Optical proximity sensor with ambient light and temperature compensation
First Claim
1. A light-based proximity sensor, comprising:
- a light source that emits light towards an external object;
a photodetector that is configured to measure light from the light source that has reflected off of the external object;
an ambient light correction circuit that corrects signals from the photodetector for photodetector efficiency changes due to changes in how much ambient light is received by the photodetector; and
an efficiency correction factor generator interposed between the photodetector and the ambient light correction circuit, wherein the ambient light correction circuit comprises a first input that receives an efficiency correction factor signal from the efficiency correction factor generator and a second input that receives an uncorrected photodetector signal from the photodetector.
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Accused Products
Abstract
An electronic device may be provided with a proximity sensor. The proximity sensor may include a light source such as a light-emitting diode and a light detector such as a photodiode. The light-emitting diode may be driven with an alternating current drive signal so that alternating current light is produced. The alternating current light may reflect off of an external object and may be received by the photodiode. The photodiode may receive a direct current light signal associated with the presence of ambient light. The efficiency of the photodiode may be affected by the level of ambient light and the efficiency of the light-emitting diode may be affected by the temperature of the light-emitting diode. Ambient light correction circuitry and temperature correction circuitry may be used to ensure that proximity sensor readings are not adversely affected by changes in operating temperature and ambient lighting conditions.
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Citations
19 Claims
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1. A light-based proximity sensor, comprising:
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a light source that emits light towards an external object; a photodetector that is configured to measure light from the light source that has reflected off of the external object; an ambient light correction circuit that corrects signals from the photodetector for photodetector efficiency changes due to changes in how much ambient light is received by the photodetector; and an efficiency correction factor generator interposed between the photodetector and the ambient light correction circuit, wherein the ambient light correction circuit comprises a first input that receives an efficiency correction factor signal from the efficiency correction factor generator and a second input that receives an uncorrected photodetector signal from the photodetector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A light-based proximity sensor, comprising:
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a light-emitting diode that is configured to emit light towards an external object; a photodetector that is configured to measure light from the light-emitting diode that has reflected off of the external object; a low-pass filter that extracts only a direct current component from a photodetector signal from the photodetector; a high-pass filter that extracts only an alternating current component from the photodetector signal; an efficiency correction factor generator that generates an efficiency correction factor based on the direct current component; an ambient light correction circuit that receives the efficiency correction factor and the alternating current component and generates a corresponding corrected photodetector signal; and a temperature correction circuit that corrects the corrected photodetector signal from the ambient light correction circuit for light-emitting diode efficiency changes due to changes in temperature of the light-emitting diode. - View Dependent Claims (12, 13, 14)
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15. Proximity sensor circuitry, comprising:
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a photodiode that is configured to receive an alternating current light signal emitted by a light-emitting diode and reflected from an external object and that is configured to receive a direct current ambient light signal; a transimpedance amplifier that produces a photodiode signal having an alternating current component associated with the alternating current light signal and a direct current component associated with the direct current ambient light signal; a first filter that extracts the alternating current component; a second filter that extracts the direct current component; and a correction circuit with a first input that receives the alternating current component and a second input that receives the direct current component, wherein the correction circuit is configured to produce a corresponding corrected photodiode signal that is corrected for efficiency changes due to fluctuations in how much ambient light is received by the photodiode. - View Dependent Claims (16, 17, 18, 19)
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Specification