CD Player Control & Tracking Ece-e 443 Kai Chung Wong

Overall construction of a CD 120mm diameter disk of polycarbonate plastic Active Data starts at 46mm, ends at 117mm “Pits” and “Lands” represent the data Data is circling from inside to outside Each track is approximate 0.5um wide, with 1.6um separating each track

Tracking System of CD Spindle motorSpindle motor Radial tracking driveRadial tracking drive Focusing actuatorFocusing actuator

Spindle motor: Control speed of rotating disc. Speed is regulated, mainly to maintain a linear reading speed. Control speed of rotating disc. Speed is regulated, mainly to maintain a linear reading speed. Two Mode Constant Linear Velocity(CLV) Constant Linear Velocity(CLV) V constant Motor must rotate slower as the laser moves towards the outside edge of disc Constant Reading Velocity Constant Angular Velocity(CAV) Constant Angular Velocity(CAV) W constant Motor speed constant Data transfer rate is higher in outer tracks then inner tracks

Radial Tracking Motor: Move the focus lens to different distances radially along the disc to read different tracks. Move the focus lens to different distances radially along the disc to read different tracks. Move slowly radially outwards as the disc progresses from start to finish Move slowly radially outwards as the disc progresses from start to finish

Focusing Actuator: Made by coil of wires, very low torque Made by coil of wires, very low torque Moves the focus lens up and down in order for the light to maintain a steady focus on the tracks. Moves the focus lens up and down in order for the light to maintain a steady focus on the tracks.

Misalignment Detection

Main Bean

Questions? Questions?

Reference m m D.htm D.htm