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: 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: 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: 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: In a device for directing light longitudinally forwardly, the combination comprising a light source, and a protective, transparent envelope extending about the light source; a drum lens having a body extending about the light source and envelope, for refracting light from the source; a light reflector extending about the drum lens body, for forwardly and convergently re-directing refracted light received from the drum lens body; and a correcting lens for receiving a collimating re-directed light screened from the reflector.

Abstract: An apochromatic lens system which includes, in this order from the object, a positive first lens group and a positive second lens group; wherein the following conditions are satisfied:.nu..sub.I+ <80 (1).nu..sub.II+ >70 (2)1.1<f.sub.I /f<2.0 (3)wherein.nu..sub.I+ designates the largest Abbe number of a positive lens element in the first lens group;.nu..sub.II+ designates the largest Abbe number of a positive lens element in the second lens group;f.sub.I designates the focal length of the first lens group; andf designates the focal length of the entire lens system.

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: A telephoto lens includes, in the following order from the object side, a positive cemented lens component composed of a biconvex lens and a biconcave lens and having a meniscus shape as a whole with the convex side facing the object side, and a negative meniscus lens component with the convex side facing the image side.

Abstract: A variable focal length optical system includes, in the following order from an object side, a first lens unit having a negative refractive power and a second lens unit having a positive refractive power, wherein the focal length of an entire lens system changes when a distance between the first lens unit and the second lens unit is changed, and the following condition is satisfied:0.3<f2/.vertline.f1.vertline.<0.5where f1 is the focal length of the first lens unit, and f2 is the focal length of the second lens unit.

Abstract: The internal focusing telephoto lens of the invention has a focusing group with a small effective diameter and small focusing movement amount and maintains favorable optical performance. The internal focusing telephoto lens of the invention includes, in the following order from the object side; a first lens group that has a positive refractive power, a second lens group that has negative refractive power, and a third lens group that has a positive refractive power. The first and second lens groups form a substantially afocal system and focusing is performed by moving the second lens group along the optical axis. The first lens group includes, in the following order from the object side, a front group that has a positive refractive power and a rear group, which has about the same positive refractive power as the front group, and satisfies specified conditions.

Abstract: Disclosed is a telephoto-type lens system of a head separated charge coupled device (CCD) camera, which includes a first lens group having a positive focal length, a second lens group having a negative focal length, and a third lens group. The first lens group has a first convex lens surface facing an object and an upper convex surface. The third lens group has a second lens with a negative focal length joined to a first lens with a positive focal length. An image angle greater than 29.degree. and high definition images can be achieved with the present invention.

Abstract: The lens system includes, in order from an object side, a 1-st lens unit having a positive refractive power which has at least two positive lens elements and a negative lens element positioned on an image side of said positive lens elements, a 2-nd lens unit having a positive refractive power and a 3-rd lens unit having a positive refractive power. During focusing, both 1-st and 3-rd lens units are fixed, whereas the 2-nd lens unit is movable along an optical axis. The lens system satisfies at least one of the conditions 1.8<F1/f<2.4 and 0.8<F2/f<0.96.

Abstract: In a large-aperture medium-range telephoto lens system, which includes, in the following order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and attains focusing by moving the second and third lens units along the optical axis while the first lens unit is fixed in position, the telephoto lens system satisfies:______________________________________ 0.8 < f1/f < 1.5 -3.0 < f2/f < -1.0 0.7 < f3/f < 1.0 0.02 < .vertline.x2/x3.vertline. < 0.

Abstract: A high-aperture-ratio inner-focus telephoto lens comprises a first lens group of positive refracting power, a second lens group of negative refracting power and a third lens group of positive refracting power arranged in the named order from the object side, in which the first lens group and the second lens group form a substantially afocal system, focusing is effected by moving the second lens group along the optical axis, and the first lens group has a front group of positive refracting power and a rear group of weak positive refracting power arranged in the named order from the object side.

Abstract: In an internal focus telephoto lens comprised, in succession from the object side, of a first lens unit of positive refractive power, a second lens unit of negative refractive power and a third lens unit of positive refractive power, the first lens unit of positive refractive power and the second lens unit of negative refractive power together forming a substantially afocal system, focusing being effected by the second lens unit, the first lens unit has a front group of positive refractive power and a rear group having weak positive refractive power relative to the front group, the first group being comprised, in succession from the object side, of a positive lens component, a positive lens component and a negative lens component, the second lens unit has, in succession from the object side, at least a negative lens component and a negative lens component, and the third lens unit has a positive lens component, and various predetermined conditions are satisfied.

Abstract: A photographic lens system includes a positive meniscus lens whose the both lens surfaces are shaped in a aspherical surface respectively, the lens is arranged to satisfy the following inequality:0.02<t/L<0.05wherein the length of a diagonal line of an image forming plane on said image forming surface is 2L and the lens thickness on the optical axis is t.

Abstract: The telephoto lens is in each case put together from two different lens systems, a front group and a focusing group. The object-side front groups have fixedly arranged lens elements or lens element groups and the image-side focusing groups have mutually displaceable lens elements or lens element groups. The focal lengths of the focusing groups are chosen such that with the front groups, they produce telephoto lenses of different overall focal lengths. The front groups can be combined in a modular manner with the focusing groups. Telephoto lenses having excellent imaging performances can be put together with reduced production expenditure. The numerical data of a number of lens parts are specified.

Abstract: A telephoto lens system that adopts an inner focusing method and that is capable of satisfactory correction of aberrations while insuring an adequate back focus without increasing the overall lens length. The present telephoto lens system comprises, in order from the object side, a positive first lens group, a negative second lens group and a positive third lens group. The system can be focused on a close-up object by moving the second lens group toward the image. The first lens group comprises a positive first sub-group 1a and a positive second sub-group 1b separated from the first sub-group airspace. The system satisfies the following conditions:(1) 1.4<f/f.sub.1 <2.0(2) -3.5<f/f.sub.2 <-2.5(3) 0.4<f/f.sub.1b <1.0(4) 0.1<d.sub.1ab /f.sub.1 <0.3where f is the focal length of the overall system; f.sub.1 is the focal length of the first lens group; f.sub.2 is the focal length of the second lens group; f.sub.1b is the focal length of the sub-group 1b; and d.sub.

Abstract: A zoom lens system is arranged in three lens groups, in the order from object side to image plane side, that the first lens group has negative refractive power, the second lens group has positive refractive power, and the third lens group has negative refractive power. During zooming operation from wide angle position to telephoto position, the three lens groups vary the separations therebetween and together move toward the object side of the lens system. The first lens group of the lens system is composed of a negative lens element and a positive lens element.

Abstract: A stop device for a zoom lens includes an aperture-stop provided between a front lens group and a rear lens group. The front lens group, the rear lens group, and the aperture-stop are moved relative to each other by a motor, to carry out a zooming operation. The motor is provided behind the front lens group and the aperture-stop, and the aperture-stop is positioned closed to a front end of the motor when the aperture-stop is at its rearmost position.