Compact Discs

CD Players

Parts

-CD Players read data from the bumps that are placed on Compact Discs

        -3 Major Components

                -Drive Motor (spins disc and can rotate between 200 and 500 times/minute)

                -Laser and Lens System (read the bumps on compact discs)            

                        In order to better understand lasers, check out the LASER section here.

                -Tracking Mechanism (moves the laser along the tracks in order to read from the inside to the outside of the CD)

Inside a CD Player

How Does A CD Player Read A CD?

Laser Focus

-A CD Player's job is to focus the red single-beam laser onto the bumps of the CD

        -laser reads the "play side" of the CD (it goes through polycarbonate layer since it is clear and reflects off of the shiny aluminum layer)

                -the reflection goes back to an opto-electronic device that detects changes in light

                        -the bumps reflect differently than the rest of the aluminum and therefore the opto-electronic sensor interprets it into bits, which form bytes

Tracking

-There is a tracking system that makes sure that the laser is centered on the spiral track at all times

        -as the track moves towards the outside of the disc, the laser follows

-As laser reads the outer parts of the disc the bumps should move faster past the laser, so in order to keep a constant rate of bumps moving past the laser there is a spindle motor which slows the CD down

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This page is not that of a real company but is for a chemistry assignment for General Chemistry 140 at Monmouth College.