Cathode-ray tube

Discoveries and Development of CRTs
– Cathode rays were discovered by Julius Plücker and Johann Wilhelm Hittorf.
– Hittorf observed that unknown rays were emitted from the cathode, traveling in straight lines.
– Arthur Schuster demonstrated cathode rays could be deflected by electric fields.
– William Crookes showed cathode rays could be deflected by magnetic fields.
– J. J. Thomson measured the charge-mass-ratio of cathode rays, revealing they consisted of negatively charged particles smaller than atoms.
– Kenjiro Takayanagi demonstrated a CRT television receiver with a mechanical video camera in 1926.
– By 1927, Takayanagi improved the resolution to 100 lines, unmatched until 1931.
– Philo Farnsworth created a television prototype in 1927.
– The CRT was named in 1929 by inventor Vladimir K. Zworykin.
– RCA was granted a trademark for the term ‘cathode-ray tube’ in 1932.

Evolution and Advancements of CRTs
– Allen B. DuMont developed CRTs that could last 1,000 hours of use in the 1930s.
– Telefunken manufactured the first commercially made electronic television sets with CRTs in 1934.
– In 1947, the cathode-ray tube amusement device, the earliest known interactive electronic game, was created.
– From 1949 to the early 1960s, there was a shift from circular CRTs to rectangular CRTs.
– RCA produced the first mass-produced color CRTs in 1954.
– The first rectangular color CRTs were made in 1954.
– Brighter rare earth phosphors replaced dimmer and cadmium-containing phosphors in 1965.
– The size of CRTs increased over time, reaching 43 inches by 1989.
– Experimental 31-inch CRTs were developed.
– CRTs were used as memory devices, with the screen not intended to be visible to observers.

Superseding Technologies for CRTs
– Since the mid-late 2000s, CRTs have been superseded by flat-panel display technologies.
– LCD, plasma display, and OLED displays are cheaper to manufacture and run.
– Flat-panel displays are significantly lighter and less bulky than CRTs.
– Flat-panel displays can be made in very large sizes, unlike CRTs.
– CRTs make up most of the weight of CRT TVs and computer monitors.
– LCDs started replacing CRTs in the late 90s to early 2000s.
– Hitachi stopped CRT production in 2001.
– Sony stopped CRT production in Japan in 2004.
– LCD monitor sales exceeded CRTs in 2003-2004.
– LCD TV sales exceeded CRTs in some markets in 2005.

Uses and Manufacturing Companies of CRTs
– CRTs still used in some industries where replacement is costly or no substitute is available.
– Airline industry uses CRT instruments in glass cockpits.
– Some military equipment still utilizes CRT technology.
– CRTs are popular for retrogaming due to compatibility with certain games and light gun functionality.
– As of 2022, at least one company manufactures new CRTs for specific markets.
– Manufacturing companies include Corning Precision Materials, Corning Inc., Nippon Electric Glass, Videocon, and Sony.

Construction and Components of CRTs
– CRT body consists of a screen/faceplate/panel, a cone/funnel, and a neck.
– The joined parts are known as the bulb or envelope.
– The neck is made from a glass tube, while the funnel and screen are made by pouring and pressing glass into a mold.
– CRT glass needs special properties to shield against x-rays and provide light transmission.
– The glass used on the screen affects color reproduction and purity in Color CRTs.
– The screen may have an anti-glare or anti-reflective coating.
– CRTs may also have an anti-static coating.
– The leaded glass in the funnels of CRTs may contain 21 to 25% of lead oxide (PbO).
– The neck may contain 30 to 40% of lead oxide.
– The screen may contain 12% of barium oxide and 12% of strontium oxide.
– CRTs may have a metal funnel insulated with polyethylene instead of glass.
– Some CRTs had ceramic or blown Pyrex funnels instead of pressed glass.
– Early CRTs did not have a dedicated anode cap connection, the funnel was the anode connection.
– The funnel is coated on the inside and outside with a conductive coating, making it a capacitor.
– CRTs must be discharged before handling to prevent injury.
– The size of the screen is measured as the face diagonal and the viewable image size/area.
– The viewable image may be square or rectangular, with black edges that can be curved or flat.
– The weight of a CRT is mostly from the thick glass screen, comprising 65% of the total weight.
– Metal clip expands on the inside of an anode button.
– Connection insulated by silicone suction cup.
– Anode button must be specially shaped to establish a hermetic seal.
– Button may consist of 3 nested cups made of Nickel-Chromium-Iron alloy.
– X-rays may leak through the anode button.
– New button and clip design reduces x-ray leakage.
– X-ray shielding may be built into the clip.
– X-rays emitted by CRTs increase with higher voltages and currents.
– Unregulated high voltage power supply leads to higher x-ray emission.
– Flyback Transformer, also known as Integrated High Voltage Transformer (IHVT), contains primary and secondary windings for different voltages.
– Main secondary winding supplies high anode voltage to the CRT.
– Magnetic field collapse induces high voltage in windings.
– Retrace Timing Capacitor slows the collapse of the magnetic field.
– Electron Gun emits electrons that hit the phosphors on the screen.
– Contains a Source:  https://en.wikipedia.org/wiki/Cathode-ray_tube

Cathode-ray tube (Wikipedia)

"Picture tube" redirects here. For the PaintShop Pro image type, see PaintShop Pro § Picture tubes.

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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. The images may represent electrical waveforms on an oscilloscope, a frame of video on an analog television set (TV), digital raster graphics on a computer monitor, or other phenomena like radar targets. A CRT TV 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 cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons.

In CRT TVs 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. In modern CRT monitors and TVs the beams are bent by magnetic deflection, using a deflection yoke. Electrostatic deflection is commonly used in oscilloscopes.

The tube is a glass envelope which is heavy, fragile, and long from front screen face to rear end. Its interior must be close to a vacuum to prevent the emitted electrons from colliding with air molecules and scattering before they hit the tube's face. Thus, the interior is evacuated to less than a millionth of atmospheric pressure. As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity. The face is typically made of thick lead glass or special barium-strontium glass to be shatter-resistant and to block most X-ray emissions. This tube make up most of the weight of CRT TVs and computer monitors.

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 thinner. Flat-panel displays can also be made in very large sizes whereas 40–45 inches (100–110 cm) was about the largest size of a CRT.

A CRT works by electrically heating a tungsten coil which in turn heats a cathode in the rear of the CRT, causing it to emit electrons which are modulated and focused by electrodes. The electrons are steered by deflection coils or plates, and an anode accelerates them towards the phosphor-coated screen, which generates light when hit by the electrons.