cathode-ray tube display screens quotation

A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen.waveforms (oscilloscope), pictures (television set, computer monitor), radar targets, or other phenomena. A CRT on a television set is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term

In CRT television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference.magnetic deflection, using a deflection yoke. Electrostatic deflection is commonly used in oscilloscopes.

Since the mid-late 2000"s, CRTs have been superseded by flat-panel display technologies such as LCD, plasma display, and OLED displays which are cheaper to manufacture and run, as well as significantly lighter and less bulky. Flat-panel displays can also be made in very large sizes whereas 40 in (100 cm) to 45 in (110 cm)

Cathode rays were discovered by Julius Plücker and Johann Wilhelm Hittorf.cathode (negative electrode) which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, and William Crookes showed they could be deflected by magnetic fields. In 1897, J. J. Thomson succeeded in measuring the charge-mass-ratio of cathode rays, showing that they consisted of negatively charged particles smaller than atoms, the first "subatomic particles", which had already been named George Johnstone Stoney in 1891. The earliest version of the CRT was known as the "Braun tube", invented by the German physicist Ferdinand Braun in 1897.cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. Braun was the first to conceive the use of a CRT as a display device.

The first cathode-ray tube to use a hot cathode was developed by John Bertrand Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922.

In 1926, Kenjiro Takayanagi demonstrated a CRT television receiver with a mechanical video camera that received images with a 40-line resolution.Philo Farnsworth created a television prototype.Vladimir K. Zworykin.: 84 RCA was granted a trademark for the term (for its cathode-ray tube) in 1932; it voluntarily released the term to the public domain in 1950.

In 1947, the cathode-ray tube amusement device, the earliest known interactive electronic game as well as the first to incorporate a cathode-ray tube screen, was created.

In the mid-2000s, Canon and Sony presented the surface-conduction electron-emitter display and field-emission displays, respectively. They both were flat-panel displays that had one (SED) or several (FED) electron emitters per subpixel in place of electron guns. The electron emitters were placed on a sheet of glass and the electrons were accelerated to a nearby sheet of glass with phosphors using an anode voltage. The electrons were not focused, making each subpixel essentially a flood beam CRT. They were never put into mass production as LCD technology was significantly cheaper, eliminating the market for such displays.

Beginning in the late 90s to the early 2000s, CRTs began to be replaced with LCDs, starting first with computer monitors smaller than 15 inches in size,Hitachi in 2001,Flat-panel displays dropped in price and started significantly displacing cathode-ray tubes in the 2000s. LCD monitor sales began exceeding those of CRTs in 2003–2004

Despite being a mainstay of display technology for decades, CRT-based computer monitors and televisions are now virtually a dead technology. Demand for CRT screens dropped in the late 2000s.

A popular consumer usage of CRTs is for retrogaming. Some games are impossible to play without CRT display hardware, and some games play better. Reasons for this include:

The design of the high voltage power supply in a product using a CRT has an influence in the amount of x-rays emitted by the CRT. The amount of emitted x-rays increases with both higher voltages and currents. If the product such as a TV set uses an unregulated high voltage power supply, meaning that anode and focus voltage go down with increasing electron current when displaying a bright image, the amount of emitted x-rays is as its highest when the CRT is displaying a moderately bright images, since when displaying dark or bright images, the higher anode voltage counteracts the lower electron beam current and vice versa respectively. The high voltage regulator and rectifier vacuum tubes in some old CRT TV sets may also emit x-rays.

Since it is a hot cathode, it is prone to cathode poisoning, which is the formation of a positive ion layer that prevents the cathode from emitting electrons, reducing image brightness significantly or completely and causing focus and intensity to be affected by the frequency of the video signal preventing detailed images from being displayed by the CRT. The positive ions come from leftover air molecules inside the CRT or from the cathode itself

Burn-in is when images are physically "burned" into the screen of the CRT; this occurs due to degradation of the phosphors due to prolonged electron bombardment of the phosphors, and happens when a fixed image or logo is left for too long on the screen, causing it to appear as a "ghost" image or, in severe cases, also when the CRT is off. To counter this, screensavers were used in computers to minimize burn-in.

Various phosphors are available depending upon the needs of the measurement or display application. The brightness, color, and persistence of the illumination depends upon the type of phosphor used on the CRT screen. Phosphors are available with persistences ranging from less than one microsecond to several seconds.

Doming is a phenomenon found on some CRT televisions in which parts of the shadow mask become heated. In televisions that exhibit this behavior, it tends to occur in high-contrast scenes in which there is a largely dark scene with one or more localized bright spots. As the electron beam hits the shadow mask in these areas it heats unevenly. The shadow mask warps due to the heat differences, which causes the electron gun to hit the wrong colored phosphors and incorrect colors to be displayed in the affected area.

Aperture grille screens are brighter since they allow more electrons through, but they require support wires. They are also more resistant to warping.

