Abstract: A telephoto lens unit (1) having a lens barrel that supports a telephoto lens and capable of being mounted on and dismounted from a camera body (16) comprises a front lens barrel section (11) that supports the telephoto lens with the subject side defined as the front, and a rear lens barrel section (13) that can be mounted on and dismounted from the front lens barrel section. The distance from the image-most surface of the telephoto lens to the image formation plane of the telephoto lens is kept sufficiently long. Converter lens units (12, 14) for elongating or shortening the focal distance are mounted on the front lens barrel section (11) instead of the rear lens barrel section (13) to provide interchangeable telephoto lenses for a camera having different focal lengths. Also, an erecting prism unit (15) and an eyepiece unit (17) can be connected instead of the rear lens barrel section to enable the telephoto lens to function as a terrestrial telescope.

Abstract: The disclosed internal focusing large-aperture medium telephoto lens has as lens groups a positive first lens group, a positive second lens group, and a third lens group, in that order from the object side. When focusing on nearby objects, the first lens group and the third lens group have a fixed position relative to the image surface, and the second lens group displaces toward the object side. The second lens group has only one negative lens, and, in order from the object side, has at least a positive lens, a negative lens, and a positive lens. The following expression is fulfilled: ?0.5<(R1+R2) (R1?R2)<?0.1 (wherein, R1: radius of curvature of the object side surface of the negative lens in the second lens group; R2: radius of curvature of the image side surface of the negative lens in the second lens group).

Abstract: Disclosed are a projection lens that has a small size, a simple inner focus structure, a high optical performance, and a wide angle of view of about 75 degrees or more, and a projection display device. A projection lens includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in this order from a magnification side. A fifth lens arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus. The projection lens satisfies the following conditional expression: 3.0<DG12/f<6.0 where DG12 indicates a distance between the first lens group and the second lens group and f indicates the focal length of the entire lens system.

Abstract: It is preferable that an image forming optical system includes in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a subsequent lens group having a positive refractive power as a whole, and that the third lens group includes only a cemented lens having a negative refractive power, which includes a positive lens and a negative lens in order from the object side. Moreover, it is preferable that a cemented surface of the cemented lens in the third lens group has a shape which is convex toward an image side.

Abstract: An image-capture apparatus includes a variable magnification lens, imaging means for converting an image taken by the variable magnification lens into an electrical image signal, and imaging control means. By referring to a conversion coordinate coefficient, the image control means moves a point on the image and outputs the new image signal. In the variable magnification lens, in order from the object side, a first lens group having positive refractive power, a second lens group that has negative refractive power and performs a variable magnification action by shifting on an optical axis, a third lens group having positive refractive power, a fourth lens group that has negative refractive power and a fifth lens group having positive refractive power are arrayed.

Abstract: Provided is a zoom lens system including: in order from an object side to an image side, a first lens unit having a positive refractive power; an aperture stop; and a second lens unit, in which the first lens unit includes a first-a lens unit having a positive refractive power and a first-b lens unit having a negative refractive power which moves along an optical axis in focusing, the first-b lens unit includes at least one negative lens and at least one positive lens, and the following conditional expression is satisfied: 0.020<?gF1?0.6438+0.001682×vd1<0.100, where ?gF1 denotes a partial dispersion ratio of a material of the positive lens, and vd1 denotes Abbe number of the positive lens.

Abstract: An imaging lens includes first to fourth lens units in order from the object side to the image side. The first, third, and fourth lens units have a positive refractive power. The second and fifth lens units have a negative refractive power. During focusing from an object at infinity to a close object, the first, third, and fifth lens units do not move, and the second and fourth lens units respectively move toward the image side and the object side. The fifth lens unit includes a fifth-a lens unit having a negative refractive power which moves in a direction having a component perpendicular to an optical axis to shift a image position, and a fifth-b lens unit having a positive refractive power. Focal lengths of the third lens unit, the entire system of the imaging lens, the fifth-a lens unit, and the fifth-b lens unit are adequately set.

