Abstract: An optical magnification adjustment system being capable of minutely correcting magnification. A first lens 1 of plano-convex is installed on the side of an object surface 5, and a second lens 2 of concave-plano is installed on the side of a formed image surface 7. By controlling the center space d between the first lens and the second lens, the image is enlarged or reduced. The radii of curvature R2 and R3 of the convex surface of the first lens and the concave surface of the second lens are respectively set according to the following equations. R2=(1−n1)/&phgr;2 R3=(n2−1)/&phgr;3 where, &phgr;2 and &phgr;3 represent optical power, and n1 and n2 represent refraction indexes, respectively.

Abstract: A camera-attachment lens system includes a positive condenser lens system and a positive image-forming lens system, and satisfies the following conditions: 1.5<fa/fco<2.4  (1) 0.08<DO/fa<0.16  (2) 1.65<Nco  (3) wherein fa: the combined focal length of the condenser lens system and the image-forming lens system; fco: the focal length of the condenser lens system; DO: the distance from the image-forming plane of the objective optical system to the most objective-optical-system side surface of the condenser lens system; and Nco: the refractive index of the condenser lens system.

Abstract: A wide converter lens system includes an assembly of two or more specified kinds of lens units and a meniscus concave lens to be attached in front of this assembly. The frame for this assembly is detachably attachable to a watertight underwater housing containing a camera in a non-airtight, non-watertight manner so as to increase the field angle of the camera. The assembly of lenses includes at least a plano-concave lens with its flat surface facing forward away from the camera and a plano-convex lens with its flat surface facing the camera. In between, there may be any number of lenses such as an achromatic double lens combination for correcting distortions and aberrations of different types. The meniscus concave lens is provided with a sealing mechanism for detachably attaching itself to the front part of the frame of the lens assembly and serves to further increase the field angle of the camera in water.

Abstract: An extender optical system, for insertion between a photographic main lens and a camera body for changing the focal length of the lens system as a whole to the long focus side, is formed of, in order from the object side, a first lens group having negative refractive power, a second lens group formed of a single negative lens, and a third lens group having positive refractive power. The negative lens that constitutes the second lens group is made to move in directions that are normal to the optical axis so as to correct for what would otherwise be blurred images due to vibrations. Various conditions are preferably satisfied so as to ensure high image quality over the entire field of view.

Abstract: A camera-attachment lens system includes a positive condenser lens system and a positive image-forming lens system, and satisfies the following conditions:

Abstract: An adaptor lens is provided for attachment between a lens of a camera and a camera body, in order to provide the camera with adaptor lens attached, a smaller effective screen size than the camera without the adaptor lens attached. The adaptor lens is formed of, in order from the object side, a front lens group and a rear lens group. The front lens group is formed of, in sequential order from the object side, a negative lens element and at least one meniscus lens element with its concave surface on the object side. The rear lens group is formed of, in sequential order from the object side, a positive lens element with a convex surface on the object side, and a negative lens element. Various conditions are, preferably, satisfied in order to maintain favorable correction of axial chromatic aberration and lateral color.

Abstract: Optical adapter for adapting cine-camera objective to video camera, which includes spectral splitter of light into three spectral bands, and three receivers each associated with one spectral band, the three receivers having the same format, the distance between the entrance of spectral splitter and the sensitive surfaces of the receivers being different for three spectral bands. The objective is a single-image focal plane objective for all three spectral bands and has a second given format. The adapter includes first optical device conveying image between the image focal plane of the objective and the sensitive surfaces of the receivers, and second optical device achieving a relative axial offset of the three spectral bands so that the differences in distance are compensated for. The first and second optical devices have overall magnification changing the format of the image of the objective into the receiver common format.

