Abstract: A retrofocus lens system has a negative first, a positive second and a positive third lens group. The first lens group includes an aspheric first lens, a negative meniscus second and third lenses that are convex on the large conjugate side, and a negative meniscus fourth lens being convex on the small conjugate side. The second lens group includes a positive fifth lens and a sixth lens joined to the fifth lens. The third lens group includes a positive meniscus seventh lens being convex on the small conjugate side, a biconcave eighth lens, a positive ninth lens joined to the eighth lens, a biconvex tenth and eleventh lenses, and an aspheric twelfth lens. The system satisfies 0.8<f2/f3<1.5, 1.6<|f1|/f<2.

Abstract: Compactness of a projection type image display apparatus is realized by achieving miniaturization and wide-angle of a projection lens apparatus while various kinds of aberration are satisfactorily compensated. A first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power are positioned in this order, from a screen side, toward an image display element side, in the projection lens apparatus.

Abstract: A tilt projection optical system that performs enlarged projection from the primary image plane on the reduction side to the second image plane on the enlargement side without forming an intermediate real image while being located at an angled position, said tilt projection optical system has, sequentially from the primary image plane side, a refractive lens group including an aperture; a bending mirror that rotates the optical axis for the optical system after said bending mirror by approximately 90 degrees; and an optical group including at least one reflective surface that has a negative power; wherein the construction is such that the radius of the circle that encompasses all the light rays involved in the image formation on the screen and that is parallel to the surfaces of each lens of the refracting lens group enlarges once and then converges in terms of its radius on the enlargement side from the aperture of the refracting lens group, and wherein the predetermined condition is met.

Abstract: A projection lens having a first lens group of negative refractive power and a second lens group of positive refractive power, in order from the enlarging side of the projection lens. A stop is positioned within a specified distance of the projection lens element surface nearest the reducing side. The second lens group consists of four lens elements of positive, positive, negative, and positive refractive power, in order from the enlarging side. Specified conditions are preferably satisfied in order to make the projection lens compact and to ensure that various aberrations are favorably corrected.

Abstract: Partial objective for illumination of an image field in an illuminating device of a microlithographic projection exposure apparatus, arranged between a aperture plane and an image plane. The partial objective comprises a first lens group and a second lens group with a lens with a first aspheric lens surface. The second lens group has at least a first lens with negative refractive power and at least a second lens with positive refractive power. The maximum field height Yimmax within the image field is at least 40 mm; the image-side numerical aperture is at least 0.15. The distribution of the chief ray angles PF over the field heights Yim within the image field is given by a pupil function PF(Yim), which consists of a linear contribution c1·Yim and a non-linear contribution PFNL(Yim), the non-linear contribution PFNL(Yim) being at least +15 mrad for the maximum positive field height Yimmax.

Abstract: A light-source device comprising: a rod integrator having an injection end and an emitting end; a lens unit for collecting a luminous flux emitted from the emitting end; and, a diaphragm. The rod integrator forms a plurality of imaginary light-source points, each of which virtually emits the luminous flux toward the emitting end. The diaphragm is disposed in the vicinity of a plane on which the lens unit forms the images of the imaginary light-source points, and selectively blocks luminous flux emitted from each of the images of the imaginary light-source points.

Abstract: A projection display apparatus having a light source for generating a white light, a liquid crystal panel for modulating an incident light from the light source, a polarizing plate which is located at a light exiting side of the liquid crystal panel for polarizing a light from the liquid crystal panel passed therethrough and a cooling liquid for cooling at least the liquid crystal panel and the polarizing plate. A projection lens device having plural lens elements which is located at a light exiting side of the polarizing plate is provided for projecting the light passed through the polarizing plate. One of the plural lens elements located nearest the polarizing plate has a negative refractive power in a center region containing an optical axis thereof and has a positive refractive power in a peripheral portion of the center region.

Abstract: The invention relates to an optical device for focusing a substantially elliptical laser beam comprising: means for collimating a substantially elliptical laser beam so to generate a collimated beam of substantially elliptical profile; means for circularizing the collimated beam so to generate a beam of substantially circularized profile; and means for focusing the circularized beam. The device according to the invention allows on one side to achieve better results in terms of increasing the depth of focus and overall efficiency of the system, and on the other side to allow reading of optical codes also when these are tilted with respect to the scan direction of an angle up to 45° (tilt angle).

