EP0991128A2
Expired / Lapsed
EP
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Dynamic range extension of CCD imagers
Assignee: BAE Systems Information and Electronic Systems Integration Inc
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Filing: 1999-09-09
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Granted: —
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Expires: 2019-09-09
Abstract
Abstract Dynamic range extension (DRE) is achieved in CCD imagers with charge overflow structures by varying the potential V G on the gate electrodes (18) of the pixel signal charge wells during charge integration. The wells are formed to function with the charge overflow structures, e.g., vertical overflow drains, VODs, a) to control the signal charge spreading due to illumination overload and/or b) as a means for the control of signal integration time. Two different V G levels are applied to the gate electrodes (18), the lower of the two levels V G - LOW is applied for a long duration and the higher level V G - HIGH is applied for a shorter duration during charge integration. At low levels of incident illumination on the CCD surface, charge signals are integrated without saturation, but, at levels of very intense illumination during the period with voltage V G - LOW on the gates, the pixel wells will saturate before the end of charge integration, resulting in the vertical overflow drain (VOD) operating to dump excess charge to the substrate. With the subsequent imposition of V G - HIGH for a short time period near the end of the integration interval, pixel well saturation is delayed and signals corresponding to high intensity are not lost. Consequently, imposing V G - HIGH for a short time period near the end of the integration interval (a) increases pixel charge storage capacity and (b) shortens the exposure time, which combination allows high intensity signal information to be integrated without loss by saturation.
Inventors
- 👤 Kenneth A. Hoagland
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 11:30
CPC Classifications
H; H10; H10F; H10F39/00; H10F39/10; H10F39/12; H10F39/15; H10F39/158; H04; H04N; H04N25/00; H04N25/60; H04N25/62; H04N25/621; H04N25/622
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
194 words
A method of achieving dynamic range extension (DRE) in a
CCD imager exposed to combined low and high intensity
illumination, said imager having a CCD imaging surface for
converting incident illumination into electrical charge, and gate
electrodes (18) acting on said surface having a voltage V G applied thereto to form pixel signal charge wells at well sites
below said surface during charge integration, comprising the
steps of: imposing a voltage V G - LOW on said gate electrodes (18) at
the pixel signal charge integration well sites, said voltage
V G - LOW being of a level that results in signal charge
wells above the reference signal level for automatic light
control used in CCD imager systems and of a time duration
equal to a large percentage of the total time of charge
integration; and then imposing a voltage V G - HIGH on said gate electrodes
(18) at the pixel signal charge integration well sites, said
voltage V G - HIGH being of a level that is above the level
of voltage V G - LOW and of a comparatively short time
duration with respect to the total time of charge
integration.
Claim 2
Dependent Claim
43 words
A method as in claim 1 wherein voltage V G - LOW is set
at a level to achieve a maximum pixel well capacity equal to from
25% to 50% of the full 100% well capacity achieved with voltage
V G - HIGH.
Claim 3
Dependent Claim
37 words
A method as in claim 1 wherein the reference signal
level for automatic light control used in CCD imager systems,
which the voltage V G - LOW is set above, is 1/4 to 1/2 full well
saturation.
Claim 4
Dependent Claim
29 words
A method as in claim 1 wherein voltage V G - LOW is
imposed for a time duration greater than about 90% of the total
time of charge integration.
Claim 5
Dependent Claim
18 words
A method as in claim 1 wherein said pixel signal charge
integration well sites contain overflow drains (OD).
Claim 6
Dependent Claim
16 words
A method as in claim 5 wherein said overflow drains (OD)
comprise vertical overflow drains (VOD).
