Focusing state determining apparatus

A focusing state determining apparatus for a camera including a plurality of picture-imaging elements for different colors, the focusing state determining apparatus comprising:

• a focus-imaging element provided separately from the picture-imaging elements;
• a color separation optical system which separates subject light entering the focusing state determining apparatus through a taking lens into a plurality of colors of light respectively entering the plurality of picture-imaging elements, wavelength bands of the plurality of colors of light being different to each other;
• a first beam splitter included in the color separation optical system, the first beam splitter splitting one of the plurality of colors of light into light entering the focus-imaging element and light entering the picture-imaging element of a corresponding color;
• and
• a second beam splitter which divides the light exiting from the first beam splitter toward the focus-imaging;
• wherein
• an optical path length between the taking lens and the focus-imaging element is different from an optical path length between the taking lens and one of the plurality of picture-imaging elements,
• focus evaluation values are obtained from high frequency components of image signals captured by the focus-imaging element and the one of the plurality of picture-imaging elements, and
• a focusing state of the taking lens with respect to the plurality of picture-imaging elements is determined according to the focus evaluation values.

A focusing state determining apparatus for a camera including a plurality of picture-imaging elements for different colors, the focusing state determining apparatus comprising:

• a focus-imaging device that is provided separately from the picture-imaging elements and includes first and second focus-imaging elements;
• a color separation optical system which separates subject light entering the focusing state determining apparatus through a taking lens into a plurality of colors of light respectively entering the plurality of picture-imaging elements, wavelength bands of the plurality of colors of light being different to each other;
• a first beam splitter included in the color separation optical system, the first beam splitter splitting one of the plurality of colors of light into light entering the focus-imaging device and light entering the picture-imaging element of a corresponding color;
• and
• a second beam splitter which splits the light exiting from the first beam splitter toward the focus-imaging device into light entering the first focus-imaging element and light entering the second focus-imaging element, wherein:
• an optical path length between the taking lens and the first focus-imaging element is different from an optical path length between the taking lens and the second focus-imaging element;
• focus evaluation values are obtained from high frequency components of image signals captured by the first and second focus-imaging elements;
• and
• a focusing state of the taking lens with respect to the plurality of picture-imaging elements is determined according to the focus evaluation values.

A method for determining a focusing state of a camera including a plurality of picture-imaging elements for different colors, the method comprising:

• separating subject light, entering the camera through a taking lens, into a plurality of colors of light with different wavelength bands, each of the plurality of colors of light entering one of the plurality of picture-imaging elements, respectively;
• splitting one of the plurality of colors of light into two parts one of which enters a focus-imaging element, provided separately from the picture-imaging elements, and one of which enters the picture-imaging element of a corresponding color;
• capturing image signals using the focus-imaging element and one of the plurality of picture-imaging elements;
• obtaining focus evaluation values from the captured image signals;
• and
• determining a focusing state based on the focus evaluation values;
• wherein
• optical path lengths from the taking lens to the plurality of picture-imaging elements are equal to each other, and
• an optical path length between the taking lens and the focus-imaging element is different from the optical path lengths from the taking lens to the plurality of picture-imaging elements.