Focus detection sensitivity amendment manner and optical pickup

摘要

PURPOSE:To reduce the fluctuation of focus sensitivity and to facilitate highly precise focusing by detecting the size of a spot on a three division light-receiving element and a division line orthogonal direction deviation amount and correcting deviation with that at the time of initialization. CONSTITUTION:A focus error signal FE1 is generated by a difference signal between the light quantity of a light-receiving surface (b) in the three division light-receiving element 7 and the light quantity of light-receiving surfaces (a) and (c) on both ends. A spot signal SP is generated by the difference signal between the light quantity of the light-receiving surfaces (a) and (c) on both end parts. The signals FE1 and Sp are inputted to a focus detection sensitivity correction circuit 11 and a focus error signal FE2 is generated based on a previously decided sensitivity correction coefficient, and a focus is controlled by the signal FE2. Thus, deviation at the time of setting detection sensitivity is corrected, and sensitivity fluctuation is reduced, whereby correspondence to an adjustment error, an environmental condition and secular change can easily be executed.