Abstract: Provided is a telephoto lens system. The telephoto lens system includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, which are arranged sequentially from an object side to an image side. Focusing is performed by moving the second lens group along an optical axis. The first lens group comprises (from object to image side) a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface, a positive meniscus lens having a convex surface at the object side, a negative meniscus lens having a convex surface at the object side, and a positive lens having an object side surface whose radius of curvature is greater than that of an image side surface.

Abstract: A telephoto lens having a vibration proof function is provided and includes: in order from an object side of the telephoto lens, a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a third lens group having a positive refractive power. The second lens group is moved along an optical axis thereof to perform focusing. The third lens group includes a 3a-th group having a positive refractive power and a 3b-th group having a negative refractive power in the order from the object side. The 3a-th group is moved in a direction orthogonal to the optical axis to correct an image vibration of a taken image. The telephoto lens satisfies a specific conditional expression.

Abstract: A telephoto lens system includes a positive first lens group, a positive second lens group, a diaphragm, a negative third lens group constituting a focusing lens group, and a positive fourth lens group. The first lens group includes a positive first lens element, a positive second lens element, and a negative third lens element. The second lens group includes a negative or a positive fourth lens element and a positive or negative fifth lens element which are cemented to each other. The third lens group includes a positive or negative sixth lens element and a negative or positive seventh lens element which are cemented to each other. The fourth lens group includes one positive eighth lens element. Upon focusing on an object at infinity to an object at a closer distance, the third lens group is moved toward the image. The telephoto lens system satisfies the following conditions.

Abstract: An optical system for imaging an object on an image acquisition unit includes a first lens unit, a second lens unit, a third lens unit, a fourth lens unit, a fifth lens unit, and a sixth lens unit disposed from the object in the direction of the image acquisition unit. The second lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??gF>0.025. The third lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??gF<?0.0015. The fifth lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: ??gF<?0.005. According to the disclosed system, the secondary spectrum is reduced and a relative aperture is sufficient so that the optical system is usable in a telescopic sight.

Abstract: To provide a lens system advantageous for downsizing a moving group and suitable for large aperture ratio formation and ultra telescopic formation while maintaining an excellent optical function from a long distance to a close range. A first lens group having a positive refracting power, a second lens group having a negative refracting power, a third lens group having a positive refracting power, and a fourth lens group having a negative refracting power are provided in order from an object side. The first lens group includes a first sub group and a second sub group. The second sub group is provided with a refracting power stronger than that of the first sub group and a following condition equation is satisfied. 1.5<f1a/f1b<2.2??(1) where, f1a denotes a focal length of the first sub group and f1b denotes a focal length of the second sub group.

Abstract: At least one exemplary embodiment is directed to an imaging optical system which includes a first lens unit having a positive refractive power and a second lens unit having a negative refractive power. The first lens unit includes a first lens sub-unit including a single lens having a positive refractive power, a second lens sub-unit including a diffractive optical part and having a positive refractive power, and a third lens sub-unit having a negative refractive power. The first to third lens sub-units are disposed in this order from the object side to the image side. The diffractive optical part can be convex towards the object side and the following condition can be satisfied: 0.05<L1/OTL<0.2 where L1 denotes a distance between the first lens sub-unit and the second lens sub-unit and OTL denotes the total optical length.

Abstract: A collapsible type optical unit is described that is capable of moving its optical system between a working position and a retracted position as well as an image-pickup apparatus including the optical unit. The optical unit and the image-pickup apparatus are capable of acquiring lens-position information by detecting a position of a lens barrel supported to be movable with respect to a fixed barrel. The collapsible type optical unit includes a second group lens frame movable along a direction of its optical axis with respect to a fixed ring and rear barrel, and a solid-state image-pickup device provided behind the second group lens frame, in which on the movable second group lens frame, a position-detecting means for detecting a position of the second group lens frame is provided.

