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Abstract

A light spot position measuring method uses an optical converter such as a cylindrical lens, a two-dimensional image pickup device such as a CCD image sensor and an image processing or computing unit. The cylindrical lens converts a light spot to a linear image intersecting a reference axis direction. The image sensor captures the linear image and produces corresponding pixel data. The computing unit processes the pixel data and derives a position of the light spot along the reference axis direction. In the light spot position measuring method, an orthogonal coordinate system is first set relative to a pixel array of the image sensor. The coordinate system has main and auxiliary axes orthogonal to each other. Subsequently, the linear image is projected to be inclined relative to the coordinate system with an angle of the linear image relative to the auxiliary axis smaller than that relative to the main axis. Subsequently, the pixel data is processed to effect linear-approximation of the linear image to derive a corresponding straight line. Further, another one-dimensional position of the straight line in a direction of the main axis is detected in terms of a one-dimensional position in a direction of the auxiliary axis by a magnified scale. Finally, the position of the light spot is derived based on a result of the detection of the one-dimensional position of the straight line. This measuring method may also be applied to derivation of a two-dimensional position of the light spot.

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