Method and apparatus for ambient light detection
First Claim
Patent Images
1. An imaging device, comprising:
- a pixel array comprising a plurality of pixels, wherein the plurality of pixels each comprise a photosensor, a floating diffusion node, a transfer transistor for transferring charge from the photosensor to the floating diffusion node, and a reset transistor for resetting the floating diffusion node;
an ambient light detection circuit connected to the array and comprising;
a capacitor for storing charge generated by at least some pixels of the pixel array, anda voltage control circuit for providing a first voltage on said capacitor prior to said charge storage, and for measuring the time for said voltage on said capacitor to rise from said first voltage to a second voltage in response to said stored charge generated by said at least some pixels; and
a timing and control circuit for turning on the reset transistor of at least some of the pixels to transfer charge from the floating diffusion nodes to the capacitor.
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Abstract
An imaging method and apparatus which use a pixel array for capturing images and for measuring ambient light conditions.
40 Citations
25 Claims
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1. An imaging device, comprising:
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a pixel array comprising a plurality of pixels, wherein the plurality of pixels each comprise a photosensor, a floating diffusion node, a transfer transistor for transferring charge from the photosensor to the floating diffusion node, and a reset transistor for resetting the floating diffusion node; an ambient light detection circuit connected to the array and comprising; a capacitor for storing charge generated by at least some pixels of the pixel array, and a voltage control circuit for providing a first voltage on said capacitor prior to said charge storage, and for measuring the time for said voltage on said capacitor to rise from said first voltage to a second voltage in response to said stored charge generated by said at least some pixels; and a timing and control circuit for turning on the reset transistor of at least some of the pixels to transfer charge from the floating diffusion nodes to the capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 9, 10, 11)
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7. (canceled)
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8. (canceled)
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12. An imaging device comprising:
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a pixel array comprising a plurality of pixels; and an ambient light detection circuit connected to the array and, comprising; an integration circuit for integrating charge produced by at least some pixels of the pixel array, the integration circuit comprising; a capacitor for storing the charge produced by said at least some pixels, and a switch connected in series with the capacitor for resetting the charge on the capacitor to a first voltage when the switch is closed; and a detection circuit for determining an ambient light level based on charge integrated by said integration circuit. - View Dependent Claims (13, 15)
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14. (canceled)
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16. A method of measuring an amount of ambient light impinging on a pixel array, comprising:
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integrating voltage on a capacitor representing a collective current generated by at least some pixels of the pixel array; measuring the time it takes the voltage on the capacitor to increase from a first voltage to a second voltage; and using said measurement to determine an amount of ambient light impinging on said at least some pixels. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. An imaging system comprising:
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a lighted display unit for displaying information; a control circuit for controlling the brightness of said lighted display unit using a signal representing the ambient light the imaging system is exposed to; and an imaging device, comprising; a pixel array containing a plurality of pixels, and an ambient light detection circuit connected to the array for outputting the signal representing the ambient light, the ambient light detection circuit comprising; a capacitor for storing charge commonly generated by at least some pixels of the pixel array, and a voltage control circuit comprising, a multiplexer for supplying an operating voltage to the pixel array during an image capture mode and for supplying the first voltage to the pixel array to detect an amount of ambient light during a light detection mode; a differential amplifier for outputting the difference between the first voltage and the voltage on the capacitor; a comparator for determining when the output of the differential amplifier is equal to a second voltage; a switch connected in parallel with the capacitor for resetting the charge on the capacitor to the first voltage when the switch is closed; and a control logic unit for closing the switch when the output of the differential amplifier is equal to the second voltage, for measuring an average amount of time it takes for the output of the differential amplifier to equal the second voltage, and for outputting the signal representing an amount of detected ambient light.
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25. An imaging system comprising:
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a lighted display unit for displaying information; a control circuit for controlling the brightness of said lighted display unit using a signal representing the ambient light the imaging system is exposed to; and an imaging device, comprising a pixel array containing a plurality of pixels and an ambient light detection circuit connected to the array for outputting the signal representing the ambient light, the ambient light detection circuit comprising; a capacitor for storing charge commonly generated by at least some pixels of the pixel array, and a voltage control circuit comprising, a multiplexer for supplying an operating voltage to the pixel array during an image capture mode and for supplying the first voltage to the pixel array to detect an amount of ambient light during a light detection mode; a comparator for determining when the voltage on the capacitor is equal to a second voltage; a switch connected in series with the capacitor for resetting the charge on the capacitor to the first voltage when the switch is closed; and a control logic unit for closing the switch when the voltage on the capacitor is equal to the second voltage, for measuring an average amount of time it takes for the voltage on the capacitor to equal the second voltage, and for outputting the signal representing the ambient light.
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Specification