Light sensor
First Claim
Patent Images
1. A light sensor comprising:
- a light transducer exposed to light, the exposed light transducer operative to accumulate charge in proportion to light incident over a predetermined integration period; and
a sensor logic in communication with the exposed light transducer, the sensor logic operative to (a) reset the charge accumulated in the exposed light transducer at the beginning of the predetermined light integration period, (b) measure the charge accumulated by the exposed light transducer over the predetermined light integration period, and (c) determine a pulse having a width based on the measured accumulated exposed light transducer charge.
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Abstract
Light sensors having a wide dynamic range are used in a variety of applications. A wide dynamic range light sensor includes an exposed photodiode light transducer accumulating charge in proportion to light incident over an integration period. Sensor logic determines a light integration period prior to the beginning of integration and the charge is reset. Charge accumulated by the exposed light transducer over the light integration period is measured and a pulse having a width based on the accumulated charge is determined.
47 Citations
30 Claims
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1. A light sensor comprising:
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a light transducer exposed to light, the exposed light transducer operative to accumulate charge in proportion to light incident over a predetermined integration period; and
a sensor logic in communication with the exposed light transducer, the sensor logic operative to (a) reset the charge accumulated in the exposed light transducer at the beginning of the predetermined light integration period, (b) measure the charge accumulated by the exposed light transducer over the predetermined light integration period, and (c) determine a pulse having a width based on the measured accumulated exposed light transducer charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A light sensor package comprising:
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an enclosure having a window for receiving light, the enclosure admitting at least a power pin, a ground pin, and an output 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 over an integration period;
a light-to-voltage circuit in communication with the exposed light transducer, the light-to-voltage circuit operative to output a light voltage signal based on charge accumulated by the exposed light transducer; and
a voltage-to-pulse circuit in communication with the light-to-voltage circuit, the voltage-to-pulse circuit operative to output a pulse on the output pin, the pulse width based on the light voltage signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A light sensor comprising:
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a light transducer overlaying a substrate, the light transducer operative to accumulate charge generated by light incident on the light transducer in a light transducer well formed in a region of the substrate proximate the light transducer, the light transducer having an intrinsic light transducer capacitance;
a floating diffusion formed in the substrate, the floating diffusion having a diffusion well formed in a region of the substrate underlying the floating diffusion when the charge is reset, the floating diffusion operative to eliminate charge in the diffusion well when the charge is reset, the floating diffusion charge determining an output potential, the floating diffusion having an intrinsic floating diffusion capacitance; and
a transmission gate between the light transducer and the floating diffusion, a transmission well formed in a region of the substrate between the region of the substrate underlying the light transducer and the region of the substrate underlying the floating diffusion, the transmission well having a depth shallower than the light transducer well and the diffusion well, the transmission gate having an intrinsic transmission gate capacitance;
wherein, when the charge is reset, charge in the light transducer well above the depth of the transmission well flows through the transmission well, through the floating diffusion, and is eliminated; and
wherein, during a light integration period, charge produced by light incident on the light transducer flows through the transmission well and into the diffusion well, producing output voltage inversely proportional to the floating diffusion capacitance, until the diffusion well is filled to the depth of the transmission well wherein charge produced by light incident on the light transducer fills the light transducer well, the transmission well, and the diffusion well, producing output voltage inversely proportional to the sum of the floating diffusion capacitance, the light transducer capacitance, and the transmission gate capacitance;
thereby providing a first sensitivity during charge accumulation in the diffusion well only and a second sensitivity during charge accumulation in the diffusion well, the transmission well, and the light transducer well, the first sensitivity greater than the second sensitivity. - View Dependent Claims (23)
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24. A light sensor comprising:
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an exposed light transducer operative to accumulate charge in proportion to light received on the exposed light transducer over an integration period; and
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 said integration period. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification