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Non-Contact Sensor for Two-Dimensional Translation and Rotation

IP.com Disclosure Number: IPCOM000040574D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Hollis, RL: AUTHOR [+2]

Abstract

Relative planar displacement and orientation of a moving part equipped with fixed light sources is measured with high resolution over a limited range by non-contact optical sensors. Two-dimensional optical position sensors, called lateral effect photodiodes, are well known and are commercially available. The position of the centroid of a spot of light is inferred from measured photocurrents (see the figure): x a (x1 - x2)/(x1 + x2), y a (y1 - y2)/(y1 + y2), Here, x1, x2, y1, y2 refer to the lateral cell currents. If the lateral cell 1 is attached to the fixed part, for example, and a light- emitting diode (LED) light source is attached to the moving part located above the cell surface, then x and y is the relative displacement of the two parts.

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Non-Contact Sensor for Two-Dimensional Translation and Rotation

Relative planar displacement and orientation of a moving part equipped with fixed light sources is measured with high resolution over a limited range by non-contact optical sensors. Two-dimensional optical position sensors, called lateral effect photodiodes, are well known and are commercially available. The position of the centroid of a spot of light is inferred from measured photocurrents (see the figure): x a (x1 - x2)/(x1 + x2),

y a (y1 - y2)/(y1 + y2), Here, x1, x2, y1, y2 refer to the lateral cell currents. If the lateral cell 1 is attached to the fixed part, for example, and a light- emitting diode (LED) light source is attached to the moving part located above the cell surface, then x and y is the relative displacement of the two parts. Submicron resolution is extended to include the measurement of angular orientation: to provide planar angular information in addition to displacement information, a pair of light spots a and b, located along the diagonal axis of the lateral effect cell are arranged to blink on and off alternately to provide two sets of position coordinates: xa a (x1a - x2a)/(x1a + x2a),

ya a (y1a - y2a)/(y1a + y2a),

xb a (x1b - x2b)/(x1b + x2b),

yb a (y1b - y2b)/(y1b + y2b). This information is combined to provide both relative displacement and angle: x a (xa + xb)/2,

y a (ya + yb)/2,

r = arctan (ya - yb).

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(xa - xb) For small angles, the arctangent function can be v...