Abstract: A projection lens for use with LCD panels is provided. The lens has a first lens unit which includes a strong negative lens element having an aspherical surface which provides distortion correction, and a second lens unit which includes a first lens subunit separated by an airspace from a second lens subunit, wherein the first lens subunit has a strong positive power and the second lens subunit has a weaker power. The second lens subunit can include a negative lens element, followed by a positive lens element, followed by a plastic lens element having an aspherical surface. The projection lens has a field of view of at least 35° so that the overall projection lens system has a compact size.

Abstract: A projection lens comprises, successively from the enlargement side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power. A lens part disposed closest to the reduction end in the first lens group is moved on the optical axis so as to carry out a focus adjustment. The projection lens satisfies 0.8<DG12/f<3.0, where DG12 is the distance between the first and second lens groups, and f is the focal length of the whole system.

Abstract: Projection lens systems (13) for use in CRT projection televisions (10) are provided. From the screen side, the systems have three lens units (U1, U2, U3), the first two units (U1, U2) forming a retrofocus lens and the third unit (U3) being associated with the CRT during use and serving to correct field curvature. At its screen end, the first lens unit (U1) has a negative element (E1) which has a screen surface (S1) which is concave to the screen. The second lens unit (U2) has two positive subunits (US1, US2), the first subunit (US1) being a color correcting doublet composed of glass and the second subunit having a positive lens element (E2) at its screen end. The projection lens systems are fully color corrected, have f/#'s of 1.0 for an infinite conjugate, have half fields of view of at least 25°, and are economical to manufacture.

Abstract: Projection lenses and projection lens systems are telecentric between an illumination subsystem and a set of imagers. The lenses and systems can exhibit color fringing correction, uniform imager illumination, athermalization, and component articulation for improved imaging. The lenses and systems may be employed in display apparatuses, such as folded display apparatuses that have decreased footprint size, but long effective projection lengths.

Abstract: Disclosed is an imaging optical system and an image forming apparatus that provide a small-size design and high resolution. An optical system (telecentric optical system) between the composite focus 4d of an imaging surface side and a laser array 1 is divided into a second lens group 4b and a third lens group 4c and the distance D2 between the third lens group 4c and the laser array 1 is shortened, whereby the spread of incident light into the third lens group 4c is reduced and the aperture of the third lens 4c is reduced. Also, the principal light beam 2a of beam 2 from the laser array 1 is bent at two stages, the second lens group 4b and the third lens group 4c, and the distance D1 between the second lens group 4b and the third lens group 4c is increased, whereby the bend of the principal light beam 2a of the laser beam 2 in the second lens group 4b and the third lens group 4c is reduced, with the result that small aberration is obtained.

Abstract: Projection optical systems are provided for use in an exposure apparatus that have a numerical aperture greater than 0.63, a reduced field curvature of pupil at the aperture stop and are able to maintain imaging performance. Further, the present invention avoids degradation in the imaging performance when the numerical aperture is changed.

Abstract: Projection lens for use with pixelized panels are provided which consist of a first lens unit which has a negative power and a second lens unit which has a positive power. The V-values and Q-values of the lens elements of the first and second lens units are selected so that the projection lenses can simultaneously have: (1) a high level of lateral color correction, including correction of secondary lateral color; (2) low distortion; (3) a large field of view in the direction of the image (screen); (4) a telecentric entrance pupil; and (5) a relatively long back focal length.

Abstract: The present invention provides a projection lens for projecting light from a light source onto a screen to form a magnified image, including two joined lenses, each of which includes a negative lens and a positive lens. The difference in the refractive index and the Abbe number between the negative lens and the positive lens in each of the joined lenses and the partial dispersion ratio of the negative lens and the positive lens of the second joined lens are specified. Thus, a large angle of view and a long back focal length can be achieved while satisfying distortion aberrations, telecentric properties and magnification chromatic aberrations.

