Abstract: An objective lens system 10 uses Germanium lens elements including a positively-powered objective lens (A), a positively-powered intermediate lens (B) and a negatively-powered field lens (C). The field lens (C) flattens the Field curvature of the system. The intermediate lens (B) corrects astigmatism and has an aspheric surface (3).

Abstract: A zoom lens having three lens groups of positive, positive, and negative refractive power, in order from the object side. A diaphragm is positioned between the first and second lens groups. When zooming from the wide-angle end to the telephoto end, the diaphragm and the third lens group are moved as a unit while the spacing between the first lens group and the diaphragm increases, the spacing between the diaphragm and the second lens group increases, and the spacing between the second lens group and the third lens group decreases. Further, the zoom lens is constructed so as to satisfy the following condition-0.75<R.sub.G21 /f.sub.w <-0.23where R.sub.G21 is the radius of curvature of the surface of the second lens group that is nearest the object side, and f.sub.w is the focal length of the zoom lens at the wide-angle end.

Abstract: A three-group zoom lens having positive, positive and negative refractive power, in order from the object side. A diaphragm is positioned between the first and second lens groups and nearest the second lens group. Zooming is performed by changing the spacings between the lens groups such that, when power is varied from the wide-angle end to the telephoto end, the distance between the first lens group G.sub.1 and the second lens group G.sub.2 increases, while the distance between the second lens group and the third lens group G.sub.3 decreases. The second lens group includes, in order from the object side, a meniscus lens element L.sub.4 having negative refractive power with its concave surface on the object side, a biconvex lens element L.sub.5, a negative lens element L.sub.6 and a biconvex lens element L.sub.7.

Abstract: The zoom lens according to the present invention comprises three lens units. More specifically, there is a front lens unit of positive refractive power, a middle lens unit of positive refractive power, and a rear lens unit of negative refractive power. The front lens unit has a positive lens element and a negative lens element airspaced from the positive lens element. During zooming from a wide-angle to a telephoto position, the front and the rear lens units simultaneously move the toward an object side. The middle lens unit also moves toward the object side, but by a shorter net axial distance than the distance traveled by the front and rear lens units. The "net axial distance" refers to the axial distance between one zoom and another zoom position of a lens unit. The lens elements have sufficient optical powers, spacings and radii of curvature to provide for a large zoom ratio ZR and to maintain an overall compactness so that L.sub.v /f.sub.t <0.9 and ZR =f.sub.t /f.sub.w >2.5, where L.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: An illumination optical system having an afocal optical system includes a first group of lenses having negative refracting power, a second group of lenses having positive refracting power and being positioned further away from a light source than the first group of lenses, and a third group of lenses having positive refracting power and being positioned further away from the light source than the second group of lenses, wherein the afocal optical system expands a parallel beam of light emitted from the light source or converts the parallel beam of light into a parallel beam having equivalent magnification.

Abstract: A compact variable focal length optical system is suitable for high zoom ratio. At least a first lens group having a positive refractive power, a second lens group, and a third lens group having a negative refractive power are provided. At least the first lens group is moved toward an object side of the system to satisfy a particular conditional equation so that a distance between the first and second lens groups is increased and a distance between the second and third lens groups is changed. In certain constructions, a first lens group having a positive refractive power, a second lens group having a negative refractive power positioned adjacent to and on an object side of the first lens group, and a third lens group positioned adjacent to and on an image side of the first lens group are provided. The first lens group includes at least two sub-lens groups.

Abstract: An inexpensive achromatic object lens for a microscope has a magnification of about 20 and a relatively long working distance. Aberrations are satisfactorily corrected even at the periphery of the image. The object lens includes a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power in this order from the object side. The first lens group consists of a positive lens and a cemented lens which is composed of a negative lens and a positive lens. The second lens group consists of a positive lens for converting the divergent light flux that has exited the first lens group into convergent light flux. The third lens group consists of a negative meniscus lens with its concave surface facing the image side. The object lens satisfies the conditions 4.0.ltoreq.f1/d0.ltoreq.15.0, 55.ltoreq.v2p, and 35.ltoreq.v1p-v1n.

Abstract: The zoom lens according to the present invention comprises three lens units. More specifically, there is a front lens unit of positive refractive power consisting of a positive lens element and a negative lens element, a middle lens unit of positive refractive power, and a rear lens unit of negative refractive power. During zooming from a wide-angle to a telephoto position, the front lens unit and the rear lens unit simultaneously movable towards an object side during zooming from a wide angle to a telephoto position. The middle lens unit moves towards the object side at a relatively slower speed than that at which the front and the rear lens units are moved. The lens elements have sufficient optical powers, spacings and radii of curvature to provide for a large zoom ratio ZR and to maintain an overall compactness so that L.sub.v /f.sub.t <0.9 and ZR=f.sub.t /f.sub.w >2.3, where L.sub.v is the distance from the front vertex of the lens system to the film plane in the telephoto position, f.sub.

Abstract: A standard lens system composed, in order from the object side, of a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power: the first lens unit being composed of at least one positive meniscus lens component which has a convex surface on the object side, and at least one doublet which consists of a positive meniscus lens component and a negative lens component; the second lens unit being composed of at least one cemented doublet which consists of a negative lens element and a positive lens element, and a positive lens component; and the third lens unit being composed of at least one positive lens component and a negative lens component or at least one negative lens component.