Abstract: The purpose is to provide a large-aperture-ratio internal focusing telephoto lens applicable to a wider photographing area by equipping a vibration reduction function capable to satisfactorily correct a camera shake and the like with securing superb optical performance. The large-aperture-ratio internal focusing telephoto lens includes, in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. The second lens group G2 is moved along an optical axis upon changing focus from infinity to a close-range object. The first lens group G1 has at least two cemented lenses and satisfies a given conditional expression. Either one of the cemented lens satisfies a given conditional expression.

Abstract: An optical system includes an optical member made of a solid material being a mixture prepared by dispersing inorganic particles in a transparent medium. The transparent medium and the inorganic particles of the solid material, and the volume ratio of the inorganic particles to the transparent medium are set so that the optical system can appropriately correct aberrations such as chromatic aberrations.

Abstract: An intermediate telephoto lens system includes a positive front lens group, a variable-aperture diaphragm, and a positive rear lens group, in this order from the object. The positive front lens group includes a positive first lens element L1, a positive second lens element L2 and a negative third lens element L3, in this order from the object. The positive rear lens group includes cemented lens elements having a negative fourth lens element L4 and a positive fifth lens element L5, and a positive sixth lens element L6, in this order from the object. The intermediate telephoto lens system satisfies the following condition: 2.0<f/f12<3.0 ??(1) wherein f designates the focal length of the entire intermediate telephoto lens system; and f12 designates the combined focal length of the positive first lens element L1 and the positive second lens element L2.

Abstract: A telephoto lens system of a four-lens-group arrangement includes a negative first lens group, a positive or negative second lens group, a negative third lens group and a positive fourth lens group. The telephoto lens system of the four-lens-group arrangement is constituted by less than six lens elements in total. The positive or negative second lens group is constituted by a positive lens element and a negative lens element which are cemented to each other, in this order from the object. The positive lens element has a convex surface with a larger curvature facing toward the object. The positive or negative second lens group satisfies the following condition: 0.8<f2p/|f2n|<1.4.

Abstract: An image-pickup optical system includes, from the object side to the image side, a first lens unit having positive optical power, an aperture stop, and a second lens unit. A diffractive optical element and a lens composed of extraordinary partial dispersion material are appropriately disposed in the optical system. The image-pickup optical system is capable of reducing the generation of flare and ghosts at the diffractive optical element and effectively correcting chromatic aberration.

Abstract: A telephoto lens is provided and has three lens groups as a whole. A first lens group includes a first positive lens having a meniscus shape and having a convex surface on an object side thereof, a negative lens arranged on an image side of the first positive lens and having a concave surface on the image side thereof, and a second positive lens arranged on the image side of the negative lens and having a convex surface on the object side thereof. Further, the following Condition Equations are satisfied. ?11 designates an Abbe number of the first positive lens, ?12 designates an Abbe number of the negative lens, ?13 designates an Abbe number of the second positive lens.

Abstract: The invention relates to an electronic imaging system wherein an image pickup device is horizontally located while ensuring the space for a reflective member thereby achieving height, length and cost reductions. The imaging system comprises a taking lens and an image pickup device. The taking lens comprises a front lens group G1 consisting of a negative lens component and a positive lens component and having positive refracting power and a rear lens group G2 consisting of a negative lens element and a positive lens element and having positive refracting power, with an aperture stop S interposed between the front lens group G1 and the rear lens group G2. The taking lens satisfies conditions (1) and (2). 2.8<fB/IH<4.5 ??(1) 2<SF<3 ??(2) Here fB is back focus of the taking lens, IH is a length that is half the diagonal length of the effective plane of the electronic image pickup device, and SF is a shape factor for the negative lens component in the front lens group.

