Patent US6525769B1 successfully refreshed from Google Patents.
US6525769B1
Expired / Lapsed
US
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Method and apparatus to compensate for dark current in an imaging device
Assignee: Intel Corp
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Filing: 1998-12-30
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Granted: 2003-02-25
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Expires: 2018-12-30
Abstract
Abstract An imaging device includes a compensation circuit for reducing an effect of dark current generated during operation. The compensation circuit calculates an initial dark current offset value using optically dark regions of a photo sensitive array. The compensation circuit also automatically adjusts the initial dark current offset value as output signals from successive rows of the photo sensitive array are transferred. The compensation circuit can calculate the initial dark current offset value each time an image is captured, thereby compensating for variables such as temperature.
Inventors
- 👤 Brent D. Thomas
- 👤 Morteza Afghahi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:42
CPC Classifications
H; H04; H04N; H04N25/00; H04N25/60; H04N25/63; H04N25/633; H04N25/70; H04N25/76; H04N25/77
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
195 words
An imaging device comprising: an imaging array comprising a plurality of photo sensitive pixels arranged in a plurality of rows and columns, the imaging array further comprising an active area which can be selectively exposed to incident light to capture an image, a first optically dark area located adjacent to the active area and comprising at least one row of photo sensitive pixels, and a second optically dark area located adjacent to the active area and comprising at least one column of photo sensitive pixels, the photo sensitive pixels of the first and second optically dark areas are shielded from incident light; and a compensation circuit coupled to the imaging array, the compensation circuit generates an initial dark current offset value from the first optically dark area, and adjusts the initial dark current offset value using the second optically dark area, the compensation circuit comprises: a buffer circuit coupled to receive an output signal from the imaging array, a reference circuit to selectively couple a reference voltage to an input node of the buffer circuit, and an integration circuit to generate the initial dark current offset value, and adjust the initial dark current offset value.
Claim 2
Dependent Claim
195 words
An imaging device comprising: an imaging array comprising a plurality of photo sensitive pixels arranged in a plurality of rows and columns, the imaging array further comprising an active area which can be selectively exposed to incident light to capture an image, a first optically dark area located adjacent to the active area and comprising at least one row of photo sensitive pixels, and a second optically dark area located adjacent to the active area and comprising at least one column of photo sensitive pixels, the photo sensitive pixels of the first and second optically dark areas are shielded from incident light; and a compensation circuit coupled to the imaging array, the compensation circuit generates an initial dark current offset value from the first optically dark area, and adjusts the initial dark current offset value using the second optically dark area, the compensation circuit comprises: a buffer circuit coupled to receive an output signal from the imaging array, a reference circuit to selectively couple a reference voltage to an input node of the buffer circuit, and an integration circuit to generate the initial dark current offset value, and adjust the initial dark current offset value.
Claim 3
Dependent Claim
13 words
The imaging device of claim 1 wherein the imaging device is a camera.
Claim 4
Dependent Claim
38 words
The imaging device of claim 1 wherein the reference circuit is-coupled to the buffer circuit through a switch circuit which is selectively activated when either the first or second optically dark areas are coupled to the compensation circuit.
Claim 5
Dependent Claim
38 words
The imaging device of claim 1 wherein the integration circuit is coupled to an input node of the buffer circuit through a switch circuit which is selectively activated when the active area is coupled to the compensation circuit.
Claim 6
Dependent Claim
79 words
An imaging device compensation circuit comprising: an input node for receiving an output signal from an optically sensitive device; a buffer circuit coupled to the input node; a reference voltage circuit coupled to an input node of the buffer circuit via a first switch circuit; and an integrator circuit coupled to an output signal of the buffer circuit, the integrator circuit having an output signal coupled to an input node of the buffer circuit via a second switch circuit.
Claim 7
Dependent Claim
79 words
An imaging device compensation circuit comprising: an input node for receiving an output signal from an optically sensitive device; a buffer circuit coupled to the input node; a reference voltage circuit coupled to an input node of the buffer circuit via a first switch circuit; and an integrator circuit coupled to an output signal of the buffer circuit, the integrator circuit having an output signal coupled to an input node of the buffer circuit via a second switch circuit.
