Image sensing apparatus and image sensing method using image sensor having two or more different photoelectric conversion characteristics
An image sensing apparatus and an image sensing method of the invention are configured in such a manner that an image sensor having two or more different photoelectric conversion characteristics is used, a gain of image signals having the respective photoelectric conversion characteristics acquired by the image sensor is calculated based on the image signals having the respective photoelectric conversion characteristics, and gain control is performed with respect to each of the photoelectric conversion characteristics, using the calculated gain. This arrangement enables to control the imaging sensitivity without changing the dynamic range.
1. An image sensing apparatus, comprising:
an image sensor having two or more different photoelectric conversion characteristics, and adapted to output image signals having the respective photoelectric conversion characteristics individually;
an amplifying section for amplifying the image signals having the respective photoelectric conversion characteristics;
a gain controlling section for controlling a gain of the amplifying section;
an output section for outputting the image signals having the respective photoelectric conversion characteristics amplified by the amplifying section; and
an image generating section for synthesizing the image signals outputted from the output section to generate an image, wherein
the gain controlling section calculates a gain of the image signals having the respective photoelectric conversion characteristics based on the image signals having the respective photoelectric conversion characteristics to control the gain of the amplifying section by using the calculated gain with respect to each of the photoelectric conversion characteristics, and
the photoelectric conversion characteristics of the image sensor include two or more linear characteristics whose sensitivity is different from each other.
2. The image sensing apparatus according to claim 1 , wherein
the gain controlling section controls the gain of the amplifying section by using at least the gain of the image signal having the photoelectric conversion characteristic whose sensitivity is highest, out of the two or more different photoelectric conversion characteristics.
3. The image sensing apparatus according to claim 1 , wherein
the photoelectric conversion characteristics of the image sensor include a linear characteristic and a logarithmic characteristic.
4. The image sensing apparatus according to claim 3 , wherein
the gain controlling section calculates the gain of the image signal having the linear characteristic based on the image signal having the linear characteristic to control the gain of solely the image signal representing an image having a lowest luminance after the image generation by using the calculated gain.
5. The image sensing apparatus according to claim 1 , wherein
the gain controlling section calculates the gain of the image signal having the linear characteristic whose sensitivity is highest, out of the two or more linear characteristics, based on the image signal having the linear characteristic with the highest sensitivity to control the gain of solely the image signal representing an image having a lowest luminance after the image generation by using the calculated gain.
6. The image sensing apparatus according to claim 5 , wherein
the image generating section selects a signal component of a first image signal whose signal level is equal to or lower than a predetermined signal level, and a signal component of a second image signal whose signal level is higher than the predetermined signal level to synthesize the selected signal component of the first image signal and the selected signal component of the second image signal so as to generate an image, the first image signal having the photoelectric conversion characteristic which has undergone the gain control, and the second image signal being obtained by subjecting the image signal having the photoelectric conversion characteristic other than the photoelectric conversion characteristic which has undergone the gain control, to data conversion in accordance with the calculated gain.
7. The image sensing apparatus according to claim 1 , wherein
the gain controlling section controls the gain of the image signal other than the image signal representing an image having a highest luminance after image generation by using the calculated gain.
8. An image sensing apparatus, comprising:
an image sensor having two or more different photoelectric conversion characteristics, and adapted to output image signals having the respective photoelectric conversion characteristics individually;
an amplifying section for amplifying the image signals having the respective photoelectric conversion characteristics;
a gain controlling section for controlling a gain of the amplifying section;
an output section for outputting the image signals having the respective photoelectric conversion characteristics amplified by the amplifying section; and
an image generating section for synthesizing the image signals outputted from the output section to generate an image, wherein
the gain controlling section calculates a gain of the image signals having the respective photoelectric conversion characteristics based on the image signals having the respective photoelectric conversion characteristics to control the gain of the amplifying section by using the calculated gain with respect to each of the photoelectric conversion characteristics,
the photoelectric conversion characteristics of the image sensor include a linear characteristic and a logarithmic characteristic,
the gain controlling section calculates the gain of the image signal having the linear characteristic based on the image signal having the linear characteristic to control the gain of solely the image signal representing an image having a lowest luminance after the image generation by using the calculated gain, and
the image generating section selects a signal component of a first image signal whose signal level is equal to or lower than a predetermined signal level, and a signal component of a second image signal whose signal level is higher than the predetermined signal level to synthesize the selected signal component of the first image signal and the selected signal component of the second image signal so as to generate an image, the first image signal having the photoelectric conversion characteristic which has undergone the gain control, and the second image signal being obtained by subjecting the image signal having the photoelectric conversion characteristic other than the photoelectric conversion characteristic which has undergone the gain control, to data conversion in accordance with the calculated gain.
9. An image sensing method, comprising:
a step of outputting, from an image sensor having two or more different photoelectric conversion characteristics, image signals having the photoelectric conversion characteristics individually;
a step of amplifying the image signals having the respective photoelectric conversion characteristics;
a step of controlling a gain in the amplifying step; and
a step of outputting the image signals having the respective photoelectric conversion characteristics amplified in the amplifying step, wherein
the gain controlling step includes
a step of calculating a gain of the image signals having the respective photoelectric conversion characteristics based on the image signals having the respective photoelectric conversion characteristics, and
a step of controlling the gain in the amplifying step by using the gain obtained in the gain calculating step with respect to each of the photoelectric conversion characteristics, wherein
the photoelectric conversion characteristics of the image sensor include two or more linear characteristics whose sensitivity is different from each other.
10. The image sensing method according to claim 9 , wherein
the gain controlling step includes a step of controlling the gain in the amplifying step by using at least the gain of the image signal having the photoelectric conversion characteristic whose sensitivity is highest, out of the two or more different photoelectric conversion characteristics.
11. The image sensing method according to claim 9 , wherein
the photoelectric conversion characteristics of the image sensor include a linear characteristic and a logarithmic characteristic.
12. The image sensing method according to claim 11 , wherein
the gain controlling step includes
a step of calculating the gain of the image signal having the linear characteristic based on the image signal having the linear characteristic, and
a step of controlling the gain of solely the image signal representing an image having a lowest luminance after image generation by using the gain obtained in the gain calculating step.
13. The image sensing method according to claim 9 , wherein
the gain controlling step includes
a step of calculating the gain of the image signal having the linear characteristic whose sensitivity is highest, out of the two or more linear characteristics, based on the image signal having the linear characteristic with the highest sensitivity, and
a step of controlling the gain of solely the image signal representing an image having a lowest luminance after image generation by using the gain obtained in the gain calculating step.
14. The image sensing method according to claim 9 , wherein
the gain controlling step includes a step of controlling the gain of the image signal other than the image signal representing an image having a highest luminance after image generation by using the gain obtained in the gain calculating step.