Matsushita Electric Industrial Co., Ltd.

Yasuo Nakajima

Yoshiharu Yamamoto

Yoshitomi Nagaoka

Shusuke Ono

Yoshito Miyatake

Takashi Nagata

Yasuhiro Tanaka

Hiroaki Okayama

Hisayuki Ii

Syusuke Ono

Shinichi Tanaka

Kenichi Ikeda

Masaaki Sunohara

Keizo Ishiguro

Teruo Kitani

Hiroshi Ikushima

Tsugio Murao

Kitokazu Hagiwara

Rieko Hiramoto

Michio Ishibashi

A first lens group having a negative refracting power and a second lens group having a positive refracting power are arranged in order from the photographing object side. Zooming is performed by changing the aerial interval between the first and second lens groups, and both the first and second lens groups have one or more aspheric surfaces. The first lens group includes two negative lenses and a positive lens which are arranged in order from the object side, and the second lens group includes a positive lens, a cemented lens having a positive lens and a negative lens, and a positive lens which are arranged in order from the object side.

Wide-angel aspheric zoom lens

A zoom lens assembly includes, in succession order from the object side, a first fixed lens group of a positive refractive power including a negative lens, a positive lens and a positive meniscus lens; a second movable lens group of a negative refractive power including a negative meniscus lens, a positive lens and a positive lens for effecting a variation of image magnification by moving along an optical axis of the zoom lens assembly; a third fixed lens group of a positive refractive power having at least one aspherical face and including a positive lens and a negative lens; and a fourth movable lens group of a positive refractive power including having at least one aspherical surface and also including negative and positive lenses cemented together.

Zoom lens assembly

A zoom lens of this invention comprises in successive order from the object side a first group having a positive refractive power and fixed, a second group having a negative refracting power for effecting a variation of image magnification by moving on the optical axis, a third group having a positive power for effecting a light condensing action and fixed, and a fourth group moving on the optical axis so as to keep an image surface position to be changed in response to a move of the second group and a move of the object in a constant positional relation with the reference surface. Comparatively large air space is provided between the third and fourth groups of the zoom lens.

Zoom lens

A projection lens for projecting images displayed on an image display device having angle-of-view dependency has high image focusing characteristics corresponding to high definition images, wide field angle, and telecentric characteristics. In addition, a projection television system using the same can be minimized in its size.

Projection lens and projection television system using the same

A lens controls the chromatic aberration of an objective lens for practical use in an optical disk system. The lens has first and second aspherical surfaces each providing a positive refractive power for focusing a light through a transparent plate and satisfies a condition: ##EQU1## where f.sub.L =focal length of the lens, d.sub.c =thickness of the transparent plate, n.sub.c =refractive index of the transparent plate, .lambda.=center wavelength of the light, NA=numerical apperture of the lens, .nu..sub.L =local dispersion of the lens, and .nu..sub.c =local dispersion of the transparent plate. The local dispersion of each element is expressed by: ##EQU2## where n.sub.80 is refractive index at a center wavelength .lambda. nm, n.sub..lambda. +5 a refractive index at .lambda.+5 nm, and n.sub..lambda. -5 a refractive index at .lambda.-5 nm.

Objective lens for optical disk system and optical head using the same

A single lens having first and second aspherical surfaces each having a positive power is usable for, an objective lens of an optical pickup for an optical recording medium. The lens satisfies the following conditions:

Single optical lense with diffraction limit converging capability and

A selective shading device has a number of shading plates or planar members and a supporting body that holds the plates or planar members in such a manner that they are arrranged radially with respect to an optical axis. The device blocks sagittal bundles of rays. A preferred example of the supporting body is a cylindrical frame that holds the shading plates perpendicularly to the inner surface thereof. Alternatively, the shading planar members are formed within a lens element along the edge thereof.

Selective shading device and an optical device using the same

A high definition projection lens for projecting on a screen an enlargement of an image appearing on a high resolution CRT is disclosed. The projection lens comprises a first lens having a positive optical power and a convex surface facing the screen, a meniscus second lens having a positive optical power, a third lens having bi-concave surfaces and a negative optical power, a fourth lens having a positive optical power, a fifth lens having bi-convex surfaces and a positive optical power, and a sixth lens having a negative power and an aspheric concave surface facing the fifth lens.

Projection lens for high definition TV

A projection lens for projecting an image appearing on a cathode-ray tube onto a screen, small in residual aberrations, having a high imaging performance, also having a large aperture ratio and a wide field angle, suitable for a video projector having a high definition of, say, 1,125 scanning lines. The projection lens has, successively from the screen side, a Gauss type lens system, a positive lens mainly for enlarging the aperture ratio, and a negative lens mainly for widening the field angle, which negative lens has a strongly concave surface at the screen end.

Projection lens

A color corrected projection lens with a large aperture ratio and a wide angle of view for producing on a screen an enlargement of an image appearing on a CRT, the lens having sequentially from the screen end a first unit of a bi-convex element having a positive power with a strongly convex surface directed toward the screen end, a second unit of a bi-concave element having a negative power and being located at or in the vicinity of the entrance pupil position of the entire lens system, a third unit of a bi-convex element having a positive power, and a fourth unit having a negative power with a strongly concave surface directed toward the screen end.

Color corrected projection lens

A projection lens having a large aperture ratio has 3 units for projecting an enlargemen of an image appearing on a CRT onto a screen. The first unit from the screen has a negative power so that the entrance pupil is moved toward the screen to thereby improve off-axis vignetting factor. The second unit consists of two positive power lens elements so that the positive power of the entire system is shared by the second unit and the temperature characteristic is improved by using a positive power glass lens element as one of the two positive power lens elements. The third unit has a negative power to correct curvature of field.

A compact projection lens for projecting an enlargement of an image appearing on a cathode ray tube (CRT) onto the screen. The projection lens has a first lens having a positive optical power and at least one aspheric surface, surface of the first lens that faces the screen being convex, a second lens having bi-convex surfaces and a positive optical power, and a third lens having a negative optical power and an aspheric concave surface facing the second lens. The focal length f.sub.1 of the first lens and the focal length f.sub.2 of the second lens are selected for satisfying a condition of

Compact projection lens

A projection lens apparatus for projecting an image from a CRT onto a remote screen. The lens apparatus is basically a Petzval type for a large aperture ratio and comprises three lenses. The first lens is a plastic lens having at least one aspherical surface and the third lens has a bi-aspherical surface. To reduce the thermal drift of the focal position, the second lens is a glass lens, having relatively largely positive optical power.

Projection lens apparatus

A projection television apparatus having a retrofocus type projection lens system which has a sufficiently long back focus, a small F number and a large distortion. The lens system is constructed with five components and five lenses and comprises a first lens which is a negative meniscus lens that has at its screen side a convex surface, a second lens which is a biconvex lens, a third lens which is a biconcave lens, a fourth lens which is a positive lens, and a fifth lens which is a biconvex lens, and which is defined by the following four conditions, i.e.

Projection television apparatus

A projection television apparatus which has three monochromatic cathode-ray tubes, two type of dichroic mirrors, and a lens. Red, green and blue images from the three tubes are combined into the color image by the two types of dichroic mirrors and the resulting image is enlarged and projected on the screen by one lens. The two types of dichroic mirrors are crossed at a right angle in the shape of an 'X'. Each type of dichroic mirror is split in two through the line of intersection and the two parts of the respective dichroic mirrors of each type have different transmission characteristics, so that color shading is improved.

Growing community of inventors

Ibaraki, Japan

Yasuo Nakajima