Abstract: A zoom lens of the rear focus type is disclosed, including, from front to rear, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, the second lens unit being moved toward the image side when zooming from the wide-angle end to the telephoto end, while moving the fourth lens unit to compensate for the image shift with zooming, and focusing being performed by moving the fourth lens unit. The third lens unit consists of a positive single lens having an aspheric surface. The fourth lens unit includes a negative first lens and a positive second lens, and at least one of lens surfaces of the the first and second lenses is aspherical.

Abstract: Lubricating oil compositions comprising a base oil and a halogen containing ester of phosphoric acid having a specified structure in an amount in the range of from 0.01 to 5 parts by weight relative to 100 parts by weight of the base oil, and lubricating oil compositions further comprising an epoxy compound in an amount in the range of from 0.1 to 5 parts by weight relative to 100 parts by weight of the base oil.

Abstract: For a single lens reflex camera in which an image bearing beam from the photographic objective is reflected by a movable mirror to the finder system, techniques are disclosed that the mirror is made half-reflective, and the transmitted light of the mirror is conducted by a supplementary optical member consisting of, at least, a prism fixedly secured (not movable relative) to the mirror toward an image sensor such as that of a focus detector positioned outside the optical axes of the objective and finder, that the movable mirror is made to take a quite different direction of movement from that to which the reflected beam from the mirror goes, and that as an image pickup device such as CCD is arranged on the optical axis of the objective and behind the movable mirror, the optical characteristics of optical members such as a filter positioned in front of the image pickup device are made equivalent to those of the supplementary optical member.

Abstract: An objective lens comprising a front lens group of positive power followed by a diaphragm, and a rear lens group of positive power axially movable for focusing and comprised of a plurality of members with the strongest diverging surface of concave curvature being arranged toward the front of the lens.

Abstract: In the disclosed finder, an auxiliary lens for changing the magnification power is inserted into the space between an objective lens and an eyepiece. The size of the viewfield frame is simultaneously changed to maintain a constant percentage of the viewfield of the finder. The required rate of change of magnification power that the auxiliary lens must attain to leave the size of the viewfield frame of the finder unchanged can be reduced with the advantage of minimizing the bulk and size of the finder.

Abstract: A photographic optical apparatus including a beam splitter for splitting the optical path of an objective lens, a video pickup device arranged in one of the split optical paths, an optical low pass filter and a color separation filter arranged between the beam splitter and the video pickup device, a prism for changing the direction of the optical path arranged on the other split optical path, an eyepiece arranged on the optical path of the light coming through the prism, a pre-assumed image plane lying between the beam splitter and the prism and an image correcting plate of equal optical thickness to the sum of the lengths of the optical paths of the optical low pass filter and the color separation filter. The plate is arranged between the pre-assumed image plane and the beam splitter. The image correcting plate also serves to split off part of the light and then to guide it to a sensor for light metering.

Abstract: An image pickup apparatus including an electrical image sensor, means for detecting the reflection of a light beam incident on the image sensor, and control means for controlling the operation of the image sensor in accordance with the output of the detecting means so that the output signal of the image sensor has always a proper level.

Abstract: The disclosed finder system is constructed with three prisms. The first prism has a first entrance face, a first reflection face and a first exit face. The second prism has a second entrance face in contact with the first exit face, a second reflection face, and a second exit face. The third prism has a third entrance face in contact with the second exit face, a pair of roof-type reflection faces, a third reflection face in a common plane with the third entrance face, and a third exit face. Light entering through a photographic objective lens reflects from a quick return mirror to a focusing screen on which an image of an object forms. Light from the image reflects from the first reflection face to a direction parallel with an optical axis of the lens. The second reflection face then reflects the light progressively farther away from the optical axis to the pair of roof faces.

Abstract: A conversion type varifocal lens system comprising a master lens which has a front assembly of positive power and a rear assembly of negative power, and a supplementary lens upon insertion into, or removal from, the space between the front and rear assemblies to change the focal length of the entire system.

Abstract: The disclosed finder system includes, from front to rear, a first objective lens of negative power, an optical member having a half-mirror, an eyepiece of positive power and a viewfinder frame arranged near the eyepiece to be observed by the eyepiece with the aid of a reflection from the half-mirror. The finder system satisfies the condition 0.2<d/D<0.6 where D is the air separation between the first objective lens and the eyepiece lens and d is the air separation between the optical member and the eyepiece lens. Thus the first objective lens is exchangeable for a second objective lens of different power from that of the first objective lens to change the magnification of the finder system.

