Application Of Critical-angle Method On The Focus Servo

This paper analyses the critical angle method that often use in focus detected. We receive two relations, the first relation between refractive index of the critical-angle prism and focus-error signal; the second relation between numerical aperture of object lens and out-of-focus error signal. We simulate the practicality system to experimentalize, obtain the relation between defocus and focus error signal, make it a condition that NA=0.625 and n=1.7979. Compare the theory curve with the experimental curve, analyse the difference between the two curve.This paper analyses emphatically the position error and manufacture error of critical-angle prism the position error and aberration of object lens the position error and manufacture error of the polarization beam splitter the position error of the detector, and come out their relations.