| 摘要 |
PURPOSE:To obtain a correct focus error signal by correcting the increase/ decrease in an output of each photoelectric conversion element due to the position deviation of a spot formed by a reflected light with a difference signal. CONSTITUTION:A focus error signal FE=A+D-(B+C) including an error is obtained at an output terminal of a subtraction circuit 4 by using photoelectric conversion outputs A,B,C,D obtained from a reflected light spot 23 which irradiates a 4-split detector 1. On the other hand, a difference between sums (A+C) and (B+D) of outputs of photoelectric conversion elements on the 4-split detectors 1 respectively adjacent in the vertical direction is obtained at the output terminal of the subtraction circuit 7. Moreover, a difference between sums (A+B) and (C+D) of outputs of photoelectric conversion elements on the 4-split detectors 1 respectively adjacent in the horizontal direction is obtained at the output terminal of the subtraction circuit 10. The differences are attenuated by an attenuation coefficient depending on variable resistors 17,18 and fed to the focus error signal FE and a corrected focus error output FEO is obtained at an output terminal 19. Thus, an error component invaded in the focus error signal is reduced by a simple adjustment. |
