Patent ID: 7095443

Claim:
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; and 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, wherein: optical path lengths from the taking lens to the plurality of picture-imaging elements are equal to each other; 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; 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.