Patent ID: 6243336
Filing Date: 2001-06-05
Classification: G11B,H02K

Abstract:
For use in an optical disc system having a lens and a disc to be read, an improved focus capture system, comprising:means for impinging light upon the disc to be read;means for monitoring a Quad Sum signal that is derived from a transmitted beam and a reflected beam that are divided from a light beam returning from the disc;means for moving said lens to a first position, for moving said lens away from said first position and toward said disc being read while looking for the maximum Quad Sum signal, and for moving said lens back away from said disc;means for monitoring the total light of said transmitted beam and said reflected beam;means for determining, during said monitoring of light, when said total light of said transmitted beam and said reflected beam is above one-half the peak value measured;means for searching for the first zero crossing;means for determining when said Quad Sum signal exceeds one-half peak amplitude; andmeans for closing focus when said Quad sum signal exceeds one-half peak amplitude.