Abstract: The present invention discloses an image pickup optical system which has a first lens unit with positive optical power, a second lens unit with negative optical power, a third lens unit with positive optical power, and a fourth lens unit in order from an object side to an image side, where the second lens unit moves toward an image side and the third lens unit moves toward an object side respectively during focusing from an infinite object to a short distance object. The first lens unit has a first lens sub-unit, and a second lens sub-unit in order from an object side to an image side, and corrects a blur of a taken image by moving the second lens sub-unit so as to have a component in a direction orthogonal to an optical axis. Thereby, the present invention realizes the image pickup optical system which can always obtain a favorable image even if a shake of a camera or the like arises.

Abstract: An electronic zoom image input method that enables zooming without declining the resolution by receiving an input image transmitted through a fixed focal distance optical system having a function of compressing the circumferential part of the input image by means of a photo detector with a uniform pixel density and subjecting the received image to image correction and conversion to obtain an output image. Three dimensional image input system is realized by preparing each image input system of both left and right view with this electronic zoom image input method.

Abstract: The present invention provides a high-performance, thin wide-angle lens suitable for imaging elements with high pixel counts. The wide-angle lens includes, from an object side to an image plane side: a first lens group including a first lens having a negative refractive power and a second lens having a positive refractive power; and a second lens group including a third lens having a negative refractive power, a fourth lens having a positive refractive power, and a fifth lens having a positive refractive power. The fourth lens is bonded to the third lens. The fifth lens is formed with at least one of its convex surfaces being an aspherical surface.

Abstract: A telephoto lens system includes a positive first lens group, a negative second lens group and a positive third lens group. Upon focusing, the second lens group moves toward the image, and the telephoto lens system satisfies the following conditions: 1.35<f/f1<1.80 . . . (1); 1.30<|f/f2|<1.85 . . . (2); 0.48<f/f3<0.75 . . . (3) and 0.10<|L2/f2|<0.22 . . . (4); wherein f designates the focal length of the entire telephoto lens system; f1 designates the focal length of the first lens group; f2 designates the focal length of the second lens group; f3 designates the focal length of the third lens group; and L2 designates the distance between the second lens group and the third lens group when an object at an infinite photographing distance is in an in-focus state.

Abstract: A telephoto lens for a grating scale measurement system includes a pair of aspheric lenses that together operate at finite conjugates with minimal spherical aberrations. Identical aspheric lenses provide a subsystem with a magnification of 1×, and a magnifying system typically including one or more negative lens increases the magnification of an intensity pattern to enable accurate measurement of the phase of the intensity pattern.

Abstract: Telecentric projection lenses for use with pixelized panels (PP) are provided. The projection lenses have a negative first unit (U1) which has at least one negative meniscus element (N1) having at least one aspheric surface and a positive second unit (U2) which has at least one positive element (P1) having at least one aspheric surface. The lens' aperture stop (AS) is located between the two units, and a third lens unit (U3) may be used in the vicinity of the aperture stop to improve the correction of axial color. The lenses have small forward vertex distances, small clear apertures, and long back focal lengths which make them particularly well-suited for use in the manufacture of compact projection systems.

Abstract: An intermediate telephoto lens system includes a first lens group and a second lens group. The first lens group includes a first lens element, a second lens element, a third lens element, an aperture stop, cemented lens elements constituted by a fourth lens element and a fifth lens element, and a sixth lens element. The second lens group includes a seventh lens element and an eighth lens element. Upon focusing, only the first lens group moves along the optical axis. The intermediate telephoto lens system satisfies the following condition: (&ngr;′1-1+&ngr;′1-2)/2>102 . . . (1); &ngr;′1-1: the dispersion ratio of the first lens element; &ngr;′1-2: the dispersion ratio of the second lens element; &ngr;′=(nd−1)/(ng−nF); nd: the refractive index of the d-line for each lens element; ng: the refractive index of the g-line for each lens element n the refractive index of the F-line for each lens element.

