| 摘要 |
PURPOSE:To attain a high response speed and a high resolution, by a method wherein an optical filter whose transmittivity for incident light increases monotonously in a prescribed direction is disposed on the path of the light. CONSTITUTION:When a light beam L is applied at a prescribed angle to a substance 7 to be inspected, the direction of a reflected light R thereof is varied in accordance with the unevenness of the substance 7 to be inspected, and it is found by detecting the position of incidence in an optical fiber 5. The reflected light R is divided in two by a beam splitter 8, and a split reflected beam R1 enters a photosensitive element 9 through the filter 5, while a divided reflected light R2 enters a photosensitive element 10. Detected light intensity values S1 and S2 detected thereby are sent to an arithmetic circuit 11. The filter 5 adopted herein has a characteristic of transmittivity T (X) expressed by the formula I. When the light intensity of the light R is denoted by Ii, the light intensities of the beams R1 and R2 are Ii/2 respectively. Since the ranges of the two lights are identical, the ratio between the detected values S1 and S2 becomes equal to the ratio between light beam intensities I and I0 after and before the light passes through the filter 5. Accordingly, an incidence position X1 can be determined by an operation in the circuit 11 on the basis of the formula II.
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