Abstract: Disclosed are an adaptor lens for increasing a magnification of a scope and a sight comprising the same. The adaptor lens for increasing a magnification of a scope of the present invention comprises: an adapter lens body detachably coupled to a sight main body having an objective lens group; a convex lens part provided in the adapter lens body so as to be disposed in front of the objective lens group; and a concave lens part provided in the adapter lens body and disposed between the convex lens part and the objective lens group.

Abstract: An image processing apparatus calculates the distance in a depth direction of an object in an image by using a plurality of images whose blur amount is different. The image processing apparatus has: an acquisition unit configured to acquire distance range information for designating a range of a distance to be calculated; a determination unit configured to determine a photographing condition of each of images photographed, on the basis of the distance range information; and a calculation unit configured to calculate the distance by using a plurality of images photographed in the respective photographing conditions determined by the determination unit.

Abstract: An optical macro adaptor assembly comprising two or more lens components arranged successively along the optical axis thereof, configured to be mounted in front of the objective lens of a telescope, and acting to reduce the minimum focus distance of the telescope to permit the telescope to be used in environments requiring a close focus. The optical macro assembly can be a Galilean-type optical system of approximately unit magnification with adjustable spacing between the lens elements to allow for focusing.

Abstract: Methods and apparatus for capturing or generating images using multiple optical chains operating in parallel are described. Pixel values captured by individual optical chains corresponding to the same scene area are combined to provide an image with at least some of the benefits which would have been provided by capturing an image of the scene using a larger lens than that of the individual lenses of the optical chain modules. By using multiple optical chains in parallel at least some benefits normally obtained from using a large lens can be obtained without the need for a large lens. Furthermore in at least some embodiments, a wide dynamic range can be supported through the use of multiple sensors with the overall supported dynamic range being potentially larger than that of the individual sensors. Some lens and/or optical chain configurations are designed for use in small handheld devices, e.g., cell phones.

Abstract: A surgical microscope 1 comprises an imaging system 2 providing a magnified multidimensional image of an object 3 disposable in a focal plane 4 of the imaging system 2 along at least one optical imaging path 2a, 2b. The imaging system 2 comprises an objective 5 having at least two lens groups 6, 7, through which the at least one optical imaging path 2a, 2b passes consecutively, and which define the focal plane 4 of the imaging system 2. At least one lens group 6 of the objective is moveable along its optical axis relative to the at least one other lens group 7 of the objective. The objective's first lens group 6 located directly adjacent to the focal plane 4 along the at least one optical imaging path 2a, 2b consists of at least three optical lenses 61, 62, 63 and has altogether a negative optical power.

Abstract: Provided is a camera apparatus including a lens apparatus which is attachable thereto and detachable therefrom, the camera apparatus including: an optical system; and an optical element which is insertable to and removable from an optical path of the optical system, in which: the optical element includes a surface having positive refractive power; and the optical system includes a surface having negative refractive power.

Abstract: A tele-side converter lens including a first unit having a positive refractive power and a second unit having a negative refractive power, in which: the first unit includes one or two positive lenses; the second unit includes one negative lens and one or two positive lenses; and average Abbe constant and partial dispersion ratio of materials of positive lenses constituting the first unit, average Abbe constant and partial dispersion ratio of materials of positive lenses constituting the second unit, an Abbe constant and a partial dispersion ratio of materials of the negative lenses constituting the second unit, combined Abbe constants of materials of the lenses constituting the respective first and second units, focal lengths of the first and second units, a refractive index of a material of a positive lens disposed closest to the object side, and a magnification of the tele-side converter lens are appropriately set, respectively.

Abstract: A wide converter lens that is disposed on an object side of a main lens and changes the viewing angle, wherein the wide converter lens includes: a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, wherein the first lens, the second lens, and the third lens are sequentially ordered from the object side to the image side, and the wide converter lens satisfies the following inequality: 2vd?50 where 2vd is an Abbe number of the second lens.

