Cmos image sensor with noise cancellation

22.The image sensor of claim 21, wherein said control circuit causes said pixel to provide a sampled light response output signal and a sampled second reference output signal.

23.The image sensor of claim 22, further comprising a first subtraction circuit that provides a difference between said sampled reset output signal and said sampled first reference output signal to create a noise signal, and provides a difference between said sampled second reference output signal and said sampled light response output signal to create a normalized light response signal.

24.The image sensor of claim 23, further comprising a second subtraction circuit that subtracts said noise signal from said normalized light response signal.

25.The image sensor of claim 21, wherein said pixel includes a photodetector coupled to a reset transistor that has a sampling state in a triode region.

26.The image sensor of claim 23, wherein said first subtraction circuit includes a capacitor that stores at least one of said sampled output signals.

27.The image sensor of claim 23, further comprising a memory cell that is coupled to said first subtraction circuit and which stores said noise signal.

28.The image sensor of claim 27, wherein said memory cell stores a multi-level noise signal.

29.The image sensor of claim 28, further comprising an analog to digital converter coupled to said pixel and a digital to analog converter coupled to said analog to digital converter and said memory cell, said digital to analog converter provides a storage reference signal that is subtracted from said stored multi-level noise signal.

30.The image sensor of claim 24, wherein said sampled first reference output signal has the same voltage as said sampled second reference output signal.

31.An image sensor, comprising:

• a pixel;
• and,
• control means for causing said pixel to provide a sampled reset output signal and a sampled first reference output signal.

32.The image sensor of claim 31, wherein said control means causes said pixel to provide a sampled light response output signal and a sampled second reference output signal.

33.The image sensor of claim 32, further comprising first subtraction means for providing a difference between said sampled reset output signal and said sampled first reference output signal to create a noise signal, and providing a difference between said sampled second reference output signal and said sampled first light response output signal to create a normalized light response signal.

34.The image sensor of claim 33, further comprising second subtraction means for subtracting said noise signal from said normalized light response signal.

35.The image sensor of claim 31, wherein said pixel includes a photodetector coupled to a reset transistor that has a sampling state in a triode region.

36.The image sensor of claim 33, wherein said first subtraction means includes a capacitor that stores at least one of sampled output signals.

37. The image sensor of claim 33, further comprising memory means for storing said noise signal.

38.The image sensor of claim 37, wherein said memory means stores a multi-level noise signal.

39.The image sensor of claim 38, further comprising analog to digital means for converting said noise signal to a digital bit string and digital to analog means for converting said digital bit string to said multi-level noise signal, said digital to analog means provides a storage reference signal that is subtracted from said stored multi-level noise signal.

40.The image sensor of claim 34, wherein said sampled first reference output signal has the same voltage as said sampled second reference output signal.

42.The method of claim 41, wherein a multi-level noise signal is stored in a memory cell.

43.The method of claim 41, wherein said first reference output signal has the same voltage as said second reference output signal.

45.The image sensor of claim 44, wherein said control circuit resets said reset transistor to generate a sampled reset output signal.

46.The image sensor of claim 45, wherein said output transistor provides a sampled light response output signal, and then said control circuit drives said reset transistor to the triode region to generate a sampled second reference output signal.

47.The image sensors of claim 44, further comprising a capacitor coupled to said output transistor.

48.The image sensor of claim 47, further comprising a memory cell coupled to said capacitor, said memory cell including a storage capacitor.

49.The image sensor of claim 46, wherein said first reference output signal has the same voltage as said second reference output signal.

51.The image sensor of claim 50, wherein said control means switches said reset transistor to generate a sampled reset output signal.

52.The image sensor of claim 51, wherein said control means switches said output transistor provides a sampled light response output signal and a sampled second reference output signal.

53.The image sensors of claim 50, further comprising a capacitor coupled to said output transistor.

54.The image sensor of claim 53, further comprising a memory cell coupled to said capacitor, said memory cell including a storage capacitor.

55.The image sensor of claim 52, wherein said first reference output signal has the same voltage as said second reference output signal.

56.A method for generating a reference signal from a pixel of an image sensor, the pixel having a reset transistor and an output transistor connected to a photodetector, the reset transistor being connected to an IN line, the output transistor being connected to an OUT line, comprising:

• switching the reset transistor into a triode region, providing a reference signal on the IN line so that an output reference signal is provided on the OUT line;
• and,
• sampling said output reference signal.

57.The method of claim 56, further comprising resetting the reset transistor.

58.An image sensor, comprising:

• a pixel that provides a reset output signal and a first reference output signal;
• and,
• a first subtraction circuit that is coupled to said pixel, said first subtraction circuit provides a difference between said reset output signal and said first reference output signal.