Abstract: A projector optical system has a reflection-type display panel, an illumination optical system for illuminating the reflection-type display panel, and a projection optical system for projecting the images displayed on the reflection-type display panel onto a screen. The projection optical system has, from the screen side, a front lens unit and a rear lens unit. A light-deriving means for directing illumination light toward the reflection-type display panel is disposed between the front and rear lens units. Additionally, the following condition is fulfilled: 0.2<&phgr;F/&phgr;<0.9 where &phgr;F represents the optical power of the front lens unit of the projection optical system, and &phgr; represents the optical power of the entire projection optical system.

Abstract: A retro focus lens having three lens groups arranged, in order from the longer conjugate length side of the lens, as follows: a negative first lens group G.sub.1, a positive second lens group G.sub.2, and a positive third lens group G.sub.3. The first group G.sub.1 includes, in order from the longer conjugate length side of the lens, a first lens element L.sub.1 of small positive refractive power and made of plastic with an aspherical surface, a second lens element L.sub.2 of negative refractive power that is made of glass and has a concave surface facing the shorter conjugate length side of the lens, and a third lens element L.sub.3 of negative refractive power with a concave surface facing the shorter conjugate length side of the lens, there being no additional lens elements between the first lens element L.sub.1 and the third lens element L.sub.3.

Abstract: An optical device for optically scanning an information plane includes a radiation source for supplying a scanning beam, and an objective system for focusing the scanning beam to a scanning spot on the information plane. The temperature dependence of the objective system can be compensated by a compensator which includes a planoconvex first element and a planoconcave second element arranged between the radiation source and the first element, the convex surface of the first element confronting the concave surface of the second element, and the refractive indices of the first and the second element being equal at the design temperature but having a different temperature dependence.

Abstract: Focusable, color corrected, high performance projection lens systems are provided which include three lens units (U1, U2, U3), the first lens unit being composed of two subunits (U.sub.S1, U.sub.S2). The lens systems can have f/190 's less than 1.0, total fields of as much as 90.degree., low vignetting losses, and MTF values greater than 0.5 at 10 cycles/mm through 0.85 of the full field. By varying the space between the first and second lens units, these performance levels can be maintained as the lens system is focused over a range of conjugates of approximately .+-.7.5% from a center value of about 4 meters. The lens systems can be used in such demanding applications as flight simulators.

Abstract: A projection lens device for extensively projecting an original image being displayed on an image source, such as a liquid crystal panel, upon a screen, comprising in sequence from the screen: a first lens group having a negative refractive power as an entire system thereof, and including at least a meniscus lens of negative refractive power, which has a convex surface toward the screen side; a second lens group having a positive refractive power as an entire system thereof, and including cemented lenses having a negative refractive power, one of which has convex surfaces at both sides and a first Abbe's number and the other of which has concave surfaces at both sides and a second Abbe's number being smaller than the first Abbe's number; and a third lens group having a negative refractive power as an entire system thereof, and including at least a lens which has a concave surface at a center thereof toward the screen.

Abstract: A projection optical unit comprises a frame, a projection lens, a dichroic prism for synthesizing red image light, green image light and blue image light, and three liquid crystal display panels for red, green and blue. A lens mounting portion on which the projection lens is mounted, a prism mounting portion on which the dichroic prism is mounted, and three mounting surfaces on which the three liquid crystal display panels are respectively mounted are formed in the frame. The projection lens, the dichroic prism, and the three liquid crystal display panels are mounted on the frame. The three liquid crystal display panels are mounted through a focus adjusting mechanism comprising a belleville spring and a screw. The two liquid crystal display panels for red and blue are further subjected to CG adjustment (adjustment for matching pixels of the liquid crystal display panels for read and blue with pixels of the liquid crystal display panel for green) by an eccentric screw.

Abstract: A projection lens for use with a pixelized panel (LCD) is provided. The lens has two positive lens units with an aperture stop between them. The optical powers of each of the units are such that f1 is substantially shorter than f2, where f1 and f2 are the focal lengths of the first lens unit and the second lens unit, respectively, the first lens unit being on the system's long conjugate side and the second lens unit being on the short conjugate side. The ratio of f1 to f2 is preferably less than about 0.75.

