System for enhanced astigmatic focus signal detection

An auto-focus system of an optical access unit for reading and writing data from and to a plurality of information layers of an optical storage medium having data stored on at least a first information layer, a second information layer, and a third information layer, the system comprising:

• an astigmatic lens which creates a first focal line image and a second focal line image for refracting light rays reflected from an addressed layer, wherein one of the information layers is the addressed layer and the remaining information layers are the non-addressed layers;
• and
• a confocal aperture placed at the first focal line image created by the astigmatic lens, wherein the confocal aperture passes the light rays reflected from the addressed layer, and blocks generally the light rays reflected from the non-addressed layers.

An auto-focus system of an optical access unit for reading or writing data on a plurality of information layers of an optical storage medium, comprising:

• an astigmatic lens which creates a plurality of focal line images for refracting light rays reflected from an addressed layer from one of the plurality of information layers of the optical storage medium;
• and
• a confocal aperture placed at the one of the plurality of focal line images created by the astigmatic lens, wherein the confocal aperture passes the light rays reflected from the addressed information layer, and wherein the confocal aperture blocks generally the light rays reflected from the non-addressed information layers.