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; and
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.
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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.
22 Citations
20 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; and 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. 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; and a temperature correction circuit that corrects a photodetector signal from the photodetector for light-emitting diode efficiency changes due to changes in temperature of the light-emitting diode. - View Dependent Claims (13, 14, 15, 16)
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17. 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 that receives the alternating current component and that uses the direct current component in producing a corresponding corrected photodiode signal that is corrected for photodetector efficiency changes due to fluctuations in how much ambient light is received by the photodetector. - View Dependent Claims (18, 19, 20)
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Specification