Patent ID: 7495760

Claim:
An estimating apparatus of the amount of optical distortion of light transmitted through a transparent plate member with unevenness of refractive power of the transparent plate member, comprising: means for irradiating a grid pattern having an array of a bright portion and a dark portion with a constant pitch and a constant width; means for picking-up said grid pattern by using an image pickup device including a CCD pixel array; means for inputting a signal from said image pickup device, as gray image data; means for supporting and conveying said transparent plate member in an optical line ranging from said grid pattern to said image pickup device; and image processing means for processing the gray image data inputted from said image pickup device, wherein, upon picking-up the image of the grid pattern on said image pickup device, 4n±α CCD pixels of the CCD pixel array correspond to n grids, where n and α are integers greater than zero and α is less than or equal to n/10, thereby generating a moiré fringes, and said image processing means comprises: means for calculating a plurality of types of sine waves that are deviated in phase at 90° from image data of said moiré fringes; means for obtaining a phase angle at each pixel based on said plurality of types of sine waves; and means for calculating refractive power of the optical distortion based on a difference in phase angles between the pixels.