Abstract: A wide-angle converter lens capable of being detachably mounted on an enlargement side of an imaging lens includes a first optical element, at least one optical element having negative refractive power, and at least one optical element having positive refractive power, wherein, when an average value of relative partial dispersions of the first optical element and all optical elements of which the sign of refractive power is the same as that of the first optical element is denoted by ?gF_ave, a relative partial dispersion of the first optical element is denoted by ?gF, and an Abbe number of the first optical element is denoted by ?d, these numerical values satisfy appropriate relationships.

Abstract: A teleconverter lens system is attachable to or detachable from an object side of a main lens system and facilitates performing telephotographing. A photographing apparatus includes the teleconverter lens system. The teleconverter lens system includes: a first lens having a negative refractive power; a second lens having a positive refractive power; a third lens having a negative refractive power; and a fourth lens having a positive refractive power, wherein the first, second, third, and fourth lenses are sequentially arranged from an object side to an image side of the teleconverter lens system. The first and second lenses are cemented together, and the second lens has a meniscus shape in which a convex surface is formed on the object side of the second lens.

Abstract: A wide-angle converter lens capable of being detachably mounted on an enlargement side of an imaging lens includes a first optical element, at least one optical element having negative refractive power, and at least one optical element having positive refractive power, wherein, when an average value of relative partial dispersions of the first optical element and all optical elements of which the sign of refractive power is the same as that of the first optical element is denoted by ?gF_ave, a relative partial dispersion of the first optical element is denoted by ?gF, and an Abbe number of the first optical element is denoted by ?d, these numerical values satisfy appropriate relationships.

Abstract: Optical lens attachments and cameras are disclosed. The attachment comprises a coupling mechanism for mating engagement with at least one of a camera and an optical lens. A barrel is coupled at one end to the coupling mechanism. A negative lens unit is coupled to the other end of elongated barrel. A diopter lens is disposed between the barrel and the coupling mechanism. The coupling mechanism, the diopter lens, and the barrel are aligned with an optical axis. Also disclosed is a double swivel optical system, comprising a negative lens unit, a mirror oriented at an angle to the optical axis of the negative lens unit, a roof prism for rotating incident light rays by 90 degrees and inverting an image, a rotation mechanism permitting rotation of the negative lens unit about a vertical axis, an image rotator comprising a prism that can invert an image, the prism disposed within the image rotator, and another rotation mechanism permitting rotation of the roof prism about an optical axis of the image rotator.

Abstract: An illumination optical system for illuminating an object surface using light from a light source, the illumination optical system includes, a first optical system that includes a movable unit that is movable along an optical axis, said first optical system guiding the light to the object surface and varying an irradiation area on a certain plane, and a second optical system that can be located on and removed from an optical path of said first optical system, the second optical system varies, when located on the optical path of said first optical system, the irradiation area on the certain plane in cooperation with said first optical system, while maintaining a shape of a light intensity distribution on the certain plane, relative to the irradiation area irradiated only by said first optical system.

Abstract: A MEMS-based display device is described, wherein an array of interferometric modulators are configured to reflect light through a transparent substrate. The transparent substrate is sealed to a backplate and the backplate may contain electronic circuitry fabricated on the backplane. The electronic circuitry is placed in electrical communication with the array of interferometric modulators and is configured to control the state of the array of interferometric modulators.

Abstract: A teleconverter lens system is attachable to or detachable from an object side of a main lens system and facilitates performing telephotographing. A photographing apparatus includes the teleconverter lens system. The teleconverter lens system includes: a first lens having a negative refractive power; a second lens having a positive refractive power; a third lens having a negative refractive power; and a fourth lens having a positive refractive power, wherein the first, second, third, and fourth lenses are sequentially arranged from an object side to an image side of the teleconverter lens system. The first and second lenses are cemented together, and the second lens has a meniscus shape in which a convex surface is formed on the object side of the second lens.

