Patent ID: 6288986
Filing Date: 2001-09-11
Classification: G11B

Abstract:
An apparatus for generating a focus error signal from a read light beam retuning from an optical storage media comprising:a first optical lens disposed in the path of said read light beam;a birefringent plate disposed in the path of said read light beam after said first optical lens, said birefringent plate creating a first focal plane of a first polarization and a second focal plane of a second polarization for said read light beam;a pinhole disposed in the path of said read light beam after said birefringent plate and in close proximity to said first and second focal planes;a polarizing beam splitter disposed in the path of said read light beam after said second focal plane, said polarizing beam splitter creating a first polarization beam and a second polarization beam from said read light beam;a first optical detector disposed in the path of said first polarization beam;a second optical detector disposed in the path of said second polarization beam; 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.