CRT monitors can still outperform LCD and OLED monitors in input lag, as there is no signal processing between the CRT and the display connector of the monitor, since CRT monitors often use VGA which provides an analog signal that can be fed to a CRT directly. Video cards designed for use with CRTs may have a RAMDAC to generate the analog signals needed by the CRT.multisyncing.

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.

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;aperture grille of tensioned vertical wires to achieve the same result.

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.

The solution to the static convergence and purity problems is a set of color alignment ring magnets installed around the neck of the CRT.magnetic fields parallel to the planes of the magnets, which are perpendicular to the electron gun axes. Often, one ring has two poles, another has 4, and the remaining ring has 6 poles.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.

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.

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 geometry parameters through electronics under user control.

Color CRT displays in television 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.deform (bend) the shadow mask, causing a permanent color distortion on the display which looks very similar to a magnetization effect.

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.

Beam-index tubes, also known as Uniray, Apple CRT or Indextron,Philco to create a color CRT without a shadow mask, eliminating convergence and purity problems, and allowing for shallower CRTs with higher deflection angles.

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.TV80, and in many Sony Watchmans 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.

Radar CRTs such as the 7JP4 had a circular screen and scanned the beam from the center outwards. 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.

In oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television 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. Televisions 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 15,000 volts. 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.

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.

Most oscilloscopes have a 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 plastic. An internal graticule eliminates parallax error, but cannot be changed to accommodate different types of measurements.

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.

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.

In some vacuum tube radio sets, a "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.

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.

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 tubes).

Flood-beam CRTs are small tubes that are arranged as pixels for large video walls like Jumbotrons. 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. 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.light-emitting diode displays. Unfocused and undeflected CRTs were used as grid-controlled stroboscope lamps since 1958.Electron-stimulated luminescence (ESL) lamps, which use the same operating principle, were released in 2011.

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.

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,

At low refresh rates (60 Hz and below), the periodic scanning of the display may produce a flicker that some people perceive more easily than others, especially when viewed with peripheral vision. Flicker is commonly associated with CRT as most televisions run at 50 Hz (PAL) or 60 Hz (NTSC), although there are some 100 Hz PAL televisions that are flicker-free. Typically only low-end monitors run at such low frequencies, with most computer monitors supporting at least 75 Hz and high-end monitors capable of 100 Hz or more to eliminate any perception of flicker.sonar or radar may have long persistence phosphor and are thus flicker free. If the persistence is too long on a video display, moving images will be blurred.

This problem does not occur on 100/120 Hz TVs and on non-CGA (Color Graphics Adapter) computer displays, because they use much higher horizontal scanning frequencies that produce sound which is inaudible to humans (22 kHz to over 100 kHz).

High vacuum inside glass-walled cathode-ray tubes permits electron beams to fly freely—without colliding into molecules of air or other gas. If the glass is damaged, atmospheric pressure can collapse the vacuum tube into dangerous fragments which accelerate inward and then spray at high speed in all directions. Although modern cathode-ray tubes used in televisions and computer displays have epoxy-bonded face-plates or other measures to prevent shattering of the envelope, CRTs must be handled carefully to avoid personal injury.

Under some circumstances, the signal radiated from the electron guns, scanning circuitry, and associated wiring of a CRT can be captured remotely and used to reconstruct what is shown on the CRT using a process called Van Eck phreaking.TEMPEST shielding can mitigate this effect. Such radiation of a potentially exploitable signal, however, occurs also with other display technologies

As electronic waste, CRTs are considered one of the hardest types to recycle.phosphors, both of which are necessary for the display. There are several companies in the United States that charge a small fee to collect CRTs, then subsidize their labor by selling the harvested copper, wire, and printed circuit boards. The United States Environmental Protection Agency (EPA) includes discarded CRT monitors in its category of "hazardous household waste"

Musgraves, J. David; Hu, Juejun; Calvez, Laurent (8 November 2019). "Cathod Ray-Tube Design". Springer Handbook of Glass. Springer Nature. p. 1367. ISBN 978-3-319-93728-1.

Martin, André (1986). "Cathode Ray Tubes for Industrial and Military Applications". In Hawkes, Peter (ed.). Advances in Electronics and Electron Physics. Vol. 67. Academic Press. pp. 183–328. doi:10.1016/S0065-2539(08)60331-5. ISBN 9780080577333. Evidence for the existence of "cathode-rays" was first found by Plücker and Hittorf ...

Lehrer, Norman, H. (1985). "The Challenge of the Cathode-Ray Tube". In Tannas, Lawrence E. Jr. (ed.). Flat-Panel Displays and CRTs. New York: Van Nostrand Reinhold Company Inc. pp. 138–176. doi:10.1007/978-94-011-7062-8_6. ISBN 978-94-011-7062-8.

Harland, Doug. "Picture Tubes: Motorola Prototype Rectangular Color CRT". www.earlytelevision.org. Early Television Museum. Retrieved 11 November 2021.

Keller, Peter A. (October 2007). "Tektronic CRT History: Part 5: The hybrid years: 1961-64" (PDF). The Tube Collector. Vol. 9, no. 5. Ashland, Oregon: Tube Collectors Association. p. 5. Retrieved 11 November 2021.