Abstract: Attachments for adjusting optical properties of image forming optical systems. An example refocus flip optic adaptor for a night vision goggle may include an adaptor housing for detachably mounting to an objective lens assembly of the night vision goggle and an optical element holder pivotably mounted to the adaptor housing such that a refocus lens (or other optical element) mounted to the optical element holder is selectively positionable in an operative position in which the refocus lens is axially aligned with the objective lens of the night vision goggle and an inoperative position in which the refocus lens and the optical element holder do not affect an image viewable through the night vision goggle. In some example embodiments, the optical element viewing diameter may be substantially the same as objective lens viewing diameter. Example optical elements may affect optical properties such as objective lens focus, optical filtering, and magnification.

Abstract: A MEMS-based display device is described, wherein an array of interferometric modulators are configured to reflect light through a transparent substrate. The transparent substrate is sealed to a backplate and the backplate may contain electronic circuitry fabricated on the backplane. The electronic circuitry is placed in electrical communication with the array of interferometric modulators and is configured to control the state of the array of interferometric modulators.

Abstract: A wide converter lens that is disposed on an object side of a main lens and changes the viewing angle, wherein the wide converter lens includes: a first lens having a negative refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, wherein the first lens, the second lens, and the third lens are sequentially ordered from the object side to the image side, and the wide converter lens satisfies the following inequality: 2vd?50 where 2vd is an Abbe number of the second lens.

Abstract: A switchable magnification lens used to vary the magnification of an image going to be captured by a camera. The switchable magnification lens includes an outer barrel and a switchable magnification unit detachably arranged in the outer barrel and connected to the zoom lens. The image will be magnified while passing through the switchable magnification unit from a first end to a second end, and the image will be shrunk while passing through the switchable magnification unit from the second end to the first end. The switchable magnification unit is able to change its orientation with respect to the outer barrel. The image will be magnified while the first end is away from the camera and the second end is toward the camera, and the image will be shrunk while the first end is toward the camera and the second end is away from the camera.

Abstract: An afocal Galilean attachment lens is disclosed, with the lens comprising, along an optical axis, a first lens group with overall negative optical power and a second lens group with overall positive power. The first and second lens groups are arranged to define a Galilean configuration. The lens also has exit and an entrance pupils with respective diameters DEX and DEN that define a pupil magnification PM=DEX/DEN>4 and in some embodiments PM>10. The afocal Galilean attachment lens also has a length parameter defined LP>200 and in some embodiments LP>700. The extreme length of the afocal Galilean attachment allows for photographing or filming objects that are remote or otherwise hard to photograph while also providing a relatively large depth of field.

Abstract: The extender lens apparatus is detachably attached to an image-forming optical system including a first main lens unit disposed closest to an object and a second main lens unit disposed between the first main lens unit and an image plane. The apparatus includes a first extender lens unit to be inserted in a space closer to the first main lens unit than the second main lens unit, and a second extender lens unit to be inserted in a space closer to the image plane than the second main lens unit. The first extender lens unit has a magnification increasing effect. The apparatus is capable of varying a magnification of the image-forming optical system while maintaining good optical performance without greatly increasing the entire length of the image-forming optical system.

Abstract: A configuration where a first group having a positive refractive power and a positive second group having a positive refractive power are placed sequentially from the object side is basically used. As the first group, a wide-angle first group and a telephoto first group are selectively switched over to be placed on the optical axis, thereby switching over the focal length between the wide-angle side and the telephoto side. Since the configuration in which the first group placed on the object side is switched is employed, adherence of dust or the like to the imaging surface due to the switching of the focal length can be prevented from occurring. Each group is configured by a minimum number of lenses. The whole system has a configuration which has a reduced number of lenses, and which is small and simple.

Abstract: An optical plate for an imaging camera is proposed that is used for further deepening the depth of field. The optical plate is orthogonal to the optical axis, that, in shape, (1) is an optical plate that has the same effective aperture diameter as the imaging camera and is attached in front thereof to deepen the depth of field, and on the incidence plane or exit plane, is equipped with first and second regions in the effective aperture, the first region being on the inside (or is an outside region), with a surface shape curvature that increases going from optical axis to periphery, and a thickness that becomes thicker going from the center to the periphery, that delays the phase of transmitted light more at the periphery than the center, the second region being on the outside (or is an inside region) which has a plane parallel plate shape.

