2/1 A Look at Monitors

• Roll call

• Video: monitors

• Step-by-step lecture

Watch the Video

1: the DAC & Video Card

• CPU sends info to the DAC

• DAC: Digital-to-Analog Converter

2A: How many colors are there?

Name colors possible mode

Standard VGA 16 4 bit

256 color mode 256 8 bit

High Color 65,536 16 bit

True Color 16,777,216 24 bit

3. Sending it to the monitor

• 3 electron guns – RED, GREEN, BLUE

• CRT: “Cathode Ray Tube”

• video card’s signals tell the intensity needed for each gun

4. The magnetic yoke

• The magnetic deflection yoke bends the electron beams from the guns.

4A. Terms

• Resolution: # pixels displayed horizontally and vertically

• Refresh rate: how quickly the image is redrawn

5. Only the Shadow (Mask) knows...

• Purpose: to keep the electron beams sharp and on target.

5. Only the Shadow (Mask) knows...

Dot pitch: distance from one hole’s center to another.

5. Only the Shadow (Mask) knows...

Aperture Grille: “Stripe Pitch” -- distance from center of column to the next.

5. Only the Shadow (Mask) knows...

Slot Mask: “Stripe Pitch” -- distance from center of column to the next.

6. The Phosphors

• Material that glows.

• Different type for each color.

• “Persistence”: phosphor keeps glowing after electron beam leaves.

7. Raster scanning

• “Raster”: the area that is hit by the electron beams.

• Line by line.

• each line is called a scan line.

8. Raster scanning

• “Field”: a complete sweep of the screen.

• “Refresh”: And do it again!

• Refresh rate usually at least 60 times per second.

9. The cheap way out.

• “Interlacing”: scan every OTHER line.

• Can be seen sometimes as a flicker.