Efficient charge transferring in CMOS imagers
First Claim
Patent Images
1. A method of operating a pixel cell comprising:
- initiating an integration period for the pixel cell during which a photosensor collects photo-charges;
applying a first signal level to a transfer gate of the pixel cell during the integration period such that a first amount of photo-charges are transferred from the photosensor to a storage region; and
applying a second signal level to the transfer gate during the integration period such that a second amount of photo-charges are transferred from the photosensor to the storage region, said second signal level being a pulsed signal.
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Abstract
Methods for operating a pixel cell include efficient transferring of photo-charges using multiple pulses to a transistor transfer gate during a charge integration period for an associated photosensor. The pixel cell can be operated with efficient transfer characteristics in either normal or high dynamic range (HDR) mode. The high dynamic range can be realized by either operating an optional HDR transistor or by fluctuating the voltage applied to a reset gate.
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Citations
30 Claims
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1. A method of operating a pixel cell comprising:
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initiating an integration period for the pixel cell during which a photosensor collects photo-charges;
applying a first signal level to a transfer gate of the pixel cell during the integration period such that a first amount of photo-charges are transferred from the photosensor to a storage region; and
applying a second signal level to the transfer gate during the integration period such that a second amount of photo-charges are transferred from the photosensor to the storage region, said second signal level being a pulsed signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A high dynamic range method of operation for a pixel cell comprising the acts of
transferring charges located at a photosensor to an anti-blooming storage region; -
applying a first reset voltage to a reset gate;
decreasing the voltage applied to the reset gate at pre-determined intervals during an integration period for the pixel to increase a potential barrier between a charge storage region and a drain region; and
pulsing a voltage applied to a transfer gate of a transfer transistor during the integration period to decrease the potential barrier between said photosensor and said charge storage region. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. An imager device comprising:
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a pixel array comprising a plurality of pixel cells each comprising;
a photosensor for generating photo-charges during an integration period;
a storage region for storing the generated photo-charges; and
a transfer gate for transferring charges from the photosensor to the storage region, wherein the transfer gate is adapted to receive a first signal and at least one pulsed second signal during the integration period; and
a control circuit for controlling the signals applied to the transfer gates. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A method of operating a pixel cell, said method comprising:
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lowering a potential barrier between a photosensor and a storage region by applying a first voltage level to a transfer transistor gate during an integration period so as to allow photo-charges at the photosensor to flow to the storage region; and
lowering the potential barrier between the photosensor and the storage region further by applying a second voltage level to the transfer transistor gate during the integration period, wherein the second voltage level is higher than the first voltage level. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification