Patent ID: 7421195

Claim:
An apparatus for acquiring focusing information, comprising: an optical system configured to focus light coming from an object, at a predetermined position, in order to photograph the object and acquire a focused image of the object; a luminance-information acquiring unit configured to acquire luminance information items about corresponding regions of at least two of a plurality of images which differ in unclearness and which have been formed by the light that has passed through at least one part of the optical system; a control unit configured to control a state of at least one of the optical system and the luminance-information acquiring unit in accordance with an input command value; a spread-parameter calculating unit configured to calculate a spread parameter from a plurality of luminance information items acquired by the luminance-information acquiring unit; a storage unit configured to store a table that shows a relation between spread parameters and command values supplied to the control unit to acquire a focused image of the object, and information that designates a command value corresponding to an inflection point on an approximated curve showing the relation that the spread parameters have with the command values; and a command-outputting unit configured to output the command value to the control unit in order to acquire a focused image of the object, by using the spread parameter calculated by the spread-parameter calculating unit and the table stored in the storage unit, at least one of the luminance information items acquired by the luminance-information acquiring unit having been acquired under a specific condition established by inputting to the control unit the command value corresponding to the inflection point that is designated on the basis of the information stored in the storage unit.