Abstract: A compact wide-angle photographic lens system with a short overall length comprising a transparent plate member having at least one surface formed as an aspherical surface expressed by the following formulas for which aberrations are corrected favorably.

Abstract: A lens meter includes a target, a collimator lens system for forming an image of the target, a member having a reflecting surface facing the collimator lens system, and an indicating plate disposed at the focal point of the collimator lens system, and at a side opposite to the reflecting member relative to collimator lens system. The reflecting member is placed on the optical axis of the collimator lens system at a side opposite to the target relative to the collimator lens system. The reflecting member is movable along the optical axis and the target is placed at the focal point of the collimator lens system. The lens meter may further include a beam splitter for dividing the optical axes into two optical axes. In this case, the target is placed on one of the divided axes and the indicating member is placedon the other divided axis. Further improvement may be attained by providing in a suitable arrangement two polarizing plates and a quarter-wave plate.

Abstract: A front zoom system and a rear zoom system are coupled in said order from an object side, wherein said rear zoom system comprises a fixed positive lens group, a negative compensator lens group in which its first plane has its convex plane facing an object side and its last plane has its concave plane facing an image side, a negative variator lens group in which the lens group itself is virtually achromated, and a fixed relay lens group, being positioned in the order given from an object side. While the magnification variation range is enlarged by consecutively performing the zooming operation of the front zoom system and the zooming operation of the rear zoom system, aberrations at that time are satisfactorily corrected. The focal distance of the variator lens group is made short in comparison with that of the compensator lens group, thus the amount of shifting of this lens group is reduced for making the rear zoom system compact.

Abstract: In a wide angle lens system, there are arranged, in succession from the object side toward the image side, a divergent first lens group having its surface of smaller curvature facing the object side, a divergent, meniscus, second lens group having its convex surface facing the object side, the first and second lens groups defining therebetween a divergent, meniscus-shaped air chamber having its convex surface facing the object side, a convergent, meniscus, third lens group consisting of a plurality of lenses, a convergent, meniscus, fourth lens group consisting of a plurality of lenses, and a divergent, meniscus, fifth lens group having its convex surface facing the image side.

Abstract: An infra red lens of very high aperture greater than F/0.75 specially adapted to transmit a waveband in the infra red range comprises from front to back in the order given (a) at least one positive meniscus element convex towards the front, (b) a negative meniscus element concave towards the front, (c) a positive meniscus element convex towards the front and (d) a positive element having a front surface convex towards the front. In a preferred embodiment there is a single positive meniscus element (a) convex towards the front in front of the negative meniscus element (b) and in another embodiment there are two positive meniscus elements (a) convex towards the front in front of the negative meniscus element (b). The back element (d) which has a front surface convex towards the front may be a meniscus element or may be convex-plano or biconvex.

Abstract: An objective for video disks of two-component three-lens configuration satisfying the following conditions and having high resolving power and large numerical aperture.(1) 1.25 .gtoreq. f.sub.1 /f .gtoreq. 0.85(2) 2 .gtoreq. .vertline.r.sub.2 .vertline./d.sub.1 .gtoreq. 1(3) n.sub.2 - n.sub.3 .gtoreq. 0.2(4) 1.1 .gtoreq. r.sub.4 /f .gtoreq. 0.82(5) 1 .gtoreq. d.sub.2 /f .gtoreq. 0.

Abstract: A retrofocus-type wide-angle photographic lens system having a predetermined airspace in said lens system and arranged to be focused on an object at a short distance and, at the same time, to prevent aggravation of aberrations by moving a rear lens group positioned on the image side of said airspace toward a front lens group positioned on the object side of said airspace.

Abstract: A parfocal low-magnification microscope objective lens system comprises, in succession from the object side, a positive first lens member, a negative second lens member and a positive third lens member. The first lens member has its concave surface facing the object; the second lens member includes at least one negative meniscus lens component with its concave surface facing the object; and the third lens member includes a positive lens component with that surface thereof sharper in radius of curvature facing the image plane side. The lens system satisfies the following four conditions: d.sub.A <f.sub.A <d.sub.A + .vertline.f.sub.B .vertline.; d.sub.A <d.sub.B ; .vertline.f.sub.B .vertline.<.vertline.f.sub.A .vertline.; and .vertline.d.sub.B .vertline.>.vertline.f.sub.B .vertline.; where f.sub.A and f.sub.B are the focal lengths of the first and the second lens member, respectively, d.sub.

Abstract: An optical interferometer, particularly for use in measurements of length, employs a light transmissive splitting cube which is provided with three beam splitting faces in parallel to each other. A light bundle entering the splitting cube is split into two partial light bundles.After passage of an optical path within the splitting cube both partial light bundles interfere with each other and produce an interference pattern. Light portions of said interference pattern interfere with each other after having passed separate light paths. Both interference patterns so produced are 90.degree. phase-shifted relative to each other. This phase shift permits a unique determination of direction in variations of length.

