title=Cathode ray apparatus|access-date=4 October 2009}}</ref><ref>{{cite web |url=https://patents.google.com/patent/US2824250|title=INPUT|access-date=4 October 2009}}</ref>

===Nimo===
{{Main|Nimo tube}}
[[File:Nimo tube BA0000-P31 showing digit 9.jpg|thumb|right|Nimo tube BA0000-P31]]
Nimo was the trademark of a family of small specialised CRTs manufactured by [[Industrial Electronic Engineers]]. These had 10 electron guns which produced electron beams in the form of digits in a manner similar to that of the charactron. The tubes were either simple single-digit displays or more complex 4- or 6- digit displays produced by means of a suitable magnetic deflection system. Having little of the complexities of a standard CRT, the tube required a relatively simple driving circuit, and as the image was projected on the glass face, it provided a much wider viewing angle than competitive types (e.g., [[nixie tube]]s).<ref>{{cite web |url=http://www.tube-tester.com/sites/nixie/dat_arch/BA0000-P31.pdf |archive-url=https://web.archive.org/web/20071025051757/http://www.tube-tester.com/sites/nixie/dat_arch/BA0000-P31.pdf |archive-date=2007-10-25 |url-status=live |title=IEE Nimo CRT 10-gun readout tube datasheet  |work=tube-tester.com|access-date=1 December 2009}}</ref> However, their requirement for several voltages and their high voltage made them uncommon.

===Flood-beam CRT===
{{Main|Electron-stimulated luminescence}}
Flood-beam CRTs are small tubes that are arranged as pixels for large [[video wall]]s like [[Jumbotron]]s. The first screen using this technology (called [[Diamond Vision]] by Mitsubishi Electric) was introduced by [[Mitsubishi Electric]] for the [[1980 Major League Baseball All-Star Game]].<ref>{{Cite web|url=https://signsofthetimes.com/new-york-yankees-choose-mitsubishi-electric-diamond-vision/|title=New York Yankees Choose Mitsubishi Electric Diamond Vision|first=Jacob|last=Rieskamp|date=27 March 2009|website=Signs of the Times}}</ref><ref>{{cite web
|url=https://www.mitsubishielectric.com/sites/news/2018/pdf/0308.pdf|title=Mitsubishi Electric Receives IEEE Milestone for Outdoor Large-Scale Color Display System |website=mitsubishielectric.com|access-date=27 March 2024}}</ref> It differs from a normal CRT in that the electron gun within does not produce a focused controllable beam. Instead, electrons are sprayed in a wide cone across the entire front of the phosphor screen, basically making each unit act as a single light bulb.<ref>{{cite web|url= http://www.decadecounter.com/vta/articleview.php?item=947|title= Futaba TL-3508XA 'Jumbotron' Display|date= 11 March 2010|access-date= 19 December 2014|website= The Vintage Technology Association: Military Industrial Electronics Research Preservation|publisher= The Vintage Technology Association|archive-date= 19 December 2014|archive-url= https://web.archive.org/web/20141219191429/http://www.decadecounter.com/vta/articleview.php?item=947|url-status= usurped}}</ref> Each one is coated with a red, green or blue phosphor, to make up the color sub-pixels. This technology has largely been replaced with [[light-emitting diode]] displays. Unfocused and undeflected CRTs were used as grid-controlled [[Strobe light|stroboscope lamps]] since 1958.<ref>{{cite web |url=http://www.mif.pg.gda.pl/homepages/frank/sheets/074/c/CL60.pdf |publisher=[[Ferranti]], Ltd. |title=''Vacuum light sources — High speed stroboscopic light sources'' data sheet |date=August 1958 |access-date=7 May 2017 |archive-date=20 September 2016 |archive-url=https://web.archive.org/web/20160920125303/http://www.mif.pg.gda.pl/homepages/frank/sheets/074/c/CL60.pdf |url-status=dead }}</ref> [[Electron-stimulated luminescence]] (ESL) lamps, which use the same operating principle, were released in 2011.<ref>{{Cite web|url=https://gadgetwise.blogs.nytimes.com/2011/04/04/vu1-light-bulb-delayed-again/|title=Vu1 Light Bulb Delayed (Again)|first=Eric A.|last=Taub|date=4 April 2011}}</ref>

===Print-head CRT===
CRTs with an unphosphored front glass but with fine wires embedded in it were used as [[Printer (computing)#Liquid ink electrostatic printers|electrostatic print head]]s in the 1960s. The wires would pass the electron beam current through the glass onto a sheet of paper where the desired content was therefore deposited as an electrical charge pattern. The paper was then passed near a pool of liquid ink with the opposite charge. The charged areas of the paper attract the ink and thus form the image.<ref>{{cite web|date=1 November 1960|title=''CK1366 CK1367 Printer-type cathode ray tube'' data sheet|url=https://frank.pocnet.net/sheets/138/c/CK1366.pdf|access-date=29 July 2017|publisher=[[Raytheon Company]]|archive-date=19 December 2019|archive-url=https://web.archive.org/web/20191219151157/http://www.frank.mif.pg.gda.pl/sheets/138/c/CK1366.pdf|url-status=live}}</ref><ref>{{cite web|date=1 November 1960|title=''CK1368 CK1369 Printer-type cathode ray tube'' data sheet|url=https://frank.pocnet.net/sheets/138/c/CK1368.pdf|access-date=29 July 2017|publisher=[[Raytheon Company]]|archive-date=19 December 2019|archive-url=https://web.archive.org/web/20191219151614/http://www.frank.mif.pg.gda.pl/sheets/138/c/CK1368.pdf|url-status=live}}</ref>

