Importance

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Abstract

An optical position detector is provided with an image forming member 1, a scale plate 2, and an image pickup 3, which are disposed sequentially along an optical axis in the order mentioned, and a position computing unit 10 connected to the image pickup 3. The scale plate 2 has a plurality of pattern elements arranged periodically along a front coordinate plane perpendicularly intersecting the optical axis. The image forming member 1 condenses a light beam emitted from an object point 4 and converts the same into a reference light converging into an image forming point and, at the same time, spot-illuminates a part, of the scale plate 2 with the reference light, and projects a certain pattern element in a magnified scale. The image pickup 3 has a light receiving surface disposed along a rear coordinate plane perpendicularly intersecting the optical axis and picks up the shadow of the pattern clement projected in the magnified scale and outputs corresponding image data. The position computing unit 10 processes the image data and derives rear coordinate value of the shadow of the projected pattern element, and further determines a position of the image forming point on the basis of the rear coordinate value of the shadow and a front coordinate value of the certain pattern element, and thereby determines the position of the object point on the basis of the position of the image forming point.

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First Claim