Photodetector array arrangement for optical encoders
AssigneeAvago Technologies ECBU IP (Singapore) Pte. Ltd.
InventorsChee Chong Hin, Michael A. Robinson
Life of this patent
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Abstract
An optical encoder utilizes a photodetector array having at least two photodetectors with different surface areas that generate different amounts of photocurrent when they are simultaneously lit by an LED. Because the photodetectors generate different amounts of photocurrent when simultaneously lit, the photodetectors produce unambiguous results that can be used to index a coding element such as a codewheel. Another optical encoder utilizes one index photodetector that is aligned with an index track and another index photodetector that is aligned with a position track of a coding element to index the coding element.
Claims15
An optical encoder comprising:
- a coding clement having an index track with at least one transparent section and a separate position track having multiply transparent sections;
- a light source positioned to output light to the index and position tracks;
- an index photodetector array positioned to detect light that passes through the transparent section of the index track, the index photodetector array comprising first and second photodetectors with different surface areas and a combined width dimension that allows the entire index photodetector array to be simultaneously lit by light that passes through the transparent section of the index track;
- and
- a separate position track photodetector array positioned to detect light that passes through the transparent sections of the position track.
An optical encoder for indicating the rotational movement of a shaft comprising:
- a codewheel having an index track with at least one transparent section;
- a light emitting diode (LED) positioned to output light to the index track;
- and
- an index photodetector array positioned to detect light that passes through the transparent section of the index track, the index photodetector array comprising first and second photodetectors with different surface areas and a combined width dimension that allows the entire index photodetector array to be simultaneously lit by light that passes through the transparent section of the codewheel;
- wherein the index track of the codewheel includes an opaque section with a width dimension that matches the width dimension of the first photodetector.
An optical encoder for indicating the rotational movement of a shaft comprising:
- a codewheel having an index track with at least one transparent section;
- a light emitting diode (LED) positioned to output light to the index track;
- and
- an index photodetector array positioned to detect light that passes through the transparent section of the index track, the index photodetector array comprising first and second photodetectors with different surface areas and a combined width dimension that allows the entire index photodetector array to be simultaneously lit by light that passes through the transparent section of the codewheel;
- wherein the index track comprises a primarily opaque track with the at least one transparent section comprising a transparent section with a width dimension that matches the width dimension of the first photodetector.
Dependencies are inferred from the claim text.