Abstract: This invention relates to a screen system for color reproduction wherein screens differing in angle and screen line spacing from color separation to color separation are utilized in each case in the individual color separations. Special screens are specified, whereof the tolerance ranges are situated at 2.degree. for the angles and at approximately 12% for the screen fineness.

Abstract: A retro-focus type wide angle lens has in succession from an object side a first negative meniscus lens having a convex surface facing the object side, a second positive lens, a third biconvex lens, a fourth negative doublet consisting of a biconvex lens and a biconcave lens, a fifth positive lens, and a sixth positive lens. Although this retro-focus type wide angle lens is formed of six lens groups and seven lens components, its field angle or angle of view is about 66.degree., its aperture ratio is 1:1.6, its total length is very short, the aperture of its first divergent lens group is very small and its various aberrations are satisfactorily compensated for.

Abstract: A process for determining the location and/or the alignment of the axis or point of symmetry of an optical surface of a precision optical element, such as an aspheric lens. A fiducial surface is provided on the element, comprising a surface which has a predetermined location and alignment relative to the axis or point of symmetry of the optical surface of the element. Predetermined light waves are impinged against the fiducial surface. The nature of the fiducial surface is such that the light waves are transmitted or reflected in a manner that is a function of the location and/or the alignment of the fiducial surface. The characteristic transmission or reflection of light waves can be resolved by various conventional optical techniques such as by interferometry, thereby precisely indicating the location and/or alignment of the optical surface.

Abstract: An optical system comprising at least two gradient index lenses further includes spacer means of substantially homogenous substance affixed therebetween to provide increased light throughput by substantial maximization of the optical invariant of the system.

Abstract: An apparatus for converting of zooming photographing to macro photographing and vice versa in a zoom lens assembly comprising a mount securing lens barrel, a convert ring fitted on the periphery of the mount securing, an actuation ring which is fitted on the convert ring, wherein the apparatus comprises a ball retaining groove provided on the mount securing lens barrel, a radial through hole on the convert ring, a ball which is located in the elongated hole so as to move therein, a ball receiving hole provided on the actuation ring, said ball being located between the ball retaining groove and the radial through hole during rotating of the actuation ring for focusing at one zooming end position thereof, to prevent the convert ring from rotating relative to the mount securing lens barrel, said ball coming out of the ball retaining groove when the actuation ring rotates for macro photographing so that the ball comes between the radial through hole and the ball receiving hole to make the convert ring integral wi

Abstract: A zoom lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens group having positive refractive power, the zoom lens system being arranged to be zoomed from the wide position to the teleposition by keeping the second lens group fixed in respect to the image surface and moving the first and third lens groups respectively toward the direction away from the image surface and arranged to be focused on an object at the infinite distance up to an object at a short distance by moving the first lens group only toward the direction away from the image surface, the zoom lens system having a large zoom ratio and being compact in size.

Abstract: An assembly for adapting any of several different models of commercially-available slit lamps (10) into an optic examination unit capable of being used for routine eye examinations and also capable of taking high quality photographs of what is being viewed through an ocular of the slit lamp. The assembly is comprised of an illumination means (30a, 30b, 30c) having both a steady light source (69) and a strobe source (80), a camera support arm (55) for supporting a camera (57) in proper position for taking photographs through an ocular (26a) of the slit lamp, an eyepiece adaptor housing (59) and a camera sleeve (56) adapted to be connected into the lens receiving opening of the camera.To assemble the present invention into a slit lamp, the original light source of the slit lamp is removed and is replaced with the present illumination source. The original eyepiece housing is removed and is replaced with the present eyepiece adaptor housing.

Abstract: The present invention relates to a zoom lens system having a new structure for use with still cameras, which is wide magnification-variable and compact whose zoom ratio is about three times.A positive third lens group of a conventional zoom lens comprising three lens group, i.e. positive, negative and positive is divided into two positive lens groups to thereby decrease the refractive power of each lens group and an airspace therebetween being increased and decreased, whereby enhancing the effect of magnification-variation or rendering it possible to be utilized for correction of aberration.Further, a positive lens group having a weak refractive power is arranged between image planes to effect correction of aberration. As a result, there is obtained a zoom lens system having a new arrangement of refractive power in order of positive, negative, positive, positive and positive.

Abstract: A hand-held keratometer is formed of a handle mounting a circular ring of transparent material having a roughened surface to collect incident light and project a circle of light for use in measuring roundness and, therefore, astigmatism of an eye while being held in the hand of a surgeon, the keratometer carrying indicia to permit the surgeon to radially locate the axis of astigmatism and determine the extent of astigmatism.

