Image sensor device having improved noise suppression capability and a method for supressing noise in an image sensor device

• US 7,545,418 B2
• Filed: 07/17/2006
• Issued: 06/09/2009
• Est. Priority Date: 07/17/2006
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Beck, Jeffery Steven, Lim, Yan Ping, Mentzer, Ray Alan
• Primary Examiner(s): Ye; Lin
• Assistant Examiner(s): CAMARGO, MARLY S.B.
• Application Number:
  US11/457,956
• Publication Number:
  US 20080012966A1
• Time in Patent Office: 1,058 Days
• Field of Search: 348/193, 348294-324, 348241-251
• US Class Current: 348/241
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/633 by using optical black pixels
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

An image sensor device is provided that has an uncovered imaging array of pixels and a covered global reference non-imaging array of pixels. The pixel samples of the global reference non-imaging array are used to remove noise from the pixel samples of the imaging array. The control signals and control lines that are used to sample the pixels of the imaging array are separate from and independent of the control signals and control lines that are used to sample the pixels of the global reference non-imaging array of pixels. For each row of pixels of the imaging array that is sampled, the same row of pixels of the global reference non-imaging array is sampled. The global reference row has no or very few offsets or variations to ensure that noise removal is performed effectively.

Claims

1. An image sensor device comprising:

an uncovered imaging array having M rows and N columns of pixels;

a covered global reference non-imaging array comprising at least one global reference row, as at least one dark row of non-imaging pixels;

imaging array sampling logic configured to sample each of the M rows of pixels of the uncovered imaging array to obtain M sets of image pixel sample values, each of the M sets of image pixel samples having N image pixel sample values;

global reference non-imaging array sampling logic configured to sample one dark row of said covered global reference row non-imaging array to obtain a set of reference pixel sample values, and wherein said one dark row is sampled simultaneously with the sampling of each respective row of the M rows of the uncovered imaging array such that M sets of the reference pixel sample values from the one dark row are obtained;

averaging circuitry configured to average each of the M sets of the reference pixel sample values to obtain M average values each associated with a respective set of the image pixel sample values of the M sets; and

imaging array sample selection circuitry configured to select the N image pixel sample values of a respective set of the M sets of image pixel sample values from the uncovered imaging array;

difference circuitry, for each of the M sets of image pixel sample values of the uncovered imaging array, configured to receive the selected set of image pixel sample values and the average value associated with the selected set of image pixel sample values of the uncovered imaging array from the averaging circuitry,

wherein the difference circuitry is further configured to subtract the average value associated with the selected set of image pixel sample values from each of the N image pixel sample values of the selected set to obtain M sets of N output image sample values.

2. The image sensor array of claim 1, wherein the imaging array sampling logic further comprises:

imaging array sampling circuitry configured to sample each of the M rows of the uncovered imaging array, wherein for each row of the uncovered imaging array that is sampled, a set of N image pixel sample values is obtained such that M sets of N image pixel sample values are obtained, wherein

the imaging array sample selection circuitry is configured to select for each of the N image pixel sample values obtained by the imaging array sampling circuitry, and to forward the selected N image pixel sample values to the difference circuitry.

3. The image sensor device of claim 2, wherein the global reference non-imaging array sampling logic further comprises:

global reference sampling circuitry configured to sample said one dark row concurrently with the sampling of each respective row of the M rows of the uncovered imaging array to obtain the M sets of reference pixel sample values.

4. The image sensor device of claim 1, wherein:

the imaging array sampling logic includes analog-to-digital conversion (ADC) circuitry that converts each of the M sets of N image pixel sample values into M sets of N digital image sample values; and

the global reference sampling logic includes further ADC circuitry that converts each of the M sets of reference pixel sample values into M sets of N digital reference pixel sample values, the averaging circuitry averaging the N digital reference sample values of each of the M sets of digital reference pixel sample values to obtain M digital average values, the difference circuitry subtracting digital average value associated with a respective set of image pixel sample values from the N digital image pixel sample values of the respective, associated set of image pixel sample values to obtain M sets of N digital output image sample values.