Claim 8
Dependent Claim
38 words
The imaging device of claim 1 wherein said buffer circuit includes a sample and hold unit to perform a sample and hold operation on an analog output signal from the imaging array to generate an analog output signal.
Claim 9
Dependent Claim
195 words
An imaging device comprising: an imaging array comprising a plurality of photo sensitive pixels arranged in a plurality of rows and columns, the imaging array further comprising an active area, a first optically dark area comprising at least one row of pixels, and a second optically dark area located adjacent to the active area and comprising at least one column of pixels; and a compensation circuit coupled to the imaging array, the compensation circuit generates an initial dark current offset value from an output signal of the first optically dark area, and adjusts the initial dark current offset value using an output signal of the second optically dark area, said compensation circuit including: a sample and hold circuit to perform a sample and hold operation on an analog charge signal from the imaging array to generate an analog output signal; an integration circuit to maintain a dark current offset value at an output thereof, said dark current offset value being derived from said analog output signal of said sample and hold circuit; and a first switch circuit to controllably couple said output of said integration circuit to an input of said sample and hold circuit.
Claim 10
Dependent Claim
195 words
An imaging device comprising: an imaging array comprising a plurality of photo sensitive pixels arranged in a plurality of rows and columns, the imaging array further comprising an active area, a first optically dark area comprising at least one row of pixels, and a second optically dark area located adjacent to the active area and comprising at least one column of pixels; and a compensation circuit coupled to the imaging array, the compensation circuit generates an initial dark current offset value from an output signal of the first optically dark area, and adjusts the initial dark current offset value using an output signal of the second optically dark area, said compensation circuit including: a sample and hold circuit to perform a sample and hold operation on an analog charge signal from the imaging array to generate an analog output signal; an integration circuit to maintain a dark current offset value at an output thereof, said dark current offset value being derived from said analog output signal of said sample and hold circuit; and a first switch circuit to controllably couple said output of said integration circuit to an input of said sample and hold circuit.
Claim 11
Dependent Claim
24 words
The imaging device of claim 1 wherein: said integration circuit is coupled to an input node of the buffer circuit through a switch circuit.
Claim 12
Dependent Claim
23 words
The imaging device of claim 1 wherein: said switch circuit is selectively activated when the active area is coupled to the compensation circuit.
Claim 13
Dependent Claim
27 words
The imaging device of claim 1 wherein: said compensation circuit determines the initial dark current offset value each time the active area is exposed to incident light.
Claim 14
Dependent Claim
18 words
The imaging device compensation circuit of claim 5 wherein: said buffer circuit includes a sample and hold unit.
Claim 15
Dependent Claim
30 words
The imaging device compensation circuit of claim 1 wherein: said reference voltage circuit generates a reference voltage that is related to an approximated initial dark current of said imaging array.
Claim 16
Dependent Claim
38 words
The imaging device comoensation circuit of claim 5 wherein: said optically sensitive device includes an imaging array having a plurality of active photo elements and a plurality of optically dark photo elements that are shielded from incident light.
Claim 17
Dependent Claim
33 words
The imaging device compensation circuit of claim 13 further comprising: a controller to activate said first switch circuit when said input node is receiving information from said plurality of optically dark photo elements.
Claim 18
Dependent Claim
32 words
The imaging device compensation circuit of claim 13 further comprising: a controller to activate said second switch circuit when said input node is receiving information from said plurality of active photo elements.
Claim 19
Dependent Claim
25 words
The imaging device of claim 7 comprising: a controller to activate said first switch circuit when the active area is coupled to the compensation circuit.
Claim 20
Dependent Claim
26 words
The imaging device of claim 7 comprising: a controller to deactivate said first switch circuit when an optically dark area is coupled to the compensation circuit.
Claim 21
Dependent Claim
30 words
The imaging device of claim 7 comprising: a reference circuit to selectively couple a reference voltage to the input of the sample and hold circuit via a second switch circuit.
Claim 22
Dependent Claim
26 words
The imaging device of claim 18 comprising: a controller to activate said second switch circuit when an optically dark area is coupled to the compensation circuit.