Abstract: A projection optical system includes, in order from a first conjugate point side of longer distance to a second conjugate point side of shorter distance, a first lens unit in which negative lenses included therein are larger in number than positive lenses included therein, and a second lens unit in which positive lenses included therein are larger in number than negative lenses included therein, wherein design parameters are determined such that an off-axial principal ray intersects an optical axis at a point between the first lens unit and the second lens unit and telecentricity is made on the second conjugate point side, and wherein the second lens unit includes, in order from the second conjugate point side, a negative lens of meniscus form convex toward the second conjugate point side and a positive lens whose both surfaces are convex.

Abstract: The present invention is to a projection lens having three lens groups of positive, negative, and positive refractive power, in order from the enlarging side. The lens is especially suitable for projection televisions that employ a liquid crystal display panel. Because the lens is of the inner focus type, wherein either a single element of the second lens group, or such an element with additional elements of the second lens group that are shifted as a unit during focusing, the focusing mechanism can be small, simple, and fast. Specified conditions are satisfied to ensure that the projection lens is compact and yet has a sufficient back focus to enable other components to be inserted, is telecentric so as to provide an image that does not decrease in intensity at the periphery thereof and provides a bright image with well corrected aberrations.

Abstract: A projection lens for projecting, on a projection screen, an enlargement of an image appearing on a cathode ray tube (CRT) corrects for optical aberrations by minimizing the number of lens elements, and can be manufactured at low cost. The projection lens includes, successively from an image side to an object side, a first lens group comprising a single lens element of generally positive meniscus shape, a second lens group comprising a single positive lens element, a field stop, and a third lens group having a concave surface facing the image side.

Abstract: A first lens group U1 having a positive optical power, a second lens group U2 having a negative optical power and a third lens group U3 having a negative optical power are disposed in the order from a screen end. For focusing action, the first lens group U1 and the second lens group U2 respectively move in a same direction for different quantities, while the third lens group U3 remains fixed. The aperture ratio of projection lens as a whole is 1:1.1, the magnification of projection is in a range of -0.025 to 0.100.

Abstract: An illumination system includes a light source and an optical system for projecting light from the light source to a surface to be illuminated, wherein the optical system includes an optical element having a paraxial power of substantially zero and having an aspherical surface, and the optical element is movable along an optical axis when an illuminance distribution on the surface to be illuminated is to be changed.

Abstract: A retrofocus projection lens system comprising, in order from a large conjugate side a first lens group having a negative refracting power and including a plurality of lenses, a second lens group having a positive refracting power, and a third lens group having a positive refracting power and including a plurality of lenses. The lens of the first lens group which is nearest to the large conjugate side is an aspherical lens, and the lens of the third lens group which is nearest to a small conjugate side is an aspherical lens. The retrofocus projection lens system desirable satisfy the following conditional expressions (1) to (3):1.8<D.sub.1 /f<3.0 (1)1.1<f.sub.2 /f.sub.3 <1.6 (2)1.5<.vertline.f.sub.1 .vertline./f<2.3 (3)where a symbol f.sub.1 designates a focal length of the first lens group, a symbol f.sub.2 designates a focal length of the second lens group, a symbol f.sub.

Abstract: A projection lens for use with LCD or DMD panels is provided. The lens has three lens units, the first unit having a weak power, at least one aspheric surface, a high dispersion negative lens element, and a low dispersion positive lens element, the second lens unit having a positive power, and the third lens unit having a negative power and an overall meniscus shape. The projection lens satisfies the following relationships:0.3>D.sub.23 /f.sub.0 >0.1,.vertline.f.sub.1 .vertline./f.sub.0 >1.3, andBFL/f.sub.0 >0.3where (i) f.sub.0 is the effective focal length of the combination of the first, second, and third lens units; (ii) f.sub.1 is the effective focal length of the first lens unit; (iii) D.sub.23 is the distance between the second and third lens units; and (iv) BFL is the back focal length of the combination of the first, second, and third lens units for an object located at infinity along the long conjugate side of the projection lens.