Abstract: A retrofocus type wide angle objective lens comprising a negative lens group N and a positive lens group P having a diaphragm therein arranged in this order from the object side, said negative lens group N being constructed from a divergent front lens group F and a rear lens group R. When the lens is focused to a close object, only the rear lens group R located in the divergent light bundle from said front lens group F is moved in a different manner from that in which the other lens groups are moved in unison to effect good correction of aberrations in close photography.

Abstract: An extremely high speed wide angle objective lens system, wherein a reducing Newtonian finder telescope is arranged in front of an objective lens group which produces a real image on an image plane. Rules or conditions are stated, and several specific examples are given. In many of the examples, the back focus distance is relatively large, thus making the lens system suitable for use with a mirror reflex camera where room is needed for swinging the reflex mirror.

Abstract: A system for adding or subtracting in real-time image detail of first and second images. In a first embodiment a plane parallel reflective image shear plate superimposes a first radiation beam carrying the first image with a second radiation beam carrying the second image to achieve exact registration of similar image detail. Depending upon the phase difference between the first and second beams, the beams either destructively or constructively interfere. Constructive interference results in amplitude addition of image detail in the first and second images. Destructive interference results in an image having only image detail which is different between the first and second images. A second embodiment adds a plane parallel source shear plate to the structure of the first embodiment, which results in several significant advantages. In the second embodiment radiation from a light source is first directed against the source shear plate which shears the radiation to derive the first and second radiation beams.

Abstract: There is disclosed an evaluating circuit for use with a photoelectric transducer and an electronic photometer. The photometer comprises indicators, all of which are variable, and comprises a combining device arranged to combine by an inverse computing operation.

Abstract: A system for monitoring the optical figure of a surface utilizes an interferometer and a source of light to provide a measuring beam and a reference beam. Reflective spots are mounted respectively at a number of sample points on the surface and the measuring beam of light is focussed by optical means to provide an image field that includes the reflective spots which are oriented to reflect light from the measuring beam back to the optical means to form a conjugate image of the field of spots on light intensity detectors. The reference beam, whose path length is modulated, is combined with the light reflected from the spots to the detectors. There are separate detector elements for measuring the intensity of the combination of reference beam light and measuring beam light reflected from at least two different spots at one time.

Abstract: A wide angle lens which is designed to achieve miniaturization without sacrificing optical quality is disclosed.

Abstract: An objective of variable focal length affording an aperture ratio of about 1:1.0 to 1:1.4 for narrow film projectors and microscopes comprising at least six lens members separated by air spaces, characterized by the following construction and arrangement of the lens members:A. a first lens member confronting the longer conjugate or the projection screen, respectively, said first lens member having dispersing power and the surface thereof with the larger radius of curvature confronts the film or the shorter conjugate respectively;B. a second displaceably arranged lens member having collective power and containing outer surfaces of approximately the same radii of curvature;C. a third collecting lens member having differently curved outer surfaces, wherein the surface confronting the shorter conjugate or the film, respectively, possesses the larger radius of curvature and separated from the lens surface of the following fourth lens member by a small air space;D.

Abstract: A negative meniscus lens, a biconvex lens, a cemented biconcave lens, a cemented positive meniscus lens, a positive meniscus lens, and a positive lens arranged from the front to rear in this order constitute a retrofocus lens having a large diameter and short length with reduced aberrations. The air separation between the first lens and the second lens is designed to be longer than 0.45f and shorter than 0.75f to make the overall length of the lens system small without extremely increasing the refractive power of the first lens. The ratio of the radius of curvature of the front face of the second lens to that of the rear face thereof is designed to be greater than 0.33 and less than 0.6 to compensate for the spherical aberration and coma due to the first lens. The cemented face of the cemented biconcave lens located behind the second lens is designed to be convex to the rear.

Abstract: A wide angle lens which is designed to achieve miniaturization without sacrificing optical quality is disclosed.

Abstract: A continuously variable anamorphic lens containing two sets of four elements between which is placed two achromatized prisms. The anamorphic magnification is varied by the tilting of the prisms.

Abstract: A system and method provides electro-optical in situ measurements of the mass per unit volume of particulate matter suspended in a fluid medium. A beam of electromagnetic radiation is directed through a portion of the medium and radiation back-scattered from an optically defined volume thereof is detected and utilized to provide an indication of the mass of the particles per unit volume of the medium. The beam is preferably a periodically interrupted beam of substantially monochromatic light having a wavelength of the order of magnitude of the mean diameter of the particles of interest. In one embodiment, the d.c. component of the detection signal is filtered out to eliminate the effect of any background radiation.