Cathode Ray Tubes

1
Cathode Ray Tubes

• Alex Chen
• Stock P6
• October 12th, 2004

2
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!

3
Basic Monitor Interface

• The basic interface between any monitor and the
  computer, whether CRT or LCD, is identical. Its
  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.

4
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

5
What do you already know about Cathode Ray Tubes?
6
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

7
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).

8
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
  tubes 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

9
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).

10
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.

11
Where can you see it?

• Look right in front of you. Theyre big and fat
  what else can they be?

12
Some Various Information

• If you work near the back of a cathode ray
  computer monitor, youll 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

13
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.

14
Works Cited

• I used
• Wikipedia (http//www.wikipedia.org)
• Howthingswork
• About.com