1. 2/10 The CD-ROM Drive Roll Call Video Step-by-step discussion

2. CD-ROM Drive Movie Time! (2 parts)

3. 1. CD-ROM Drive A variable-speed motor keeps the area at the detector at the same speed. If the detector moved toward the hub, the motor would spin faster.

4. 1A. The Detector The detector consists of the laser diode, prism, light- sensitive diode, and the objective lens and focusing coil. laser diode objective lens focusing coil prism light-sensitive diode mirror

5. 2. The laser shoots The laser shoots a beam of light, through the prism and off the mirror, that is focused better by the focusing coil.

6. 3. The beam hits the disc The laser beam strikes a reflective layer on the bottom of the disc. A layer of plastic protects the reflective surfaces.

7. 4. The surface: lands and pits The surface of the reflective layer alternates between lands and pits. Land: flat area. Pit: depressions in the layer. Courtesy of http://www.microserve.net/~tpetchy/DVD.shtml

8. 5. Pits scatter. Light that strikes a pit is scattered.

9. 5A. Land bounces. Light that strikes a land is reflected straight back at the detector.

10. 5.2 Boingy, boingy, boingy The reflected light bounces in the prism toward the light-sensitive diode.

11. 6. CD-ROM Drive Each light pulse in the diode generates a small electrical voltage, sent on to the processor. These voltages are timed to generate a stream of 1’s and 0’s.