Claim 7
Independent Claim
221 words
A system for achieving dynamic range extension (DRE) in
a CCD imager having a CCD imaging surface for converting incident
illumination into electrical charge, and gate electrodes (18)
acting on said surface having a voltage V G applied thereto to
form pixel signal charge wells at well sites below said surface
during charge integration, comprising: means for imposing a voltage V G - LOW on said gate
electrodes (18) at the pixel signal charge integration well
sites during the incidence of high intensity illumination on
said CCD imaging surface, said voltage V G - LOW being of a
level that results in signal charge wells above the
reference signal level for automatic light control used in
CCD imager systems and of a time duration equal to a large
percentage of the total time of charge integration; and means for imposing a voltage V G - HIGH on said gate
electrodes (18) at the pixel signal charge integration well
sites during the incidence of high intensity illumination on
said CCD imaging surface, said voltage V G - HIGH being of a
level that is above the level of said voltage V G - LOW and
being imposed for a comparatively short time duration with
respect to the total time of charge integration following
the imposition of said voltage V G - LOW.
Claim 8
Dependent Claim
45 words
A system as in claim 7 further comprising means for
setting voltage V G - LOW at a level to achieve a maximum pixel
well capacity equal to from 25% to 50% of the full 100% well
capacity achieved with voltage V G - HIGH.
Claim 9
Dependent Claim
57 words
A system as in claim 7 wherein said means for imposing
voltage V G - LOW in setting the level of voltage V G - LOW above
the reference signal level for automatic light control used in
CCD imager systems, sets the voltage V G - LOW at a level of 1/4
to 1/2 full well saturation.
Claim 10
Dependent Claim
31 words
A system as in claim 7 further comprising means for
imposing voltage V G - LOW for a time duration greater than about
90% of the total time of charge integration.
Claim 11
Dependent Claim
18 words
A system as in claim 7 wherein said pixel signal charge
integration well sites contain overflow drains (OD).
Claim 12
Dependent Claim
16 words
A system as in claim 7 wherein said overflow drains
(OD) comprise vertical overflow drains (VOD).
Claim 13
Independent Claim
282 words
A system for extending the dynamic range of a CCD
imager with overflow drains (OD) incorporated into its pixel
structures containing pixel signal charge integration wells
therein, said pixel structures comprising: a substrate (10) of one conductivity type; a region of opposite conductivity type on said substrate,
said region being shaped to collect excess signal charge
spilling from said pixel signal charge integration wells; a region of said one conductivity type deposited in the
upper surface of said pixel structure containing said pixel
signal charge integration wells; two channel stop regions of strong opposite conductivity
type deposited on opposite sides of said region of said one
conductivity type; and a gate electrode on a dielectric layer located above said
regions on said upper surface of said well portion; and said system further comprising: means for imposing a voltage V G - LOW on said gate electrode
(18) during the incidence of high intensity illumination on
said CCD imaging surface, said voltage V G - LOW being of a
level that results in signal charge wells above the
reference signal level for automatic light control used in
CCD imager systems and of a time duration that is a large
percentage of the total time of charge integration; and means for imposing a voltage V G - HIGH on said gate
electrode (18) during the incidence of high intensity
illumination on said CCD imaging surface, said voltage V G -HIGH
being of a level that is above the level of said
voltage V G - LOW and being imposed for a comparatively short
time duration with respect to the total time of charge
integration following the imposition of said voltage V G - LOW.
Claim 14
Dependent Claim
44 words
A system as in claim 13 further comprising means for
setting voltage V G - LOW at a level to achieve a maximum pixel
well capacity equal to 25% to 50% of the full 100% well capacity
achieved with voltage V G - HIGH.
Claim 15
Dependent Claim
57 words
A system as in claim 13 wherein said means for imposing
voltage V G - LOW in setting the level of voltage V G - LOW above
the reference signal level for automatic light control used in
CCD imager systems, sets the voltage V G - LOW at a level of 1/4
to 1/2 full well saturation.
Claim 16
Dependent Claim
31 words
A system as in claim 13 further comprising means for
imposing voltage V G - LOW for a time duration greater than about
90% of the total time of charge integration.
Claim 17
Dependent Claim
16 words
A system as in claim 13 wherein said overflow drain
comprises a vertical overflow drain (VOD).
References Cited (Backward Citations)
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