Dual conversion gain imagers
First Claim
Patent Images
1. An imager device, comprising:
- a floating diffusion region, connected to receive stored charge from a photosensitive device; and
a circuit connected to said floating diffusion region, said circuit providing said floating diffusion region with at least a dual conversion gain switchable between first and second conversion gains, said circuit comprising a capacitive element and a dual conversion gain switching element, said dual conversion gain switching element being controlled to disconnect said capacitive element from said floating diffusion region such that said floating diffusion region has the first conversion gain during a first lighting condition and connect said capacitive element to said floating diffusion region such that said floating diffusion region obtains the second conversion gain during a second lighting condition.
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Abstract
An imager with dual conversion gain floating diffusion regions. The dual conversion gain regions yield (1) high conversion gain and sensitivity to achieve excellent low light performance and (2) high full well capacity and conversion gain to achieve high dynamic range. A dual conversion gain element is coupled between each floating diffusion node and a respective capacitor. The dual conversion gain element switches in the capacitance of the capacitor to change the conversion gain of the floating diffusion node from a first conversion gain to a second conversion gain. The imager may be a CMOS or CCD type imager.
114 Citations
121 Claims
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1. An imager device, comprising:
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a floating diffusion region, connected to receive stored charge from a photosensitive device; and a circuit connected to said floating diffusion region, said circuit providing said floating diffusion region with at least a dual conversion gain switchable between first and second conversion gains, said circuit comprising a capacitive element and a dual conversion gain switching element, said dual conversion gain switching element being controlled to disconnect said capacitive element from said floating diffusion region such that said floating diffusion region has the first conversion gain during a first lighting condition and connect said capacitive element to said floating diffusion region such that said floating diffusion region obtains the second conversion gain during a second lighting condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A CMOS imager pixel, comprising:
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a photosensor for accumulating stored charge; a diffusion region, connected to receive the charge from the photosensor, said diffusion region having a first conversion gain; and a conversion gain altering circuit connected to said diffusion region, said conversion gain altering circuit being controlled to change the first conversion gain to the second conversion gain and to change the second conversion gain to the first conversion gain, said conversion gain altering circuit comprising a capacitive element and a dual conversion gain switching element, said dual conversion gain switching element being controlled to disconnect said capacitive element from said diffusion region such that said diffusion region has the first conversion gain during a first lighting condition and connect said capacitive element to said diffusion region such that said diffusion region obtains the second conversion gain during a second lighting condition. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A CMOS imager pixel, comprising:
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a photosensor for accumulating stored charge; a first transistor being controlled to reset said pixel; a second transistor being controlled to transfer the stored charge from the photosensor; a floating diffusion region connected to receive the charge from said photosensor through said second transistor, said floating diffusion region having a first conversion gain; a capacitive element; and a third transistor coupled between said floating diffusion region and said capacitive element, said third transistor being controlled to connect said capacitive element to said floating diffusion region during a first lighting condition such that said floating diffusion region obtains at least a second conversion gain, said third transistor being controlled to disconnect said capacitive element from said floating diffusion region during a second lighting condition. - View Dependent Claims (35, 36, 37)
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38. A CMOS imager pixel, comprising:
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a photosensor for accumulating stored charge; a first transistor being controlled to reset said pixel; a second transistor being controlled to transfer the stored charge from the photosensor; a floating diffusion region connected to receive the charge from said photosensor through second transistor, said floating diffusion region having a first conversion gain; a third transistor; and a capacitive element coupled between said diffusion region and said third transistor, said third transistor being controlled to connect said capacitive element to said floating diffusion region during a first lighting condition such that said floating diffusion region obtains at least a second conversion gain, said third transistor being controlled to disconnect said capacitive element from said floating diffusion region during a second lighting condition. - View Dependent Claims (39, 40, 41)
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42. A CMOS imager pixel, comprising:
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a photosensor for accumulating stored charge, said photosensor having a first charge storing capacity; a first transistor being controlled to reset said pixel; a diffusion region connected to receive the charge from said photosensor, said diffusion region having a second charge storing capacity different from the first charge storing capacity, said diffusion region having a first conversion gain based on the second charge storing capacity; a capacitive element; and a second transistor coupled between said diffusion region and said capacitive element, said second transistor being controlled to connect said capacitive element to said diffusion region such that said diffusion region obtains a third charge storing capacity and a second conversion gain based on the third charge storing capacity. - View Dependent Claims (43, 44, 45)
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46. A CMOS imager pixel, comprising:
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a photosensor for accumulating stored charge, said photosensor having a first charge storing capacity; a first transistor being controlled to reset said pixel; a diffusion region connected to receive the charge from said photosensor, said diffusion region having a second charge storing capacity different from the first charge storing capacity, said diffusion region having a first conversion gain based on the second charge storing capacity; a second transistor; and a capacitive element coupled between said diffusion region and said second transistor, said second transistor being controlled to connect said capacitive element to said diffusion region such that said diffusion region obtains a third charge storing capacity and a second conversion gain based on the third charge storing capacity. - View Dependent Claims (47, 48, 49)
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50. A CCD imager comprising:
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a register for inputting and outputting photo-generated charge; a diffusion region, connected to receive the photo-generated charge from said register, said diffusion region having a first conversion gain; and a conversion gain altering circuit connected to said diffusion region, said conversion gain altering circuit being controlled to change the first conversion gain to the second conversion gain and to change the second conversion gain to the first conversion gain, said conversion gain altering circuit comprising a capacitive element and a dual conversion gain switching element, said dual conversion gain switching element being controlled to disconnect said capacitive element from said diffusion region such that said diffusion region has the first conversion gain during a first lighting condition and connect said capacitive element to said diffusion region such that said diffusion region obtains the second conversion gain during a second lighting condition. - View Dependent Claims (51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62)
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63. An imager system, comprising:
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a processor; and an imaging device electrically coupled to said processor, said imaging device comprising a pixel array, at least one pixel of said array comprising; a photosensor for accumulating stored charge, a diffusion region, connected to receive the charge from the photosensor, said diffusion region having a first conversion gain, and a conversion gain altering circuit connected to said diffusion region, said conversion gain altering circuit being controlled to change the first conversion gain to the second conversion gain and to change the second conversion gain to the first conversion gain, said conversion gain altering circuit comprising a capacitive element and a dual conversion gain switching element, said dual conversion gain switching element being controlled to disconnect said capacitive element from said diffusion region such that said diffusion region has the first conversion gain during a first lighting condition and connect said capacitive element to said diffusion region such that said diffusion region obtains the second conversion gain during a second lighting condition. - View Dependent Claims (64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84)
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85. An imager system, comprising:
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a processor; and an imaging device electrically coupled to said processor, said imaging device comprising; a floating diffusion region, connected to receive stored charge from a photosensitive device; and a circuit connected to said diffusion region, said circuit providing said diffusion region with multiple conversion gains by switching in a first capacitive element during a first lighting condition to achieve a first conversion gain, switching in a second capacitive element during a second lighting condition to achieve a second conversion gain, said first and second conversion gains being different than a conversion gain of the diffusion region.