5. The image sensor device of claim 1, further comprising:

an uncovered non-imaging array, coupled to the covered global reference non-imaging array, and configured to have a parasitic capacitance that at least approximately matches a parasitic capacitance of the imaging array.

6. The image sensor device of claim 1, wherein the covered global reference non-imaging array comprises at least first and second dark rows of non-imaging pixels, and wherein the first dark row corresponds to said one dark row sampled by the global reference sampling logic to obtain said M sets of reference pixel sample values, the first and second dark rows of non-imaging pixels being adjacent to each other.

7. The image sensor device of claim 1, further comprising:

imaging array signal control lines for sampling the rows of imaging pixels of the imaging array; and

global reference signal control lines for sampling said one dark row of non-imaging pixels, and wherein the imaging array signal control lines are separate from the global reference signal control lines.

8. The image sensor device of claim 1, wherein:

the covered global reference row non-imaging array comprises at least first and second dark rows of non-imaging pixels;

the first dark row of non-imaging pixels corresponds to said one dark row;

said one dark row is located near an upper portion of the image sensor device; and

the second dark row of non-imaging pixels is located near a lower portion of the image sensor device.

9. The image sensor device of claim 1, wherein:

the covered global reference row non-imaging array comprises at least first and second dark rows of non-imaging pixels;

the second dark row corresponds to said one dark row of non-imaging pixels;

the first dark row is located near an upper portion of the image sensor device; and

said one dark row of non-imaging pixels is located near a lower portion of the image sensor device.

10. The image sensor device of claim 1, wherein:

the covered global reference row non-imaging array comprises at least first and second dark rows of non-imaging pixels;

the first dark row corresponds to said one dark row of non-imaging pixels;

the second dark row of non-imaging pixels is located near a first side portion of the image sensor device;

said same one dark row of non-imaging pixels is located near a second side portion of the image sensor device; and

the first side portion is generally opposite the second side portion.

11. An image sensor device comprising:

an uncovered imaging array having M rows and N columns of pixels, the imaging array having a parasitic capacitance;

an uncovered non-imaging array having M rows and P columns of non-imaging pixels, the uncovered non-imaging array having a second parasitic capacitance that at least approximately matches the parasitic capacitance of the imaging array; and

a covered global reference non-imaging array comprising at least one dark row of non-imaging pixels coupled to the uncovered non-imaging array such that the parasitic capacitance experienced by a imaging pixel and by a non-imaging pixel sampled simultaneously are approximately the same capacitance.

12. The image sensor device of claim 11 further comprising:

imaging array sampling logic configured to sample each of the M rows of pixels of the uncovered imaging array to obtain M sets of image pixel sample values, each of the M sets of image pixel samples having N image pixel sample values;

global reference non-imaging array sampling logic configured to sample one dark row of to obtain a set of reference pixel sample values, and wherein said one dark row is sampled simultaneously with the sampling of each respective row of the M rows of the uncovered imaging array such that M sets of reference pixel sample values from the one dark row are obtained;

averaging circuitry configured to average each of the M sets of reference pixel sample values to obtain M average values each associated with a respective one of the rows of the uncovered imaging array; and

difference circuitry, for each of the M rows of the uncovered imaging array, configured to receive the selected image pixel sample values from the imaging array sample selection circuitry and the M average values from the averaging circuitry, the difference circuitry being configured to subtract the associated average values for the respective row of the uncovered imaging array from each of the N image pixel sample values of the associated set of image pixel sample values to obtain M sets of N output image sample values.

13. The image sensor device of claim 12, wherein the imaging array sampling logic comprises:

imaging array sampling circuitry configured to sample each of the M rows of the uncovered imaging array, wherein for each row of the uncovered imaging array that is sampled, a set of N image pixel sample values is obtained such that M sets of N image pixel sample values are obtained; and

imaging array sample selection circuitry configured to select the N image pixel sample values obtained by the imaging array sampling circuitry, and to forward the selected N image pixel sample values to the difference circuitry.

