Method and apparatus for column-wise suppression of noise in an imager
First Claim
1. A method of reducing column noise in an imager, said method comprising the steps of:
- generating an offset value for each of a plurality of pixel columns in the imager, said offset value derived from a plurality of pixel output values;
selecting a number of the plurality of pixel columns which have offsets which exceed a set criteria; and
applying a noise-reducing factor to pixels in said selected pixel columns.
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Accused Products
Abstract
A method, column circuit, imager and imaging system having noise-reducing and memory-saving capabilities. An offset value for each of a plurality of pixel columns in the imager is generated. A predetermined number of the plurality of pixel columns having corresponding offset values that are greater in value than all other generated offset values are selected. Noise is reduced in each of the selected pixel columns by applying the corresponding offset values to pixel outputs from each selected pixel column. The memory requirements of the imager are reduced by only storing offset values corresponding to the selected pixel columns. Memory is also conserved by reducing bit depth and only storing a single offset value for each of the plurality of pixel columns.
82 Citations
42 Claims
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1. A method of reducing column noise in an imager, said method comprising the steps of:
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generating an offset value for each of a plurality of pixel columns in the imager, said offset value derived from a plurality of pixel output values;
selecting a number of the plurality of pixel columns which have offsets which exceed a set criteria; and
applying a noise-reducing factor to pixels in said selected pixel columns. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of reducing column noise in an imager, said method comprising the steps of:
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generating an offset value for each of a plurality of pixel columns in the imager, said offset value derived from a plurality of pixel output values;
selecting a predetermined number of the plurality of pixel columns having corresponding offset values that are greater in value than the unselected generated offset values; and
reducing noise in each of the selected pixel columns by applying the corresponding offset values to pixel outputs from the selected pixel columns. - View Dependent Claims (16, 17, 18, 19)
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20. A method of reducing column noise in an imager, said method comprising the steps of:
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generating a column offset value for each of the plurality of pixel columns in the imager, said column offset value derived from a plurality of pixel output values; and
reducing pixel output noise by applying a channel gain factor to said column offset values to obtain a plurality of channel modified column offset values, each of the plurality of channel modified column offset values pertaining to a set of channel-specific pixels in each of the plurality of pixel columns, and summing each of the plurality of channel modified column offset values with the corresponding pixel outputs. - View Dependent Claims (21, 22, 23, 24, 25)
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26. An imager, comprising:
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a pixel array having a plurality of column lines; and
a circuit coupled to said column lines and configured to generate an offset value for each of said plurality of column lines, select a predetermined number of the plurality of said column lines having corresponding offset values that are greater in value than the unselected generated offset values, and reduce noise in each of the selected pixel columns by applying a noise reducing factor approximately equal to the corresponding offset value to pixel outputs from the selected pixel columns. - View Dependent Claims (27, 28, 29, 30)
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31. An imager, comprising:
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a pixel array having a plurality of column lines; and
a circuit coupled to said column lines and configured to generate an offset value for each of said plurality of column lines in the imager, and reduce noise in each of said plurality of column lines by applying a channel gain factor to the corresponding offset values to obtain a plurality of channel modified offset values, each of the plurality of channel modified offset values pertaining to a set of channel data in each of said plurality of column lines, and to sum each of the plurality of channel modified offset values with a noise reducing factor approximately equal to the corresponding offset value to pixel outputs from the selected column lines. - View Dependent Claims (32, 33, 34, 35, 36)
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37. An imaging system, comprising:
an imager, said imager comprising;
a pixel array having a plurality of column lines; and
a circuit coupled to said column lines and configured to generate an offset value for each of said plurality of column lines, select a predetermined number of the plurality of said column lines having corresponding offset values that are greater in value than the unselected generated offset values, and reduce noise in each of the selected pixel columns by applying a noise reducing factor approximately equal to the corresponding offset value to pixel outputs from the selected pixel columns. - View Dependent Claims (38, 39, 40, 41)
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42. A method of manufacturing an imaging device, said method comprising the acts of:
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fabricating a pixel array, said pixel array being organized into a plurality of rows and columns;
fabricating a plurality of reference pixels, each reference pixel configured to output a reference signal to a corresponding column; and
fabricating a noise reducing circuit configured to generate average column offset values for each column by using a plurality of pixel output signals generated in response to the reference signals, and to apply said average column offset values to a selected number of the corresponding columns.
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Specification