Cathode Ray Tubes

Alex Chen

Stock P6

October 12th, 2004

How Does it Compare to Other Monitors Now?

• Advantages: Cheaper on the market now, due to being established longer

• Disadvantages:• Produces x-rays; some are not blocked by lead shield• Disposal: have to deal with lead; illegal to just dump

in trash• Big, bulky, power hungry (110 watts; compared to 35

watt LCDs)• Accounts for 80% of electricity use in typical home

computer setup!

Basic Monitor Interface

• The basic interface between any monitor and the computer, whether CRT or LCD, is identical. It’s just the structure of the display that differs.

• An UXGA adapter takes digital data sent by application programs, stores it in VRAM or some equivalent, and converts the data from digital into analog data for transmission to the monitor.

Transmission from PC to Monitor

• The display information is in analog form, so it is send to the monitor through a VGA cable.

• There are many signals, all of these combined into a composite signal by the VGA cord

What do you already know about Cathode Ray Tubes?

Structure of Cathode Ray Tube

• Etymology: “Cathode rays” in a vacuum tube. Cathode rays are high energy electrons emitted from the heated cathode (-) of a vacuum tube

How Does it Work

• Electron gun is weak particle accelerator (only electrons(-)).

• Aims electrons at phosphor screen where they light up the image

• Small heater heats cathode (-), emits electron cloud that is focused into an electron beam by two anodes(+): accelerating anode and focusing anode.

• Black-and-white monitors only have one electron gun; color monitors have three (RGB).

Variations of CRTs

• Metal screen filled with holes sitting just behind phosphor layer. Electron guns each send beam through hole to a single pixel triad of tube’s phosphor layer.

• Aperture Grill - Looks kind of like a grill; with lines jutting down the screen packed together in strips

• Shadow Mask – - packed together in clusters. If you look closely, you can see little individual dots, known as pixels

Why So Big and Bulky?

• Standard cathode ray tube technology requires a certain distance between beam projection device and screen (kind of like mile-long particle accelerators).

How Long has it Been Around?

• Invented in 1896 by Ferdinand Braun• First used for oscilloscopes, then for

television, and finally for computers. • Philo Farnsworth developed the

cathode ray tube that would be used for television and other electronic displays

• Responsible for many contributions to physics, but this is a computer programming class, not a physics class.

                                           

Where can you see it?

• Look right in front of you. They’re big and fat; what else can they be?

Some Various Information

• If you work near the back of a cathode ray computer monitor, you’ll be dosed with more radiation than if you were working at the front of it.

• Do not put a power magnet near a cathode ray tube; can cause magnetization of the shadow mask

The Future of CRTs

• Because CRTs now offer no real advantages over LCD monitors, they will become obsolete soon. The price of LCDs is already decreasing.

Works Cited

• I used…

• Wikipedia (http://www.wikipedia.org)

• Howthingswork

• About.com