Abstract: A projection lens for use with LCD or DMD panels is provided. The lens has three lens units, the first unit having a negative power and at least one plastic lens element having two aspheric surfaces, a second lens unit having a negative power or a weak positive power and at least one color correcting doublet, and a third lens unit having a positive power and an aspheric surface either on a glass element or on a weak plastic element. The projection lens has a back focal length to focal length ratio of at least 3.0, the ratio being achieved by arranging the first, second, and third lens units so that:D.sub.12 /f.sub.0 >1.0,D.sub.23 /f.sub.0 >0.7,and1.5<(D.sub.12 +D.sub.23 +BFL)/BFL<4.0where: f.sub.0 is the effective focal length of the combination of the first, second, and third lens units; BFL is the back focal length of the combination of the first, second, and third lens units; D.sub.12 is the distance between the first and second lens units; and D.sub.

Abstract: A projecting optical system includes, in order from the side of a screen, a first lens unit of positive refractive power of retrofocus type and a second lens unit composed of one positive lens, wherein parameters of the projecting optical system are determined such that an off-axial principal ray crosses an optical axis between the first lens unit and the second lens unit, and the following condition is satisfied:0.2<D2f/f<0.95 (1)where D2f is a distance from a vertex of a lens surface facing the screen side of the second lens unit to an original-image display plane, and f is a focal length of the projecting optical system.

Abstract: Negative, positive, and positive lens groups are disposed successively from the larger conjugate length side, and focal length adjustment is effected by the convex lens disposed on the smallest conjugate length side of the first lens group, thereby yielding a long back focus and a telecentric characteristic, decreasing distortion and chromatic aberration, and simplifying the focusing structure. Successively from the larger conjugate length side, a first lens group G.sub.1 having a negative refracting power and including a convex lens L.sub.5 disposed on the smallest conjugate length side, a second lens group G.sub.2 having a positive refracting power and causing a luminous flux diverged by the first lens group G.sub.1 to become substantially afocal, and a third lens group G.sub.3 having a positive refracting power are disposed, and the convex lens L.sub.5 disposed on the smallest conjugate length side of the first lens group G.sub.1 is moved on an optical axis so as to effect focus adjustment.

Abstract: A telecentric projection lens system comprises, in order from the magnifying side to the reducing side, a positive power first lens group including, in order from the magnifying side, at least first and second concave meniscus lens elements and one cemented lens element, a negative power second lens group comprising a concave lens element and a convex meniscus lens element, and a positive power third lens group, and satisfies the following conditions:0.75<f1/f<1.20f2/f<-1.201.20<f3/f<1.70where f is the overall focal length of the telecentric projection lens system at the standard projection distance, f1, f2 and f3 are the focal lengths of the first, second and third lens groups.

Abstract: The invention is directed to a high-resolution high-apertured objective which includes an object plane (1); a first lens group (LG1); a second lens group (LG2) downstream of the first lens group; a beamsplitter (17, 18, 22, P) downstream of the second lens group; a concave mirror (21); a system diaphragm (A) interposed between the beamsplitter and the concave mirror; a third lens group (LG3); the objective defining an image plane and being configured to provide a reduction scale (.beta.) in the range of -0.4 to -0.15 and an image side numerical aperture greater than 0.5. The first and second lens groups (LG1, LG2) are configured to conjointly reduce the sine of the marginal ray angle. The reduction can be up to 40%. Preferably, the second lens group (LG2) can be configured to alone reduce the sine of the marginal ray angle. It is preferable that the sine of the marginal ray angle (sin R.sub.LG1) after the first lens group (LG1) is not less than the sine of the marginal ray angle (sin R.sub.

Abstract: Telecentric retrofocus lenses and projection systems comprising such lenses are disclosed. The lenses are compact and provide a wide field of view (>70.degree.) with effective distortion correction. The lenses comprise, in order from the image side, a first lens group G1, comprising an aspheric lens having a negative focal length, an aperture, and a second lens group having a positive focal length and having a lens that has maximum refractive power among the lenses of the second lens group. Conditions apply to the ratio of the focal lengths of the first and second lens groups and the distance between the aperture and the focal length of the lens within the second lens group having maximum refractive power. The conditions effectively provide compact, wide-field, low-aberration images. Projection systems using these lenses are also disclosed.

