Abstract: An optical imaging lens set from an object side toward an image side along an optical axis in order includes: a first lens element having an image-side surface with a convex portion in a vicinity of its circular periphery, a second lens element having an object-side surface with a convex portion in a vicinity of its optical axis, a third lens element having an object-side surface with a concave portion in a vicinity of its optical axis, a fourth lens element with positive refractive power, and a plastic fifth lens element having an image-side surface with a concave portion in a vicinity of its optical axis.

Abstract: This invention provides an optical imaging lens system in order from an object side to an image side comprising five non-cemented lens elements with refractive power: a first lens element with positive refractive power having a convex object-side surface; a second lens element with positive refractive power; a third lens element with negative refractive power, and both surfaces being aspheric; a fourth lens element having a convex image-side surface, and both surfaces being aspheric; and a plastic fifth lens element having a concave image-side surface, both surfaces being aspheric, and at least one inflection point is formed on at least one of the surfaces thereof. By such arrangement, the refractive power of the optical imaging lens system can be effectively distributed with improved light converging power so that the total track length can be shortened effectively, and the aberration of system can be corrected to facilitate high image quality.

Abstract: An objective optical system whose outer diameter is reduced, whose overall length is increased, in which chromatic aberrations are well corrected, and which is suitable for in-vivo examination with a high numerical aperture is realized.

Abstract: An optical device with five air-spaced optical elements. An optical device in the form of an eyepiece is disclosed with a center negative lens and two outer positive lenses on each side of the intermediate negative lens. The eyepiece transmits light from an object to an exit pupil along angles corresponding to the position of a focus point on an object. In a preferred embodiment the positive lenses are identical.

Abstract: A projection lens for a projection type of television system which comprises a positive power first lens having a convex surface on the image side, a positive power second lens having a convex surface on the image side, third biconcave lens, a positive power fourth meniscus lens having a convex surface on the object side and a positive power fifth lens having a convex surface on the image side arranged in order from the image side to the object side satisfies the following conditions: 0.35<F12/F<0.65 −3.0<F3/F<−1.3 0.5<F5/F<0.85 0.35<BF/F<0.55 where F12 is the composite focal length of the first and second lens elements, F3 is the focal length of the third lens element, F5 is the focal length of the fifth lens element, F is the focal length of the projection lens, and BF is the back focal distance of the projection lens.

Abstract: A zoom lens 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, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, zooming from a wide-angle end to a telephoto end being effected by moving the second lens unit toward the image side, and shifting of an image plane due to zooming being compensated for by moving the fourth lens unit, wherein the second lens unit consists of four separate single lenses including three negative lenses and one positive lens, and the third lens unit has at least one positive lens both surfaces of which are aspherical.

Abstract: A UV image forming optical system includes a collimating lens which collimates light emitted from a UV light source, and an imaging lens which forms an image of the collimated UV light transmitted through the collimating lens. A rear focal point of the collimating lens adjacent to the imaging lens is located closer to the imaging lens than a last lens surface of the collimating lens on the light emission side. A front focal point of the imaging lens adjacent to the collimating lens is located within the imaging lens. A lens system for UV radiation is also provided, which can be used as an imaging lens for the UV image forming optical system.

Abstract: Binoculars designed to provide a large aided static field of view are provided. The binoculars are characterized by S/D ratios of above 2.8, where S is the binoculars' aided static field of view calculated by multiplying the binoculars' magnifying power by the binoculars' semi field of view in object space and D is given by tan.sup.-1 [(R.sub.ex +1.5)/13], where R.sub.ex is the radius of the binoculars' exit pupil and where R.sub.ex and the constants 1.5 and 13 are measured in millimeters. As a result of the increased S/D ratio, the binoculars of the invention minimize the sensation of tunnel vision which normally occurs when binoculars are used and reduce the user's apprehension of missing activities in his or her peripheral vision. In certain embodiments, a movable field lens unit is employed to provide variable power and a negative corrector lens unit is employed for aberration correction and to minimize the size of the binoculars. The binoculars are suitable for mass production and general consumer use.