| 摘要 |
PURPOSE:To improve accuracy, by providing a photoelectric detector, wherein a light shielding film is formed at a part of a light receiving surface, providing a driving means, which displaces the detector so that the light shielding film crosses a point image, and providing a signal processing means, which detects the converged state of the point image from the change in output of the detector. CONSTITUTION:The output of a function generator 14 is applied to a first actuator 12. A photoelectric detector 10 is driven in correspondence with the function. The output of the detector is changed in correspondence with the displacement of the detector 10 by the light shielding film 11. A low pass filter 13 feeds back the lower-region component of the output of the detector 10. The central position of the displacement is controlled so that the edge part of the film 11 is moved back and forth, crossing the point image 5, with the point image 5 as the center. A signal processing means 15 performs the operation required to detect the distribution of the amount of the light of the point image. A second actuator 16 drives the detector 10 along the light axis of luminous flux 1 in correspondence with the output of the means 15 so that the quality of the image becomes the best. Thus the quality of the image is evaluated. |
