| 摘要 |
PURPOSE:To correct the unbalance of the quantity of light due to the influence of image height by splitting luminous flux from an optical image formation system to two areas bounding on each other about a surface containing an optical axis and guiding them to two photodetecting element groups of a photodetection sensor, and removing low frequency components of their outputs. CONSTITUTION:Luminous flux split into two through a stripe mask 2 about the surface containing the optical axis 4 of an image forming lens 1 is incident to photodetecting elements A1-An, and B1-Bn arrayed alternately on the photodetection sensor 3 made of a CCD. Their outputs are read out through a control circuit 31 and a CCD driving circuit 32 and inputted to S/H (sample and hold) circuits 33 and 34 through buffer amplifiers 3d and 3e; and the outputs of the circuits 33 and 34 are sent to a signal processing circuit 37 after low frequency components are removed through low-cutting filters 35 and 36. The circuit 37 processes the input to generate a focus information signal. Then, the unbalance of the quantity of light due to the influence of image height is removed by the filters 35 and 36. |
