Moisture detecting system using semiconductor light sensor with integral charge collection
First Claim
Patent Images
1. A system for detecting moisture on a surface comprising:
- a light emitter for directing light at the surface;
a light sensor for receiving light that is emitted from the light emitter and strikes the surface, wherein the light sensor accumulates charge in response to incident light over a variable integration period; and
a control circuit coupled to the light sensor for detecting moisture on the surface based on the intensity of light received by the light sensor.
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Accused Products
Abstract
Moisture detection permits moisture removal equipment, such as automotive windshield wipers and defogger systems, to be operated automatically. A system for detecting moisture on a surface includes a light emitter directed at the surface. The presence of moisture is based on the intensity of light from the emitter reflected by the surface and received by a light sensor. The light sensor accumulates charge in response to incident light over a variable integration period.
143 Citations
28 Claims
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1. A system for detecting moisture on a surface comprising:
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a light emitter for directing light at the surface;
a light sensor for receiving light that is emitted from the light emitter and strikes the surface, wherein the light sensor accumulates charge in response to incident light over a variable integration period; and
a control circuit coupled to the light sensor for detecting moisture on the surface based on the intensity of light received by the light sensor. - View Dependent Claims (2)
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3. A system for detecting moisture on a surface on a surface based on the intensity of light received by a light sensor from a light emitter directed at the surface wherein the light sensor accumulates charge in response to incident light over a variable integration period, and wherein the light sensor comprises:
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a light transducer exposed to light operative to accumulate charge in proportion to light incident over the integration period; and
a sensor logic in communication with the exposed light transducer, the sensor logic operative to (a) determine the light integration period prior to beginning integration, (b) reset the charge accumulated in the exposed light transducer at the beginning of the determined light integration period, (c) measure the charge accumulated by the exposed light transducer over the determined light integration period, and (d) output a pulse having a width based on the measured accumulated exposed light transducer charge. - View Dependent Claims (4, 5, 6, 7)
reset the charge accumulated in the shielded light transducer at the beginning of the determined light integration period;
measure the charge accumulated by the shielded light transducer over the determined light integration period; and
output a pulse having a width based on the difference between the measured accumulated exposed light transducer charge and the measured accumulated shielded light transducer charge.
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7. A system for detecting moisture as in claim 6 wherein the light sensor is further operative to:
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receive an integration pulse, the width of the integration pulse determining the integration period; and
generate the output pulse after the integration pulse, the difference in time between the end of the integration pulse and the start of the output pulse indicative of the amount of thermal noise in the light sensor.
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8. A system for detecting moisture on a surface on a surface based on the intensity of light received by a light sensor from a light emitter directed at the surface wherein the light sensor accumulates charge in response to incident light over a variable integration period, and wherein the light sensor comprises:
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an enclosure having a window for receiving light, the enclosure admitting a power pin, a ground pin, and a signal pin;
an exposed light transducer disposed within the enclosure, the exposed light transducer operative to accumulate charge in proportion to light received through the window incident on the exposed light transducer;
a light-to-pulse circuit disposed within the enclosure and in communication with the exposed light transducer, the power pin, and the ground pin, the light-to-voltage circuit operative to output an output pulse, the output pulse width based on charge accumulated by the exposed light transducer over an integration period; and
a sensor logic disposed within the enclosure, the sensor logic in communication with the light-to-pulse circuit, the power pin, the ground pin, and the signal pin, the sensor logic operative to (a) receive an integration pulse on the signal pin, (b) determine the integration period based on the width of the integration pulse, and (c) output the output pulse on the signal pin.
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9. A system for detecting moisture on a window having an inner surface and an outer surface comprising:
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an emitter operative to emit light at the window;
a light sensor operative to receive light reflected from the outer surface, a level of reflected light indicative of moisture on the outer surface, the light sensor further operative to output a discrete light signal based on the level of light incident on the light sensor over a light integration period; and
a control logic in communication with the emitter and the light sensor, the control logic operative to (a) receive a first light signal from the light sensor with the emitter turned off, (b) turn on the emitter, (c) receive a second light signal from the light sensor, and (d) determine the presence of moisture based on the first light signal and the second light signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
generate a sequence of integration period signals, each integration period signal in the sequence specifying a different light integration period; and
determine the light level based on a resulting light signal having a pulse width within at least one preset width threshold.
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12. A system for detecting moisture as in claim 9 wherein the light sensor comprises:
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a light transducer exposed to light operative to accumulate charge in proportion to light incident over the light integration period; and
a sensor logic in communication with the exposed light transducer, the sensor logic operative to (a) determine the light integration period prior to beginning integration, (b) reset the charge accumulated in the exposed light transducer at the beginning of the determined light integration period, (c) measure the charge accumulated by the exposed light transducer over the determined light integration period, and (d) output a pulse having a width based on the measured accumulated exposed light transducer charge.
