Abstract: A zoom lens having two groups of lens components including from the object side a positive group and a negative group. The positive group includes two lens units, a weak unit, and a positive unit, while the negative group has at least one negative lens component and provides most of the magnification change during zooming.

Abstract: Zoom projection lens systems are provided which have 1) an entrance pupil which remains at a substantially fixed position as zooming takes place, and 2) a operative aperture stop, distinct from the system's physical aperture stop, which moves through lens surfaces as zooming takes place. The fixed entrance pupil allows for efficient coupling to a light source throughout the magnification range of the system. Methods which can be used to design and produce zoom lens systems of this type and which employ a pseudo-aperture stop are also disclosed.

Abstract: A real image zooming viewfinder comprising three optical units with refracting optical power and an additional moving reflective optical unit. Zooming is accomplished by moving one of the refractive optical units and the additional reflective optical unit or by moving the first and the second optical units. The need for field lens is eliminated by having the first and the second unit cooperate to make the finder system telecentric with respect to principal rays at the intermediate image plane.

Abstract: A real image zooming viewfinder comprising three optical units with refracting optical power and an additional moving reflective optical unit. Zooming is accomplished by moving one of the refractive optical units and the additional reflective optical unit. A parallax correction can be achieved by moving laterally a first optical unit with refractive power.

Abstract: A compact high zoom ratio lens comprising from the object end a front positive stationary lens unit, a negative variating lens unit, a positive variating lens unit and a compensate lens unit, the variating lens units and the compensator lens unit being axially moveable to vary the equivalent focal length of said lens, the compensator group having an object magnification change of less than twenty-five percent over the zoom range of the lens.

Abstract: A two lens unit zoom lens of plus, minus configuration where the rear negative group provides the primary variator function and the positive first lens unit consists of a negative sub-unit and a positive sub-unit and where the sub-units may move differentially during zooming.

Abstract: A zoom taking lens for a photographic single lens reflex (SLR) camera. The lens has an air space between elements of the lens, which air space is large enough to accommodate reflective means for directing rays which have passed through elements of the lens in front of the reflective means, to viewfinder means. By being able to accommodate the reflective means within the length of the lens and with the reflective means being axially movable the back focal length of the lens may be much smaller than is the case in a conventional SLR camera in which the reflective means is movable into and out of the back focal length between the rearmost element of the lens and the film of the camera.

Abstract: A compact wide-angle zoom lens with short back focus comprises a forwardmost negative power lens unit movable for focusing and compensation during zooming, followed by a positive power variator lens unit comprising a forward positive power lens sub-unit movable for zooming and a rearward lens sub-unit also movable for zooming.

Abstract: A partially color corrected projection lens having three groups comprising from the image end a first group serving to correct aberrations, a second group supplying essentially all of the positive power of the lens and a third negative group where the second group comprises two positive elements with a negative element therebetween.

Abstract: A wide angle projection lens which comprises from the image end a first lens unit of negative power having at least one aspheric surface, a second positive lens unit comprising at least two elements and a third negative element having an aspheric concave to the image, where the first lens unit provides negative power to the overall lens and serves as an aberration corrector including some field curvature.

Abstract: A compact SLR camera embodies a zoom taking lens and a diagonal reflecting member along the axis of the taking lens that diverts the optical ray path coming through the lens element forwardly thereof to a viewing screen. The reflecting member is movable along the axis of the taking lens in coordination with the corresponding zooming movement of an adjacent lens element so that the reflecting member and the lens element occupy the same location during different stages of zooming; thereby eliminating the long back focus dictated by the fixed location of the reflecting member in conventional SLR cameras.

Abstract: An automatic focusing zoom lens which comprises a first positive group, a second variator group, a third compensator group, and a relay lens including an autofocus detector which receives a portion of the light entering the fourth group and controls a motor which drives the compensator group to maintain focus of the lens as well as compensating or the shift in focal plane due to movement of the variator group to change the equivalent focal length of the lens.

Abstract: A projection lens for a cathode ray tube display which comprises from the image end a first lens unit of relatively weak optical power serving primarily to correct aperture dependent aberrations, a second lens unit of strong positive power permitting decreased equivalent focal length and resulting wide field angle, and a third lens unit having a strongly concave image side surface and serving to correct the Petzval curvature of the surfaces of the other lens units. The second lens unit comprises two elements of overall biconvex shape separated by an air gap. The facing surfaces of the two elements of the second lens unit are of relatively weak optical power and at least one of the surfaces of the two elements of the second lens unit is aspheric to contribute to the corrections provided by said second lens unit.

Abstract: A projection lens for a cathode ray tube display which comprises from the image end, a first group of relatively weak optical power serving primarily to correct aperture dependent aberrations, a second group of strong positive power, and a third negative group having a strongly concave image side surface and which serves as a field flattener and to correct the Petzval curvature of the services of the elements of the other groups. The second group comprises two elements which provide substantially all of the positive power of the lens and which define an air meniscus therebetween with the minor dimension at the optical axis. The optical powers of the second group bear a predetermined ratio and have a minor dimension at the optical axis.

Abstract: The goggles include a pair of optical assemblies, each having two intersecting optical paths, including a see-through path with a large field of view on a straight line of sight to the viewed object, and a folded path which includes an objective lens set, an intensifier which converts visible and infrared light to a visible intensified light, and an eyepiece lens set, arranged in a loop in a plane perpendicular to the see-through path. Infrared and visible light from the viewed object enters both paths. A dichroic prism combiner at the intersection of the paths reflects intensified light from the folded path into the see-through path and transmits all other light. In one embodiment a dichroic prism separator is disposed at the intersection of the paths forward of the combiner for transmitting a portion of the incoming visible light along the see-through path and reflecting the remainder of the incoming light to the folded path.

Abstract: A compact projection lens for a cathode ray tube comprises from the image end, a first group of positive power which corrects aperture dependent aberrations, a second positive group and a third group which corrects for field curvature and distortion. A mirror is inserted between the first and second groups to fold the optical axis.

Abstract: A zoom lens which will continuous close focus to a magnification of 1:4, comprising three groups where the third group from the object end is stationary, the second group moves axially to vary the equivalent focal length, and the first group moves axially in predetermined relation to the second group to compensate for the variation in focal length, and is also independently movable axially to focus the lens.

Abstract: The present invention relates to coilable extensible rules or the like. More specifically, the present invention is concerned with a new and improved optical sensing system for extensible tape rules of the type that provide a visual display of the measurment readings, such as the digital tape rule described in the Hildebrandt et al U.S. Pat. No. 4,161,781, the disclosure of which is incorporated herein by reference.

Abstract: A new and improved zoom lens comprises four groups. The powers of the groups from the object end to the image end are positive, negative, negative, and positive, respectively. The first group is stationery for zooming but moves for close focusing. The second and third groups move in the same direction for zooming.

Abstract: A projection lens for a cathode ray tube comprises three groups. The overall positive power of the lens is provided by the first and second groups. The third group of negative power primarily corrects for Petzval curvature. In one form, the second group comprises a bi-convex element and a positive element. In preferred forms some of the lens surfaces are aspheric.