Abstract: A photographic lens including a focus ring rotatable between prescribed end limits corresponding respectively with an infinite focus setting and a relatively close focus setting is provided with an adjustable range stop assembly for selectively setting one end limit at a position corresponding with a focus setting at which scenes or events are anticipated by the photographer. In one preferred form, the range stop assembly comprises a selector switch carried by the focus ring for movement of a control pin between stops on the lens housing wherein one of the stops is defined by a plurality of lands at different circumferential positions whereby the permissible range of focus ring rotation is selected in accordance with the position of the control pin.

Abstract: Improvement in a small-size wide angle lens having a refractive power arrangement of so-called telephoto type, which has been demanded to meet the need of miniaturization of cameras. The lens of this type is composed of a front group having a positive refractive power and a rear group of negative meniscus lenses wherein a convex surface thereof is directed towards the image and greatly curved. In accordance with the present invention, there is provided a small-size wide angle lens wherein said rear group comprises two negative meniscus lenses, and the specific conditions are imposed on the lenses of said rear group to thereby make the aperture ratio small and provide well-corrected various aberrations, particularly, coma aberration.

Abstract: A photographic lens including a focus ring rotatable about a lens housing between prescribed end limits to displace a focusing lens element between positions corresponding respectively with relatively long and relatively short focus settings, wherein a range stop assembly is provided for selectively adjusting the end limits at focus settings corresponding with positions at which scenes or events are anticipated by the photographer. In a preferred form, the range stop assembly comprises a pair of axially slidable adjustment sleeves normally biased into locked positions for rotation with the focus ring and respectively supporting control pins extending into cam grooves on a fixed portion of the lens housing to define the end limits of focus ring rotation.

Abstract: An afocal telescope (20) comprises an objective system (21) and an eyepiece system (23) aligned on a common optical axis (19), the objective system (21) forming a real image (24) of radiation received from object space (17) and eyepiece system (23) being arranged to provide a magnified view of the object space scene at a pupil .phi. in image space (18). The eyepiece system (23) is formed by a triplet of lens elements A,B,C of which A and B are positively powered and C is negatively powered. Element C has a concave refractive surface (6) adjacent image (24) and a convex refractive surface (5) which is separated from the adjoining refractive surface (4) of element B by an air space which, in the axial direction, is substantially zero on the axis (19) and which progressively increases in magnitude as the distance off axis increases.

Abstract: A high-performance large aperture ratio telephoto lens system comprising a first lens group having positive refractive power, a second lens group having negative refractive power and a third lens unit having positive refractive power, the large aperture ratio telephoto lens system being arranged to fulfill the conditions shown below and to have the focal length about 200 mm to 300 mm and F number about F2.(1) 0.4f<f.sub.I <0.8f(2) 0.2f<.vertline.f.sub.II .vertline.<0.5f(3) 0.3f<F.sub.III <0.8f.

Abstract: The invention contemplates an operation microscope which incorporates an eye-fixation feature to enable a patient's eye (under microscope observation) to precisely maintain infinity focus and viewing alignment, either with the central axis of the microscope or at desired controllable offset therefrom. Embodiments are shown for incorporation of this feature both as part of the field-illumination optical system associated with the microscope, and otherwise, but nevertheless also utilizing part of the observational optical system of the microscope.

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 reflective afocal beam expander optical system is disclosed for transmitting electromagnetic (EM) energy. The beam expander, in the preferred embodiment, is comprised of a reflective afocal system including a section of a primary parabolic mirror, a section of a secondary parabolic mirror, and a beam splitter. The two mirrors have a common axis of rotational symmetry and a common focus point and the centerline of the incoming EM energy is displaced from the axis of rotational symmetry. The beam splitter is positioned with respect to the primary mirror to receive the edge rays of the EM energy and cause the EM energy to be folded and exit through a window while clearing all optical elements. A viewing system having a viewing axis through the beamsplitter allows a viewer to see through the same window as the exiting EM energy. A second refractive afocal optical system is made integral to the specific laser system being used in order to control beam expansion ratios.

Abstract: An optical read-out lens system for optically recorded disks comprising a first, second, third and fourth lenses in which the first lens is a negative meniscus lens, the second lens is a positive lens, the third lens is a positive lens and the fourth lens is a positive meniscus lens, the optical read-out lens system being arranged that the working distance is long and offaxial aberrations are corrected favorably and, moreover, arranged to be small in size, light in weight and low in price.

Abstract: This invention is directed to a restricted off-axis field optical system having a broad spectral range, which first and second nearly concentric optical subsystems, said subsystems being constructed and arranged with respect to each other so that variation in performance of one subsystem with wavelength substantially balances that of the other. That is, the subsystems are constructed and arranged with respect to each other so that the sum of the refractive power is nearly zero and the sum of the reflective power is also nearly zero.

Abstract: A working distance detecting device for ophthalmic instruments has two annular slits in the illuminating system. One of the annular slits has a light-shading portion of a predetermined width. A light-receiving portion is provided around the object lens so as to receive beams of light reflected at the cornea of the eye to be examined. The working distance can be detected at the light-receiving portion by the image of the light-shading portion of the annular slit.