Abstract: A telephoto type objective comprising a front lens group and a rear lens group axially spaced apart from each other. The front lens group has a positive refracting power and which remains stationary during focusing. The rear lens group has a negative refracting power and is comprised of two movable lens members for focusing. When the two movable lens members are moved along the optical axis toward an image plane, the telephoto type objective is caused to focus an object at a near distance from its focusing on an object at a far distance with the resulting amount of movement of the rear lens member being larger than that of movement of the front movable lens group.

Abstract: A view finder system for a single lens reflex camera which provides in the field of the finder an image of a photographic information indicator such as a distance adjusting ring, diaphragm adjusting ring and the like movably mounted in the lens barrel which is connected to the camera body. The view finder includes a pentagonal roof prism in combination with supplementary optical means optically connected thereto, said supplementary optical means comprising a sub-prism having an exit face cemented to the front non-reflecting face of the pentagonal roof prism, an entrance face and a reflecting face, and a mirror element spaced apart from the sub-prism. The mirror element is arranged above the sub-prism to face down optically both the indicator and the sub-prism, so that a light beam from the indicator is reflected by the mirror element to the sub-prism and thereby directed through the pentagonal roof prism to provide an image of the indicator in the field of finder.

Abstract: A method and an apparatus is disclosed for detecting the sharpness of the object image suited for optical instruments such as a camera and for adjusting the focus of the optics by means of photoelectric means presenting a non-linear resistance-illumination characteristics such as CdS or CdSe. Such an object image may be formed by means of the optics on the above mentioned photoelectric means presenting the electrodes at both ends along the longer side of a photoelectric semiconductor whose longer side is extremely long as compared with the shorter side as well as on the above mentioned photoelectric means presenting the electrodes at both ends along the shorter side of the photoelectric semiconductor. An object distance measuring system which digitally displays the distance between camera and photographing object when an automatic focusing operation is carried out is also disclosed.

Abstract: The present invention relates to a method and a device for detecting visibility of the image of an object for adjusting the focus of an optical system. The invention is especially suitable to an optical instrument such as camera, using photo-electric conversion elements having non-linear resistance -- intensity of illumination characteristics such as cadmium sulfide CdS or cadmium selenide CdSe, etc. The invention is characterized in that the photo-electric effect of the above mentioned photo-electric conversion elements will have mutually reverse characteristics depending on the properties inherent to the photo-electric conversion elements, to the arrangement of the electrode and the electric circuit, and further on the state of the image of an object formed on said photo-electric conversion elements. An electric circuit to enhance object image visibility is disclosed which makes use of these characteristics.

Abstract: A device for automatic control of the quantity of light from an electronic flash tube including a silicon controlled rectifier connected in series with the flash tube, a circuit for applying a reverse voltage between the main electrodes of said silicon controlled rectifier so as to open said rectifier, and a switching element connected between said reverse voltage applying circuit and said silicon controlled rectifier. Responsive to the output signal from the reverse voltage applying circuit, the switching element short-circuits the gate electrode and cathode of the rectifier. With this arrangement, it is possible to decrease the capacity of a commutation capacitor constituting part of the reverse voltage applying circuit.

Abstract: The present invention relates to a photo-electric conversion element suitable for use in a system for detecting object image visibility and a method for detecting object image visibility employing the same and also relates to a device therefor. The photo-electric conversion element is characterized by having a first electrode at both ends of the direction along with a short side of a photo-semiconductor which has an extremely shorter short side as compared to its long side, and having a second electrode discretely formed at both ends of the direction along with its long side. Further an element with electrical characteristics being non-linear is connected to or formed at each of the above mentioned electrodes.

Abstract: The finder device forms the images of a plural number of photographing information indication bodies, provided on the exterior of the camera in a row extending in a direction other than parallel to one side edge of the focussing screen of the camera, in the neighborhood of the rectangular image of the focussing screen to extend in a row in a direction parallel to such side edge of the focussing screen and closely adjacent this side.

Abstract: The viewfinder includes a pentagonal roof prism having a front non-reflecting surface and a rear light exit surface adjacent an eyepiece. A sub-prism is mounted on the front non-reflecting surface and includes an incident light entry surface, intermediate reflecting surfaces, one of which is substantially coplanar with the front non-reflecting surface of the pentagonal roof prism, and a final reflecting surface arranged to reflect light directly through the front non-reflecting surface and the light exit surface of the pentagonal prism into, or adjacent, the field of view of an operator looking through the eyepiece.

Abstract: An image sharpness detecting system employing two photoconductive cells of different geometry which permits detection of an optimum degree of sharpness of an image formed thereon regardless of variation in the direction of light distribution of the image relative to the electrodes of the cells. Differences between light response characteristics of these two cells due to the different geometry thereof are compensated for by providing optical means such as filter arranged between the cells, whereby the system is made accurately and reliably responsive to variation of light distribution even at low total light levels.

Abstract: This invention relates to a system for automatic focus adjustment of an optical system particularly adapted for use in a photographic camera which utilizes non-linear resistance versus illumination response characteristics which are prominent in photoconductive cells such as cadmium sulfide and cadmium selenide cells. In one embodiment, a pair of photoconductive cells, one of which has a photoconductive surface having elongated side portions which contact the electrodes along the length of the elongated side portions and another cell which has an elongated photoconductive surface and shortened end portions and which contact the electrodes only at the shortened end portions, are arranged so that portions of an image-forming light beam entering through an objective of the camera are directed to the photoconductive surfaces on which similar real images of an object are formed.

Abstract: A system for detecting the distinction of the object image characterized in that respectively on a photoelectric transducing element presenting electrodes on both extremities along the longer sides of a photoelectric semiconductor presenting considerably short sides as compared with the long sides and on a photoelectric transducing element presenting electrodes on both extremities along the shorter sides of a photoelectric semiconductor presenting considerably short sides as compared with the long sides an object image is formed by means of an optics and that the distinction of the above mentioned object image is detected by detecting the electric characteristics variable corresponding to the distinction of the above mentioned object image, of each of the above mentioned photoelectric transducing elements.