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86. An imager system, comprising:
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a processor; and an imaging device electrically coupled to said processor, said imaging device comprising; a register for inputting and outputting photo-generated charge; a diffusion region, connected to receive the photo-generated charge from said register, said diffusion region having a first conversion gain, and a conversion gain altering circuit connected to said diffusion region, said conversion gain altering circuit being controlled to change the first conversion gain to one of multiple conversion gains by switching in and connecting a corresponding capacitance to the diffusion region and to change said one of multiple conversion gains to said first conversion gain by disconnecting said corresponding capacitance from said diffusion region.
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87. A method of operating an imager device, said method comprising:
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storing photo-generated charge in a diffusion region having a charge storing capacity that is less than a charge storing capacity of a photosensitive device generating the photo-generated charge; outputting a first signal representing the stored photo-generated charge; changing a conversion gain of the diffusion region by changing the charge storing capacity of the region; and outputting a second signal representing the stored photo-generated charge in the diffusion region having the changed conversion gain. - View Dependent Claims (88, 89, 90, 91, 92, 93, 94, 95, 96, 100, 101)
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97. A method of operating an imager device, said method comprising:
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transferring photo-generated charge to a diffusion region having a charge storing capacity that is less than a charge storing capacity of a photosensitive device generating the photo-generated charge; determining an amount of the stored charge; comparing the amount to a predetermined threshold; changing a conversion gain of the diffusion region by changing the charge storing capacity of the region if it is determined that the amount of stored charge exceeds the threshold; and outputting a signal indicative of the charge in the diffusion region. - View Dependent Claims (98, 99, 102, 103, 104, 105, 106)
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107. A method of operating a CMOS imager device, said method comprising:
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providing a photosensor having a first capacitance; providing a diffusion region having a second capacitance that is less than the first capacitance; storing photo-generated charge from the photosensor in the diffusion region; determining an amount of the stored charge; comparing the amount to a predetermined threshold; and adding a third capacitance to the diffusion region such that the combination of the second and third capacitances is greater than the first capacitance if it is determined that the amount of stored charge exceeds the threshold. - View Dependent Claims (108, 109, 110, 111, 112, 113, 114, 115)
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116. A method of fabricating a dual conversion gain pixel, said method comprising the steps of:
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providing a substrate; providing a photosensitive region within the substrate; providing a floating diffusion region within said substrate, the floating diffusion region having a first capacitance; and providing a conversion gain altering circuit within the substrate, wherein the conversion gain altering circuit is controllable to add a second capacitance to the capacitance of the diffusion region, said act of providing the gain altering circuit comprises forming a capacitive element within the substrate and forming a transistor within the substrate, wherein the transistor is connected between the diffusion region and the capacitive element such that when the transistor is activated, a capacitance of the capacitive element is added to the first capacitance. - View Dependent Claims (117, 118, 119)
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120. A method of fabricating a dual conversion gain pixel, said method comprising the steps of:
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providing a substrate; providing a photosensitive region within the substrate; forming a first transistor within the substrate for resetting the pixel; providing a floating diffusion region within said substrate, the floating diffusion region having a first capacitance; providing a second transistor between the photosensitive region and the floating diffusion region, the second transistor being controllable to transfer charge from the photosensitive region to the floating diffusion region; forming a capacitive element within the substrate; and forming a third transistor within the substrate, wherein the third transistor is connected between the diffusion region and the capacitive element such that when the third transistor is activated, a capacitance of the capacitive element is added to the first capacitance.
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121. A method of fabricating a dual conversion gain pixel, said method comprising the steps of:
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providing a substrate; providing a photosensitive region within the substrate; forming a first transistor within the substrate for resetting the pixel; providing a floating diffusion region within said substrate, the floating diffusion region having a first capacitance and being connected to the photosensitive region; forming a capacitive element within the substrate; and forming a second transistor within the substrate, wherein the second transistor is connected between the diffusion region and the capacitive element such that when the second transistor is activated, a capacitance of the capacitive element is added to the first capacitance.
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Specification