Abstract: A zoom lens comprising, in the order of an increasing distance from an object; a fixed first lens group (1) having a positive refractive power; a second lens group (2) containing an aspherical surface, having a negative refractive power and being in charge of a variable power action by being moved; a fixed third lens group (3) containing an aspherical surface and having a positive refractive power; and a fourth lens group (4) containing an aspherical surface, having a positive refractive power and moving while following up a moving object point; wherein the surface on the image plane side of a lens positioned closest to the image plane in the third lens group (3) has a concave plane having a strong refractive power with respect to the image plane and a relation, 2.0<L/CL1<2.

Abstract: A variable magnification optical system includes, in order from an object side to an image side, a first lens unit of positive refractive power, a second lens unit of negative refractive power arranged to move along an optical axis during variation of magnification, the second lens unit including, in order from the object side to the image side, a first lens (L21) of negative refractive power and of meniscus form having a concave surface facing the image side, a second lens (L22) of negative refractive power, a third lens (L23) of positive refractive power and a fourth lens (L24) of negative refractive power, a third lens unit of positive refractive power, at least a part of the third lens unit being moved in such a way as to have a component perpendicular to the optical axis to displace an image formed by the variable magnification optical system, and a fourth lens unit of positive refractive power arranged to move along the optical axis during the variation of magnification, wherein the following condition

Abstract: A rear focus type zoom lens has, in succession from the object side, a first lens unit L1 of positive refractive power, a second lens unit L2 of negative refractive power, a third lens unit L3 of positive refractive power and a fourth lens unit L4 of positive refractive power. The second lens unit is moved toward the image plane side to effect a focal length change from the wide angle end to the telephoto end. The fourth lens unit is moved to correct the fluctuation of the image plane resulting from a focal length change and the fourth lens unit is moved to effect focusing. The third lens unit has a stop most adjacent to the image plane side. The surface thereof adjacent to the stop is convex toward the image plane side and aspherical.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit of positive optical power, and a second lens unit of negative refractive power, wherein focusing from an infinitely distant object to a closest object is effected by moving the second lens unit toward the image side along an optical axis, and the second lens unit consists of one negative lens. Further, it is desirable that the following conditions are satisfied: d2 L1(&lgr;)/d &lgr;2>0 d2 T1(&lgr;)/d &lgr;2<0 &ngr;2>30 where L1(&lgr;) is an aberration coefficient of longitudinal chromatic aberration of the first lens unit, T1(&lgr;) is an aberration coefficient of lateral chromatic aberration of the first lens unit, &lgr; is a wavelength of light, and &ngr;2 is an Abbe number of material of the negative lens of the second lens unit.

Abstract: An intermediate telephoto lens system includes a first lens group 1, and a second lens group 2. The first lens group 1 includes a first lens element, a second lens element, a third lens element, an aperture stop, cemented lens elements constituted by a fourth lens element and a fifth lens element, and a sixth lens element. The second lens group 2 includes a seventh lens element, and an eighth lens element. Upon focusing, only the first lens group 1 moves along the optical axis. The intermediate telephoto lens system satisfies the following condition: (&ngr;′1-1 +&ngr;′1-2)/2>102 . . . (1); &ngr;′1-1: the dispersion ratio of the first lens element; &ngr;′1-2 the dispersion ratio of the second lens element; &ngr;′=(nd-1)/(ng-nF); nd: the refractive index of the d-line for each lens element; ng: the refractive index of the g-line for each lens element; nF: the refractive index of the F-line for each lens element.

Abstract: A wide-angle zoom lens includes a front lens unit with positive refracting power and a rear lens unit with negative refracting power so that spacing between the front lens unit and the rear lens unit is changed to thereby vary the magnification of the zoom lens.

Abstract: A lens system has a plurality of lenses, a stop, and a diffractive surface, the entire lens system moves during focusing, and the lens system satisfies the condition of &bgr;≧0.5, where &bgr; is a maximum photographic magnification.

Abstract: A telephoto lens system includes a positive first lens group, a negative second lens group and a positive third lens group.

