Color CRT Display

1. Color CRT Display

2. Contents Objective Basic Techniques - Beam Penetration method -The Shadow - Mask method. Beam Penetration : How it Works ? Shadow Mask: How it Works ?

3. Objective • This was one the earlier CRTs to produce color displays. Coating phosphors of different compounds can produce different colored pictures. But the basic problem of graphics is not to produce a picture of a predetermined color, but to produce color pictures, with the color characteristics chosen at run time. Back

4. Basic Techniques • There are two popular techniques for producing color displays with a CRT are: 1.Beam-penetration method 2.Shadow-mask method Back

5. Beam Penetration method (1) • Two layers of phosphor (red and green) are coated onto the inside of the CRT screen. • The display color depends on haw far the electron beam penetrates into the phosphor layers.

6. Beam Penetration Method(2) • The speed of the electrons, and the screen color at any point, is controlled by the beam acceleration voltage.

7. Beam Penetration Method(3) The beam penetration method: • Used with random scan monitors • Only four colors are possible (red, green, orange, and yellow). • Quality of pictures is not as good as with other methods. Back

8. The Shadow - Mask method

9. Shadow Mask Method(1) The color CRT has: • Three color phosphor dots (red, green and blue) at each point on the screen • Three electron guns, each controlling the display of red, green and blue light.

10. Shadow Mask Method(2) • We obtain color variations by varying the intensity levels of the three electron beam. Shadow mask methods are: • Used in raster scan system (including color TV) • Designed as RGB monitors.

11. Shadow Mask Method(3) • High quality raster graphics system have 24 bits per pixel in the frame buffer (a full color system or a true color system). BACK

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