Mekeel, Tim; Knowles, Laura (12 September 2013). "RCA pioneers remember making the first color TV tube". LancasterOnline. LNP Media Group Inc. Archived from the original on 4 August 2021. Retrieved 11 November 2021.

US 3440080, Tamura, Michio & Nakamura, Mitsuyoshi, "Cathode ray tube color screen and method of producing same", published 1969-04-22, assigned to Sony Corp.

Warren, Rich (30 September 1991). "TV makers tuning in to flat screens to help round out sales". chicagotribune.com. Chicago Tribune. Retrieved 11 November 2021.

EP 0088122B1, "Large metal cone cathode ray tubes, and envelopes therefor" calls it faceplate US 20040032200A1, "CRT having a contrast enhancing exterior coating and method of manufacturing the same" also calls it faceplate US 20060132019A1, "Funnel for use in a cathode ray tube"

Ha, Kuedong; Shin, Soon-Cheol; Kim, Do-Nyun; Lee, Kue-Hong; Kim, Jeong-Hoon (2006). "Development of a 32-in. slim CRT with 125° deflection". Journal of the Society for Information Display. 14 (1): 65. doi:10.1889/1.2166838. S2CID 62697886.

"GW-12.10-130: NEW APPROACH TO CATHODE RAY TUBE (CRT) RECYCLING" (PDF). www.glass-ts.com. 2003. Archived from the original (PDF) on 13 November 2020. Retrieved 11 December 2020.

Lee, Ching-Hwa; Hsi, Chi-Shiung (1 January 2002). "Recycling of Scrap Cathode Ray Tubes". Environmental Science & Technology. 36 (1): 69–75. Bibcode:2002EnST...36...69L. doi:10.1021/es010517q. PMID 11811492.

Xu, Qingbo; Li, Guangming; He, Wenzhi; Huang, Juwen; Shi, Xiang (August 2012). "Cathode ray tube (CRT) recycling: Current capabilities in China and research progress". Waste Management. 32 (8): 1566–1574. doi:10.1016/j.wasman.2012.03.009. PMID 22542858.

"TV and Monitor CRT (Picture Tube) Information". repairfaq.cis.upenn.edu. Archived from the original on 22 November 2020. Retrieved 8 December 2020. 90 degrees in monitors, 110 in TVs

Ozawa, Lyuji (15 January 2002). "Electron flow route at phosphor screens in CRTs". Materials Chemistry and Physics. 73 (2): 144–150. doi:10.1016/s0254-0584(01)00360-1.

Gassler, Gerhard (2016). "Cathode Ray Tubes (CRTS)". Handbook of Visual Display Technology. pp. 1595–1607. doi:10.1007/978-3-319-14346-0_70. ISBN 978-3-319-14345-3.

den Engelsen, Daniel; Ferrario, Bruno (1 March 2004). "Gettering by Ba films in color cathode ray tubes". Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena. 22 (2): 809–817. Bibcode:2004JVSTB..22..809D. doi:10.1116/1.1689973.

DeBoer, Clint. "Cathode Ray Tube (CRT) Direct View and Rear Projection TVs". Audioholics Home Theater, HDTV, Receivers, Speakers, Blu-ray Reviews and News.

US 7138755B2, "Color picture tube apparatus having beam velocity modulation coils overlapping with convergence and purity unit and ring shaped ferrite core"

Ozeroff, M. J.; Thornton, W. A.; Young, J. R. (29 April 1953). Proposed Improvement in Evacuation Technique for TV Tubes (PDF) (Report). Archived (PDF) from the original on 15 February 2020.

Goetz, D.; Schaefer, G.; Rufus, J. (4 June 1998). "The use of turbomolecular pumps in television tube production". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 5 (4): 2421. doi:10.1116/1.574467.

Yin, Xiaofei; Wu, Yufeng; Tian, Xiangmiao; Yu, Jiamei; Zhang, Yi-Nan; Zuo, Tieyong (5 December 2016). "Green Recovery of Rare Earths from Waste Cathode Ray Tube Phosphors: Oxidative Leaching and Kinetic Aspects". ACS Sustainable Chemistry & Engineering. 4 (12): 7080–7089. doi:10.1021/acssuschemeng.6b01965.

"Implementing Display Standards in Modern Video Display Technologies" (PDF). www.cinemaquestinc.com. Archived (PDF) from the original on 14 June 2016. Retrieved 11 December 2020.

Martindale, Jon (17 September 2019). "New Report States CRT Monitors Are Still Better Than Modern Gaming Displays". Digital Trends. Retrieved 11 December 2020.

Bowie, R.M. (December 1948). "The Negative-Ion Blemish in a Cathode-Ray Tube and Its Elimination". Proceedings of the IRE. 36 (12): 1482–1486. doi:10.1109/JRPROC.1948.232950. S2CID 51635920.

Dudding, R.W. (1951). "Aluminium backed screens for cathode ray tubes". Journal of the British Institution of Radio Engineers. 11 (10): 455–462. doi:10.1049/jbire.1951.0057.