Abstract: A rear conversion lens, for attachment to the rear of a main lens, is formed of only three lens groups of positive, negative, and positive refractive power, respectively, in order from the object side. The first lens group is formed of a first lens element of negative meniscus shape with its convex surface on the object side, and a second lens element of positive refractive power that is biconvex. The second lens group is formed of a third lens element that is biconcave, and a fourth lens element of negative refractive power with a concave surface on the object side. The third lens group is formed of a fifth lens element that is biconvex, and a sixth lens element of negative meniscus shape with its convex surface on the image side. Various conditions are satisfied to facilitate ease of manufacture and to assure good optical performance.

Abstract: An adaptor lens is provided for attachment between a lens of a camera and a camera body, in order to provide the camera with adaptor lens attached, a smaller effective screen size than the camera without the adaptor lens attached. The adaptor lens is formed of, in order from the object side, a front lens group and a rear lens group. The front lens group is formed of, in sequential order from the object side, a negative lens element and at least one meniscus lens element with its concave surface on the object side. The rear lens group is formed of, in sequential order from the object side, a positive lens element with a convex surface on the object side, and a negative lens element. Various conditions are, preferably, satisfied in order to maintain favorable correction of axial chromatic aberration and lateral color.

Abstract: A corrective lens for a rifle scope comprising a removable flexible tubular boot attachable to an end of the scope and having a corrective lens suited to the user to eliminate the wearing of eyeglasses while sighting through the scope. The lens can fit within the boot or be threaded onto the boot by means of a lens cap.

Abstract: A corrective lens for a rifle scope comprising a removable flexible tubular boot attachable to an end of the scope and having a corrective lens suited to the user to eliminate the wearing of eyeglasses while sighting through the scope. The lens can fit within the boot or be threaded onto the boot by means of a lens cap.

Abstract: A method of converting a frame-format in a taking optical system comprises steps of arranging a plurality of lens units constituting the taking optical system except for the lens unit disposed at the object-side end or at the image-side end and determining the configuration of the lens unit disposed at the object-side end or at the image-side end based on the desired frame-format.

Abstract: A reduction optical system for reducing an image without re-forming the image formed by a main optical system, such as a zoom lens system, wherein the lens having the strongest positive optical power within the reduction optical system satisfies the following conditions: −2.5<(rP1−rP2)/(rP1+rP2)<−0.3, and 1.2<&phgr;P/&phgr;s<5.0, where rP1 represents the radius of curvature on the object side of the positive lens, rP2 represents the radius of curvature on the image side of the positive lens, &phgr;P represents the optical power of the positive lens, and &phgr;s represents the optical power of the total system of the reduction optical system.

Abstract: A zoom lens for television broadcasting cameras suitable for both regular and high definition television (HDTV) format cameras is disclosed. The zoom lens is formed of a zoom lens main body having four lens groups and a supportive lens attachment that may be removably inserted in the optical path of the fourth lens group. In order from the object side, the first lens group is stationary when zooming and has positive refractive power, the second lens group has negative refractive power and moves to accomplish zooming, the third lens group may be of either negative or positive refractive power and shifts in position when zooming in order to maintain the image surface at a fixed position, and the fourth lens group is composed of two sub-assemblies which are fixed in position and separated from one another a distance sufficient to enable a supportive lens attachment to be inserted in the light path of the zoom lens when the zoom lens is used for imaging onto an image sensor having HDTV format.

Abstract: An attachment lens optical system for extending a focal length of a camera lens and balancing axial chromatic aberrations of the camera lens comprises, in order from the object side, a first lens group having a negative power single lens element, a second lens group including a cemented doublet of a biconcave lens element and a biconvex lens element, a positive power third lens group including three lens elements, and a negative power fourth lens group including a cemented doublet of two lens elements.

Abstract: A telescopic objective lens system comprises a positive first lens group and a second lens group, in this order from the object. The second lens group comprises a first sub-lens group and a second sub-lens group, wherein the first sub-lens group is combined with the first lens group to be used for correcting axial chromatic aberration, the second sub-lens group is combined with the first lens group to be used for correcting field curvature; and wherein the combination of the first lens group and the first sub-lens group, and the combination of the first lens group and the second sub-lens group can be alternatively selected.

