Focus detection device and focus detection method

A focus detection device having a plurality of focus detection regions in an image field of an optical system, the device comprising:

• a plurality of charge accumulation type image sensors corresponding to said plurality of focus detection regions, that output an image signal for detecting a focus adjustment condition of each focus detection region;
• a region selector that selects a focus detection region from among the plurality of focus detection regions for focus detection;
• an image sensor controller that controls said plurality of charge accumulation type image sensors regardless of their selection state by the region selector, said image sensor controller controlling a charge accumulation time of each of the charge accumulation type sensors so that output of each of the charge accumulation type sensors can be maintained at an appropriate level, regardless of brightness, wherein said image sensor controller computes the charge accumulation time based on image signals output from the charge accumulation type image sensors;
• and
• a focus detection computation system that performs a computation process on the image sensor signals repeatedly output from the image sensors corresponding to the selected focus detection region, said focus detection computation system repeatedly detecting the focus adjustment condition of the selected focus detection region.

A focus detection method for a focus detection device including a plurality of focus detection areas on a photography screen of a photography optical system, the method comprising:

• providing a plurality of charge accumulation type photoelectric converters in correspondence to said plurality of focus detection areas;
• outputting, with said photoelectric converters, pairs of image signals corresponding to a light intensity distribution of a subject image formed by the optical system;
• computing a focus adjustment condition of the photography optical system based on the pairs of image signals output from the photoelectric converters;
• controlling charge accumulation of the photoelectric converters based on at least one image signal from the pair of image signals output from the photoelectric converters;
• selecting an area where focus detection is performed from among the plurality of focus detection areas;
• and
• computing a charge accumulation time based on at least one image signal from the pair of image signals output from the photoelectric converters, and outputting a signal corresponding to light intensity incident on each of the photoelectric converters, wherein, in the photoelectric converters corresponding to the non-selected focus detection areas, the method comprising interrupting charge accumulation and then monitoring the light intensity in the photoelectric converters corresponding to the non-selected focus detection areas.

A focus detection method for a plurality of focus detection regions arranged in an image field of an optical system, the method comprising:

• selecting a focus detection region from among the plurality of focus detection regions for focus detection;
• repeatedly operating a plurality of charge accumulation type image sensors to output an image signal corresponding to said plurality of focus detection regions regardless of the focus detection region selected state;
• controlling a charge accumulation time of each of the charge accumulation type sensors so that output of each of the charge accumulation type sensors can be maintained at an appropriate level, regardless of brightness, and computing the charge accumulation time based on image signals output from the charge accumulation type image sensors;
• performing a computation process on the image sensor signal repeatedly output from the image sensor corresponding to the selected focus detection region;
• and
• repeatedly detecting the focus adjustment condition of the selected focus detection region.