Ohno, K.; Kusunoki, T. (5 August 2010). "ChemInform Abstract: Effect of Ultrafine Pigment Color Filters on Cathode Ray Tube Brightness, Contrast, and Color Purity". ChemInform. 27 (33): no. doi:10.1002/chin.199633002.

Abend, U.; Kunz, H. -J.; Wandmacher, J. (1 January 1981). "A vector graphic CRT display system". Behavior Research Methods & Instrumentation. 13 (1): 46–50. doi:S2CID 62692534.

"Futaba TL-3508XA "Jumbotron" Display". The Vintage Technology Association: Military Industrial Electronics Research Preservation. The Vintage Technology Association. 11 March 2010. Retrieved 19 December 2014.

"CK1366 CK1367 Printer-type cathode ray tube data sheet" (PDF). Raytheon Company. 1 November 1960. Archived from the original (PDF) on 19 December 2019. Retrieved 29 July 2017.

"CK1368 CK1369 Printer-type cathode ray tube data sheet" (PDF). Raytheon Company. 1 November 1960. Archived from the original (PDF) on 19 December 2019. Retrieved 29 July 2017.

Lambert, N.; Montie, E.A.; Baller, T.S.; Van Gorkom, G.G.P.; Hendriks, B.H.W.; Trompenaars, P.H.F.; De Zwart, S.T. (1996). "Transport and extraction in Zeus displays". Philips Journal of Research. 50 (3–4): 295. doi:10.1016/S0165-5817(97)84677-3.

Doyle, T.; Van Asma, C.; McCormack, J.; De Greef, D.; Haighton, V.; Heijnen, P.; Looymans, M.; Van Velzen, J. (1996). "The application and system aspects of the Zeus display". Philips Journal of Research. 50 (3–4): 501. doi:10.1016/S0165-5817(97)84688-8.

van Eck, Wim (1 December 1985). "Electromagnetic radiation from video display units: An eavesdropping risk?". Computers & Security. 4 (4): 269–286. CiteSeerX doi:10.1016/0167-4048(85)90046-X.

Yuan, Wenyi; Li, Jinhui; Zhang, Qiwu; Saito, Fumio; Yang, Bo (1 January 2013). "Lead recovery from cathode ray tube funnel glass with mechanical activation". Journal of the Air & Waste Management Association. 63 (1): 2–10. doi:10.1080/10962247.2012.711796. PMID 23447859. S2CID 24723465.

Lu, Xingwen; Ning, Xun-an; Chen, Da; Chuang, Kui-Hao; Shih, Kaimin; Wang, Fei (1 June 2018). "Lead extraction from Cathode Ray Tube (CRT) funnel glass: Reaction mechanisms in thermal reduction with addition of carbon (C)". Waste Management. 76: 671–678. doi:10.1016/j.wasman.2018.04.010. PMID 29650298. S2CID 4800544.

Yin, Xiaofei; Tian, Xiangmiao; Wu, Yufeng; Zhang, Qijun; Wang, Wei; Li, Bin; Gong, Yu; Zuo, Tieyong (20 December 2018). "Recycling rare earth elements from waste cathode ray tube phosphors: Experimental study and mechanism analysis". Journal of Cleaner Production. 205: 58–66. doi:10.1016/j.jclepro.2018.09.055. S2CID 105023020.

Yu, Miao; Liu, Lili; Li, Jinhui (1 January 2016). "An overall Solution to Cathode-Ray Tube (CRT) Glass Recycling". Procedia Environmental Sciences. 31: 887–896. doi:

Herat, Sunil (2008). "Recycling of Cathode Ray Tubes (CRTs) in Electronic Waste". CLEAN – Soil, Air, Water. 36 (1): 19–24. doi:10.1002/clen.200700082. hdl:

Goldwasser, Samuel M. (28 February 2006). "TV and Monitor CRT (Picture Tube) Information". repairfaq.org. Archived from the original on 26 September 2006.

Manufacturer of standard & custom cathode ray tube & electroluminescent displays. Features include 17 in. to 23 in. LCD, rugged steel & aluminum construction, optional resistive or capacitive touch-screens, light textured powder coated black color, contrast filters, transmissive daylight modification, hard coated vandal shields, 16.7 million display colors, anti-glare hard coating, analog RGB input, weight ranging 13 lbs to 24 lbs & 1280 x 1024 SXGA or 1600 x 1200 UXGA or 920 x 1200 maximum resolution. Applications include use for rack, wall, panel or kiosk installations in commercial, military & broadcast industries. One year limited warranty. RoHS compliant. Meet NEMA & Military Spec.

In a cathode ray tube, the "cathode" is a heated filament. The heated filament is in a vacuum created inside a glass "tube." The "ray" is a stream of electrons generated by an electron gun that naturally pour off a heated cathode into the vacuum. Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. This screen is coated with phosphor, an organic material that glows when struck by the electron beam.

There are three ways to filter the electron beam in order to obtain the correct image on the monitor screen: shadow mask, aperture grill and slot mask. These technologies also impact the sharpness of the monitor"s display. Let"s take a closer look at these now.