Abstract: A projection lens system has a wide angle with small value for back focus, superior telecentric characteristics, and small distortion. The projection lens system includes a first lens group having a negative refractive power and a second lens group having a positive refractive power. The focal length of the entire system, the focal length of the first lens group and the focal length of the second lens group satisfy conditional formulas.

Abstract: A wide angle lens is made of three groups so as to satisfy a predetermined conditional expression concerning abbe number, thereby making it telecentric and yielding no eclipse in its peripheral luminous flux. Also, an apparatus accommodating it is made compact as a whole. This wide angle lens comprises, arranged in the following order from the screen side toward the liquid crystal side, a first lens group composed of a concave lens (L1), whose concave surface having a large radius of curvature is directed toward a smaller conjugate side (liquid crystal panel), and a convex lens (L2); a second lens group composed of one concave lens (L3) and two convex lenses (L4) and (L5); and a third lens group composed of a Fresnel lens (L6) which is disposed near a liquid crystal panel (L7; 4). The abbe number .nu. 1 of the lens L1 which is the concave lens in the first lens group is 57.8, whereas the abbe number .nu. 2 of the lens (L3) which is the concave lens in the second lens group is 25.

Abstract: To use a beam splitting optical system smaller than the conventional beam splitters and to set a longer optical path between a concave, reflective mirror and an image plane. A light beam from an object surface travels through a first converging group to enter a beam splitter, and a light beam reflected by the beam splitter is reflected by a concave, reflective mirror to form an image of patterns on the object surface inside the concave, reflective mirror. A light beam from the image of the patterns passes through the beam splitter and thereafter forms an image of the patterns through a third converging group on an image plane.

Abstract: In the projection optical system that projects an image of the first object onto the second object with a fixed reduction ratio and a projection aligner equipped therewith, said projection optical system comprises, viewed from said first object side, in order of succession, the first group of lenses with positive refractive power, and the second group of lenses virtually consists of afocal system, and the third group of lens with positive refractive power, and if the focal length of the overall system is represented by F, the projection magnification ratio of said projection optical system is represented by B, the distance between said first object and said second object is represented by L, and when a ray from the second object side of said projection optical system that is parallel to the optical axis of said projection optical system is incident on said projection optical system, a distance between a point where an extension on the first object side of said ray intercepts the optical axis and said first ob

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: Magnification correction for small field scanning of large blanks is provided by adding magnification adjusting elements (lenses) to a double pass Wynne-Dyson lens or other type of one-to-one projection lens. The magnification adjusting optical elements includes two pairs of low power lenses, one associated with each of the input and output prisms of a Wynne-Dyson lens. Movement of the magnification adjusting optics provides positive or negative magnification as needed to correct for any expansion or compaction of the blank relative to the reticle (mask) and hence maintain alignment. Further magnification correction is provided by a small velocity relative movement between the reticle and the blank by means of a secondary stage in the scan direction. This corrects for any alignment error in the scan direction and may be used independently of the optical correction technique with any type of projection lens.

Abstract: A wide-projection angle liquid crystal projection lens system including a condensing lens, installed opposite to a light-emitting surface of an image-forming element for emitting image rays to be magnified and projected onto a screen of a projection display system, for converging the image rays incident thereto, a first lens group, installed opposite to a light-emitting surface of the condensing lens, for compensating for chromatic aberration of the image rays converged and emitted from the condensing lens, a second lens group for changing a direction of the image rays emitted from the first lens group, and a third lens group for magnifying the image rays emitted from the second lens group and projecting the magnified image rays to a reflecting mirror. According to the system, the optical axis of the system can be changed over about 90.degree. utilizing the prism provided in the projection lenses, and thus the height and depth of the projection display system is reduced to a minimum.

