Patent ID: 6728192
Filing Date: 2004-04-27
Classification: G11B

Abstract:
A tracking error signal detection apparatus comprising:a light source to radiate a light beam; a converging optical system to converge the light beam radiated from the light source on a reflecting body in a minute spot; a beam splitting means to split the light beam reflected and diffracted by the reflecting body; a photodetector to sense the beam split by the beam splitting means and output a signal according to the quantity of light; and a signal processing portion to process a signal outputted from the photodetector to generate a tracking error signal; wherein a physical change which brings a change of reflectivity is formed on the reflecting body, a light beam is converged on the reflecting body so that the size of the light beam in a direction parallel to the physical change is larger than the size of the light beam in a direction orthogonal to the physical change, wherein the size of an aperture of the converging optical system at the reflecting body side in the direction parallel to the physical change is larger than the size of the aperture in the direction orthogonal to the physical change, and wherein a light beam reflected by the reflecting body as well as a light beam traveling from the light source to the reflecting body passes through the aperture of different sizes.