Single return path orthogonally-arranged optical focus and tracking sensor system

Abstract

An apparatus and method for providing tracking and focus error signals for controlling an application of a radiation beam to a data track of an optical storage medium. A data signal, indicative of data stored on the medium, may also be provided. One apparatus in accordance with the present invention includes a multi-element beam separator, such as a quad prism, having first, second, third and fourth separator elements for separating a return beam reflected and diffracted from the data track into first, second, third and fourth portions, respectively. In other embodiments, more or less than four separator elements and return beam portions could be used. A focusing lens converges the portions of the return beam onto a detector array. The first and second separator elements, arranged on opposite sides of a plane substantially parallel to a reference plane defined by an optical axis of the radiation beam and a tangent to the data track, separate the return beam along at least one plane substantially parallel to the reference plane, and the resulting first and second portions are used to generate a tracking error signal. The third and fourth separator elements, arranged adjacent to and on opposite sides of the first and second separator elements, separate the return beam along planes substantially perpendicular to the reference plane, and the resulting third and fourth portions are used to generate a focus error signal.

Dependencies are inferred from the claim text.