Image capturing apparatus, image capturing system, and processing method

An image capturing system comprising:

• an image capturing apparatus including:
• an infrared cutoff filter;
• an image capturing device having a plurality of pixels for detecting light transmitted through the infrared cutoff filter;
• four optical filters disposed on a light-detecting surface of the image capturing device, the four optical filters having different filter characteristics;
• and
• a processor for processing pixel signals generated by the pixels of the image capturing device;
• wherein the four optical filters include a first filter for transmitting light having a wavelength longer than a first wavelength, a second filter for transmitting light having a wavelength longer than a second wavelength, a third filter for transmitting light having a wavelength longer than a third wavelength, and a fourth filter for transmitting light having a wavelength longer than a fourth wavelength;
• and
• the infrared cutoff filter transmits light having a wavelength shorter than a fifth wavelength;
• the processor comprises:
• a blue-component calculator for calculating a blue-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the first filter from a pixel signal output from the pixel that detects light applied to the infrared cutoff filter;
• a green-component calculator for calculating a green-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the second filter from the pixel signal output from the pixel that detects light transmitted through the first filter;
• and
• a red-component calculator for calculating a red-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the third filter from the pixel signal output from the pixel that detects light transmitted through the second filter;
• wherein the first wavelength, the second wavelength, the third wavelength, the fourth wavelength, and the fifth wavelength are related to each other such that the first wavelength<the second wavelength<the third wavelength<the fourth wavelength<the fifth wavelength;
• a controller for controlling the image capturing device;
• and
• a light-emitting apparatus for emitting infrared radiation toward a subject for a prescribed period, the infrared radiation including radiation having a wavelength longer than the fourth wavelength and shorter than the fifth wavelength;
• wherein the image capturing device includes a plurality of first pixels for detecting the light applied to the infrared cutoff filter, the light transmitted through the first filter, the light transmitted through the second filter, and the light transmitted through the third filter, and a plurality of second pixels for detecting the light transmitted through the fourth filter;
• and
• the controller controls the first pixels so as not to store photoelectrons produced thereby during a first period in which reflected light of at least the radiation emitted from the light-emitting apparatus is applied to the image capturing device, and to store photoelectrons produced thereby during a second period in which reflected light is not applied to the image capturing device, for thereby obtaining luminance information of ambient light, which is independent of the reflected light.

A method of processing pixel signals in an image capturing apparatus including an infrared cutoff filter, an image capturing device having a plurality of pixels for detecting light transmitted through the infrared cutoff filter, and four optical filters disposed on a light-detecting surface of the image capturing device, the four optical filters having different filter characteristics, wherein the four optical filters include a first filter for transmitting light having a wavelength longer than a first wavelength, a second filter for transmitting light having a wavelength longer than a second wavelength, a third filter for transmitting light having a wavelength longer than a third wavelength, and a fourth filter for transmitting light having a wavelength longer than a fourth wavelength, the infrared cutoff filter transmits light having a wavelength shorter than a fifth wavelength, and the first wavelength, the second wavelength, the third wavelength, the fourth wavelength, and the fifth wavelength are related to each other such that the first wavelength<the second wavelength<the third wavelength<the fourth wavelength<the fifth wavelength, the method comprising the steps of:

• calculating a blue-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the first filter from a pixel signal output from the pixel that detects light applied to the infrared cutoff filter;
• calculating a green-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the second filter from the pixel signal output from the pixel that detects the light transmitted through the first filter;
• and
• calculating a red-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the third filter from the pixel signal output from the pixel that detects the light transmitted through the second filter.

A method of processing pixel signals in an image capturing system including an infrared cutoff filter, an image capturing device having a plurality of pixels for detecting light transmitted through the infrared cutoff filter, four optical filters disposed on a light-detecting surface of the image capturing device, the four optical filters having different filter characteristics, a controller for controlling the image capturing device, and a light-emitting apparatus for emitting infrared radiation toward a subject for a prescribed period, the infrared radiation including radiation having a wavelength longer than a fourth wavelength and shorter than a fifth wavelength, wherein the four optical filters include a first filter for transmitting light having a wavelength longer than a first wavelength, a second filter for transmitting light having a wavelength longer than a second wavelength, a third filter for transmitting light having a wavelength longer than a third wavelength, and a fourth filter for transmitting light having a wavelength longer than the fourth wavelength, the infrared cutoff filter transmits light having a wavelength shorter than the fifth wavelength, and the first wavelength, the second wavelength, the third wavelength, the fourth wavelength, and the fifth wavelength are related to each other such that the first wavelength<the second wavelength<the third wavelength<the fourth wavelength<the fifth wavelength, wherein the image capturing device includes a plurality of first pixels for detecting the light applied to the infrared cutoff filter, the light transmitted through the first filter, the light transmitted through the second filter, and the light transmitted through the third filter, and a plurality of second pixels for detecting the light transmitted through the fourth filter, the method comprising the steps of:

• controlling the first pixels so as not to store photoelectrons produced thereby during a first period in which reflected light of at least the radiation emitted from the light-emitting apparatus is applied to the image capturing device, and to store photoelectrons produced thereby during a second period in which the reflected light is not applied to the image capturing device;
• calculating a blue-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the first filter from a pixel signal output from the pixel that detects light applied to the infrared cutoff filter;
• calculating a green-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the second filter from the pixel signal output from the pixel that detects the light transmitted through the first filter;
• and
• calculating a red-component pixel signal by subtracting a pixel signal output from the pixel that detects light transmitted through the third filter from the pixel signal output from the pixel that detects the light transmitted through the second filter.