Abstract: The invention relates to a zoom lens system of two-group construction, one lens for each group, which is less susceptible to aberration variations even upon zooming and can be much more increased in terms of lens aperture and zoom ratio. The zoom lens system of two-group construction comprises, in order from an object side thereof, a first lens group G1 having negative refracting power and a second lens group G2 having positive refracting power and in which a focal length thereof is varied by moving both the lenses while an optical axis separation therebetween is varied. The first lens group G1 consists of one concave lens having a strong concave surface directed toward an image plane side of the zoom lens system and formed of a homogeneous medium, and the second lens group G2 consists of one convex lens formed of a homogeneous medium. A stop S is located between the first lens group G1 and the second lens group G2.

Abstract: A wide-angle zoom lens system having a short optical total length not only at the wide-angle end but also at the telephoto end and a reduced telephoto ratio despite the fact that it has a high zoom ratio, with a view to achieving a reduction in size of cameras. The zoom lens system has a first lens unit G1 of positive refractive power, a second lens unit G2 of negative refractive power, a third lens unit G3 of positive refractive power, and a fourth lens unit G4 of negative refractive power. When the zoom lens system is zoomed from the wide-angle side to the telephoto side, each of the lens units moves toward the object side such that the space between the first lens unit G1 and the second lens unit G2 increases, whereas the space between the third lens unit G3 and the fourth lens unit G4 decreases.

Abstract: The object of the invention is to reduce the size of a camera by the provision of a zoom lens system which has a high zoom ratio and a small telephoto ratio at the wide-angle and telephoto end, and is simple in lens arrangement and reduced in size during lens collapsing. The zoom lens system comprises a positive first lens group G1, a positive second lens group G2 and a negative third lens group G3. For zooming from a wide-angle end to a telephoto end of the system, each lens group moves toward the object side while a spacing between the first lens group and the second lens group becomes wide and a spacing between the second lens group and the third lens group becomes narrow. The first lens group G1 comprises at least one set of a negative lens and a positive lens. The second lens group G2 includes an aperture stop and comprises at least one set of a negative lens and a positive lens. The third lens group G3 comprises one set of a positive lens and a negative lens.

Abstract: A projection lens of the following structure was invented for the purpose of providing a bright projection optical system with the F-number of approximately 2 or lower while maintaining good optical characteristics, in an image display apparatus. The projection lens is constructed of six lens units, a first lens unit L1 of a negative optical power, a second lens unit L2 of a positive optical power, a third lens unit L3 of a positive optical power, a fourth lens unit L4 of a negative optical power, a fifth lens unit L5, and a sixth lens unit L6 of a positive optical power, in the order named from the enlargement conjugate side, and four lens units (L2 to L5) out of the lens units move toward the enlargement conjugate side during zooming from the wideangle extreme to the telephoto extreme.

Abstract: The internal focusing telephoto lens includes a first lens group I of positive refractive power, a second lens group II of negative refractive power and a third lens group III of positive refractive power, arranged in order from an object side. The second lens group II is movable along an optical axis for focusing. The first lens group I includes a first positive lens I-1, a second positive meniscus lens I-2 whose object side surface is convex, a third positive meniscus lens I-3 whose object side surface is convex and a fourth negative meniscus lens I-4 whose object side surface is convex, in order from the object side. At least two of the first positive lens I-1, the second positive meniscus lens I-2 and the third positive meniscus lens I-3 in the first lens group I satisfy the following conditions (1) and (2); 1.55<nI<1.75  (1) 61<&ngr;I  (2) where nI is refractive index and &ngr;I is Abbe number of the lenses in the first lens group I.

Abstract: A rear-focusing telephoto lens system includes a positive front lens group, and a positive rear lens group, in this order from the object The front lens group includes at least two positive lens elements, each of which has a large-curvature convex surface facing toward the object, and a negative lens element having a large-curvature concave surface facing toward the image. The rear lens group includes at least one lens element which has a convex surface facing toward the object, and is positioned at the most object-side in the rear lens group. Upon focusing, only the rear lens group moves along the optical axis, and the lens system satisfies the following condition: 0.5<f/fF<0.8  (1) wherein f designates the focal length of the entire lens system; and fF designates the focal length of the front lens group.

