Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-11-28
2003-02-25
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C348S308000
Reexamination Certificate
active
06525304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to solid-state image sensors. More particularly, the present invention relates to a frame store imager that converts and stores the image information digitally in each pixel.
2. The Prior Art
Frame store imagers are known in the prior art. Thus far, frame store imaging schemes have usually been based on storage of the image signal level on an intra-pixel capacitor as an analog voltage.
While analog pixel sensors have been used successfully, they have several problems. First, leakage during readout limits the signal-to-noise ratio and also the maximum array size. Transistor scaling will decrease the size of transistor devices but at the expense of increased noise of numerous kinds. It is presently believed that pixel size will be limited to about 3 um by optical properties such as diffraction and that Moore's law will continue to apply, thus making inevitable the use of more transistors per pixel.
There have been several frame store imaging schemes that convert the analog image signal to a digital signal within the pixel. U.S. Pat. No. 5,461,425 to Fowler et al. and U.S. Pat. No. 5,801,657 to Fowler et al. are examples of such schemes.
BRIEF DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, a digital storage pixel sensor according to the present invention includes a photodiode coupled to a reset potential through a reset transistor that reverse biases the photodiode. The photodiode is coupled to a storage capacitance through a transfer transistor. The storage capacitor is coupled to a first input of a voltage comparator. A second input of the voltage comparator is coupled to the analog ramp voltage output of a ramp generator. The ramp generator starts an n-bit counter at the beginning of each voltage ramp. As presently preferred, the n-bit counter is configured as a Gray code counter.
After an exposure interval, the transfer switch turns off to temporarily store the analog signal at the first input to the comparator. When the ramp voltage passes the voltage established by charge accumulation in the pixel sensor, the comparator changes state. The comparator output writes the present count of the counter into an n-bit dynamic random access memory (DRAM) word disposed in the imager. To read the memory contents, the counter outputs are disabled and a read signal is supplied to the n-bit DRAM word. The counter lines then serve as output column lines for the imager's DRAM.
According to a second aspect of the present invention, an array of digital storage pixel sensors is provided. According to a presently preferred embodiment, each imager in the array is served by the same n-bit counter and analog ramp voltage and the n-bit column line outputs are common to all digital storage pixel sensors in individual columns of the array and also serve as column output lines for all of the DRAM words in individual columns of the array. DRAM words in individual rows of the array are selected for output by row-enable signals provided to the digital storage pixel sensors in individual rows of the array.
REFERENCES:
patent: 5227887 (1993-07-01), Dohi et al.
patent: 5276521 (1994-01-01), Mori
patent: 5461425 (1995-10-01), Fowler et al.
patent: 5742047 (1998-04-01), Buhler et al.
patent: 5801657 (1998-09-01), Fowler et al.
patent: 6330030 (2001-12-01), O'Connor
patent: 6377303 (2002-04-01), O'Connor
patent: 0 605 898 (1994-07-01), None
patent: 0 707 416 (1996-04-01), None
patent: 0 954 167 (1999-03-01), None
patent: WO 99/27708 (1999-06-01), None
Fowler et al., Techniques for Pixel Level Analog to Digital Conversion.
Yang et al., A 128×128 Pixel CMOS Area Image Sensor with Multiplexed Pixel Level A/D Conversion.
Fowler et al., A CMOS Area Image Sensor with Pixel Level A/D Conversion.
Yang et al., A Nyquist-Rate Pixel-Level ADC for CMOS Image Senors.
Yang et al., A 640×512 CMOS Image Sensor with Ultrawide Dynamic Range Floating-Point Pixel-Level ADC.
Nitayama et al., Future Directions for DRAM Memory Cell Technology.
Chye Huat Aw, et al. “A 128×128-Pixel Standard-CMOS Image Sensor With Electronic Shutter”, IEEE International Solid-State Circuits Conference, 1996, pp. 4-39 to 4-40.
Guang Yang, et al. “A Snap-Shot CMOS Active Pixel Imager For Low-Noise, High-Speed Imaging”, IEEE, 1998, pp. 45-48.
Hon-Sum Philip Wong, “CMOS Image Sensors-Recent Advances and Device Scaling Considerations”, IEDM, 1997 IEEE, pp. 201-204.
Hon-Sum Philip Wong, et al. “CMOS Active Pixel Image Sensors Fabricated Using a 1.8-V, 025-&mgr;m CMOS Technology”, IEEE, Apr., 1998, pp. 889-894.
Orly Yadid-Pecht, et al. “A Random Access Photodiode Array for Intelligent Image Capture”, IEEE Transactions on Electron Devices, vol. 38, No. 8, Aug. 1991, pp. 1772-1780.
Hiroki Miura, et al., “A 100 Frame/s CMOS Active Pixel Sensor For 3D-Gesture Recognition System”, IEEE International Solid-State Circuits Conference, Jun. 1999, pp. 142-143.
Yoshiaki Hagiwara, “High-Density and High-Quality Frame Transfer CCD Imager With Very Low Smear, Low Dark Current, and Very High Blue Sensitivity”, IEEE Transactions on Electron Devices, vol. 43, No. 12, Dec. 1996, pp. 2122-2130.
Peter B. Denyer, et al., “On-Chip CMOS Sensors For VLSI Imaging Systems”, VLSI 91, Proceedings of the IFIP TC 10/WG 10.5 International Conference on Very Large Scale Integration, Aug. 1991, pp. 4b.1.1 to 4b.2.1.
Fowler, et al., “Techniques for Pixel Level Analog to Digital Conversion”; Information Systems Laboratory, Sanford University, Abstract and Introduction, 11 pages.
Yang, et al., “A 128×128 pixel CMOS Area Image Sensor with Multiplexed Pixel Level A/D Conversion”; Information Systems Laboratory; Stanford University; Sanford, CA 94305; pp. 1-4.
Yang, et al., “Anyquist Rate Pixel Level ADC for CMOS Image Sensors”, Information Systems Laboratory; Sanford University, Sanford, CA 94305; pp. 1-4.
Fowler, et al., a CMOS Area Image Sensor with Pixel Level A/D Conversion, Information Systems Laboratory; Sanford University, Sanford, CA 94305 Nov. 20, 1995; pp. 111.
Yang, et al., “A 640×512 CMOS Image Sensor with Ultra Wide Dynamic Range Floating-Point Pixel-Level ADC”; Information System Laboratory, Electrical Engineering Dept.; Stanford University, Sep. 8, 1998; coversheet, pp. 1-10.
Yang, et al., “A 640×512 CMOS Image Sensor with Ultrawide Dynamic Range Floating-Point Pixel-Level ADC”; IEEE Journal of Solid-State Circuits, vol. 34; No. 12, Dec. 1999; pp. 1821-1834.
Yang, et al., “A Nyquist-Rate Pixel-Level ADC for CMOS Image Sensors”, IEEE Journal of Solid-State Circuits, vol. 34, No. 3, Mar. 1999; pp. 348-356.
Dong Milton B.
Lyon Richard F.
Merrill Richard B.
Turner Richard M.
Allen Stephone B.
Foveon, Inc.
Hill Bradford
Sierra Patent Group Ltd.
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