Patent ID: 6088309
Filing Date: 2000-07-11
Classification: G11B

Abstract:
A method for controlling vertical alignment of a light beam producing laser used for reading information from or writing information to a rotatable information storage medium, said method comprising the steps of:directing a first light beam from said laser toward said medium;directing a second beam of light split from said first beam toward said medium, said second beam being directed substantially parallel to said first beam;varying the direction of impingement of said light from said second beam, with respect to said medium, in an oscillatory manner at a frequency .omega.;supplying light, from said second beam, which has been reflected from said medium, to a photodetector which produces an electrical signal substantially proportional to power in light input thereto;determining, from phase and frequency content of said electrical signal, when said second laser beam is oriented substantially perpendicularly to said medium; andcontrolling the orientation of said laser based on a result of the determining step so that said first beam is substantially perpendicular to said medium.