Abstract: A configuration where a first group having a positive refractive power and a positive second group having a positive refractive power are placed sequentially from the object side is basically used. As the first group, a wide-angle first group and a telephoto first group are selectively switched over to be placed on the optical axis, thereby switching over the focal length between the wide-angle side and the telephoto side. Since the configuration in which the first group placed on the object side is switched is employed, adherence of dust or the like to the imaging surface due to the switching of the focal length can be prevented from occurring. Each group is configured by a minimum number of lenses. The whole system has a configuration which has a reduced number of lenses, and which is small and simple.

Abstract: A compact wide converter lens having a small front-lens diameter. When attached to an object side of a main lens system, the wide converter lens provides reduced degradation of aberrations to achieve high optical performance. The wide converter lens includes a first negative lens element disposed most proximate to the object side and whose object-side surface is concave, a second positive lens element disposed at an image side of the first lens element, and a third negative lens element disposed at an image side of the second lens element. The following conditions are satisfied: 1.0<(r1?r2)/(r1+r2)<2.0 ?40<f1/D<?7, wherein r1 and r2 respectively represent curvature radii of the object-side and image-side surfaces of the first lens element, f1 represents a focal length of the first lens element, and D represents a spatial distance between the second and third lens elements.

Abstract: An apparatus includes an optical sensor, a lens system, and an optical stop system. The optical sensor includes photocells each of which has a respective photocell active area in a capture plane. The lens system includes lenses each of which is operable to focus light from a respective subfield of a scene into a corresponding focused beam. The optical stop system includes aperture systems each of which confines a corresponding one of the focused beams to a respective illumination area in the capture plane. In a method, light from respective subfields of a scene is focused into corresponding focused beams. Corresponding ones of the focused beams are confined to respective non-overlapping illumination areas in the capture plane. Optical data is generated from light of the focused beams illuminating the illumination areas. Motion measures indicative of movement in relation to the scene are produced from the optical data.

Abstract: An apparatus includes an optical sensor, a lens system, and an optical stop system. The optical sensor includes photocells each of which has a respective photocell active area in a capture plane. The lens system includes lenses each of which is operable to focus light from a respective subfield of a scene into a corresponding focused beam. The optical stop system includes aperture systems each of which confines a corresponding one of the focused beams to a respective illumination area in the capture plane. In a method, light from respective subfields of a scene is focused into corresponding focused beams. Corresponding ones of the focused beams are confined to respective non-overlapping illumination areas in the capture plane. Optical data is generated from light of the focused beams illuminating the illumination areas. Motion measures indicative of movement in relation to the scene are produced from the optical data.

Abstract: An optical system includes a primary lens group having a central beam path therethrough and including a front lens group and a rear lens group. An anamorphic lens group lies on the central beam path and is positioned between the front lens group and the rear lens group. The anamorphic lens group includes at least one optically powered anamorphic lens that has different enlargements of a light beam along different axes perpendicular to the central beam path. The anamorphic lens group may be mounted on structure that allows it to be removed from the central beam path. An image transceiver is either an image source that directs a light beam through the primary lens group and the anamorphic lens group, or is an image receiver that receives a light beam through the primary lens group and the anamorphic lens group.

Abstract: A converter lens includes a front unit and a rear unit disposed on an image side with respect to the front unit. The front unit has positive optical power and includes two positive lens elements. The two positive lens elements are spaced apart. The rear unit has negative optical power and includes a positive lens element and a negative lens element.

Abstract: A diffraction optical device includes a first diffraction element and a second diffraction element arranged adjacent to each other. One of the first diffraction element and the second diffraction element has a positive power, and the other has a negative power. The first diffraction element reduces the incident angle of light upon the second diffraction element. As a result, a lowering of diffraction efficiency due to the dependency thereof upon the incident angle of light is suppressed, and flare light is prevented from occurring due to diffracted light of unnecessary orders.

