Solid state image sensing device and image sensing method

• US 6,433,823 B1
• Filed: 08/26/1997
• Issued: 08/13/2002
• Est. Priority Date: 08/26/1996
• Status: Expired due to Term

• Current Assignee: Sony Semiconductor Solutions Corporation (Sony Group Corp.)
• Original Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Inventors: Nakamura, Satoshi, Takada, Kenji
• Primary Examiner(s): GARBER, WENDY RAE
• Assistant Examiner(s): Harrington, Alicia M.
• Application Number:
  US08/920,284
• Time in Patent Office: 1,813 Days
• Field of Search: 348/302, 348/308, 348/254, 348/674, 358/519
• US Class Current: 348/254
• CPC Class Codes: H04N 23/82 for controlling camera response irrespective of the scene brightness, e.g. gamma correction
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

A solid state image sensing device provided with a gamma correction circuit which corrects a logarithmically converted value derived from the logarithmic conversion of individual pixel data output from individual photoelectric conversion elements, thereby easily correcting discrepancies and differences in the gamma characteristics of the individual pixels of a photoelectric conversion element which converts a light signal to an electrical signal.

Claims

1. A solid state image sensing device comprising:

a plurality of photoelectric conversion elements, each of which possesses its own gamma characteristic and receives an optical signal and outputs an electrical signal corresponding to an amount of light received;

a logarithmic conversion unit for performing a logarithmic conversion on the electrical signal generated in the photoelectric conversion element as well as the output from the photoelectric conversion element;

a gamma correction circuit for correcting discrepancies in the gamma characteristics of each output from the photoelectric conversion element once this output has undergone the logarithmic conversion by the logarithmic conversion unit,

wherein the gamma correction circuit multiplies defined values for individual pixels and thereby performs gamma correction on an output value from a photoelectric conversion element once this output value has undergone a logarithmic conversion in a logarithmic conversion unit; and

a memory for storing data output by each photoelectric conversion element and calculates defined values based on the thus stored data,

wherein the memory stores a first output value when a beam of a first luminance is projected and stores a second output value when a beam of a second luminance different than the first is projected, and calculates the defined values based on the following expression;

2. A solid state image sensing device in accordance with claim 1, wherein each respective photoelectric conversion element has the effect of doubling a respective photoelectric current, and each said element possesses a semiconductor substrate, an amorphous semiconductor layer disposed atop the semiconductor substrate, and an electrical field-applying electrode which applies an electrical field to the amorphous semiconductor layer.

3. A solid state image sensing device in accordance with claim 1, wherein the logarithmic conversion unit possesses a number of logarithmic conversion elements equal to the number of the photoelectric conversion elements, and performs a logarithmic conversion on the output from each photoelectric conversion element and provides an output.

4. A solid state image sensing device in accordance with claim 3, having a reading device which scans and thereby sequentially reads the output from a photoelectric conversion element once this output has undergone a logarithmic conversion, and which provides an output to the gamma correction circuit.

5. A solid state image sensing device in accordance with claim 1, wherein the logarithmic conversion unit possesses an element that performs a logarithmic conversion, sequentially performs a logarithmic conversion on an output from a photoelectric conversion element by means of a logarithmic conversion unit used in common for individual photoelectric conversion elements, and provides an output.

6. A solid state image sensing device in accordance with claim 1, wherein the aforementioned gamma correction circuit possesses an A/D converter for converting to digital data an output value from a photoelectric conversion element once this output value has undergone a logarithmic conversion by a logarithmic conversion unit, and then performs gamma correction by multiplying defined values for individual pixels.

7. A solid state image sensing device comprising:

a plurality of photoelectric conversion elements, each of which possesses its own gamma characteristic and receives an optical signal and outputs an electrical signal corresponding to an amount of light received;

a logarithmic conversion unit for performing a logarithmic conversion on the electrical signal generated in the photoelectric conversion element as well as the output from the photoelectric conversion element; and

a gamma correction circuit for correcting discrepancies in the gamma characteristics of each output from the photoelectric conversion element once this output has undergone the logarithmic conversion by the logarithmic conversion unit,

wherein the gamma correction circuit comprises;

an A/D converter for converting to digital data an output value from a photoelectric conversion element once this output value has undergone a logarithmic conversion by a logarithmic conversion unit,

a memory for storing output data converted to digital data for a plurality of individual photoelectric conversion elements, and

an arithmetic circuit for calculating a defined value for a gamma correction based on data stored for a plurality of individual photoelectric conversion elements,

wherein the gamma correction circuit carries out gamma correction by multiplying the thus calculated defined value by an output value from a photoelectric conversion element converted to digital data, and outputs the thus corrected data;

wherein the memory stores reference data outputted when a uniform beam is projected on a photoelectric conversion element, and the gamma correction circuit adds the thus stored data to output data from a photoelectric conversion element converted to digital data, and discrepancies are thereby corrected, and the defined values are then used in multiplication, and an output is provided.

8. A solid state image sensing device comprising:

a plurality of photoelectric conversion elements, each of which possesses its own gamma characteristic and receives an optical signal and outputs an electrical signal corresponding to an amount of light received;

a logarithmic conversion unit for performing a logarithmic conversion on the electrical signal generated in the photoelectric conversion element as well as the output from the photoelectric conversion element; and

a gamma correction circuit for correcting discrepancies in the gamma characteristics of each output from the photoelectric conversion element once this output has undergone the logarithmic conversion by the logarithmic conversion unit,

wherein the gamma correction circuit comprises;

an A/D converter for converting to digital data an output value from a photoelectric conversion element once this output value has undergone a logarithmic conversion by the logarithmic conversion unit,

a memory for storing output data converted to digital data for a plurality of individual photoelectric conversion elements,

an arithmetic circuit for calculating a defined value for a gamma correction based on data stored for a plurality of individual photoelectric conversion elements,

wherein the gamma correction circuit carries out gamma correction by multiplying a calculated defined value by an analog output value from a photoelectric conversion element which has undergone a logarithmic conversion, and outputs the corrected analog data.

9. The solid state image sensing device of claim 8, wherein the aforementioned memory stores data output when a uniform beam is projected on a photoelectric conversion element;

and in the aforementioned gamma correction circuit, data stored for each photoelectric conversion element are added to the output data from a photoelectric conversion element which has undergone a logarithmic conversion, and discrepancies are thereby corrected; and

the aforementioned defined values are then used in multiplication, and an output is provided.

10. A solid state image sensing device comprising:

a photoelectric conversion unit provided with a plurality of photoelectric conversion elements, each of which has a different gamma characteristic and receives an optical signal and outputs an electrical signal corresponding to an amount of light received;

a logarithmic conversion unit for sequentially performing a logarithmic conversion on an electrical signal generated in each photoelectric conversion element;

an A/D converter for converting to digital data an output from the photoelectric conversion unit which has undergone a logarithmic conversion;

a memory for storing digital data converted by the A/D converter;

an arithmetic data correction circuit for calculating a corrected gamma characteristic value for a photoelectric conversion element based on data stored in the memory; and

a correction circuit for correcting a gamma characteristic by multiplying the value calculated in the arithmetic data correction circuit with an output from a photoelectric conversion element which has undergone a logarithmic conversion in the logarithmic conversion unit;

wherein the memory stores a first output value when a beam of a first luminance is projected on a photoelectric conversion element and a second output value when a beam of a second luminance different than the first is projected on a photoelectric conversion element, and an arithmetic data correction circuit determines a corrected gamma characteristic value according to the expression;