Optical element displacement detection circuit
AssigneeSTMicroelectronics (Research & Development) Limited
InventorsSteven Collins, Graeme Storm, Supriya Raveendra Hegde
Life of this patent
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Abstract
An optical element is positioned in a holder over a laser light source. The optical element includes an electrical trace that is coupled between first and second pads. A sensing circuit that is also coupled to the first and second pads performs a voltage/current sensing operation to detect displacement of the optical element and control enablement of the laser light source.
Claims26
An optical device, comprising:
- an optical element positioned over a laser light source;
- a driver circuit configured to drive said laser light source in response to an enable signal;
- a conductive trace provided at said optical element, where the conductive trace is coupled between a first pad and a second pad;
- and
- a sensing circuit comprising:
- a first current source configured to source a first current to a first resistive divider circuit which includes said conductive trace;
- a second current source configured to source a second current to a second resistive divider circuit configured to output a high reference voltage and a low reference voltage;
- a first comparator circuit having a first input coupled to receive a voltage at the first pad and a second input coupled to receive the high reference voltage;
- a second comparator circuit having a first input coupled to receive a voltage at the second pad and a second input coupled to receive the low reference voltage;
- and
- a combinational logic circuit configured to logically combine digital signals output from the first and second comparator circuits to generate said enable signal.
A sensing circuit for an optical device which includes an optical element with a conductive trace and a light source that outputs a light beam passing through said optical element, comprising:
- a first current source configured to source a first current to a first resistive divider circuit which includes a first pad and a second pad configured for connection to the conductive trace;
- a second current source configured to source a second current to a second resistive divider circuit configured to output a high reference voltage and a low reference voltage;
- a first comparator circuit having a first input coupled to receive a voltage at the first pad and a second input coupled to receive the high reference voltage;
- a second comparator circuit having a first input coupled to receive a voltage at the second pad and a second input coupled to receive the low reference voltage;
- and
- a combinational logic circuit configured to logically combine digital signals output from the first and second comparator circuits to generate an enable signal for controlling actuation of the light source.
Dependencies are inferred from the claim text.