| 摘要 |
PURPOSE:To measure the drift of a head simply and accurately, by projecting light with a specified wavelength to a head arranged at a specified position on a disc to form an interference fringe, corresponding to which the light signal thereof is converted into an electrical signal. CONSTITUTION:A head 9 is arranged at a specified position of a flat transparent disc 1. This head 9 drifts according to the rotational speed of the disc 1 upon the determination of the arranging position thereof. Then, light with a specified wavelength is projected to the head 9 through the disc 1 from an interference fringe formation means (light source 11) and (microscope 12) to form an interference fringe. The light signal from the interference fringe formation means is converted into an electrical signal by a photoelectric conversion means (TV camera 16) to be shown on a display means (monitor TV17). According to the output of the photoelectric conversion means, a signal per unit scanning period is extracted by an extraction means (1H extractor 18) and data thereof are memorized into a computer 22. Based on the data, a computation is done to determine the lifting amount of the head 9.
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