Patent ID: 6111828
Filing Date: 2000-08-29
Classification: G11B

Abstract:
An apparatus for generating a focus error signal from a read light beam returning from an optical storage media comprising:a first optical lens disposed in the path of a first light beam derived from said read light beam, said first optical lens having a first focal plane;a second optical lens disposed in the path of a second light beam derived from said read light beam, said second optical lens having a second focal plane;a first optical detector disposed in the path of said first light beam, said first optical detector after said first focal plane;a second optical detector disposed in the path of said second light beam after said second focal plane;a first pinhole disposed in the path of said first light beam after said first optical lens, said first pinhole positioned after said first focal plane and before said first optical detector;a second pinhole disposed in the path of said second light beam after said second optical lens, said second pinhole positioned before said second focal plane and before said second optical detector; andan electrical differencing circuit having a first input coupled to said first optical detector, a second input coupled to said second optical detector and an output.