US 5,548,392 A · Optical position detector having scale pattern spot-illuminated to increase resolution

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.

Claims17

Dependent claims

An optical position detector for detecting the position of at least one object point, comprising receiving means for receiving a light emitted from at least one object point, comprising image forming means, a scale plate, and image pickup means, each being disposed along the same optical axis;

and arithmetic operation means connected to the image pickup mean;
wherein the scale plate has a plurality of pattern elements arranged periodically along a front coordinate plane perpendicularly intersecting the optical axis, the image forming means includes means for condensing a light beam emitted from an object point, converting the beam into a corresponding reference light converging into a corresponding image forming point which is displaced from the front coordinate plane of the scale plate, spot-illuminating a part of the scale plate with the and projecting at least one illuminated pattern element in a magnified scale, the image pickup means has a light receiving surface which is disposed along a rear coordinate plane perpendicularly intersecting the optical axis and which picks up a shadow of the at least one illuminated pattern element projected in the magnified scale and includes means for outputting corresponding image data, and the arithmetic operation means includes means for processing the image data, deriving a rear coordinate plane value of the shadow of the at least one illuminated pattern element, determining a position of the image forming point for the reference light on the basis of the respective rear coordinate plane value and a front coordinate plane value of the at least one illuminated pattern element, and determining a position of the object point on the basis of the position of the image forming point.

An optical position detector for detecting the position of at least one object point, comprising:

receiving means for receiving a light beam which is emitted from at least one object point and converges at a particular focal point;
and arithmetic processing means connected to the receiving means;
wherein the receiving means comprises a scale plate for receiving a light beam emitted from at least one object point and having a plurality of pattern elements arranged along a first coordinate plane which is displaced from the focal point such that a light beam incident on the scale plate causes a shadow image of at least one pattern element to be projected in a magnified scale, and image pickup means including a light receiving surface disposed in a second coordinate plane for receiving a shadow image of the at least one illuminated pattern element and means for outputting corresponding image data;
and wherein the arithmetic processing means comprises means for determining a position of a respective shadow image in the second coordinate plane and for determining the position of the at least one object point in accordance therewith.

1 more element

Dependencies are inferred from the claim text.

Optical position detector having scale pattern spot-illuminated to increase resolution

Life of this patent

Optical position detector having scale pattern spot-illuminated to increase resolution

Life of this patent

Abstract

Claims17