Claim 23
Dependent Claim
25 words
The imaging device of claim 18 comprising: a controller to deactivate said second switch circuit when the active area is coupled to the compensation circuit.
Claim 24
Dependent Claim
22 words
The imaging device of claim 18 wherein: said reference voltage is related to an approximate initial dark current of said imaging array.
Claim 25
Dependent Claim
44 words
The imaging device of claim 18 further comprising: an analog to digital converter to convert said analog output signal of said sample and hold circuit to a digital signal, when said integration circuit uses said digital signal to maintain said dark current offset value.
Claim 26
Dependent Claim
88 words
An imaging device compensation circuit comprising: an input node to receive an output signal from an optically sensitive device, said optically sensitive device including an imaging array having a plurality of active photo elements and a plurality of optically dark photo elements that are shielded from incidents light; a buffer circuit coupled to input node; and an integrator circuit coupled to output signal of the buffer circuit, the integrator circuit having an output signal coupled to an input node of the buffer circuit via a first switch circuit.
Claim 27
Dependent Claim
88 words
An imaging device compensation circuit comprising: an input node to receive an output signal from an optically sensitive device, said optically sensitive device including an imaging array having a plurality of active photo elements and a plurality of optically dark photo elements that are shielded from incidents light; a buffer circuit coupled to input node; and an integrator circuit coupled to output signal of the buffer circuit, the integrator circuit having an output signal coupled to an input node of the buffer circuit via a first switch circuit.
Claim 28
Dependent Claim
31 words
The imaging device compensation circuit of claim 23 comprising: a controller to close said first switch circuit when said input node is receiving information from said plurality of active photo elements.
Claim 29
Dependent Claim
32 words
The imaging device compensation circuit of claim 23 comprising: a controller to open said first switch cirucit when said input node is receiving information from said plurality of optically dark photo elements.
Claim 30
Dependent Claim
51 words
The imaging device compensation circuit of claim 23 comprising: a reference voltage circuit coupled to an input node of the buffer circuit via a second switch circuit, and a controller to close said second switch circuit when said input node is receiving information from said plurality of optically dark photo elements.
Claim 31
Independent Claim
128 words
A method for compensating for dark current in an imaging device comprising: receiving an output signal of an imaging array at a circuit node, said imaging array having a plurality of active photo elements and a plurality of optically dark photo elements that are shielded from incident light; coupling a reference voltage to said circuit node when signal components are being received at said circuit node from said plurality of optically dark photo sensitive elements; and coupling a dark current offset value to said circuit node when signal components are being received at said circuit node from said plurality of active photo sensitive elements, wherein coupling a dark current offset value to said circuit node includes activating a switch located between an integrator unit and said circuit node.
Claim 32
Independent Claim
128 words
A method for compensating for dark current in an imaging device comprising: receiving an output signal of an imaging array at a circuit node, said imaging array having a plurality of active photo elements and a plurality of optically dark photo elements that are shielded from incident light; coupling a reference voltage to said circuit node when signal components are being received at said circuit node from said plurality of optically dark photo sensitive elements; and coupling a dark current offset value to said circuit node when signal components are being received at said circuit node from said plurality of active photo sensitive elements, wherein coupling a dark current offset value to said circuit node includes activating a switch located between an integrator unit and said circuit node.
Claim 33
Dependent Claim
34 words
The method of claim 27 , further comprising: removing said reference voltage from said circuit node when signal components are being received at said circuit node from said plurality of active photo sensitive elements.
Claim 34
Dependent Claim
29 words
The method of claim 27 , wherein: coupling a reference voltage to said circuit node includes activating a switch located between a reference voltage circuit and said circuit node.
Claim 35
Dependent Claim
22 words
The method of claim 27 , wherein: said reference voltage is related to an approximated initial dark current of said imaging array.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2006-02-24 | 2006-08-26 | 2007-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2010-02-24 | 2010-08-26 | 2011-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2014-02-24 | 2014-08-26 | 2015-02-25 | $7700.00 | Window Closed / Lapsed |