Calibration of system for recording and readback of optically detectable data.

摘要

The present invention relates to a method of calibrating a system for the recording and readback of optically detectable data of the type which comprises a record medium (30) formed from a material which is sensitive to optical radiation, means (67) for generating a beam of light (47), means (33) for scanning the beam of light relative to the surface of the medium, means (75) for selectively varying the intensity of the beam of light so as to record data at selected positions on the surface and means (79) for reading back the recorded data. The calibrating method comprises the operation of controlling the recording intensity of the beam of light so that signals from the readback means have a maximum amplitude. According to the invention the operation of controlling the recording intensity comprises utilising the beam of light to record a plurality of test patterns (29) on the surface of the medium each pattern being recorded with a different intensity of the beam of light, reading back the test patterns and generating a readback test signal from each test pattern, detecting the readback test signal having the largest amplitude, and utilising the intensity of the beam of light used to record the test pattern which generates the readback test signal having the largest amplitude for the light beam when it is recording data. The invention also relates to apparatus for implementing the above method of calibrating. <IMAGE>