Abstract: A view finder optical system comprises an optical path split mirror which divides a second optical axis from a first optical axis of an objective optical system; a predetermined image forming plane arranged on the second optical axis to have an image coming from the objective optical system formed thereon; a first prism arranged along the second optical axis to bring about reflection twice on the second optical axis and to have the incidence plane thereof and a second reflection plane on the same plane; a second prism which is disposed behind the first prism and is provided with a roof type reflection plane for a first reflection and a reflection plane for further reflecting the second optical axis after the second optical axis is reflected by the roof type reflection plane; and an eye-piece on the second optical axis after it comes out from the second prism.

Abstract: An Albada finder is constructed of an objective lens, a reflection layer, a field-of-view defining frame, and an eyepiece arranged in sequence to provide a mirror image of the frame from the reflection layer to the eyepiece. An optical device of positive power is arranged outside an optical path of the finder. An information source with an information display plate and an illuminator for illuminating the display plate are arranged so that light from the display plate comes through the optical device into the eyepiece as an oblique beam. This shortens the distance from the reflection layer to the eyepiece while achieving a sharp information display.

Abstract: The disclosed range detecting device includes a light emitting source and a first lens system including a number of lens surfaces for projecting a light beam from the source toward an object whose distance from the device is to be measured. A second lens system receives light reflected from the object, and a sensing device provides a signal corresponding to the light received by the second lens system. At least one of the lens surfaces of the first lens system is aspherical, so that the cross section of the reflected light beam impinging on the sensing device is such as to provide a well defined output signal from the device.

Abstract: The disclosed apparatus includes a finder optical system with a liquid crystal display having a plurality of strips of transparent conductive material arranged to display a frame for photography and a light metering area in the field of view of the finder. The liquid crystal display is energized in selected or all areas depending upon which position the objective lens takes when focusing and when zooming, or upon the set value of focal length in an objective lens of zoom type, and upon the in-focus signal of an auto-focus camera. The parallax between the photographic framing of viewfield and the rangefinder view is corrected and the rangefinder spot is displayed in a corrected position.

Abstract: A light measuring device for cameras with a photosensitive element positioned to receive light reflected from a film surface or shutter surface. A collection lens and a diffusion plate having a plurality of stages of different diffusing characteristics are placed between the reflecting surface and the photosensitive element. The light measuring regions can be changed over as the stages of the diffusion plate are selectively put in the path of the light traveling to the photosensitive element.

Abstract: A photographic lens having four components of characteristic forms with the 1st component counting from front being axially moved forward while the 2nd component is moved axially in a given relation to the 1st component as focusing is effected down to shorter object distances.

Abstract: A Gauss type objective having, from front to rear, a 1st lens of positive power convex toward the front, a 2nd lens of positive power also convex toward the front, a 3rd lens of negative power strongly concave toward the rear, a 4th lens of negative power strongly concave toward the front, a 5th lens of positive power strongly convex toward the rear, and a 6th lens having at least one element of positive power, whereby the 4th, 5th and 6th lenses are made axially movable for focusing, and good correction of aberrations is achieved.

Abstract: The photographic lens system disclosed includes a front lens arrangement of positive refractive power with a plurality of components having lens surfaces followed by a diaphragm. A light control includes a number of light absorbing regions on the surface of a component other than the surface adjacent the diaphragm. According to an embodiment, the light control includes a larger optically coaxial region and smaller outer regions surrounding the optically coaxial region. According to another embodiment, a negative refraction lens is arranged behind the diaphragm.

Abstract: A large aperture objective having a shorter physical length than 1.2 times the focal length thereof with an angular field of at least 54.degree. and a diaphragm positioned on the image side of the rearmost lens surface. The objective comprises five elements constituting five components of which the first and second counting from the front are positive meniscus lenses of forward convexity, the third is a negative meniscus lens of rearward concavity, the fourth is a negative meniscus lens of forward concavity, and the fifth is a bi-convex lens with its rear surface of strong curvature. The objective is characterized by fulfilling the following conditions:(1) 0.18 f<D.sub.1 <0.28 f, where D.sub.1 =d.sub.1 +d.sub.2 +d.sub.3 +d.sub.4 +d.sub.5(2) 0.08 f<D.sub.2 <0.13 f, where D.sub.2 =d.sub.7 +d.sub.8 +d.sub.9(3) 0.12 f<d.sub.6 <0.15 f(4) 0.35<(R.sub.1 /R.sub.2)<0.5(5) 0.6<(R.sub.7 /R.sub.8)<0.8(6) .vertline.R.sub.10 /R.sub.9 .vertline.<0.

Abstract: In the disclosed optical distance measuring system, a pair of mirrors spaced from each other along a base line direct light coming from a scene along two optical paths onto reflecting surfaces of a prism positioned between them and through a pair of image forming lenses positioned between the prism and the mirrors so that the prism forms images of the scene on respective photoelectric element arrays. A light baffle in front of the photoelectric element arrays forms an aperture for limiting a desired field of view and includes a light shading projection at the edge of the aperture for preventing light rays from the lenses and outside the desired field of view from impinging upon the arrays.