Imaging device having a characteristic converting section
To convert a pixel value obtained from a non-reference photoelectric conversion characteristic into a pixel value obtained from a reference photoelectric conversion characteristic without variation, and to prevent generation of fixed pattern noise in an image. An image sensor 3 is constituted of pixels having photoelectric conversion characteristics, in which a linear characteristic is on the low luminance side with respect to an inflection point, and a logarithmic characteristic is on the high luminance side with respect to the inflection point. A conversion information storage 68 stores, as conversion information, coefficients “c”, “d”, “e”, and “f” of two kinds of linear functions (y=c·log(x)+d, and y=e·log(x)+f), which are approximation equations expressing the logarithmic characteristic of each of the pixels, where y designates a pixel value, and x designates a luminance value of incident light. A linear converter 64 converts a pixel value obtained from the logarithmic characteristic into a pixel value obtained from the linear characteristic by using the approximation equations specified by the coefficients.
1. An imaging device comprising:
an imaging element constituted of a plurality of pixels having different photoelectric conversion characteristics with respect to an inflection point; and
assuming that one of the different photoelectric conversion characteristics is a reference photoelectric conversion characteristic, and the other thereof is a non-reference photoelectric conversion characteristic, a characteristic converting section which converts a pixel value obtained from the non-reference photoelectric conversion characteristic into a pixel value obtained from the reference photoelectric conversion characteristic,
wherein the characteristic converting section converts the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using predetermined conversion information with respect to each of the pixels to eliminate variation of the reference photoelectric conversion characteristic of each of the pixels after the conversion, the variation of the reference photoelectric conversion characteristic resulting from variation of the non-reference photoelectric conversion characteristic of each of the pixels,
wherein the characteristic converting section calculates an approximation equation expressing the non-reference photoelectric conversion characteristic of each of the pixels by using the conversion information to convert the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using the calculated approximation equation,
wherein the approximation equation is obtained by approximating the non-reference photoelectric conversion characteristic with a quadratic function, and
wherein the conversion information is coefficients of the quadratic function.
2. The imaging device according to claim 1 , wherein
the conversion information is a predetermined coefficient calculation function for use in determining a coefficient of the approximation equation expressing the non-reference photoelectric conversion characteristic, based on the inflection point for each of the pixels, and
the characteristic converting section calculates the coefficient of the approximation equation with respect to each of the pixels by using the coefficient calculation function, based on the inflection point for each of the pixels to convert the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using the approximation equation specified by the calculated coefficient.
3. The imaging device according to claim 1 , wherein
the reference photoelectric conversion characteristic is a linear photoelectric conversion characteristic, and
the non-reference photoelectric conversion characteristic is a logarithmic photoelectric conversion characteristic.
4. An imaging device comprising:
an imaging element constituted of a plurality of pixels having different photoelectric conversion characteristics with respect to an inflection point; and
assuming that one of the different photoelectric conversion characteristics is a reference photoelectric conversion characteristic, and the other thereof is a non-reference photoelectric conversion characteristic, a characteristic converting section which converts a pixel value obtained from the non-reference photoelectric conversion characteristic into a pixel value obtained from the reference photoelectric conversion characteristic,
wherein the characteristic converting section converts the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using predetermined conversion information with respect to each of the pixels to eliminate variation of the reference photoelectric conversion characteristic of each of the pixels after the conversion, the variation of the reference photoelectric conversion characteristic resulting from variation of the non-reference photoelectric conversion characteristic of each of the pixels,
a table storage which stores a correction table for use in correcting the non-reference photoelectric conversion characteristic of each of the pixels into a predicted non-reference photoelectric conversion characteristic common to all the pixels, wherein
the characteristic converting section corrects the pixel value obtained from the non-reference photoelectric conversion characteristic by using the conversion information and the correction table to convert the corrected pixel value into the pixel value obtained from the reference photoelectric conversion characteristic,
the correction table is a plurality of correction tables,
the conversion information is information for use in selecting a most preferable correction table, from among the plurality of the correction tables, in correcting the non-reference photoelectric conversion characteristic of each of the pixels into the non-reference photoelectric conversion characteristic common to all the pixels, and
the characteristic converting section selects one correction table from among the plurality of the correction tables by using the conversion information, and corrects the pixel value obtained from the non-reference photoelectric conversion characteristic by using the selected correction table to convert the corrected pixel value into the pixel value obtained from the reference photoelectric conversion characteristic.
5. The imaging device according to claim 4 , wherein
the reference photoelectric conversion characteristic is a linear photoelectric conversion characteristic, and
the non-reference photoelectric conversion characteristic is a logarithmic photoelectric conversion characteristic.
6. An imaging device comprising:
an imaging element constituted of a plurality of pixels having different photoelectric conversion characteristics with respect to an inflection point; and
assuming that one of the different photoelectric conversion characteristics is a reference photoelectric conversion characteristic, and the other thereof is a non-reference photoelectric conversion characteristic, a characteristic converting section which converts a pixel value obtained from the non-reference photoelectric conversion characteristic into a pixel value obtained from the reference photoelectric conversion characteristic,
wherein the characteristic converting section converts the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using predetermined conversion information with respect to each of the pixels to eliminate variation of the reference photoelectric conversion characteristic of each of the pixels after the conversion, the variation of the reference photoelectric conversion characteristic resulting from variation of the non-reference photoelectric conversion characteristic of each of the pixels,
a table storage which stores a correction table for use in correcting the non-reference photoelectric conversion characteristic of each of the pixels into a predicted non-reference photoelectric conversion characteristic common to all the pixels, wherein
the characteristic converting section corrects the pixel value obtained from the non-reference photoelectric conversion characteristic by using the conversion information and the correction table to convert the corrected pixel value into the pixel value obtained from the reference photoelectric conversion characteristic,
the correction table is a single correction table,
the conversion information is a change value for use in changing the correction table into correction tables for the respective pixels to change the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the non-reference photoelectric conversion characteristic common to all the pixels, and
the characteristic converting section converts the pixel value obtained from the non-reference photoelectric conversion characteristic into the pixel value obtained from the reference photoelectric conversion characteristic by using the respective correction tables changed by using the change value.
7. The imaging device according to claim 6 , wherein
the reference photoelectric conversion characteristic is a linear photoelectric conversion characteristic, and
the non-reference photoelectric conversion characteristic is a logarithmic photoelectric conversion characteristic.