Abstract: An optical system includes positive and negative refractive optical elements and positive and negative diffractive optical elements for diffracting light from the positive and negative optical elements.

Abstract: An optical system having a first positive optical element having an aspherical surface; and a second positive optical element having an aspherical surface. The first and second optical elements are arranged in a Keplerian configuration. The aspheric surface of the second optical element is related to the aspheric surface of the first optical element by a ray-tracing function that maps substantially all of an input light beam that is incident to the first optical element to a collimated output light beam that is output from the second optical element. The input light beam has a first axially-symmetric intensity distribution, such as a Gaussian intensity distribution, and the output light beam has a second axially-symmetric intensity distribution, such as a continuous, sigmoidal intensity distribution. Preferably, the output light beam has a Fermi-Dirac intensity distribution, and the ray-tracing function maps the input light beam to the output beam to a 1/e6 intensity radius of the input light beam.

Abstract: An objective optical system has at least three lens units having positive, negative, and positive optical powers. A fourth lens unit can have either negative or positive optical power.

Abstract: A zoom lens barrel which is an integrated zoom and focus drive type zoom lens barrel that moves lens units on a single zoom line having plurality of focusing sections and plurality of zooming sections, wherein the single zoom line has characteristic that the “rate of change of the relative distance of the two lens units with regard to a barrel rotation angle” in each focusing section becomes smaller in the focusing sections of the telephoto side.

Abstract: An optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power, the second lens unit being moved during focusing, wherein the first lens unit has a diffractive optical element of positive refractive power and a first lens subunit of positive refractive power, and the first lens subunit consists of at least one positive lens and at least one negative lens, the optical system satisfying the following conditions: 0.005<&phgr;D/&phgr;1a<0.

Abstract: A telescope eyepiece comprising a series of single-element lenses in a combination that cancels chromatism. A negative field lens produces chromatism that is partly cancelled by an intermediate positive lens. The resulting red and blue focal points behind the intermediate lens are exactly matched by the same focal points for parallel rays assumed to originate from behind the eye lens passing forward, thus creating an achromatic system that cancels the remaining chromatism. An additional one or two intermediate positive lenses may be added to increase the field of view and reduce the curvature of field. The eyepiece designer can set the distortion of the system to zero, or can adjust it in a range from minor pincushion to minor barrel distortion as desired. Spherical aberration is corrected by the selection of curves for the field lens. Astigmatism is corrected by the spacing of the field lens from the next intermediate lens.

Abstract: An offset reverse telephoto projection lens that is telecentric in modulator space and has an air equivalent back focal distance of at least 3.3 inches and preferably at least 4.0 inches. The lens comprising, from the image side, a first objective lens group 408 having a negative power and a second telecentric lens group having a positive power. The second telecentric lens group 410 is telecentric in object space such that the image of the aperture is focused at infinity and light converges on the object plane perpendicular to the axis of the lens. Embodiments of the lens have a back focal distance to effective focal length ratio of at least 0.86:1, preferably at least 1.2:1, more preferably at least 1.3:1, still more preferably at least 4.08:1, and most preferably 5.0:1. The embodiments described have a field of view between 14 degrees and 73 degrees, have throw ratios of 1.2:1 to 7:1, and an overall length ranging from less than 5 inches to 12.5 inches.

Abstract: An electronic zoom image input method that enables zooming without declining the resolution by receiving an input image transmitted through a fixed focal distance optical system having a function of compressing the circumferential part of the input image by means of a photo detector with a uniform pixel density and subjecting the received image to image correction and conversion to obtain an output image. Three dimensional image input system is realized by preparing each image input system of both left and right view with this electronic zoom image input method.