Focus detection device, focus adjustment device and camera

Abstract

A focus detection device includes: a plurality of micro-lenses at which light fluxes through an image forming optical system enter, disposed in a two-dimensional array pattern; a plurality of light receiving elements disposed in correspondence to each of the plurality of micro-lenses; a focus detection unit that executes a detection of a defocus quantity of the image forming optical system by detecting, based upon outputs from the plurality of light receiving elements, a phase difference of a plurality of light fluxes through different areas of the image forming optical system; and a recognition unit that recognizes, based upon the outputs from the plurality of light receiving elements, characteristics of a subject image formed onto the plurality of light receiving elements via the plurality of micro-lenses, wherein: the focus detection unit detects the defocus quantity through a method optimal for the characteristics of the subject image recognized by the recognition unit.

1 . A focus detection device, comprising:
 a plurality of micro-lenses at which light fluxes having been transmitted through an image forming optical system enter, disposed in a two-dimensional array pattern;   a plurality of light receiving elements disposed in correspondence to each of the plurality of micro-lenses;   a focus detection unit that executes a detection of a defocus quantity of the image forming optical system by detecting, based upon outputs from the plurality of light receiving elements, a phase difference manifested by a plurality of light fluxes having passed through different areas of the image forming optical system; and   a recognition unit that recognizes, based upon the outputs from the plurality of light receiving elements, characteristics of a subject image formed onto the plurality of light receiving elements via the plurality of micro-lenses, wherein:   the focus detection unit detects the defocus quantity through a method optimal for the characteristics of the subject image recognized by the recognition unit.   
     
     
         2 . A focus detection device according to  claim 1 , wherein:
 the characteristics of the subject image manifest as a pattern in the subject image.   
     
     
         3 . A focus adjustment device, comprising:
 a plurality of micro-lenses disposed in a two-dimensional array pattern so as to allow light fluxes, having been transmitted through an image forming optical system, to enter thereat;   a plurality of light receiving elements disposed in correspondence to each of the plurality of micro-lenses on a rear side of the micro-lens;   a recognition unit that recognizes, based upon light reception outputs from the plurality of light receiving elements, a pattern in a subject image formed onto the plurality of light receiving elements via the plurality of micro-lenses; and   a focus adjustment unit that executes focus adjustment for the image forming optical system by detecting, based upon the light reception outputs, a phase difference manifested by a pair of light fluxes having passed through different areas of the image forming optical system, wherein:   the focus adjustment unit executes focus adjustment optimal for the pattern in the subject image recognized by the recognition unit.   
     
     
         4 . A focus adjustment device according to  claim 3 , wherein:
 the recognition unit is capable of recognizing at least a cyclical pattern, an edge pattern and a gradation pattern.   
     
     
         5 . A focus adjustment device according to  claim 3 , wherein:
 in correspondence to the pattern in the subject image recognized by the recognition unit, the focus adjustment unit switches at least one of; positions of a plurality of light receiving elements selected for purposes of generating a pair of signal strings for phase difference detection, a width represented by the pair of signal strings, a quantity of light receiving elements to be used when generating the pair of signal strings and whether or not to remove a low-frequency signal from the pair of signal strings.   
     
     
         6 . A focus adjustment device according to  claim 3 , wherein:
 the focus adjustment unit makes a decision, based upon the pattern in the subject image recognized by the recognition unit, as to whether or not the detected phase difference indicates a false focus match.   
     
     
         7 . A focus adjustment device according to  claim 6 , wherein:
 upon deciding that the detected phase difference indicates the false focus match, the focus adjustment unit again detects the phase difference based upon the pair of light fluxes forming a smaller opening angle.   
     
     
         8 . A focus adjustment device according to  claim 6 , wherein:
 upon deciding that the detected phase difference indicates the false focus match, the focus adjustment unit reverses a direction along which a focusing lens included in the image forming optical system is driven.   
     
     
         9 . A focus adjustment device according to  claim 6 , wherein:
 if the recognition unit recognizes a nonuniform pattern formed, via each of the plurality of micro-lenses, on the plurality of light receiving elements disposed on the rear side of the micro-lens, and the detected phase difference is equal to or less than a predetermined threshold value, the focus adjustment unit decides that the detected phase difference indicates the false focus match.   
     
     
         10 . A focus adjustment device, comprising:
 a plurality of micro-lenses disposed in a two-dimensional array pattern so as to allow light fluxes, having been transmitted through an image forming optical system that includes a focusing lens, to enter thereat;   a plurality of light receiving elements disposed in correspondence to each of the plurality of micro-lenses at positions at which the light fluxes, having been transmitted through the micro-lens, enter;   a recognition unit that recognizes, based upon light reception outputs from the plurality of light receiving elements, a cyclical pattern in a subject image formed via the plurality of micro-lenses on the plurality of light receiving elements;   a phase difference detection unit that detects, based upon the light reception outputs, a phase difference manifested by a pair of light fluxes having passed through different areas of the image forming optical system; and   the focus adjustment unit that executes focus adjustment for the image forming optical system by driving the focusing lens based upon the phase difference detected by the phase difference detection unit, wherein:   if the cyclical pattern is recognized by the recognition unit, the focus adjustment unit drives the focusing lens along a direction in which cycles in the cyclical pattern are lengthened.   
     
     
         11 . A focus adjustment device according to  claim 10 , wherein:
 the recognition unit executes a Fourier transform on the light reception outputs and recognizes the cyclical pattern in a spatial frequency range.   
     
     
         12 . A focus adjustment device according to  claim 10 , wherein:
 the recognition unit recognizes the cyclical pattern by detecting edges from light reception outputs from the plurality of light receiving elements corresponding to at least one micro-lens among the plurality of micro-lenses.   
     
     
         13 . A focus detection device according to  claim 10 , wherein:
 the recognition unit recognizes the cyclical pattern by calculating sums of light reception outputs from the plurality of light receiving elements corresponding to at least two micro-lenses among the plurality of micro-lenses and comparing the two sums.   
     
     
         14 . A camera equipped with a focus adjustment device according to  claim 3 .