| 摘要 |
PURPOSE:To determine a null point correctly even when the curve showing the reflected light amount becomes wide, by integrating the data of the reflected light amount within a given integration range. CONSTITUTION:Both a lens 12 and a probe 14 are set in advance a predetermined distance away from an object 10 to be measured. Then, while light is irradiating the object 10, the lens 12 and the probe 14 are gradually moved towards the object 10. In accordance with the gradual movement of the lens 12 and the probe 14 by a step motor by a slight distance, the light is reflected by the object 10 to be received by a light receiving optical fiber 18, the amount of which is accordingly varied. The light passing through the lens 12 and the probe 14 and received by the optical fiber 18 is converted into analog voltage by a converter 20 which is in turn converted into digital signals at an analog- digital converter 22. Further, the data of the reflected light amount is integrated within a fixed integration range by an operation circuit 24. The integration range is equally divided into two. By obtaining a point where the difference between the integrated values within the respective integration ranges is rendered 0, the point is decided to be a minimum displacement point (null point).
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