Abstract: A zoom lens is disclosed, comprising, from front to rear, a first, second and third lens units of positive, positive and negative refractive powers, respectively, all the lens units moving forward to effect zooming from the wide-angle end to the telephoto end, the first lens unit including at least one negative and at least one positive lenses, and the second lens unit including a negative lens whose front surface is concave, a positive lens and a cemented lens composed of a negative lens whose rear surface is concave and a bi-convex lens, and the zoom lens satisfying the following condition:0.2<.beta..sub.2W /.beta..sub.3W <0.5 (where .beta..sub.2W >0, .beta..sub.3W >0)where .beta..sub.2W and .beta..sub.3W are the lateral magnifications in the wide-angle end of the second and third lens units, respectively.

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: A zoom lens includes a positive first lens group, a positive second lens group, and a negative third lens group, in this order from the subject side. The first lens group consists of a negative first lens element, a positive second lens element and a positive third lens element in this order from the object side and satisfies the following relationships:4.3<m.sub.3T <61.7<f.sub.T /f.sub.1G <331<.nu..sub.1 <550<.nu..sub.2 -.nu..sub.1 <30where "m.sub.3T " represents the lateral magnification of the third lens group at the longest focal length position, "f.sub.T " represents the focal length of the entire lens system at the longest focal length position, "f.sub.1G " represents the focal length of the first lens group, ".nu..sub.1 " represents the Abbe number of the negative first lens element of the first lens group, and ".nu..sub.2 " represents the Abbe number of the positive second lens element of the first lens group.

Abstract: A zoom lens system comprises, from the object side, a first lens unit having a positive refractive power, a second lens unit having a positive refractive power and a third lens unit having a negative refractive power. During zooming, the sizes of the first area of empty space between the first lens unit and the second lens unit and the second area of empty space between the second lens unit and the third lens unit change.

Abstract: A compact zoom lens with three lens units of positive, positive and negative optical powers, respectfully. The front and the rear lens units move together for zooming and the middle unit moves independently. There is one aspheric surface in each of the three lens units. An aperture stop is located with the front lens unit.

Abstract: A compact zoom lens with three movable lens units of positive, positive and negative optical powers, respectfully. During zooming, the axial distance between the first and the rear lens units changes less than the axial distance between the first lens unit and the middle lens unit; the middle lens unit is movable towards the object side at a relatively slower axial speed than that at which the first and third lens units are moved.

Abstract: A zoom lens system which enables favorable image quality to be obtained even when it is focused on an object at a short distance. The zoom lens system has a 1-st lens unit (G1) of positive power, a 2-nd lens unit (G2) of positive power, and a 3-rd lens unit (G3) of negative power. Zooming from the wide end toward the tele end is effected by increasing the spacing between the 1-st lens unit (G1) and the 2-nd lens unit (G2) while reducing the spacing between the 2-nd lens unit (G2) and the 3-rd lens unit (G3). The 2-nd lens unit (G2) of positive power is composed of a negative sub-lens unit (G2N) and a positive sub-lens unit (G2P), and an aperture stop is disposed between the 1-st lens unit (G1) and the 2-nd lens unit (G2) (as shown by S') or between the negative sub-lens unit (G2N) and the positive sub-lens unit (G2P) (as shown by S).

Abstract: An objective lens for a free-space photonic switching system is disclosed. The objective lens is utilized to change a collimated array of beams into an array of spots which will focus on the array of spatial light modulating elements (S-SEEDs, for example). The requirements for the lens (low f-number, field of view, etc.), result in a lens which includes an external stop, positive doublet, a positive (e.g., plano-convex) lens and a negative (e.g., field flattener) lens, the latter pair of lenses being separated by a predetermined distance d.

Abstract: An improved zoom lens system includes at least three lens groups which are arranged, in order from the object side, as a first lens group having a positive focal length, a second lens group having a positive focal length and a third lens group having a negative focal length. When zooming is carried out from the wide angle to the telephoto end, the first, second and third lens group are all moved towards the object so that the distance between the first and second lens groups increases whereas the distance between the second and third lens groups decreases. The first lens group has a first lens element with a concave lens surface on the side the closest to object while satisfying specific conditions.

Abstract: The invention provides a compact zoom lens system which has an angular coverage from wide angle to moderate telephoto and makes a relatively bright and parallax-free TTL finder possible and in which a first unit 11 having a positive power as a whole is located on the side proximate to the object. The lens system includes a reflective means 13c located more closely to the image side than the first unit 11 for guiding incident light to a finder subsystem and a movable lens unit that moves for zooming. The movable lens unit comprises a sub-unit 13a having a positive power as a whole and located on the object side of the reflective means 13c and a sub-unit 13b having a negative power as a whole and located on the images side of the reflective means 13c, or alternatively a sub-unit having a negative power as a whole and located on the object side of the reflective means and a sub-unit having a positive power as a whole and located on the image side of the reflective means.

Abstract: The invention provides a compact, light-weight varifocal lens system that has a varifocal ratio of about 3, comprises fewer lenses than in the prior art, has a short total length and is well corrected in terms of various aberrations from the wide angle to telephoto ends. This lens system comprises a first positive lens unit G1, a second positive lens unit G2 and a third negative lens unit G3, wherein varifocal motion is achieved by moving each unit in such a way that, from the wide angle to telephoto ends, the air space between the first and second lens units increases, while the air space between the second and third lens units decreases.

Abstract: A zoom lens system comprising, in the order from the object side, a first lens unit having positive refractive power, a second lens unit having positive refractive power and a third lens unit having negative refractive power, and so adapted as to vary focal length from the wide position to the tele position by displacing the first lens unit integrally with the third lens unit toward the object side and displacing the second lens unit toward the object side at a speed slower than that of the first lens unit, said zoom lens system having such a composition as to permit simplifying structure of the driving mechanism for varying focal length, a compact design and favorable performance.