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13. A system for detecting moisture as in claim 12 wherein the light sensor further comprises a light transducer shielded from light, the shielded light transducer having the same construction as the exposed light transducer, the shielded light transducer operative to accumulate charge in proportion to noise over the integration period, wherein the sensor logic is further operative to:
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reset the charge accumulated in the shielded light transducer at the beginning of the determined light integration period;
measure the charge accumulated by the shielded light transducer over the determined light integration period; and
output a pulse having a width based on the difference between the measured accumulated exposed light transducer charge and the measured accumulated shielded light transducer charge.
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14. A system for detecting moisture as in claim 13 wherein the light sensor is further operative to:
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receive an integration pulse, the width of the integration pulse determining the integration period; and
generate the output pulse after the integration pulse, the difference in time between the end of the integration pulse and the start of the output pulse indicative of the amount of thermal noise in the light sensor.
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15. A system for detecting moisture as in claim 14 wherein the control logic is further operative to:
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determine the amount of time between the end of the integration pulse and the start of the output pulse; and
determine the light sensor temperature based on the determined amount of time.
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16. A system for detecting moisture as in claim 15 wherein the control logic is further operative to disable moisture detection if the light sensor temperature exceeds a preset limit.
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17. A system for detecting moisture as in claim 9 wherein the light sensor comprises:
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an enclosure having a window for receiving light, the enclosure admitting a power pin, a ground pin, and a signal pin;
an exposed light transducer disposed within the enclosure, the exposed light transducer operative to accumulate charge in proportion to light received through the window incident on the exposed light transducer;
a light-to-pulse circuit disposed within the enclosure and in communication with the exposed light transducer, the power pin, and the ground pin, the light-to-pulse circuit operative to output an output pulse, the output pulse width based on charge accumulated by the exposed light transducer over an integration period; and
a sensor logic disposed within the enclosure, the sensor logic in communication with the light-to-pulse circuit, the power pin, the ground pin, and the signal pin, the sensor logic operative to (a) receive an integration pulse on the signal pin, (b) determine the integration period based on the width of the integration pulse, and (c) output the output pulse on the signal pin.
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18. A system for detecting moisture as in claim 17 wherein the control logic comprises at least one signal pin connected to the signal pin of the light sensor, the control logic further operative to:
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set the control logic signal pin to output mode;
determine an integration period;
generate an integration pulse on the control logic signal pin, the width of the integration pulse based on the determined integration period;
set the control logic signal pin to input mode;
receive the light sensor output pulse; and
determine a light level received by the light sensor based on the light sensor output pulse.
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19. A system for detecting moisture as in claim 18 wherein the control logic determines an integration period by cycling through a sequence of predetermined integration periods.
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20. A system for detecting moisture as in claim 9 further comprising a second light sensor operative to receive light reflected from the inner surface, a level of the reflected light indicative of moisture on the inner surface, the second light sensor further operative to output a discrete light signal based on the amount of light incident on the second light sensor over a light integration period, the control logic further operative to
(a) receive a third light signal from the second light sensor with the emitter turned off, (b) turn on the emitter, (c) receive a fourth light signal from the second light sensor, and (d) determine the presence of moisture on the inner surface based on the third light signal and the fourth light signal. -
21. A system for detecting moisture as in claim 9 wherein the presence of moisture causes an increase in the level of reflected light.
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22. A system for detecting moisture as in claim 9 wherein the presence of moisture causes a decrease in the level of reflected light.
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23. A method for determining the presence of moisture on a window comprising:
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activating a light emitter directed at the window;
determining an integration period for a light sensor positioned to receive light from the emitter reflected off the window;
determining the intensity of light incident on the light sensor over the integration period; and
determining the presence of moisture based on the intensity of the incident light. - View Dependent Claims (24, 25, 26, 27)
generating a sequence of integration period signals, each integration period signal in the sequence specifying a different light integration period;
determining if the pulse width for each resulting light signal is within at least one preset width threshold; and
determining the incident light level based on a light signal having a pulse width within the at least one preset width threshold.
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27. A method as in claim 23 further comprising:
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deactivating the light emitter;
determining an ambient light integration period for the light sensor;
determining the intensity of light incident on the light sensor over the ambient light integration period; and
determining an ambient light level based on the intensity of light incident on the light sensor over the ambient light integration period with the light emitter deactivated.
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28. A method for detecting moisture on a surface based on the intensity of light received by a light sensor from a light emitter directed at the surface, the method comprising the step of configuring the light sensor to accumulate charge in response to incident light over a variable integration period.
Specification