===Zeus – thin CRT display===
In the late 1990s and early 2000s [[Philips Research Laboratories]] experimented with a type of thin CRT known as the ''Zeus'' display, which contained CRT-like functionality in a [[flat-panel display]]. The cathode of this display was mounted under the front of the display, and the electrons from the cathode would be directed to the back to the display where they would stay until extracted by electrodes near the front of the display, and directed to the front of the display which had phosphor dots.<ref>{{cite web |url=http://www.patentstorm.us/patents/6246165/description.html |title=US Patent 6246165 – Magnetic channel cathode |author=Beeteson, John Stuart |date=21 November 1998 |url-status=dead |archive-url=https://web.archive.org/web/20130518040015/http://www.patentstorm.us/patents/6246165/description.html |archive-date=18 May 2013}}</ref><ref>{{cite web |url=http://www.freepatentsonline.com/5905336.html |title=US Patent 5905336 – Method of manufacturing a glass substrate coated with a metal oxide|author1=Van Hal |author2=Henricus A. M. |date=18 May 1990|display-authors=etal}}</ref><ref>{{cite journal |doi=10.1016/S0165-5817(97)84675-X|title=Introduction to Zeus displays|year=1996|last1=Van Gorkom|first1=G.G.P.|journal=Philips Journal of Research|volume=50|issue=3–4|page=269}}</ref><ref>{{cite journal |doi=10.1016/S0165-5817(97)84677-3|title=Transport and extraction in Zeus displays|year=1996|last1=Lambert|first1=N.|last2=Montie|first2=E.A.|last3=Baller|first3=T.S.|last4=Van Gorkom|first4=G.G.P.|last5=Hendriks|first5=B.H.W.|last6=Trompenaars|first6=P.H.F.|last7=De Zwart|first7=S.T.|journal=Philips Journal of Research|volume=50|issue=3–4|page=295}}</ref><ref>{{cite journal |doi=10.1016/S0165-5817(97)84688-8 |title=The application and system aspects of the Zeus display|year=1996|last1=Doyle|first1=T.|last2=Van Asma|first2=C.|last3=McCormack|first3=J.|last4=De Greef|first4=D.|last5=Haighton|first5=V.|last6=Heijnen|first6=P.|last7=Looymans|first7=M.|last8=Van Velzen|first8=J.|journal=Philips Journal of Research|volume=50|issue=3–4|page=501}}</ref> The devices were demonstrated but never marketed.

===Slimmer CRT===
[[File:Tabgamb.jpg|250px|thumb|right|A comparison between 21-inch Superslim and Ultraslim CRT]]

Some CRT manufacturers, both LG.Philips Displays (later LP Displays) and Samsung SDI, innovated CRT technology by creating a slimmer tube. Slimmer CRT had the trade names Superslim,<ref>{{Cite web|url=https://news.softpedia.com/news/SuperSlim-CRT-TV-Showcased-by-LG-Philips-Displays-7767.shtml|title=SuperSlim CRT TV Showcased by LG.Philips Displays|first=Tudor|last=Raiciu|website=softpedia|date=6 September 2005}}</ref> Ultraslim,<ref name="auto101">{{Cite web|url=https://news.softpedia.com/news/LG-Presents-the-Slimmest-CRT-TV-Display-49012.shtml|title=LG Presents the Slimmest CRT TV Display|first=Bogdan|last=Solca|website=softpedia|date=9 March 2007}}</ref> Vixlim (by Samsung)<ref>{{Cite web|url=https://www.eetimes.com/jousting-with-flat-panels-samsung-sdi-taps-super-slim-crt/|title=Jousting with flat panels, Samsung SDI taps super-slim CRT &#124; EE Times|date=8 November 2004 }}</ref> and Cybertube and Cybertube+ (both by LG Philips displays).<ref>{{Cite web|url=https://archive.eetasia.com/www.eetasia.com/ART_8800317098_480700_NP_f625e746.HTM|title=LG.Philips develops Cybertube+ SuperSlim CRTs|access-date=8 December 2020|archive-date=26 January 2021|archive-url=https://web.archive.org/web/20210126133218/https://archive.eetasia.com/www.eetasia.com/ART_8800317098_480700_NP_f625e746.HTM|url-status=dead}}</ref><ref>{{Cite web|url=http://www.hardwarezone.com/news/view.php?id=2466|title=LG.Philips Displays Showcases SuperSlim CRT TV :: News :: www.hardwarezone.com®|website=www.hardwarezone.com}}</ref> A {{Convert|21|in|cm|adj=on}} flat CRT has a {{Convert|447.2|mm||adj=on}} depth. The depth of Superslim was {{Convert|352|mm||2}}<ref>{{Cite web|url=http://www.lgphilips-displays.com/english/download/SuperSlim_Technology.pdf|title=Superslim Texch|date=October 13, 2007|archive-url=https://web.archive.org/web/20071013162457/http://www.lgphilips-displays.com/english/download/SuperSlim_Technology.pdf|archive-date=13 October 2007}}</ref> and Ultraslim was {{Convert|295.7|mm|}}.<ref>{{Cite web|url=https://www.oneindia.com/2007/02/05/new-ultra-slim-television-from-lgs-stable-1170664695.html|title=New Ultra Slim Television from LG's stable|date=February 5, 2007|website=www.oneindia.com}}</ref>