Focus detecting apparatus

Claim 2

A focus condition detecting apparatus for use in focussing an image of an object, comprising light sensing means including a plurality of light sensing elements spatially distributed in an array in a given plane, each of said elements providing an electrical signal representative of the intensity of light falling thereon, optical means having a central axis and an entrance pupil and positioned to form on said plane, over an optical path through said pupil, a light image of said object, cyclically operated light gating means comprising an opaque mask positioned substantially at said optical means and arranged to be rotated about said central axis of said optical means and further arranged, when so rotated, to cylically block successive spatially separate areas of said entrance pupil of said optical means, to cause light from said object to reach said sensing means cylically from said spatially separate areas and to cause said image and hence the distribution of light to shift cyclically over said array of sensing elements to an extent dependent upon the extent to which said image is out of focus on said plane, said image and light distribution remaining substantially stationary on said array of sensing elements, notwithstanding said cyclic operation of said gating means, when said image is in focus on said plane, and means connected to said sensing elements and responsive to said signals to provide an output signal representative of the condition of focus of said image on said plane.

Claim 3

The focus detecting apparatus as set forth in claim 1 wherein said means responsive to said electrical signals includes means for summing said electrical signals for providing an output signal the magnitude of which is related to the condition of focus of said image.

Claim 4

The focus detecting apparatus as set forth in claim 1 wherein said elements are photo-voltaic cells.

Claim 5

The focus detecting apparatus as set forth in claim 1 wherein said elements are photo-resistors.

Claim 6

An automatic focussing apparatus for use in focussing a principle image of an object, comprising lens means for forming a principle light image of an object on a light sensitive film, light sensing means including a plurality of light sensing elements spatially distributed in an array in a given plane, each of said elements providing an electrical signal representative of the intensity of light falling thereon, optical means having a central axis and an entrance pupil and positioned to form on said plane, over an optical path through said pupil, an auxiliary light image of said object, cylically operated light gating means comprising an opaque mask positioned substantially at said optical means and arranged to be rotated about said central axis of said optical means and further arranged, when so rotated, to cyclically block successive spatially separate areas of said entrance pupil of said optical means, to cause light from said object to reach said sensing means cyclically from said spatially separate areas and to cause said auxiliary image and hence the distribution of light to shift cyclically over said array of sensing elements to an extent dependent upon the extent to which said auxiliary image is out of focus on said plane, said auxiliary image and light distribution remaining substantially stationary on said array of sensing elements, notwithstanding said cyclic operation of said gating means, when said auxiliary image is in focus on said plane, means connected to said sensing elements and responsive to said signals to provide an output signal representative of the extent of said cyclic shifting of said auxiliary image on said plane, and control means connected to receive said output signal and connected to adjust the relative positions of said optical means and said plane, and simultaneously to adjust the relative positions of said lens means and said film, said control means being responsive to said output signal to adjust the relative positions of said optical means and said plane to those at which said output signal indicates a minimum in said cyclic shifting of said auxiliary image on said plane, the corresponding adjusted relative positions of said lens means and said film then being those which cause said principle image to be focussed on said film.

Claim 7

An automatic focussing apparatus for use in focussing a principle image of an object, comprising lens means for forming a principle light image of an object on a light sensitive film, light sensing means including a plurality of light sensing elements spatially distributed in an array in a given plane, each of said elements providing an electrical signal representative of the intensity of light falling thereon, optical means having a central axis and an entrance pupil and positioned to form on said plane, over an optical path through said pupil, an auxiliary light image of said object, cylically operated light gating means comprising an opaque mask positioned substantially at said optical means and arranged to be rotated about said central axis of said optical means and further arranged, when so rotated, to cyclically block successive spatially separate areas of said entrance pupil of said optical means, to cause light from said object to reach said sensing means cyclically from said spatially separate areas and to cause said auxiliary image and hence the distribution of light to shift cyclically over said array of sensing elements to an extent dependent upon the extent to which said auxiliary image is out of focus on said plane, said auxiliary image and light distribution remaining substantially stationary on said array of sensing elements, notwithstanding said cyclic operation of said gating means, when said auxiliary image is in focus on said plane, means connected to said sensing elements and responsive to said signals to provide an output signal representative of the extent of said cyclic shifting of said auxiliary image on said plane, and control means connected to receive said output signal and connected to adjust the relative positions of said optical means and said plane, and simultaneously to adjust the relative positions of said lens means and said film, said control means being responsive to said output signal to adjust the relative positions of said optical means and said plane to those at which said output signal indicates a minimum in said cyclic shifting of said auxiliary image on said plane, the corresponding adjusted relative positions of said lens means and said film then being those which cause said principle image to be focussed on said film.