Active pixel sensor with mixed analog and digital signal integration

• US 7,956,912 B2
• Filed: 09/29/2006
• Issued: 06/07/2011
• Est. Priority Date: 10/29/1998
• Status: Expired due to Fees

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Berezin, Vladimir
• Primary Examiner(s): WHIPKEY, JASON T
• Application Number:
  US11/529,634
• Publication Number:
  US 20070024727A1
• Time in Patent Office: 1,712 Days
• Field of Search: 348/241, 348/308, 348/297, 348/298, 348/302, 348/316
• US Class Current: 348/297
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/587 acquired sequentially, e.g. using the combination of odd and even image fields
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

An active pixel sensor includes mixed analog and digital signal integration on the same substrate. The analog part of the array forms the active pixel sensor, and the digital part of the array does digital integration of the signal.

Claims

1. A processing system comprising:

an array of active pixels of a CMOS image sensor disposed on a substrate;

a first analog signal processor for processing analog signals received from a first plurality of pixels in the array of pixels during a period of time when the plurality of pixels are exposed to an image, wherein said first plurality of pixels generates charge during said period, the first plurality of pixels is sampled multiple times during the period, and during each of the multiple times of sampling a plurality of analog signals is produced, said first analog signal processor providing each of said plurality of analog signals as processed analog signals;

a first circuit coupled to the first analog signal processor for converting each of said processed analog signals to digital signals;

a first digital signal processor coupled to the first circuit for receiving and processing said digital signals; and

a first digital memory coupled to the first digital signal processor for storing said digital signals,

wherein said digital signals are processed by said processing system to produce a plurality of processed digital signals which represents a combination of the multiple times of sampling of the first plurality of pixels during the period of time.

2. The processing system of claim 1, wherein the first circuit for converting said processed analog signals is an oversampling converter.

3. The processing system of claim 1, wherein said analog signal processor comprises column analog double sampling circuitry, wherein said column analog double sampling circuitry samples a pixel signal and a reference signal from a pixel.

4. The processing system of claim 1, further comprising:

a second analog processor for processing analog signals generated by a second plurality of pixels in the array during the period of time; and

a second circuit for converting said processed analog signals from said second analog signal processor to digital signals.

5. The processing system of claim 4, wherein said first and second analog signal processors are respectively located on first and second sides of the array of pixels.

6. The processing system of claim 1, wherein each pixel of said first plurality of pixels is sufficiently small so that it lacks sufficient capacity to integrate incoming photons for an entirety of said period.

7. The processing system of claim 1, wherein said first analog signal processor comprises at least one preamplifier with adjustable gain.

8. The processing system of claim 1, wherein the combination is a summation of the multiple times of sampling of the plurality of pixels.

9. A method of operating an imager comprising:

capturing an image with a pixel sensor array during a period in which pixels in the array are exposed to the image and generate charge;

causing said pixels in the array to each produce electrical signals representing said image;

sampling said electrical signals for each pixel multiple times during said period;

converting, after every sampling of said electrical signals for each pixel, to digital signals; and

processing said digital signals for each pixel and storing a plurality of processed digital signals, said plurality of processed digital signals representing a digital integration of the image during said period.

10. The method of claim 9, further comprising sampling reference signals for each pixel multiple times during the period.

11. The method of claim 9, wherein the sampling of said electrical signals for each pixel multiple times provides successive, instantaneous values for each pixel.

12. The method of claim 11, wherein the converting comprises column parallel analog to digital conversion.

13. The method of claim 9, wherein the processing comprises summing the digital signals.

14. The method of claim 9, wherein each respective pixel value of the plurality of processed digital signals represents a digital integration of a respective pixel of the array during the period.

15. A system comprising:

an active pixel image sensor array;

at least one circuit coupled to the array for sampling and converting analog information from a plurality of pixels in said array to digital values;

at least one digital memory and at least one processor, coupled to the circuit, for storing and combining said digital values into a single frame, wherein said plurality of pixels in said active pixel image sensor array are sampled multiple times during a single, continuous exposure of the array to an image, and sampled values are stored and combined into a single frame in said at least one digital memory, said single frame representing an integrated signal corresponding to the image during said exposure; and

a control sub-system for controlling the sampling of analog information from said pixels and said storage of digital values in said at least one digital memory.

16. The imager circuit of claim 15, further comprising at least one analog signal processor electrically connected to receive said analog information from said image sensor array and to provide said information to a column parallel analog to digital converter.

17. The imager circuit of claim 16, wherein said at least one analog signal processor comprises column analog double sampling circuitry.

18. The imager circuit of claim 16, wherein said at least one analog signal processor comprises first and second analog signal processors.

19. The imager circuit of claim 18, wherein said first and second analog signal processors are respectively located on first and second opposite sides of said image sensor array.

20. A processing system comprising:

an array of pixels disposed on a substrate;

a first column double sampling circuitry for processing a plurality of analog signals received from a first pixel in the array of pixels during a single, continuous exposure of the array to an image, wherein the first pixel is sampled multiple times during the exposure and during each sampling one of the plurality of analog signals is produced;

a first converter for converting analog signals of said first column double sampling circuitry to digital signals;

a first digital signal processor coupled to the first converter for receiving and processing said digital signals; and

a first digital memory coupled to the first digital signal processor for storing said digital signals,

wherein said digital signals stored in said first digital memory are processed by said processing system to generate a frame corresponding to the image during the exposure, the frame representing a plurality of samples of the array of pixels during the exposure.

21. The system of claim 20, wherein two of the multiple samples of the array of pixels sample instantaneous, successive information from the pixels.