Abstract: In a camera of the kind arranged to obtain an object image through a photo-taking lens at an arbitrary image plane size on a photosensitive surface by using an image plane size varying member, either the nearest shootable distance of the photo-taking lens is arranged to become shorter than the normally nearest shootable distance or the magnification varying range of the power varying part of the photo-taking lens is arranged to be expanded on the wide-angle side, as the diagonal length of the image plane size becomes shorter.

Abstract: An attachment lens satisfactorily corrects aberrations by using a diffraction surface. The attachment lens is installed on an image surface side of a master lens unit (M) serving as a photographic optical system, and it extends a focal length of the master lens unit (M) toward a longer focal length side. The attachment lens has a diffraction surface (D) which is composed of a diffraction grating shaped rotationally symmetrical with respect to an optical axis and which has a negative refractive power with respect to a diffracted light ray of a design order of diffraction. The attachment lens is adapted to satisfy a conditional expression given below when a height of an axial paraxial ray incident upon the diffraction surface, which has the negative refractive power, from an optical axis is denoted as h.sub.D, and a height of a pupil paraxial ray incident upon the diffraction surface, which has the negative refractive power, from the optical axis is denoted as H.sub.D :.vertline.h.sub.D H.sub.D .vertline.>h.

Abstract: An attachment lens optical system equipped with an oscillation isolating feature for extending a focal length of a camera lens comprises, in order from the object side, a negative power first lens group having three lens elements, a negative power second lens group having three lens elements, and a third lens group having two lens elements, at least one of the first to third lens groups being movable in a direction perpendicular to an axis of the attachment lens optical system so as to cancel an image oscillation caused due to a shake of the imaging device.

Abstract: An image magnification apparatus, for use in a video display system that displays an image of an object, comprising a connecting module for connecting the image magnifying apparatus to a lens module of the video display system, and an objective lens system for forming an optical image of the object. The apparatus also includes a conversion optical system for magnifying the optical image formed by the objective lens system. The conversion optical system further includes a first biconvex lens unit having a positive refractive power, a second biconvex lens unit having a positive refractive power, and a third biconcave lens unit having a negative refractive power.

Abstract: An optical apparatus includes an optical unit which is arranged to be inserted into and retracted from an optical path, a fixed tube, and a restricting member which is disposed at the fixed tube and restricts a position of the optical unit in a direction of an optical axis thereof when the optical unit is in a state of being inserted into the optical path.

Abstract: A rear attachment is provided to permit objective lens systems designated for a certain image format to be used for imaging on a smaller image format. Thus, a 35 mm single lens reflex camera lens can be used to create an image on a smaller format CCD array.

Abstract: A telescope includes a master telescope whose aberration has been independently corrected and which has an objective lens and an ocular lens. A rear conversion lens is provided on the image side of the objective lens of the master telescope and is made of a single lens having a concave surface that faces an object side. The rear conversion lens meets the requirements defined by the following relationships: f.sub.o '/f.sub.o >1 and 0.5<(dx.sub.2 /dh.sub.2)/(dx.sub.1 /dh.sub.1)<1.3, wherein "f.sub.o " represents the focal length of the objective lens of the master telescope; "f.sub.o '" represents the resultant focal length of the objective lens of the master telescope and the rear conversion lens; "dx.sub.1 /dh.sub.1 " represents an inclination of an incident surface of the rear conversion lens at an incident point thereof, upon which light is incident at a height h.sub.1 ; "dx.sub.2 /dh.sub.

Abstract: A rear attachment is provided to permit objective lens systems designated for a certain image format to be used for imaging on a smaller image format. Thus, a 35 mm single lens reflex camera lens can be used to create an image on a smaller format CCD array.

Abstract: An afocal optical module simulator (aoms) for use in conjunction with one or two other optical modules to simulate an afocal variator optical system. The aoms is comprised of an optical module having a front and a rear end, and includes a movable negative lens. The front end of the aoms includes a mechanism for securing a front optical module which may include as its rear most element a positive lens system which will be located juxtaposed to, but spaced from, the movable negative lens within the aoms. Similarly, the rear end of the aoms includes a mechanism for securing a rear optical module, which includes as its front most element a positive lens system which will be located juxtaposed to, but spaced from, the movable negative lens within the aoms.