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: 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: Provided is a close-up attachment lens suitably applicable to a taking lens body comprising a lens group in charge of a focus function and a lens group in charge of a zoom function completely separate from each other. The attachment lens is mounted on the taking lens body on an object side for close-up shooting. The attachment lens comprises a cemented lens having a negative refractive power as a whole, the cemented lens including a first lens with a convex surface on an object side having a positive refractive power and a second lens with a convex surface on an image plane having a negative refractive power, and a third single lens having a positive refractive power. The taking lens body comprises a focus lens group, a zoom lens group and a master lens group which are disposed independently of one another. The use of the attachment lens allows close-up shooting while maintaining various aberrations in a taking lens in a favorable condition.

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: 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 auxiliary imaging lens is attachable to the main part of zoom lens on the object side; and is configured such that, when capturing an image for a screen having an aspect ratio of 4:3, an effective imaging area having such a size that the screen having an aspect ratio of 4:3 in a case without using the auxiliary imaging lens is just held therein can be secured, and a focal length yielding a field of view area substantially on a par with a field of view area obtained when capturing an image for a screen having an aspect ratio of 16:9 can be set.

Abstract: The object of the present invention is to provide a wide converter lens capable of obtaining an angle of view of about 80° or over and having small appearance of distortion. According to one aspect, a wide converter lens for using by attaching to an object side of a photographic lens includes, in order from the object side, a first positive lens having double convex surfaces, a negative lens unit including at least one negative lens, and a second positive lens having double convex surfaces. The following conditional expression is satisfied: −0.8<(r2+r1)/(r2−r1)<0.8 where r1 denotes the radius of curvature of the object side surface of the first positive lens and r2 denotes the radius of curvature of the image side surface of the first positive lens.

Abstract: An afocal, wide converter lens is provided in order to shorten the focal length of a main lens, thereby shortening the projection distance that is needed to fully illuminate a given screen size when the wide converter lens is attached to the enlarging side of a main lens which functions as a projection lens of a projection apparatus. The wide converter lens is formed of, in sequential order in the direction from the enlarging side to the reducing side of the main lens, a lens element of positive refractive power, at least one lens element of negative refractive power, a positive meniscus lens element having its convex surface on the enlarging side, a negative meniscus lens element having its concave surface on the enlarging side, and a cemented lens of overall positive refractive power. Various conditions are satisfied in order that the wide converter lens does not degrade the optical performance of the main lens.

Abstract: A teleconverter lens is disclosed, for attachment to the enlarging side of a projection lens, wherein aberrations generated by a negative focusing lens group positioned at the enlarging side of the projection lens are not made greater by the teleconverter lens. The teleconverter lens is substantially afocal and is formed of a front lens group having negative refractive power and a back lens group having positive refractive power. The front lens group is formed of two series of combined lenses, each combined lens being a lens element of positive refractive power and a lens element of negative refractive power that are joined. The back lens group is a single combined lens formed of a lens element of positive refractive power that is joined to a lens element of negative refractive power. The teleconverter lens is detachably attachable at its back side to the enlarging side of the projection lens.

Abstract: An afocal, wide converter lens is provided in order to shorten the focal length of a main lens, thereby shortening the projection distance that is needed to fully illuminate a given screen size when the wide converter lens is attached to the enlarging side of a main lens which functions as a projection lens of a projection apparatus. The wide converter lens is formed of, in sequential order in the direction from enlarging side to the reducing side of the main lens, a lens element of positive refractive power, at least one lens element of negative refractive power, a positive meniscus lens element having its convex surface on the enlarging side, a negative meniscus lens element having its concave surface on the enlarging side, and a cemented lens of overall positive refractive power. Various conditions are satisfied in order that the wide converter lens does not degrade the optical performance of the main lens.