Displays have come a long way since the blinking green monitors in text-based computer systems of the 1970s. Just look at the advances made by IBM over the course of a decade:

IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16 different colors and increased the resolution to 640x350 pixels, improving the appearance of the display and making it easier to read text.

In 1987, IBM introduced the Video Graphics Array (VGA) display system. The VGA standard has a resolution of 640x480 pixels and some VGA monitors are still in use.

IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixel resolution in true color (16.8 million colors) and 1,024x768 resolution in 65,536 colors.

When we talk about aging equipment and the need to maintenance, upgrade or otherwise prepare for eventual failure, the focus tends to be on parts of the machinery with a high rate of problems. These are naturally the moving mechanical parts, load bearing mechanisms and the like. What often gets overlooked are the devices that may have a good reliability curve, but are an outdated or altogether obsolete technology. One of the biggest examples we have seen over resent years is the CRT, or cathode ray tube display. A CRT is a type of older style display that predates the flat panel LCD (Liquid Crystal Display), LED (Light-Emitting Diode) or Plasma displays that are in wide use now. CRT Displays utilize beams or electrons projected on to phosphorescent screen the inside of a vacuum tube. This type of display is bulky, consumes more energy and is altogether less efficient than these newer technologies, but is still in use in many machines. Why are these old displays are still being used and why should they be upgraded?

There are many reasons but primarily is a result of the difficulty in changing the display type. If the machine was built with a human machine interface that incorporated the display as a completely integrated whole, the display type may not be able to change in and out. The removal of the HMI in some cases like this would result in the whole machine having to be reprogrammed, rewired or redesigned in such a way that would not make financial sense. Because of this, engineers tend to take a wait and see approach or ignore the possible problem altogether. So, when the CRT finally does fail, and the line goes down waiting for a replacement, which due to the obsolescent nature of the technology can be very delayed.

Eventually, all electronics will fail at some point or another. Nothing lasts forever, especially if it is used every day. What you don’t want, is a failure in a device that is becoming hard and harder to get ahold of, or that fewer technicians have experience with. Therefore, it may be a smart idea to begin plan to upgrade your displays to a retrofit kit that uses a flat panel LCD or LED display. These displays are much easier to replace, have less issues with screen wear such as burn-in or ghost images and are much easier on your electric bill. Plan for downtime on the machine, or better yet, upgrade your spares if you have any, and switch them out when convenient. Upgrading away from some of the old stuff, while a bit painful in the short-term, will save you lots of stress, time and money in the long run.

If you are in need a reliable repair center that can perform any type of display repair, refurbishment or retrofit, be sure to visit us online at gesrepair.com or call us at 1-877-249-1701 to learn more about our services. We’re proud to offer Surplus, Complete Repair and Maintenance on all types of Industrial Electronics, Servo Motors, AC and DC Motors, Hydraulics and Pneumatics. Please subscribe to our YouTube page and Like Us on Facebook! Thank you!

Our results showed that the mfERGs elicited by a stimulus array created on an OLED screen were comparable to the mfERGs elicited by a stimulus array created on a CRT screen. No significant difference was observed between the P1 amplitude of the first- and second-order kernels elicited by the OLED from that elicited by the CRT whereas the P1 amplitude of the first-order kernel elicited by the LCD stimuli was significantly smaller than that elicited by the CRT in all the groups of the averaged hexagonal elements. Only a few implicit times—the N1 implicit time from rings 2, 4, and 5 and the P1 implicit time from ring 5—were significantly different between the CRT and OLED monitors. In contrast, the N1, P1, and N2 implicit times of the first-order kernels were delayed in the mfERG elicited by the LCD in all of the rings compared to the mfERGs recorded elicited by the CRT screen. These findings indicate that the OLED screens would be better for creating stimuli to elicit mfERGs.

The use of OLED screens has expanded although there are still difficulties in producing large-size OLED screens, and their relatively high cost limits their use for television screens and computer monitors. Because OLED displays do not have a backlight, their black is blacker than that of LCD screens. Under low ambient conditions, an OLED screen can have a higher contrast than CRT and LCD screens. OLEDs also have the advantage of a faster response time than standard LCD screens. The LCD displays are capable of between 1 and 16 ms response times leading to a refresh rate of 60 to 480 Hz; however, an OLED can theoretically have less than a 0.01-ms response time enabling a refresh rate of up to 100,000 Hz. Thus, OLEDs can also be used as a flicker stimulus similar to CRTs.

The photosensor measurements showed that the luminance changes of the OLED and CRT screens were very rapid and not significantly different (Figure 4). However, the luminance changes were basically different, i.e., rectangular for the OLED and a train of bursts in CRT. The practical usefulness of these two screens can be confirmed by using them for mfERG recordings as used in routine clinical settings.

