초록 ▼

A focus detecting system for detecting focusing condition of an image forming optical system to an object. In this system there are produced first and second signals corresponding to imaging conditions of object images at first and second positions on front and rear sides of and at substantially equ

A focus detecting system for detecting focusing condition of an image forming optical system to an object. In this system there are produced first and second signals corresponding to imaging conditions of object images at first and second positions on front and rear sides of and at substantially equal distances from a predetermined focal plane of said optical system, respectively, and another signal corresponding to imaging condition of an object image at third position substantially coincident with said predetermined focal plane. In accordance with these first, second and third signals, a decision is given as to the focusing condition, namely, in-focus, near-focus or far-focus condition, as well as, the distinction between correctly focused condition and considerably defocused condition.

대표청구항 ▼

A focus detecting system for detecting focusing state of an image forming optical system relative to an object, said optical system having a predetermined focal plane, and said focus detecting system comprising: (A) means for detecting imaging states of an object image formed by said optical system

A focus detecting system for detecting focusing state of an image forming optical system relative to an object, said optical system having a predetermined focal plane, and said focus detecting system comprising: (A) means for detecting imaging states of an object image formed by said optical system at first and second positions optically equivalent to before and behind said focal plane of the optical system and at a third position optically equivament to said focal plane, said detecting means producing first, second and third signals corresponding to the imaging states of the object image at said first, second and third positions, respectively; and (B) means for deciding the focusing state of said optical system relative to the object on the basis of said first, second and third signals produced by said detecting means, said deciding means being arranged to form a fourth signal on the basis of said first and second signals and to decide the focusing state by using the fourth signal together with said third signal.