Focus detector with characteristic point detection

Claim 1

A focus detector of the image correlation type, comprising: imaging optics of the image correlation type for focussing light received from an object upon which a focussing operation is to be performed; light receiver means including a first and a second array of photoelectric transducer elements, each array positioned to receive a different portion of the light passing through said imaging optics, each of said transducer elements producing an output in accordance with the intensity of the light received thereby such that each said array generates a distribution of outputs indicative of the distribution of light received by the individual transducer elements of that array; and arithmetic means for detecting an in-focus condition as a result of an arithmetic operation which is performed on said distributions, said arithmetic operation including the identification of a characteristic point on the distribution of outputs from the first array, the identification of a corresponding characteristic point in the distribution of outputs from the second array, and the detection of an in-focus condition on the basis of the relative position between that particular transducer element in said first array which produces an output corresponding to said characteristic point in said first array and that particular transducer element in the second array which produces an output corresponding to said corresponding characteristic point in said second array.