59.The image sensor of claim 58, wherein said pixel provides a light response output signal and a second reference output signal, said first subtraction circuit provides a difference between said second reference output signal and said light response output signal to create a normalized light response signal.

60.The image sensor of claim 59, further comprising a second subtraction circuit that subtracts said noise signal from said normalized light response signal.

61.The image sensor of claim 58, wherein said pixel includes a photodetector coupled to a reset transistor and a select transistor, said reset transistor has a sampling state in a triode region.

62.The image sensor of claim 58, wherein said first subtraction circuit includes a capacitor that stores at least one of said output signals.

63.The image sensor of claim 58, further comprising a memory cell that is coupled to said first subtraction circuit and which stores said noise signal.

64.The image sensor of claim 63, wherein said memory cell stores a multi-level noise signal.

65.The image sensor of claim 64, further comprising an analog to digital converter coupled to said pixel and a digital to analog converter coupled to said analog to digital converter and said memory cell, said digital to analog converter provides a storage reference signal that is subtracted from said stored multi-level noise signal.

66.The image sensor of claim 59, wherein said first reference output signal has the same voltage as said second reference output signal.

67.An image sensor, comprising:

• pixel means for providing a reset output signal and a first reference output signal;
• and,
• first subtraction means for providing a difference between said reset output signal and said first reference output signal.

68.The image sensor of claim 67, wherein said pixel means provides a light response output signal and a second reference output signal, said first subtraction means provides a difference between said second reference output signal and said light response output signal to create a normalized light response signal.

69.The image sensor of claim 68, further comprising second subtraction means for subtracting said noise signal from said normalized light response signal.

70.The image sensor of claim 67, wherein said pixel includes a photodetector coupled to a reset transistor and a select transistor, said reset transistor has a sampling state in a triode region.

71.The image sensor of claim 67, wherein said first subtraction means includes a capacitor that stores at least one of said output signals.

72.The image sensor of claim 67, further comprising memory means for storing said noise signal.

73.The image sensor of claim 72, wherein said memory means stores a multi-level noise signal.

74.The image sensor of claim 73, further comprising analog to digital means for converting said noise signal to a digital bit string and digital to analog means for converting said digital bit string to said multi-level noise signal, said digital to analog means provides a storage reference signal that is subtracted from said stored multi-level noise signal.

75.The image sensor of claim 68, wherein said first reference output signal has the same voltage as said second reference output signal.

76.A pixel image sensor, comprising:

• a CMOS pixel array that contains rows of CMOS pixels;
• and,
• a control circuit that retrieves a plurality of short exposure output signals from said rows of CMOS pixels and a plurality of long exposure output signals from said rows of CMOS pixels in a time overlapping manner.

77.The pixel image sensor of claim 76, further comprising a first subtraction circuit that provides a difference between a plurality of first reset output signals and said short exposure output signals to create a plurality of normalize short exposure output signal, and provides a difference between a plurality of second reset output signals and said long exposure output signals to create a plurality of normalize long exposure output signals.

78.The pixel image sensor of claim 77, further comprising a memory cell that stores either said normalized short exposure signals or said normalized long exposure output signals.

79.The pixel image sensor of claim 78, further comprising a first analog to digital converter coupled to said pixel array, a digital to analog converter coupled to said analog to digital converter and said memory cell, and a second analog to digital converter coupled to said memory cell.

80.The pixel image sensor of claim 79, further comprising a combiner circuit that combines short and long exposure data.

81.An active pixel image sensor, comprising:

• a CMOS pixel array that contains rows of CMOS pixels;
• and,
• control means for retrieving a plurality of short exposure output signals from said rows of CMOS pixels and a plurality of long exposure output signals from said rows of CMOS pixels in a time overlapping manner.

82.The pixel image sensor of claim 81, further comprising first subtraction means for providing a difference between a plurality of first reset output signals and said short exposure output signals to create a plurality of normalized short exposure output signals, and providing a difference between a plurality of second reset output signals and said long exposure output signals to create a plurality of normalized long exposure output signals.

83.The pixel image sensor of claim 82, further comprising memory means for storing either said normalized short exposure output signals or said normalized long exposure output signals.

84.The pixel image sensor of claim 83, further comprising first analog to digital means for converting said normalized long exposure output signal to a long exposure data and second analog to digital means for converting said normalized short exposure output signal to a short exposure data.

85.The pixel image sensor of claim 84, further comprising combiner means for combining said short and long exposure data.

