Using the transparence CD, PSD can detect the displacement of laser spot between non-placing and placing the CD, and it can be used to calculate the parallelism between optical head and spindle motor.

• 考虑在主轴上放置透明盘片,用PSD测量位移子系统测出放置透明盘片前后的光斑移动距离,就可以计算出光头与主轴马达间的平行度。