PURPOSE: To have the deleting effect and to make adjustment easy by using the optical spot in the position a little displaced on an optical from the focussing position of the diaphragm lens, an optical spot in the so-called defocussing condition and deleting the signal.
CONSTITUTION: Since the diaphragm lens is held in common the optical spot for recording and reproducing, adopts the system to irradiate simultaneously two spots, the method to drive and defocus this is not used, a collimator 35 for deletion is displaced up to ΔZ on the optical axis and fixed to a position (b). At such a time, a deleting optical system contraction lens side focus is located at the position where the focus is dislocated by ΔZ'=α.ΔZ only in the optical axis direction from a recording surface 26. Provided that here, αis a deleting optical system longitudinal scale factor. On the recording surface 26, the optical spot is defocusses, the smooth light intensity distibution has a slow cooling action and the deleting effect can be obtained. Thus, optical parts to form the optical spot for deletion are unnecessary, satisfactory deleting effects are held, and the optical information recording and reproducing device, which can be easily adjusted, can be realized.
MIZUNO SADAO
ATSUTA YASUSHI
ITO NOBORU
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