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: An attachment lens for attachment to the object side of a main camera lens in order to enable the taking of short distance shots is disclosed. The attachment lens consists of three lens elements of positive, negative, and positive refractive power, in order from the object side. The first lens element and the second lens element are coupled to form a single component. The first lens element has a convex surface on the object side. The second lens element can be of meniscus shape with its convex surface on the object side, plano-concave, or biconcave so long as its curvature matches the image side of the first lens element so that the first lens element and the second lens element may be coupled together to form a single component. Preferably, one or more specified conditions are satisfied in order maintain favorable correction of aberrations.

Abstract: The object of the present invention is to provide a wide converter lens capable of obtaining an angle of view of about 80° or over and having small appearance of distortion. According to one aspect, a wide converter lens for using by attaching to an object side of a photographic lens includes, in order from the object side, a first positive lens having double convex surfaces, a negative lens unit including at least one negative lens, and a second positive lens having double convex surfaces.

Abstract: A teleconverter lens is disclosed, for attachment to the enlarging side of a projection lens, wherein aberrations generated by a negative focusing lens group positioned at the enlarging side of the projection lens are not made greater by the teleconverter lens. The teleconverter lens is substantially afocal and is formed of a front lens group having negative refractive power and a back lens group having positive refractive power. The front lens group is formed of two series of combined lenses, each combined lens being a lens element of positive refractive power and a lens element of negative refractive power that are joined. The back lens group is a single combined lens formed of a lens element of positive refractive power that is joined to a lens element of negative refractive power. The teleconverter lens is detachably attachable at its back side to the enlarging side of the projection lens.

Abstract: An imaging optical system includes a liquid crystal lens including a first body formed of a substantially transparent birefringent liquid crystal member, a second body formed of a substantially transparent birefringent liquid crystal member, and two pairs of electrodes for adding an electric field or a magnetic field onto the first body and the second body. A rear face of the first body is aligned perpendicular to a front face of the second body, the first body and the second body have substantially symmetrical shape against a plane perpendicular to an optical axis and a plurality of optical elements are arranged front and after the liquid crystal lens. The liquid crystal lens has two distinct focal points. The system automatically switches between these focal points, based on the position of the lens with respect to the object being observed.

Abstract: An anamorphic lens attachment to be used in conjunction with a basic lens. The attachment provides a variable anamorphic ratio. The attachment comprises a first lens group having positive refractive power in a first direction, a second lens group having negative refractive power in the first direction, and a third lens group having positive refractive power in the first direction. The second lens group is movably located between the first lens group and the basic lens. The third lens group is located between the second lens group and the basic lens at a fixed distance from the first lens group. The lens groups of the attachment have neutral refractive power in a second direction substantially perpendicular to the first direction.

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: A compact video camera has an image pickup lens system providing a zooming function and a wide angle field of view. The zooming function is performed by a zoom lens, while the wide angle view is achieved via a wide angle converter. The wide angle converter, located closer to the object than the zoom lens, comprises a negative lens, a positive lens, and a reflecting member located between the negative and positive lenses. With the use of the reflecting member, an optical axis of the image pickup lens system extending from the object side to the image side of the camera may be folded. The position at which the optical axis is folded is located closer to the object side than the image side.

Abstract: The invention provides an inexpensive yet lightweight front converter lens system which is improved in terms of performance by use of a diffractive surface. A front converter lens system CL mounted on a subject-side of a master lens system ML to convert its focal length comprises at least two lens groups, each comprising a diffractive surface r.sub.1 or r.sub.2.

Abstract: An eyepiece including a positive first lens element, a negative second lens element, a positive third lens element and a positive fourth lens element is provided. The first, second, third, and fourth lens elements are spaced from one another and arranged in this order from an object side. At least one of the four lens elements is a plastic lens with at least one aspherical surface satisfying the relationships defined by;d.sup.2 x/dh.sup.2 .ltoreq.{c/(1-0.sub.+ 5c.sup.2 h.sup.2).sup.3/2 }: when c >0; andd.sup.2 x/dh.sup.2 .gtoreq.{(c/1-0.sub.+ 5c.sup.2 h.sup.2).sup.3/2 }): when c<0;wherein"c" represents paraxial curvature;"x" represents sag amount; and,"h" represents a height from an optical axis.