14. The image sensor device of claim 13, wherein the global reference non-imaging array sampling logic further comprises:

global reference sampling circuitry configured to sample said one dark row concurrently with the sampling of each respective row of the M rows of the uncovered imaging array to obtain M sets of reference pixel sample values, each of the M sets of reference pixel sample values being associated with a respective one of the M sets of image pixel sample values.

15. The image sensor device of claim 12, wherein:

the imaging array sampling logic includes analog-to-digital conversion (ADC) circuitry that converts each of the M sets of N image pixel sample values into M sets of N digital image sample values; and

the global reference sampling logic includes further ADC circuitry that converts each of the M sets of reference pixel sample values into M sets of N digital reference pixel sample values, the averaging circuitry averaging the N digital reference sample values of each of the M sets of digital reference pixel sample values to obtain M digital average values, the difference circuitry subtracting the M digital average value associated with a respective set of image pixel sample values from the N digital image pixel sample values of the respective, associated set of image pixel sample values to obtain M sets of N digital output image sample values.

16. The image sensor device of claim 12, wherein the covered global reference row non-imaging array comprises at least first and second dark rows of non-imaging pixels, and wherein the first dark row corresponds to said one dark row, said one dark row is located near an upper portion of the image sensor device, and the second dark row of non-imaging pixels is located near a lower portion of the image sensor device.

17. The image sensor device of claim 12, wherein the global reference row non-imaging array comprises at least first and second dark rows of non-imaging pixels, and wherein the second dark row of non-imaging pixels corresponds to said one dark row, the first dark row of non-imaging pixels is located near an upper portion of the image sensor device, and said one dark row of non-imaging pixels is located near a lower portion of the image sensor device.

18. A method for suppressing noise in an image sensor device, the method comprising:

sampling rows of pixels of an imaging array of the image sensor device to obtain an image pixel sample value for each pixel of the imaging array, the image pixel sample values for each row of pixels comprising respective sets of image pixel sample values;

concurrently with the sampling of each row of pixels of the imaging array, sampling a covered global reference row of non-imaging pixels of the image sensor device to obtain a dark reference pixel sample value for each pixel of the covered global reference row, the dark reference pixel sample values obtained for each sampling of the covered global reference row comprising respective sets of dark reference pixel sample values;

averaging each set of dark reference sample values to obtain a respective average dark reference sample value for each respective set of dark reference pixel sample values; and

subtracting the respective average dark reference sample value associated with a set of image pixel sample values from a respective row of the imaging array from each image pixel sample value of the set of image pixel sample values for each row of the imaging array sampled to obtain respective sets of final image sample values.

19. The method of claim 18, further comprising:

prior to averaging each set of dark reference sample values, converting the image pixel sample values and the dark reference pixel sample values into digital image pixel sample values and digital dark pixel reference sample values, respectively.

20. The method of claim 18, wherein:

imaging array signal control lines are used for sampling the rows of imaging pixels of the imaging array;

global reference signal control lines are used for sampling the dark one dark row; and

the imaging array signal control lines are separate from and independent of the global reference signal control lines.

21. The method of claim 18, further comprising:

prior to sampling the one dark row, scanning at least two rows of the global reference non-imaging array to determine which dark row of non-imaging pixels has no faulty pixels or the least number of faulty pixels, and sampling the dark row of pixels determined as having no faulty pixels or a least number of faulty pixels.

22. The method of claim 18, further comprising:

matching a parasitic capacitance of the imaging array of the image sensor device with a second parasitic capacitance of an uncovered non-imaging array of the image sensor device.

23. An image sensor device comprising:

an imaging array having a plurality pixels in rows and columns;

a non-imaging reference array including a plurality of pixels in at least one dark row;

a first sampling logic configured to sample a set of pixel values from each respective row of the imaging array;

a second sampling logic, separate for the first sampling logic, and configured to sample pixel values of one dark row of the non-imaging array such that each row of the imaging array is sampled simultaneously with the sampling of the one dark row of the non-imaging array to generate a composite correction value for each respective row of the imaging array; and

processing circuitry configured to receive each set of pixel values from each respective row of the imaging array and to subtract the generated composite correction value associated with a respective row of the imaging array from each pixel value of a corresponding set of pixel values from the imaging array for each set of pixel values.