US5233428A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic exposure control system for a solid state imager
Assignee: BAE Systems Information and Electronic Systems Integration Inc
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Filing: 1991-11-05
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Granted: 1993-08-03
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Expires: 2011-11-05
Abstract
Abstract A system and method for electronically controlling charge coupled device (CCD) light sensitivity. The present invention controls CCD light sensitivity by electrically controlling a CCD such that the CCD discharges charge for a percentage of a field integration period. In other words, the present invention electronically varies the CCD's exposure time. The present invention operates as follows. First, the present invention calculates a new exposure time for a field integration period. Second, the present invention electrically causes the CCD to discard charge accumulated by the CCD during the field integration period except during a portion of the field integration period defined by the new exposure time.
Inventors
- 👤 Steven M. Alford
- 👤 Ralph A. Layer
- 👤 Thomas H. Traynor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 05:08
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/70; H04N23/71; H04N23/73
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
107 words
A method for controlling the amount of time a charge coupled device having a charge storage area integrates an incident light-induced charge during a field integration period, the method comprising the steps of: generating a measured video level; calculating a correction factor based on the difference between said measured video level and a desired video level; calculating a new optimum exposure time for a next field integration period based on said correction factor; and electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period, said portion defined by said new optimum exposure time.
Claim 2
Independent Claim
107 words
A method for controlling the amount of time a charge coupled device having a charge storage area integrates an incident light-induced charge during a field integration period, the method comprising the steps of: generating a measured video level; calculating a correction factor based on the difference between said measured video level and a desired video level; calculating a new optimum exposure time for a next field integration period based on said correction factor; and electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period, said portion defined by said new optimum exposure time.
Claim 3
Dependent Claim
42 words
The method of claim 1, wherein said step for generating a measured video level comprises the steps of: receiving a video signal representing charge accumulated in said charge storage area: clamping said video signal to ground; and measuring said clamped video signal.
Claim 4
Dependent Claim
99 words
The method of claim 2, wherein said step for calculating a correction factor based on the difference between said measured video level and a desired video level comprises the steps of: digitizing said measured video signal; if said digitized video signal is greater than or equal to a desired value X, then calculating said correction factor according to an equation: correction factor=1-K*((N/X)-1); and if said digitized video signal is less than said desired value X, then calculating said correction factor according to an equation: correction factor=1+K*(1-(N/X)); wherein N represents said digitized video signal and K represents a damping factor.
Claim 5
Dependent Claim
37 words
The method of claim 3, wherein said step for digitizing said measured video level comprises the step of digitizing said measured video level in a range from 0 to 31, wherein said desired value X is 16.
Claim 6
Dependent Claim
28 words
The method of claim 1, wherein said step for calculating said new optimum exposure time comprises the step of multiplying said correction factor and said old exposure time.
Claim 7
Dependent Claim
66 words
The method of claim 1, wherein said step for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises the steps of: determining dump pulses needed during a discrete mode to attain said new exposure time; and generating a waveform having said dump pulses.
Claim 8
Dependent Claim
83 words
The method of claim 1, wherein said step for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises the steps of: determining dump pulses needed during a discrete mode to attain said new exposure time; determining dump intervals needed during a continuous mode to attain said new exposure time; and generating a waveform having said dump pulses and dump intervals.
Claim 9
Dependent Claim
80 words
The method of claim 1, wherein said step for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises the steps of: converting said new exposure time to a control code; using said control code to determine dump pulses needed during a discrete mode to attain said new exposure time; and generating a waveform having said dump pulses.
Claim 10
Dependent Claim
102 words
The method of claim 1, wherein said step for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises the steps of: converting said new exposure time to a control code; using said control code to determine dump pulses needed during a discrete mode to attain said new exposure time; using said control code to determine dump intervals needed during a continuous mode to attain said new exposure time; and generating a waveform having said dump pulses and dump intervals.
Claim 11
Dependent Claim
65 words
The method of claim 1, wherein said step for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of said next field integration period defined by said new optimum exposure time further comprises the step of allowing said new exposure time to change only when said new exposure time significantly differs from an old exposure time.
Claim 12
Dependent Claim
80 words
The method of claim 10, wherein said step for allowing said new optimum exposure time to change only when said new optimum exposure time significantly differs from an old exposure time comprises the steps of: if said control code equals an old exposure number minus 1, then setting said control code to said old exposure number; and if said control code equals said old exposure number minus 2, then setting said control code to said old exposure number minus 1.
Claim 13
Independent Claim
134 words
A system for controlling exposure sensitivity for a charge coupled device having a charge storage area by controlling the amount of time the charge coupled device integrates an incident light-induced charge during a field integration period, the system comprising: means for generating an analog measure of a video signal level; means for digitizing said analog measured video signal level; means for generating a correction factor based on the difference between said digitized measured video signal level and a desired video signal level; means for generating a new optimum exposure time by modifying an old exposure time with said correction factor; and means for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of a next field integration period defined by said new optimum exposure time.
Claim 14
Independent Claim
134 words
A system for controlling exposure sensitivity for a charge coupled device having a charge storage area by controlling the amount of time the charge coupled device integrates an incident light-induced charge during a field integration period, the system comprising: means for generating an analog measure of a video signal level; means for digitizing said analog measured video signal level; means for generating a correction factor based on the difference between said digitized measured video signal level and a desired video signal level; means for generating a new optimum exposure time by modifying an old exposure time with said correction factor; and means for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of a next field integration period defined by said new optimum exposure time.