87.The method of claim 86, wherein a normalized short exposure output signal is generated by obtaining a difference between a first reset output signal and one of the short exposure output signals, and a normalized long exposure output signal is generated by obtaining a difference between a second reset output signal and one of the long exposure output signals, the normalized short and long exposure signals are converted to normalized short and long exposure data and then combined.

89.The image sensor of claim 88, further comprising a light reader that includes a first capacitor and a second capacitor that are coupled to said pixel.

90.The image sensor of claim 89, further comprising a storage writer coupled to said digital to analog converter and said memory cell, a storage reader coupled to said memory cell, and a second analog to digital converter coupled to said storage reader.

91.The image sensor of claim 90, further comprising a combiner coupled to said first and second analog to digital converters.

92.The image sensor of claim 88, wherein said pixel includes a photodetector coupled to a reset transistor and a select transistor, and said reset transistor has a sampling state in a triode region.

94.The image sensor of claim 93, wherein said conversion means includes first analog to digital converter means for converting said output signal to a digital bit string and digital to analog means for converting the digital bit string to said multi-level output signal that is stored in said memory means, and second analog to digital converter means for converting said stored multi-level output signal to a digital bit string.

95.The image sensor of claim 94, further comprising combiner means for combining said digital bit strings from said first and second analog to digital converter means.

96.The image sensor of claim 95, further comprising light reader means for retrieving said output signal from said pixel means.

97.The image sensor of claim 96, further comprising storage writer means for storing said multi-level output signal into said memory means, and storage reader means for retrieving said multi-level output signal from said memory means.

98.The image sensor of claim 93, wherein said pixel means includes a pixel that includes a photodetector coupled to a reset transistor and a select transistor, said reset transistor has a sampling state in a triode region.

100.The method of claim 99, wherein the output signal is converted by converting the output signal to a digital bit string, and converting the digital bit string to the multi-level output signal that is stored in the memory cell.

101.The method of claim 99, further comprising retrieving the multi-level output signal from the memory cell and converting the retrieved multi-level output signal to a digital bit string.

103.The image sensor of claim 102, wherein said output transistor provides an output reference signal.

105.The image sensor of claim 104, further comprising a control circuit that switches said buffer to said high impedance state when said reset transistor is in a triode region state and said output transistor provides a first reference output signal, and then said control circuit resets said reset transistor to generate a reset output signal.

106.The image sensor of claim 105, wherein said output transistors provides a light response output signal, and then said control circuit drives said reset transistor to the triode region to generate a second reference output signal.

107.The image sensors of claim 104, further comprising a capacitor coupled to said output transistor.

108.The image sensor of claim 107, further comprising a memory cell coupled to said capacitor, said memory cell including a storage capacitor.

109.The image sensor of claim 106, wherein said first reference output signal has the same voltage as said second reference output signal.

110.A memory circuit, comprising:

• a digital to analog converter;
• and,
• a memory cell coupled to said digital to analog converter.

111.The memory circuit of claim 110, wherein said memory cell includes a capacitor.

112.The memory circuit of claim 110, further comprising a storage writer connected to said digital to analog converter and said memory cell and a storage reader connected to said memory cell.

113.A memory circuit, comprising:

• conversion means for converting a digital bit string to a multi-level output signal;
• and,
• memory cell means for storing said multi-level output signal.

114.The memory circuit of claim 113, wherein said conversion means includes digital to analog means for converting the digital bit string to the multi-level output signal that is stored in said memory cell means.

115.The memory circuit of claim 113, wherein said memory cell means includes a capacitor.

116.The memory of claim 114, further comprising storage writer means for storing said multi-level output signal into said memory cell means, and storage reader means for retrieving said multi-level output signal from said memory cell means.

117. A method for storing a digital bit string, comprising:

• converting the digital bit string into a multi-level output signal;
• and
• storing the multi-level output signal in a memory cell.

118. The method of claim 117, further comprising retrieving the multi-level output signal from the memory cell and converting the retrieved multi-level output signal to a digital bit string.

119.An image sensor, comprising:

• a pixel array that generates a noise image and a light response image;
• and,
• a control circuit that is connected to said pixel array and causes said pixel array to output said noise image and said light response image in a time overlapping manner.

120.The image sensor of claim 119, further comprising a subtraction circuit that provides a difference between said noise image and said light response image.

121.The image sensor of claim 119, further comprising an analog to digital converter coupled to said pixel array.

122.The image sensor of claim 119, wherein said control circuit causes said pixel array to generate a plurality of reset output signals, first reference output signals, light response output signals and second reference output signals.

123.The image sensor of claim 122, further comprising a first subtraction circuit that provides a difference between said reset output signals and said first reference output signals to create said noise image, and provides a difference between said second reference output signals and said light response output signals to create said light response image.

