Precise MOS imager transfer function control for expanded dynamic range imaging
First Claim
1. An imaging system comprising:
- a MOS pixel array having a number, r, of rows of pixels, each pixel including a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element;
a charge control voltage generation circuit including a circuit topology for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function; and
a switch circuit connected to the voltage generation circuit and connected to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels, application by the switch circuit of each of the charge control voltages to a row of pixel reset nodes being characterized by a voltage application settling time, tS, that is less than about 1Nrf, where N is an integer and f is imager frame rate.
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Accused Products
Abstract
There is provided an imaging system including a MOS pixel array having a number, r, of rows of pixels. Each pixel of the array includes a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element. A charge control voltage generation circuit is provided, having a topology for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function. A switch circuit is connected to the voltage generation circuit and to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels. The application by the switch circuit of each of the charge control voltages to a row of pixel reset nodes is characterized by a voltage application settling time, tS, that is less than about 1/Nrf, where N is an integer and f is imager frame rate. This provides the ability to implement a desired transfer function, to expand imager dynamic range, in a manner that is immune to capacitances of the imager, by causing the voltage spikes, or glitches, associated with imager row capacitance, to decay substantially completely during the time over which an imager pixel row is accessed to apply a control voltage.
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Citations
56 Claims
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1. An imaging system comprising:
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a MOS pixel array having a number, r, of rows of pixels, each pixel including a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element;
a charge control voltage generation circuit including a circuit topology for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function; and
a switch circuit connected to the voltage generation circuit and connected to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels, application by the switch circuit of each of the charge control voltages to a row of pixel reset nodes being characterized by a voltage application settling time, tS, that is less than about 1Nrf, where N is an integer and f is imager frame rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. An imaging system comprising:
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a MOS pixel array including rows of pixels, each pixel including a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element;
a charge control voltage generation circuit including a circuit topology for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function; and
a switch circuit connected to the voltage generation circuit and connected to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels, application by the switch circuit of each of the charge control voltages to the reset nodes of each of the pixels in the pixel array being characterized by a voltage application settling time, tS, that is less than about a specified duration of each control voltage in the plurality of control voltages.
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30. An imaging system comprising:
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a MOS pixel array having a number, r, of rows of pixels, each pixel including a light detecting element, a reset node connected to the light detecting element for controlling dissipation of photogenerated charge produced by the light detecting element, and a sense node connected to the light detecting element for measuring photogenerated charge produced by the light detecting element;
a charge control voltage generation circuit including a circuit topology comprising a series connection of a plurality of resistors and a current source between a power supply voltage and electrical ground, for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the light detecting element, in accordance with a corresponding pixel transfer function; and
a switch circuit connected to the voltage generation circuit and connected to the pixel array to apply voltages produced by the charge control voltage generation circuit to reset nodes of pixels, application by the switch circuit of each of the charge control voltages to a row of pixel reset nodes being characterized by a voltage application settling time, tS, that is less than about 1/Nrf, where N is an integer and f is imager frame rate.
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- 31. A charge control voltage generation circuit for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge, produced by a pixel of a MOS pixel array, in accordance with a corresponding pixel transfer function, the voltage generation circuit including a circuit topology that is characterized by a Thevenin resistance, Rth, that is less than about 1/NrfC, where N is an integer, r is a number of rows of MOS pixels in the pixel array, f is pixel array frame rate, and C is an effective capacitance of the pixel array.
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48. A charge control voltage generation circuit for producing a plurality of charge control voltages selected to control dissipation of photogenerated charge, produced by a pixel of a MOS pixel array, in accordance with a corresponding pixel transfer function, the voltage generation circuit including a circuit topology that is characterized by a settling time, tS=RthC, where Rth is the Thevenin resistance of the circuit topology and C is an effective capacitance of the pixel array, the settling time being less than about a specified duration of each control voltage in the plurality of charge control voltages.
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49. A method for controlling photogenerated charge dissipation in a pixel of a MOS imager pixel array to produce a selected pixel transfer function, the pixel array having a number, r, of pixel rows and operating at a frame rate, f, the method comprising the steps of:
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generating a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the pixel in accordance with a corresponding pixel transfer function; and
applying the generated charge control voltages to a reset node of the pixel during a pixel exposure period to control dissipation of photogenerated charge produced by the pixel, application of each of the charge control voltages being characterized by a voltage application settling time, tS, that is less than about 1/Nrf, where N is an integer. - View Dependent Claims (50, 51, 52, 53, 54, 55)
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56. A method for controlling photogenerated charge dissipation in a pixel of a MOS imager pixel array to produce a selected pixel transfer function, the pixel array including rows of pixels and operating at a frame rate, f, the method comprising the steps of:
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generating a plurality of charge control voltages selected to control dissipation of photogenerated charge produced by the pixel in accordance with a corresponding pixel transfer function; and
applying the generated charge control voltages to a reset node of the pixel during a pixel exposure period to control dissipation of photogenerated charge produced by the pixel, application of each of the charge control voltages being characterized by a voltage application settling time, tS, that is less than about a specified duration of each control voltage in the plurality of control voltages.
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Specification