An auto-focus system for a DVD reader or other optical access unit which reads andor writes information fromto at least two information layers on an optical storage medium such as a DVD or DVR. Uncorrelated noise is removed from the CCD-RAW data in the first noise reduction circuit. Generally, the local oscillator frequency associated with the sideband having a lower energy is selected. In a method of storing picture data in a compressed or decompressed data format in a data storing memory, the picture data are divided into data segments. The system allows causing an electromagnetic beam to access an otherwise difficult to access sample in, for instance, a vacuum deposition chamber, and enables achieving very closely spaced incident and spherical mirror reflected points of beam reflection from a sample surface in use.