The characteristics of OLED screens have been evaluated in detail (Cooper, Jiang, Vildavski, Farrell, & Norcia, 2013; Elze, Taylor, & Bex, 2013; Ito, Ogawa, & Sunaga, 2013), and our results are in good agreement with these earlier evaluations. Recently, the characteristics of an OLED screen (Sony PVM-2541, 24.5-in.; Sony Corporation, Tokyo, Japan) have been precisely measured from the viewpoint of its applicability to visual psychophysics (Cooper et al., 2013). The tested OLED screen was reported to have excellent luminance and color uniformity; excellent low-luminance gradation; stable white and three primary colors throughout the wide luminance range; wide color space, especially for saturated green; and rapid luminance rise/fall times. The authors stated that if large enough OLED displays were constructed, it would be ideal for vision research. However, they also stated that the concept of one frame in the PVM-2541 is different from those in an LCD or CRT display, and it is unclear whether these differences will affect the human perception of short-duration stimuli.

The luminance changes in the LCDs had a relatively slow rise from black to white and slow fall from white to black. Our previous experiments (Matsumoto et al., 2013) showed that the time delay caused a transient reduction in the averaged luminance of the entire display. To reduce the transient reduction, either decreasing the contrast of the checkerboards or using higher frequency–driven LCDs would be effective. But such a setup for the LCD screen is not easy when used in clinical practice.

When examining each component of the mfERGs, the amplitude of P1 of the first-order kernel and the amplitude of P2 of the second-order kernel elicited by an LCD screen were significantly different from those elicited by a CRT. Only the P1 amplitudes in all rings and the P2 amplitudes in rings 1 and 2 of the second-order kernel were identical between the waves elicited by the LCD and CRT screens. In addition, the implicit times of all components in all of the rings were significantly delayed when the LCD was used as a stimulator compared to that when the CRT was used. This is in good accord with the results by Kaltwasser, Horn, Kremers, and Juenemann (2009) who investigated the suitability of LCD as a visual stimulator for mfERGs. They stated that when an LCD screen was used as a stimulator, the increase in the implicit times and differences in the luminance-versus-time profile must be taken into account. Most of the LCD screens have similar properties with slow luminance rises and falls. The drive system of the LCD display used in this paper was vertical alignment (VA). This system has some advantages by having more uniform luminances and deeper black with a high contrast ratio than twisted nematic (TN) panels. The disadvantage is that they have a slower response time compared to TN panels. In the manufacturer"s specifications of the LCD monitor, the response speed is reported to be 25 ms for black-white-black, which is relatively slow. We measured the rise (black to white, 10% to 90% luminance) and fall times (white to black, 90% to 10% luminance), and the results were 6.2 and 9.6 ms, respectively (Supplemental Figure 2).

We believe that the differences of the response times, rise and fall times, and durations of the on-luminance between LCD and CRT screens were the cause of the significant differences in the values of the different components of the mfERGs obtained by the LCD as opposed to those elicited by CRT screens.

The fusion of the LCD responses implies that the m-sequences underlying the multifocal technique cannot be accurately reproduced by the LCD display. Therefore, further investigations on LCD screens with a 120-Hz refresh rate and/or inserting a black frame after each stimulus frame may be helpful to solve this. In other words, our results demonstrated that no black frames are necessary with OLEDs because no fusion occurred.

The long input lag observed in the OLED is unlikely due to the OLED itself but may be due to the Sony BKM229X RGB/Component video input module signal conversion that we used to convey the analog video signal from the VERIS mfERG system for the digital display. Our results that OLED showed negligible response time is in accordance with the results of Cooper et al. (2013). However, our results differed from theirs in that they did not evaluate the effect of input lag. This is because they used the voltage change from the photodiode placed on the monitor, so the recording was triggered by the luminance change of the monitor whereas our results showed long input lag, probably due to the video module signal conversion used in this study.

There are several limitations in this study. The frequency used was not 75 Hz, which is widely used in clinical practice. The mechanism for the differences in the implicit times between mfERGs recorded using different monitors was not determined. The properties of the luminance changes were different, and their influence on the retinal response was unknown. Investigating the influence of the different properties on the human visual system will be interesting, but we have only investigated the possibility of substituting the CRT monitor with another monitor as a visual stimulator for mfERG. We investigated a single LCD and a single OLED monitor, but the input lag and response time are unique in LCD and OLED screens. Therefore, a better LCD screen or a better OLED monitor as a visual stimulator may be found with further investigations. Moreover, we only used the S1721 Flexscan LCD monitor, which is a VA type LCD. A TN LCD, which has 5 ms of response time, may minimize the overlapping and may show similar results as OLED displays. In the literature of Cooper et al. (2013), the LG Flatron D2342 LCD, one of the TN LCDs, shows increasing slope up to 5 ms and, after that, shows a plateau (saturation) response. However, most TN LCD panels have a disadvantage in that their response time increased markedly when used under a special mode, such as fine color drawing or low-contrast conditions. Further investigations are needed to compare commercially available TN LCDs with CRTs as visual stimulators to elicit mfERGs.