Abstract: A retrofocus lens system comprises, in order from a large conjugate side: a first lens group having a negative refracting power and including a plurality of lens elements; a second lens group having a positive refracting power; and a third lens group having a positive refracting power. Each of the lens elements of the first lens group has a negative refracting power. Following conditional expressions (1) to (3) are satisfied:1.3<D.sub.1 /f<1.8 (1)0.7 <f.sub.2 /f.sub.3 <1.1 (2)1.1 <.vertline.f.sub.1 .vertline./f<1.6 (3)where D.sub.1 is air gap between the first lens group and the second lens group, f.sub.1 is a focal length of the first lens group, f.sub.2 is a focal length of the second lens group, f.sub.3 is a focal length of the third lens group, and f is a focal length of whole lens system including the first to third lens groups.

Abstract: In a negative first lens group composed of four sheets of lenses and a positive second lens group composed of four sheets of lenses, the lens in each lens group placed closest to the enlargement side is formed as a plastic lens having an aspheric surface, while predetermined conditional expressions are satisfied, whereby various kinds of aberration are made favorable and influence of changes in the plastic lens upon temperature is suppressed. A first lens group comprising a negative first lens (L1) made of a plastic lens having an aspheric surface, a negative second lens (L2), a negative third lens (L3), and a positive fourth lens (L4) and a second lens group comprising, a positive fifth lens (L5) made of a plastic lens having an aspheric surface, a negative sixth lens (L6), a positive seventh lens (L7), and a positive eighth lens (L8) are successively disposed from the enlargement side, while satisfying the following conditional expressions:-2.5<F.sub.1 /F.sub.5 <-0.3,-2.8<FG.sub.1 /FG.sub.2 <-1.

Abstract: A projection apparatus in which in order that an original image, which is compressed in a horizontal direction, may be projected onto a screen at a predetermined location by a master lens, the original image is disposed with the center thereof deviated relative to the optical axis of the master lens and in which an anamorphic lens having an optical axis inclined with respect to the optical axis of the master lens and having refractive power in a horizontal direction is disposed on the screen side of the master lens.

Abstract: A projection lens assembly having an imaging lens group, including a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a Fresnel lens group having a positive refractive power and at least one Fresnel lens surface, in this order from the enlargement side. The projection lens assembly satisfies the relationships 1.4<f.sub.1 /f<2.8, and 1.5<f.sub.2 /f<6.0. In these relationships, f represents the focal length of the whole lens system, f.sub.1 the focal length of the first lens group, and f.sub.2 the focal length of the second lens group.

Abstract: An outwardly divergent and elliptic input laser beam is converted into a collimated and circular laser beam using a single aspheric lens. An input surface of the aspheric lens has a convex hyperbolic spherical cross-sectional surface in a vertical direction normal to an optical axis and a concave spherical cross-sectional surface in a horizontal direction normal to the optical axis. An output surface of the aspheric lens has a planar cross-sectional surface in the vertical direction normal to the optical axis and a convex elliptical cross-sectional surface in the horizontal direction normal to the optical axis.

Abstract: The invention relates to a reduction projection lens system of high resolution which enables chromatic aberration to be corrected, and can be improved in terms of transmittance by making the total thickness of the vitreous material forming said lens system. This reduction projection lens system includes refractive and diffractive optical elements and uses as the light source a spectral light source having a center wavelength of up to 300 nm and a wavelength spectral bandwidth of .+-.0.5 pm to .+-.200 pm such as an ArF or KrF excimer laser. The refractive optical element includes at least one aspheric surface, and the refractive and diffractive optical elements are made of the same vitreous material, e.g., SiO.sub.2. conditions, 0.02<.vertline.d/D.vertline.<0.17 and 0.01<.vertline.h/H.vertline.<0.

Abstract: A projection lens in which a lens unit which may comprise one or two elements is closely coupled at the object end of the lens to a cathode ray tube. At the image end is a lens unit of overall weak optical power which comprises from the image end a first positive element followed by a closely spaced negative element of substantially higher dispersion. Intermediate the object side lens unit and the image side lens unit is a lens unit of substantial optical power supplying substantially all of the positive optical power of the lens. Closely spaced to this power lens unit on the object side is a negative lens element of high dispersion. This negative lens element may be considered to be part of the power lens unit.