A CD-ROM drive operates by using a laser to reflect light off the bottom of the disc. The reflected light is then read by a photo diode detector. The overall operation of a CD-ROM drives is as follows.
- The laser diode emits a low-energy infrared beam toward a reflecting mirror.
- The servo motor, on command from the microprocessor, positions the beam onto the correct track on the CD-ROM by moving the reflecting mirror.
- When the beam hits the disc, its refracted light is gathered and focused through the first lens beneath the platter, bounced off the mirror, and send toward the beam splitter.
- The beam splitter directs the returning laser light toward another focusing lens.
- The last lens directs the light beam to a photo detector that converts the light into electric impulses.
- These incoming pulses are decoded by the microprocessor and sent along to the host computer as data.