High sensitivity active pixel with electronic shutter
First Claim
1. A circuit, comprising:
- photodetecting circuitry providing an original signal;
a first FET having a gate, a drain, and a source, the first FET to provide an output current in response to receiving the original signal at the gate and a first control signal at the drain; and
storage circuitry coupled to the source for receiving the output current.
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Accused Products
Abstract
A high sensitivity active pixel for use in MOS image sensor circuits. The pixel circuit design allows the use of digital MOS fabrication processes to be used in implementing a pixel circuit having greater sensitivity (allowing increased frame rate) and greater noise immunity than certain prior art pixels. The novel pixel features a source follower configured amplifier, such as a single MOS FET, coupled between a photodetector and a storage capacitor. A light-generated signal from the photodetector is used to control the charge placed in the storage capacitor in order to develop a capture voltage. In a particular embodiment, an n-channel source follower and a p-channel output stage are combined in the pixel to make the overall transfer function of the pixel more linear and distortion-free. In particular, the pixel transfer function becomes more linear for weak light-generated signals, whereas with conventional pixels, the pixel output signals are often distorted and even suppressed when the light-generated signal is weak. The novel pixel circuit may find particular use in a portable digital image capture system such as a digital camera.
73 Citations
22 Claims
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1. A circuit, comprising:
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photodetecting circuitry providing an original signal; a first FET having a gate, a drain, and a source, the first FET to provide an output current in response to receiving the original signal at the gate and a first control signal at the drain; and storage circuitry coupled to the source for receiving the output current. - View Dependent Claims (2, 3, 4, 5)
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6. A circuit as in 5 wherein said second FET is n-channel, the circuit further comprising
a compensation circuit coupled between the gate of the second FET and a select input of the switch to raise the voltage at the gate of the second FET in response to a select signal being asserted at the select input.
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8. An imaging system, comprising:
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an optical system for being exposed to incident light; an image sensor coupled to the optical system to receive the incident light, the sensor having a plurality of pixels, each pixel having photodetecting circuitry providing an original signal representative of the incident light, an FET having a gate, a drain, and a source, the FET to provide an output current in response to receiving the original signal at the gate and a first control signal at the drain, storage circuitry coupled to the source for receiving the output current and in response providing an exposed voltage representative of the incident light, and analog-to-digital conversion circuitry coupled to the sensor for converting analog signals related to the exposed voltage in each pixel into digital signals representing raw image data. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. An image sensor comprising:
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a plurality of bitlines; and a plurality of pixels arranged as rows and columns to form an array, each pixel in one of the columns having photodetecting circuitry to provide an original signal representative of incident light detected in an integration interval, a first FET having a signal input, a control input, and signal output to provide an output current in response to receiving the original signal at the signal input and a first control signal being asserted at the control input upon completion of the integration interval, first capacitor coupled to the signal output for receiving the output current, and output stage coupled between the capacitor and a respective one of the plurality of bitlines to selectively buffer a voltage of the capacitor onto said respective one of the bitlines. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification