Patent ID: 6650613
Filing Date: 2003-11-18
Classification: G11B

Abstract:
An optical scanning device for scanning an optical record carrier, said device comprising a radiation source for emitting an incident radiation beam comprising a predetermined wavelength at a substantially linear polarisation, a reflective element located in the path of the incident radiation beam from the radiation source to the location of said optical record carrier and arranged to pass a first proportion, of the incident beam intensity which is incident upon the reflective element, towards the optical record carrier, a polarisation-altering element located in the path of the radiation beam from the reflective element to the location of said optical record carrier, and a detector for detecting a radiation beam reflected from said optical record carrier and passing along a path including the polarisation-altering element and the reflective element, the reflective element being arranged to pass a second proportion, of the reflected beam intensity incident upon the reflective element, towards the detector, the polarisation-altering element converting a linear polarisation of said incident beam into a substantially circular polarisation such that the incident and reflected beam have a different polarisation before and after passing through said polarisation-altering element respectively, characterised in that said reflective element is a partially polarising reflective element arranged such that said first proportion of intensity is greater, as a proportion, than said second proportion of intensity.