Abstract: The invention is directed to a compact rear converter lens that has a high zoom ratio of the order of 1.7 to 2.0, is corrected in terms of various aberrations in a well-balanced manner, is little affected by production errors, and is made so compact that it can be built in a compact camera. This rear converter lens that has a negative focal length comprises three lenses or a first lens of negative power, a second lens of positive power and a third lens of negative power, conforms to0.3<f.sub.1 /f.sub.3 <1 (1)0.23<d.sub.4 /.SIGMA.d<0.6 (2)where f.sub.1 and f.sub.3 are the focal lengths of the first and third lens, d.sub.4 is the axial air space between the second and third lens, and .SIGMA.d is the axial space from the first to sixth surface of the rear converter lens, and is attached on the image side of a master lens system ML.

Abstract: The rear conversion lens of the present invention is compact and maintains an excellent imaging performance even when it is mounted on a telephoto objective lens the enlargement magnification of whose focal length is relatively high, e.g. about double and whose F-number is of the order of 2-2.8, and moreover does not intercept a light beam even in the fully open state of the aperture. The rear conversion lens of the present invention is an RCL adapted to be mounted on the image side of an objective lens and having negative refractive power for enlarging the combined focal length of itself and the objective lens, and has, in succession from the objective lens side, a first lens unit of positive or negative refractive power, a second lens unit of negative refractive power and a third lens unit of positive refractive power, the first lens unit having a positive lens most adjacent to the object side, and when the air gap between the first lens unit and the second lens unit is D.sub.

Abstract: An attachment lens system comprising, in the order from the object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power; having a negative refractive power as a whole; and adapted in such a manner that magnification thereof is changed by moving at least one of the first lens unit and the second lens unit along the optical axis so as to vary the airspace reserved between these lens units. This attachment lens system composes a lens system having a high vari-focal ratio when combined with a master lens system.

Abstract: An image stabilization optical system for use in the variable magnification optical system having a first lens group followed rearwardly by a zoom section comprising a plurality of lens groups is disclosed, wherein as at least one lens group in the zoom section is made to be a compensating lens group, the optical action of each lens group is properly specified so that if the tilting of the optical system is the same, the amount of compensation movement of the compensating lens group becomes always the same regardless of the image magnification varying position.

Abstract: The present invention provides a focal length changeable lens system which comprises a master lens group of a positive refractive power having at least one negative lens element made of a synthetic resin material; and a rear conversion lens group of a negative refractive power retractably arranged on the image side of the master lens group and having at least one positive lens element made of a synthetic resin material, in order to well compensate the change of back focal length of the lens system due to the change in temperature thereof without increasing the cost of the lens system.

Abstract: A compound zoom lens optical system includes a variable focal length photographing lens consisting of a first lens group having a positive refracting power, and a second lens group having a negative refracting power from an object side in turn. A conversion lens is separably added to an image side of the variable focal length photographing lens. The conversion lens is simultaneously movable along an optical axis to be interlocked with at least one of the first and second lens groups of the variable focal length photographing lens so as to change a synthesized focal length with said variable focal length photographing lens. The variable focal length photographing lens and the conversion lens satisfy the following conditions:-1.5<.PHI..sub.1 /.PHI..sub.2 <-0.8-1.1<.PHI..sub.1 /.PHI..sub.23 <-0.2where .PHI..sub.1 is the refracting power of the first lens group, .PHI..sub.2 is the refracting power of the second lens group, and .PHI..sub.

Abstract: A variable focal length photo-taking optical system includes a photo-taking objective lens, and a conversion lens removably added to the photo-taking objective lens and relatively movable along the optic axis with at least some lens groups of the photo-taking objective lens to change the combined focal length of the photo-taking objective lens and the conversion lens.