Claim 15
Dependent Claim
52 words
The system of claim 12, wherein said means for generating an analog measure of a video signal level comprises: a clamp for clamping a video signal to ground, wherein said video signal represents charge accumulated in the charge storage area; and means, coupled to said clamp, for measuring said clamped video signal.
Claim 16
Dependent Claim
34 words
The system of claim 12, wherein said means for digitizing said analog measured video signal level comprises means for digitizing said analog measured video signal level in a range having a desired value X.
Claim 17
Dependent Claim
19 words
The system of claim 14, wherein said range is 0 to 31 and said desired value X is 16.
Claim 18
Dependent Claim
100 words
The system of claim 14, wherein said means for generating a correction factor by comparing said digitized measured video signal level with a desired video signal level comprises: means for calculating said correction factor according to an equation: correction factor=1-K * ((N/X)-1) when said digitized video signal level is greater than or equal to said desired value X; and means for calculating said correction factor according to an equation: correction factor=1+K * (1-(N/X)) when said digitized video signal level is less than said desired value X; wherein N represents said digitized video signal level and K represents a damping factor.
Claim 19
Dependent Claim
36 words
The system of claim 12, wherein said means for generating a new exposure time by modifying an old exposure time with said correction factor comprises means for multiplying said old exposure time and said correction factor.
Claim 20
Dependent Claim
85 words
The system of claim 12, wherein said means for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of a next field integration period defined by said new optimum exposure time comprises: means for converting said new optimum exposure time to a control code; means for using said control code to determine dump pulses needed during a discrete mode to attain said new optimum exposure time; and means for generating a waveform having said dump pulses.
Claim 21
Dependent Claim
110 words
The system of claim 12, wherein said means for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of a next field integration period defined by said new optimum exposure time comprises: means for converting said new optimum exposure time to a control code; means for using said control code to determine dump pulses needed during a discrete mode to attain said new optimum exposure time; means for using said control code to determine dump intervals needed during a continuous mode to attain said new optimum exposure time; and means for generating a waveform having said dump pulses and dump intervals.
Claim 22
Dependent Claim
65 words
The system of claim 19, wherein said means for electrically causing the charge coupled device to discard charge accumulated in the charge storage area during a portion of a next field integration period defined by said new optimum exposure time further comprises means for allowing said new exposure time to change only when said new optimum exposure time significantly differs from an old exposure time.
Claim 23
Dependent Claim
79 words
The system of claim 20, wherein said means for allowing said new optimum exposure time to change only when said new optimum exposure time significantly differs from an old exposure time comprises: means for setting said control code to an old exposure number when said control code equals said old exposure number minus 1; and means for setting said control code to said old exposure number minus 1 when said control code equals said old exposure number minus 2.
Claim 24
Dependent Claim
135 words
A camera imager, comprising: a charge coupled device, having a charge storage area and a drain off region, exposed to incident light during a field integration period, said charge coupled device configured to generate a video signal representing the charge accumulated in said charge storage area during the field integration period; an exposure control system, coupled to said charge coupled device, comprising: means for calculating a correction factor based on the difference between a measured video level and a desired video level; means for calculating a new optimum exposure time for a next field integration period based on said correction factor; and means for electrically causing said charge coupled device to discard charge accumulated in said charge storage area during a portion of said next field integration period defined by said new optimum exposure time.
Claim 25
Dependent Claim
135 words
A camera imager, comprising: a charge coupled device, having a charge storage area and a drain off region, exposed to incident light during a field integration period, said charge coupled device configured to generate a video signal representing the charge accumulated in said charge storage area during the field integration period; an exposure control system, coupled to said charge coupled device, comprising: means for calculating a correction factor based on the difference between a measured video level and a desired video level; means for calculating a new optimum exposure time for a next field integration period based on said correction factor; and means for electrically causing said charge coupled device to discard charge accumulated in said charge storage area during a portion of said next field integration period defined by said new optimum exposure time.
Claim 26
Dependent Claim
135 words
The camera imager of claim 22, wherein said means for calculating a new optimum exposure time for a next field integration period comprises: means for generating an analog average video signal level; means for digitizing said analog average video signal level in a range having a desired value X; means for calculating a correction factor according to an equation: correction factor=1-K*((N/X)-1) when said digitized light level signal is greater than or equal to said desired value X; means for calculating said correction factor according to an equation: correction factor=1+K*(1-(N/X)) when said digitized light level signal is less than said desired value X; and means for calculating said new optimum exposure time by multiplying said correction factor and an old exposure time; wherein N represents said digitized video signal level and K represents a damping factor.
Claim 27
Dependent Claim
19 words
The system of claim 23, wherein said range is 0 to 31 and said desired value X is 16.
Claim 28
Dependent Claim
68 words
The camera imager of claim 22, wherein said means for electrically causing said charge coupled device to discard charge accumulated in said charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises: means for determining dump pulses needed during a discrete mode to attain said new exposure time; and means for generating a waveform having said dump pulses.
Claim 29
Dependent Claim
88 words
The camera imager of claim 22, wherein said means for electrically causing said charge coupled device to discard charge accumulated in said charge storage area during a portion of said next field integration period defined by said new optimum exposure time comprises: means for determining dump pulses needed during a discrete mode to attain said new exposure time; means for determining dump intervals needed during a continuous mode to attain said new optimum exposure time; and means for generating a waveform having said dump pulses and dump intervals.
References Cited (Backward Citations)
US4800435A
Cited
JPS6468076A
Cited
US5003398A
Cited
US4984002A
Cited
US5057926A
Cited
US5040070A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-08-02 | 1997-02-01 | 1997-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-08-02 | 2001-02-01 | 2001-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-08-02 | 2005-02-01 | 2005-08-03 | $7700.00 | Window Closed / Lapsed |