| 摘要 |
PURPOSE: To prevent change of intensity distribution from being generated in detectors even through center of intensity distribution are displaced by positioning separated narrow columns having respective pairs of detectors properly and performing a setting so that center of the intensity distribution of radiant light spots are displaced along one separated narrow columns. CONSTITUTION: Centers of intensity distributions of radiant spot V1 , V2 are respectively displaced in directions crossing separated narrow columns 22, 23 by the change of the wavelength of a scanning beam and detectors 18, 19, 20, 21 respectively receive respectively different radiant light intensities. Consequently, even when the scanning beam is clearly focused on an information surface, output signals of detectors 18, 19, 20, 21 do not become equal now. Thus, new separated narrow columns of diode pairs deformed in order to eliminate the influence of the change of the wavelength with respect to a focusing error signal untill a substatial range are shown by solid lines 22', 23'. The separated narrow column 22', 23' are respective rotated by minute anglesα1 ,α2 around points M1.0 , M2.0 as compared with original narrow columns 22, 23 shown by dotted lines.
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