In conclusion, an OLED screen is a better substitute for a CRT screen on which to create stimuli to elicit mfERGs. Although the waveforms of the mfERGs are similar, they are not completely identical. We recommend that normative mfERGs elicited by OLED screens be collected from normal eyes before the mfERGs from diseased eyes are examined.

Aiken, W. R. “Development of the Thin Cathode-Ray Tube.” Journal of the Society of Motion Picture and Television Engineers, Vol. 67, No. 7, July 1958.

Schagen, P. “The Banana-Tube Display System. A New Approach to the Display of Colour Television Pictures.” Proceedings of the IEEE, 1961, Part B 108, pp. 577–586.

Howden, H. “Mechanical and Manufacturing Aspects of the Banana Tube Colour-Television Display System.” Proceedings of the IEEE, 1961, Part B 108, pp. 596–603.

Freeman, K. G., and Overton, B. R. “Appraisal of the Banana-Tube Colour Television Display System.” Proceedings of the IEEE, 1961, Part B 108, pp. 624–630.

Goede, W. F.; Gunther, J.; and Lang, J. “512 Character Alphanumeric Display Panel.” Presented at the 1972 Society for Information Display International Symposium, June 1972, published in conference proceeding and SID Journal.

Lang, J.; Goede, W.; and Playter, J. “A 160 X 256-Element Alphanumeric/Graphic Display.” Presented at the 1972 IEEE Conference on Display Devices, October 1972, published in conference proceeding, 8 pp.

Holton, W., et al., “Design Fabrication and Performance of a Flat Tube Display.” International Electron Device Meeting Proceedings, December 1977, pp. 78–80.

Kelly, J. “An Improved Field Emission Cathode for Use in Storage-Tube and Other Electron-Optical Applications.” SRI program description internal document, November 1970, 14 pp.

Ashizaki, S., Suzuki, Y., Konosu, O., & Adachi, O. (1986). 43“ direct-view color CRT. In Proceedings of Japan Display ‘86 (pp. 226–229 ). Playa del Rey, CA.: Society for Information Display.

Barten, P.G.J. (1988). CRT: present and future. In Society for Information Display 1988 Seminar Lecture Notes, Vol. 2 (pp. 8.1–8. 43 ). New York, NY: Palisades Institute for Research Services, Inc.

Basov, N.G., Bogdankevich, O.V., Naisbov, A.S., Koslovskii, V.I., Papusha, V.P., & Pechenov, A.N. (1975). Formation of a TV image on a large screen with the aid of a laser electron-beam tube. Soviet Journal of Quantum Electronics, 4, 1408.

Bhargava, R.N., Colak, S., Fitzpatrick, B.J., Cammack, D.A., & Khurgin, J. (1985). Visible e-beam pumped lasers from II-VI semiconductors. In Proceedings of the 1985 International Display Research Conference (pp. 200–203 ). New York, NY: Institute of Electrical and Electronic Engineers, Inc.

Bonye, G.R., Kavanagh, M., & Bellis, N.S. (1988). Colour CRT screens made by electron beam and UV exposure. In SID Digest, Vol. 19, (pp. 393–394 ). New York, NY: Palisades Institute for Research Services, Inc.

Bos, P.J., Buzak, T., & Vatne, R. (1985). A full-color field-sequential color display. Proceedings of the Society for Information Display, 26, 157–161.

Inaba, M., Sato, M., Higashinakagawa, E., & Ohtake, Y. (1988). Characteristics of chromium-added invar with regard to shadow masks for high-resolution colour television tubes. Displays, 9, 17–22.

Infante, C. (1988). Advances in CRT displays. Proceedings of the 1988 International Display Research Conference, (pp. 9–12 ). New York, NY: Institute of Electrical and Electronic Engineers, Inc.

Ohno, H., Amano, Y., & Inouye, H. (1989). Super-high-resolution gun with complex prefocus lens for 2Kx2K color display. In SID Digest, Vol. 20, (pp. 45–48 ). New York, NY: Palisades Institute for Research Services, Inc.

Shmulovich, J., & Kocian, D.F. (1989). Thin-film phosphors for miniature CRTs used in helmet-mounted displays. In SID Digest, Vol. 20, (pp. 200–202 ). New York, NY: Palisades Institute for Research Services, Inc.

Turner, J.A. (1989). Beam position control-color CRT design considerations. In Proceedings of Japan Display ‘89 (pp. 668–670 ). Playa del Rey, Calif.: Society for Information Display.

Wilson, I.M. (1975). Theoretical and practical aspects of electron gun design for colour picture tubes. Institute of Electrical and Electronic Engineers Transactions on Consumer Electronics, Vol CE

Yoshida, S., Ohkoshi, A., & Miyaoka, S. (1968). The “Trinitron”—a new color tube. Institute of Electrical and Electronic Engineers Transactions on Broadcast and TV Receivers, BTR-14, 19–27.

A cathode ray tube is a device that uses a beam of electrons in order to produce an image on a screen. Cathode ray tubes are also known commonly as CRTs. Cathode ray tubes are still widely used in a number of electrical devices, such as computer screens, television sets, radar screens, and oscilloscopes (signalvizualization tools used in science and engineering).

