EP0458030A1
Expired / Lapsed
EP
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Defect correction for CCD and CID imagers
Assignee: Polaroid Corp
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Filing: 1991-03-20
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Granted: —
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Expires: 2011-03-20
Abstract
Abstract A defect correction apparatus for a solid state imaging device employs a frame buffer responsively coupled to the imaging device for storing digital values of shuttered dark pixel data from image locations of the imaging device. A register responsively coupled to the imaging device and having an output coupled to the frame buffer sequentially clocks digital values of image pixel data of the imaging device into the frame buffer. A comparator having an output operatively coupled to the register and being responsively coupled to the dark pixel data of the frame buffer produces enable and inhibit outputs. When any selected element of dark pixel data is less than a threshold, indicative of an operative pixel element in the imaging device, data stored in the register corresponding to the pixel is stored in the frame buffer in response to the enable signal. When the value of the dark pixel data in the frame buffer is greater than the threshold the comparator produces an inhibit signal. The value of image data of a previous operative pixel element is thereby entered into the register and frame buffer.
Inventors
- 👤 David D. Pape
- 👤 Wanda T. Reiss
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 11:47
CPC Classifications
H; H04; H04N; H04N25/00; H04N25/60; H04N25/68; H04N25/683
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
248 words
A defect correction apparatus for a solid state imaging device having an array of pixels for producing image scene pixel data when exposed to scene light comprising: a frame buffer having memory locations corresponding to the pixels of the imaging device and being responsive to storing values of shuttered dark pixel data for each pixel in the corresponding memory locations prior to exposure of the image device to scene light; register means responsively coupled to the imaging device and having an output coupled to the frame buffer for sequentially clocking dark pixel data into the frame buffer for storage and for subsequently clocking selected image pixel data into the corresponding frame buffer locations for replacing the dark pixel data with image pixel data of the scene; and a comparator having an output operatively coupled to the register means and being responsively coupled to the frame buffer for producing enable and inhibit outputs for respectively enabling and inhibiting the register means when the dark pixel data is less than a selected threshold indicative of an operative pixel and when the dark pixel data is greater than the threshold indicative of an inoperative pixel, such that, the dark pixel data for a particular location is replaced in the buffer by image pixel data for a corresponding pixel when the pixel is operative and dark pixel data for such location is replaced by image pixel data from an operative pixel immediately prior to the defective pixel when the pixel is inoperative.
Claim 2
Dependent Claim
37 words
The defect correction apparatus of claim 1 wherein the register means includes: an analog-to-digital (A/D) converter response for producing digital outputs in response to analog inputs representative of pixel data from corresponding elements of the imaging device.
Claim 3
Dependent Claim
39 words
The defect correction apparatus of claim 2 wherein the register means includes an output storage register element responsive to the A/D converter for storing the data representative of the value of a pixel element when converted to digital data.
Claim 4
Dependent Claim
57 words
The defect correction apparatus of claim 3 wherein the register element is responsively coupled to the comparator for retaining the digital data representative of the value of a prior operative pixel element when the value of the dark pixel data is greater than the threshold whereby the image pixel data is not entered in the register element.
Claim 5
Dependent Claim
34 words
The defect correction of claim 4 wherein the A/D convertor is responsively coupled to the comparator and is respectively enabled and disabled thereby when the dark pixel data is below and above the threshold.
Claim 6
Dependent Claim
35 words
The defect correction apparatus of claim 2 further includes: means for adjusting the analog input to the A/D converter in accordance with the value of dark pixel data in the buffer for the corresponding element.
Claim 7
Dependent Claim
45 words
The defect correction apparatus of claim 6 wherein the means for adjusting the analog input comprises an automatic gain control amplifier having one input responsively coupled to the imager and an input inverted with respect to the first mentioned input responsively coupled to the buffer.
Claim 8
Dependent Claim
33 words
The defect correction apparatus of claim 6 wherein the means for adjusting the analog input comprises a digital-to-analog (D/A) converter coupled to the buffer output for covering digital pixel data to analog values.
Claim 9
Dependent Claim
14 words
The defect correction apparatus of claim 1 wherein the imaging device is a CID.
Claim 10
Dependent Claim
14 words
The defect correction apparatus of claim 1 wherein the imaging device is a CCD.
Claim 11
Independent Claim
128 words
A method for correcting defects in a multi-element imaging device having an array of pixels comprising the steps of: shuttering the array and storing dark pixel data in a frame buffer in locations corresponding to each pixel; exposing the array to image scene light and transferring image pixel data from the array; sequentially comparing the dark pixel data for each buffer location with a threshold; and storing in each dark pixel data location in the frame buffer image pixel data from either the corresponding pixel when the dark pixel data for such corresponding pixel is less than the threshold indicative of an operative pixel element; or from the prior operative pixel element when the dark pixel data is greater than the threshold indicative of an inoperative pixel element.
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