Patent ID: 8238641

Claim:
A method of measuring mirror index for evaluating image clarity of a surface of work by image analyzing a reflect image of determined pattern being projected onto the surface of work which comprises: providing a space in front of the surface of work to be measured in order to project the determined pattern thereto and taking a picture of a reflecting image of the determined pattern therefrom by positioning a cylinder-shaped hollow probe having an opened front edge so as to face the front edge of the probe in a position of contacted or close to the surface of work to be measured, projecting the determined pattern which comprises a ring pattern image of one or more parallel circle lines to a surface of work in the space for taking picture, taking a picture of the ring pattern image reflected from the surface of work by means of a taking picture device provided at a rear center of the hollow probe, calculating an amplitude or a standard deviation of a brightness distribution of resulted image data at some points positioned on radius lines extending in all directions at intervals to outside from a center of the ring pattern image, comparing the amplitude or the standard deviation with a corresponding criterion data previously measured on a criterion mirror surface to determine a relative value as the mirror index.