1977-03-10
1978-08-01
Hix, L. T.
G03B 300
Patent
active
041046528
ABSTRACT:
A single lens reflex camera having a sharp focus detecting arrangement with one or more photoelectric cell or cells of an outer zone of a light beam entering through a photo-taking lens wholly or in parts and responsive to transition of light distribution change past the point of sharp focus for producing an electrical output signal. The signal is used to provide a display in the field of view of the camera finder, thereby the accuracy of detection of a condition of sharp focus can be improved regardless of the otherwise insufficient total amount of incident light, as the distinctness of the image, or the relative position of the projection paths in an outer zone of the field is changed by a larger amount than that in the central zone. This arrangement may be embodied in such a manner that a reflex mirror which, in its viewing position, deflects the light from the photo-taking lens to a focusing screen glass is made light-permeable to half or full transmittance either in an outer annular zone or in two parts relatively spaced far from each other in symmetry with respect to the optical axis of the lens, and operates with an auxiliary mirror positioned behind the reflex mirror to deflect the light beam or beams passing through the reflex mirror out of the optical axis to the photoelectric cell or cells.
REFERENCES:
patent: 3185059 (1965-05-01), Durst
patent: 3691922 (1972-09-01), Konig et al.
patent: 3953729 (1976-04-01), Hosoe et al.
Hosoe Kazuya
Yokota Hideo
Canon Kabushiki Kaisha
Gellner M. L.
Hix L. T,.
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