A cathode ray tube consists of five major parts: an envelope or container, an electron gun, a focusing system, a deflection system, and a display screen.

Most people have seen a cathode ray tube or pictures of one. The “picture tube” in a television set is perhaps the most familiar form of a cathode ray tube. The outer shell that gives a picture tube its characteristic shape is called the envelope of a cathode ray tube. The envelope is most commonly made of glass, although tubes of metal and ceramic can also be used for special purposes. The glass cathode ray tube consists of a cylindrical portion that holds the electron gun and the focusing and deflection systems. At the end of the cylindrical portion farthest from the electron gun, the tube widens out to form a conical shape. At the flat wide end of the cone is the display screen.

Air is pumped out of the cathode ray tube to produce a vacuum with a pressure in the range of 10-2 to 10-6 pascal, the exact value depending on the use to which the tube will be put. A vacuum is necessary to prevent electrons produced in the CRT from colliding with atoms and molecules within the tube.

An electron gun consists of three major parts. The first is the cathode, a piece of metal which, when heated, gives off electrons. One of the most common cathodes in use is made of cesium metal, a member of the alkali family that loses electrons very easily. When a cesium cathode is heated to a temperature of about 1,750°F (954°C), it begins to release a stream of electrons. These electrons are then accelerated by an anode (a positively charged electrode) placed a short distance away from the cathode. As the electrons are accelerated, they pass through a small hole in the anode into the center of the cathode ray tube.

Under normal circumstances, an electron beam produced by the electron gun described above would have a tendency to spread out to form a cone-shaped beam. However, the beam that strikes the display screen must be pencil-thin and clearly defined. In order to form the electron beam into the correct shape, an electrical or magnetic lens, similar to an optical lens, can be created adjacent to the accelerating electrode. The lens consists of some combination of electrical or magnetic fields that shapes the flow of electrons that pass through it, just as a glass lens shapes the light rays that pass through it.

The electron beam in a cathode ray tube also has to be moved about so that it can strike any part of the display screen. In general, two kinds of systems are available for controlling the path of the electron beam, an electrostatic system and a magnetic system. In the first case, negatively charged electrons are deflected by similar or opposite electrical charges, and in the second case, they are deflected by magnetic fields.

In either case, two deflection systems are needed, one to move the electron beam in a horizontal direction, and the other to move it in a vertical direction. In a standard television tube, the electron beam completely scans the display screen about 25 times every second.

The actual conversion of electrical to light energy takes place on the display screen when electrons strike a material known as a phosphor. A phosphor is a chemical that glows when exposed to electrical energy. A commonly used phosphor is the compound zinc sulfide. When pure zinc sulfide is struck by an electron beam, it gives off a greenish glow. The exact color given off by a phosphor also depends on the presence of small amounts of impurities. For example, zinc sulfide with silver metal as an impurity gives off a bluish glow and with copper metal as an impurity, a greenish glow.

The selection of phosphors to be used in a cathode ray tube is very important. Many different phosphors are known, and each has special characteristics. For example, the phosphor known as yttrium oxide gives off a red glow when struck by electrons, and yttrium silicate gives off a purplish blue glow.

Cathode ray tubes differ in their details of construction depending on the use to which they will be put. In an oscilloscope, for example, the electron beam has to be able to move about on the screen very quickly and with high precision, although it needs to display only one color. Factors such as size and durability are also more important in an oscilloscope than they might be in a home television set.

In the early 2000s, flat-screen display technologies began to rapidly displace CRTs in most of their applications. While CRT televisions still remained on the market as of 2006 because of their price advantage, most computer makers were ramping down their production of CRT monitors in favor of flatscreen monitors. For example, Apple Corporation stopped shipping computers with CRT monitors in the summer of 2001, and Sony Corporation announced in 2005 that it would cease manufacture of CRT monitors. The global CRT market was forecast to plunge from about $20 billion in 1999 to about $10 billion in 2007.

The development of electronic television systems was based on the development of the cathode ray tube (CRT). A cathode ray tube aka picture tube was found in all electronic television sets up until the invention of the less bulky LCD screens.

A cathode ray is a stream of electrons leaving the negative electrode, or cathode, in a discharge tube (an electron tube that contains gas or vapor at low pressure), or emitted by a heated filament in certain electron tubes.

Besides television sets, cathode ray tubes are used in computer monitors, automated teller machines, video game machines, video cameras, oscilloscopes and radar displays.

The first cathode ray tube scanning device was invented by the German scientist Karl Ferdinand Braun in 1897. Braun introduced a CRT with a fluorescent screen, known as the cathode ray oscilloscope. The screen would emit a visible light when struck by a beam of electrons.

German, Heinrich Geissler invents the Geissler tube, created using his mercury pump this was the first good evacuated (of air) vacuum tube later modified by Sir William Crookes.

Englishmen, Sir William Crookes was the first person to confirm the existence of cathode rays by displaying them, with his invention of the Crookes tube, a crude prototype for all future cathode ray tubes.