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A focus detecting device in a single lens reflex camera having a lens system and an optical image splitter for splitting an object image into various partial images disposed at a position optically equivalent to that of a film surface in said single lens reflex camera. An array of photo-electric con

A focus detecting device in a single lens reflex camera having a lens system and an optical image splitter for splitting an object image into various partial images disposed at a position optically equivalent to that of a film surface in said single lens reflex camera. An array of photo-electric conversion devices are arranged into at least two rows, each row having a plurality of photo-electric conversion elements. The rows are disposed symmetrically with respect to a center line. The device includes an image projecting device for projecting the partial images onto the photo-electric conversion arrays. The projecting device has an optical axis which optically corresponds to said center line, the output of said conversion array defined by ##EQU## The output of the conversion array has a maximum value when proper focus is obtained. In the equation: n is the number of said photo-electric conversion elements, p is the parameter of the mutual positional relationship of said photo-electric conversion elements for obtaining output difference, m is the element number of said photo-electric conversion elements, i and i' are outputs corresponding to incident light quantities of photo-electric conversion elements in said rows, and l is an integer defined by 1≤l≤(n-1) and in the range of p.

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1. A focus detecting device in a single lens reflex camera comprising: a lens system, an optical image splitter for splitting an object image into various partial images, said image splitter disposed at a position optically equivalent to that of a film surface in said single lens reflex camera, phot

1. A focus detecting device in a single lens reflex camera comprising: a lens system, an optical image splitter for splitting an object image into various partial images, said image splitter disposed at a position optically equivalent to that of a film surface in said single lens reflex camera, photo-electric conversion means arranged into at least two rows, each row having a plurality of photo-electric conversion elements, said rows being disposed symmetrically with respect to a center line and, image projecting means for projecting said partial images onto said photo-electic conversion elements, said projecting means having an optical axis which optically corresponds to said center line, and signal processing means receiving signals from said photo-electric conversion elements for providing an output value: ##EQU## said output value of said signal processing means having a maximum value when proper focus is obtained, where: n is the number of said photo-electric conversion elements in each row, p is the parameter of the mutual positional relationship of said photo-electric conversion elements for obtaining output difference, m is the element number of said photo-electric conversion elements, i and i' are outputs corresponding to incident light quantities of photo-electric conversion elements in said rows, and l is an integer defined by 1≤l≤(n-1) and in the range of p. 2. A focus detecting device as defined in claim 1, wherein, said image projecting means has image magnification factor in a direction vertical to said center line, which is larger than that in a direction parallel thereto. 3. A focus detecting device defined in claims 1 or 2, wherein said photo-electric conversion means is self-scanning type image sensor. 4. A focus detecting device as defined in claims 1 or 2, wherein said image projecting means is a micro-prism. 5. A focus detecting device as defined in claims 1 or 2 further comprising motor means responsive to the output of said signal processing means for operating said lens system to focus on said object to provide a maximum output of said conversion means. 6. A focus detecting device as defined in claim 5 wherein said signal processing means comprises a control circuit receiving the output of said conversion means, a differential circuit receiving selective outputs of said conversion means in a predetermined order from said control circuit, an absolute value circuit receiving the output of said differential circuit, an integrating circuit for integrating the absolute value output of said absolute value circuit, a sample and hold circuit responsive to said control circuit, and an extreme value detecting circuit, said extreme value circuit providing an output to drive said motor means until the input thereto reaches a maximum value and thereafter terminating the output to said motor means, wherein said lens system is positioned at a position of proper focus when the output of the sample and hold circuit reaches a maximum value. 7. The focus detecting device of claim 1 wherein said signal processing means comprises a control circuit having: first (C) and second (C') enabling registers each having n stages, each of said n stages associated with one of said conversion elements, said first and second enabling registers providing first and second enabling outputs to said conversion elements at first and second selected stages, said first and second enabling registers havng enabling clock inputs whereby said first and second enabling outputs are shifted to adjacent stages in said first and second enabling registers in response to signals at said enabling clock inputs; first (A) and second (A') control registers having n stages each associated with one of said n stages in said first and second enabling registers, said first and second control registers providing first and second control outputs to said associated n stages of said first and second enabling registers, said first and second control registers having control clock inputs whereby said first and second control outputs are shifted to adjacent stages in said first and second control registers in response to signals at said control clock inputs, said control outputs initializing the location of said enabling outputs at the start of a subinterval; said enabling clock inputs receiving signals during said subinterval; control logic for selectively providing signals to said control clock inputs before and after said subintervals; and switch means for delivering the output of first and second conversion elements associated with said first and second selected stages to absolute difference forming and summation means so as to provide said output value. 8. A focus detecing device in a single lens reflex camera comprising: a lens system, a pair of groups of photo-electric conversion elements adjacent to one another and aligned in the form of a pair of closed curves in a plane whose position is optically equivalent to that of a film surface in said single lens reflex camera, said groups each having photo-electric conversion elements d 1, d 2, . . . d n and d 1 ', d 2 ', . . . d n ', and signal processing means receiving signals from said photo-electric conversion elements for providing an output value: ##EQU## said output value having a maximum value when proper focus is obtained, where, n is the number of each group of photo-electric conversion elements in each group, p is the parameter of the mutual positional relation of said photo-electric conversion elements for obtaining output difference, m is the element number of a photo-electric conversion element, i and i' are outputs corresponding to incident light quantities of photo-electric conversion elements in said groups, and l is an integer defined by 1≤l≤(n-1) and in the range of p. 9. A focus detecting device as defined in claim 8, wherein said pair of groups of photo-electric conversion elements are self-scanning type image sensors. 10. A focus detecting device as defined in claims 8 or 9, wherein said output value is further defined as: ##EQU## 11. A focus detecting device as defined in claim 8, further comprising an optical image splitter for splitting an object image into various partial images, said image splitter disposed at a position optically equivalent to that of a film surface in said single lens reflex camera, and image projecting means for projecting said various partial images onto said pair of groups of photo-electric conversion elements adjacent to one another and aligned in the form of a closed curve in a plane in the body of said single lens reflex camera, wherein an output defined by the following expression is detected, said output having a maximum value when proper focus is obtained, ##EQU## 12. A focus detecting device as defined in claim 11, wherein said pair of groups of photo-electric conversion elements are self-scanning type image sensors. 13. A focus detecting device as defined in claim 11, wherein saisd optical image splitter is a micro-prism. 14. A focus detecting device as defined in claims 11, 12, or 13, wherein said output value is further defined as: ##EQU## 15. A focus detecting device as defined in claims 11 or 12 further comprising motor means responsive to said output value of said signal processing means for operating said lens system to focus on said object to provide a maximum output of said conversion means. 16. A focus detecting device as defined in claim 15 wherein said signal processing means comprises a control circuit receiving the output of said conversion means, a differential circuit receiving selective outputs of said conversion means in a predetermined order from said control circuit, an absolute value circuit receiving the output of said differential circuit, an integrating circuit for integrating the absolute value output of said absolute value circuit, a sample and hold circuit responsive to said control circuit, and an extreme value detecting circuit, said extreme value circuit providing an output to drive said motor means until the input thereto reaches a maximum value and thereafter terminating the output to said motor means, wherein said lens system is positioned at a position of proper focus when the output of the sample and hold circuit reaches a maximum value.