124.An image sensor, comprising:

• a pixel array that generates a noise image and a light response image;
• and,
• control means for causing said pixel array to output said noise image and said light response image in a time overlapping manner.

125.The image sensor of claim 124, further comprising subtraction means for providing a difference between said noise image and said light response image.

126.The image sensor of claim 124, further comprising analog to digital means for converting analog data from said pixel array to digital data.

127.The image sensor of claim 124, wherein said control means causes said pixel to provide a plurality of reset output signals, first reference output signals, light response output signals and second reference output signals.

128.The image sensor of claim 127, further comprising first subtraction means for providing a difference between said reset output signals and said first reference output signals to create said noise image, and providing a difference between said second reference output signals and said first light response output signals to create said light response image.

129.A method for generating image in an image sensor, comprising:

• generating and retrieving a noise image and a light response image from a pixel array in a time overlapping manner.

130.The image sensor of claim 129, further comprising generating a difference between the noise image and the light response image.

131.The image sensor of claim 130, further comprising converting the noise and light response image to digital data before generating the difference.

132.The method of claim 129, wherein the noise image is created from a difference between a plurality of reset output signals and a plurality of first reference output signals generated within the pixel array, and the light response image is created by providing a difference between a plurality of light response output signals and a plurality of second reference output signals generated within the pixel array.

133.An image sensor, comprising:

• a pixel array that provides a first image and a second image in a time overlapping manner;
• a circuit coupled to said pixel array to digitize said first and second images.

134.The image sensor of claim 133, further comprising a light reader circuit coupled to said pixel array and said circuit.

135.The image sensor of claim 133, further comprising a combiner that combines said first and second digitized images.

136.The image sensor of claim 133, wherein said first image is a noise image and said second image is a light response image.

137.The image sensor of claim 136, wherein said pixel array generates a plurality of reset output signals, first reference output signals, light response output signals and second reference output signals.

138.The image sensor of claim 137, further comprising a first subtraction circuit that provides a difference between said reset output signals and said first reference output signals to create said noise image, and provides a difference between said second reference output signals and said light response output signals to create said light response image.

139.The image sensor of claim 133, wherein said first image is a short exposure image and said second image is a long exposure image.

140.The image sensor of claim 139, wherein said pixel array generates a plurality of first reset output signals, short exposure output signals, long exposure output signals and second reset output signals.

141.The image sensor of claim 140, further comprising a first subtraction circuit that provides a difference between said first reset output signals and said short exposure output signals to create said noise short exposure image, and provides a difference between said long exposure output signals and said second reset output signals to create said long exposure image.

142.An image sensor, comprising:

• a pixel array that provides a first image and a second image in a time overlapping manner;
• circuit means for digitizing said first and second images.

143.The image sensor of claim 142, further comprising light reader means for retrieving said first and second images from said pixel array.

144.The image sensor of claim 142, further comprising combiner means for combining said first and second digitized images.

145.The image sensor of claim 142, wherein said first image is a noise image and said second image is a light response image.

146.The image sensor of claim 145, wherein said pixel array generates a plurality of reset output signals, first reference output signals, light response output signals and second reference output signals.

147.The image sensor of claim 146, further comprising a first subtraction circuit that provides a difference between said reset output signals and said first reference output signals to create said noise image, and provides a difference between said second reference output signals and said light response output signals to create said light response image.

148.The image sensor of claim 142, wherein said first image is a short exposure image and said second image is a long exposure image.

149.The image sensor of claim 148, wherein said pixel array generates a plurality of first reset output signals, short exposure output signals, long exposure output signals and second reset output signals.

150.The image sensor of claim 149, further comprising a first subtraction circuit that provides a difference between said first reset output signals and said short exposure output signals to create said short exposure image, and provides a difference between said long exposure output signals and said second reset output signals to create said long exposure image.

152.The image sensor of claim 151, further comprising combining the first and second digitized images.

153.The image sensor of claim 151, wherein the first image is a noise image and the second image is a light response image.

154.The method of claim 153, wherein the noise image is created from a difference between a plurality of reset output signals and a plurality of first reference output signals generated within the pixel array, and the light response image is created by providing a difference between a plurality of light response output signals and a plurality of second reference output signals generated within the pixel array.

155.The image sensor of claim 151, wherein the first image is a short exposure image and the second image is a long exposure image.

156.The method of claim 155, wherein the short exposure image is created from a difference between a plurality of first reset output signals and a plurality of short exposure output signals generated within the pixel array, and the long exposure image is created by providing a difference between a plurality of long exposure output signals and a plurality of second reset output signals generated within the pixel array.