Mitsubishi Denki Kabushiki Kaisha

Eiichi Toide

Shinsuke Shikama

Mitsushige Kondo

Toshihide Kaneko

Hiroshi Kida

Masahiro Usui

Toru Yoshihara

Kazuo Tsukagoshi

Naoki Kawamoto

Mitsushige Kondou

Kazuo Iwata

Takashi Saito

Akira Daijogo

Shinji Okamori

Hidehiko Hori

Toshitaka Tachibana

Shigeru Takeuchi

Masayuki Kubota

Manabu Koike

Fusaaki Yamada

Kan Kawahara

In a light source apparatus for use with a projection type display, at least one light source is provided for emitting light. A reflector is provided correspondingly to the light source in order to gather the light emitted from the light source into a small area to form a converged luminous flux. A light guide has at least one light input section into which the luminous flux is coupled. The light input section is provided correspondingly to the light source. The light guide combines the luminous flux received through the light input sections into a single beam of luminous flux. The light-guide has at least one light output section from which said luminous flux is output. The light source apparatus may also include light-refracting element provided between the reflector and the light-guide. The light-refracting element receives the converged luminous flux from the reflector to refract the converged luminous flux so as to couple the converged luminous flux, as a uniform luminous flux, into the light-guide.

Projection type display

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:

Retrofocus lens system

A projection type display apparatus incorporating a light receiver or a light transmitter, in which the light signal is received or transmitted through a screen or condensing lens disposed in its vicinity, and hence the luminous flux utility efficiency is high. A projection type display apparatus capable of preventing deterioration of picture quality due to difference in color in the projection units, and the best picture quality is realized even when the projection lenses for different colors are composed of nearly same components.

Projection unit for projection type display apparatus

A projection lens unit includes, in accordance with the order of disposition from a screen side, a first lens group including a positive meniscus lens, a second lens group including a double convex lens, and a third lens group which corrects curvature of field, wherein the third lens group has two concave lenses. A projection lens unit includes, in accordance with the order of disposition from a screen side, a first lens having a positive meniscus form, a second lens having a negative meniscus form, a third lens which is double-convex lens having a light gathering function, a fourth lens which is disposed near the third lens and is a double-convex lens having a positive power, a fifth lens provided at its central portion with a convex surface directed to a screen and provided at its peripheral portion with a concave portion directed to the screen, and a sixth lens having a concave surface directed to the screen, wherein each of the second, fourth and fifth lenses has at least one aspherical surface.

Projection lens unit

A projection display apparatus comprises an image source having a rectangular image-displaying surface; a projecting lens assembly for magnifying and projecting the image onto a screen; and light-obstructing plate disposed in the vicinity of the nearest lens element of the projecting lens assembly to the image source. The light-obstructing plate is disposed in such a position that 0.1.ltoreq.R.sub.1 /R.sub.2 .ltoreq.0.8 where R.sub.1 is a radius of optical-axis light which is emitted toward the screen from a central point on the image-displaying surface through which the optical axis of the projecting lens assembly passes, and R.sub.2 is a radius of effective light which is emitted toward the screen from the image-displaying surface. The light-obstructing plate is provided with protrusions which are disposed at positions at a same distance from a first, or a second reference line on the light-obstructing plate so as to obstruct several pairs of flare beams, which are included in peripheral light emitted from the vicinity of four corners of the image-displaying surface and are traveling towards positions at a same distance from the first or the second reference line.

Projection display apparatus

A projection display apparatus comprises a compact CRT, a projecting lens for projecting an enlarged image of the CRT, a Fresnel lens having a converging effect, a lenticular sheet as a diffusing plate. An image that has been enlarged by the projecting lens and passed through the lenticular Fresnel lens is formed on the lenticular sheet. The apparatus further comprises a displacing mechanism for displacing the Fresnel lens, and a display mechanism for displaying information related to the direction and extent of displacement of the Fresnel lens displaced by the displacing mechanism.

A projection lens system for projecting an enlarged image onto a display screen front an image appearing on a faceplate of a cathode ray tube utilizes at least six lens groups. The first lens group, from an end closest to the display screen, is in a form of a meniscus having a negative power. The second lens group has a weak positive power and a convex surface towards the display screen. The third lens group has a strong positive power. The fourth lens group is bi-convex and has a strong positive power. The fifth lens group has a weak positive power. The sixth lens group has a negative power and a pronounced concave surface away from the display screen. The second and fifth lens groups each are made with plastic lenses with at least aspheric surfaces on one side.

Projection lens system

A projection type display apparatus comprising three projection units for projecting red, green and blue images, each having a constitution wherein a holding member for holding a CRT and a holding member for holding a projection lens are separately constituted and these holding members are connected liquid-tightly by means of a soft packing sheet, while a space surrounded by the holding members and the packing sheet is filled with a coolant liquid.

Projection type display apparatus

A projection lens system has a first lens to a sixth lens which are serially arranged in this order from a screen side. The first lens has a meniscus configuration in which a convex surface is directed toward the screen side and the power of the lens changes from positive to negative from the optical axis toward a peripheral portion of the lens. The first lens has two aspherical surfaces. The second lens has a positive power meniscus configuration in which a convex surface is directed toward the screen side. Both surfaces of the second lens are aspherical. The third lens has a positive power meniscus configuration in which a convex surface is directed toward the screen side. The fourth lens is disposed close to the third lens and has two convex surfaces. The fifth lens has a positive power meniscus configuration in which a concave surface is directed toward the screen side. Both surfaces of the fifth lens are aspherical. The sixth lens has a concave surface which has a large curvature directed toward the screen side. The surface of the sixth lens on the screen side is aspherical.

In a projection television system having display elements displaying images of respective colors, a screen on which a color image is formed by magnifying and synthesizing the images of the respective colors, projection lenses for magnifying the images on the respective display elements and projecting them onto the screen thereby to form the color image, with the optical axis of the projection lens for a first color being disposed at a right angle to the screen and the optical axes of the projection lenses for second and third colors being disposed at an angle with respect to the optical axis of the projection lens for the first color, color imbalance is reduced. This is achieved by disposing the projection lenses for the second and third colors so that their optical axes are incident on a point different from the point at which the optical axis of the projection lens for the first color is incident. In an alternative arrangement, at least one of the display elements is provided with a filler having a transmittance varied from one position to another.

Projection television system including a plurality of display elements

A light valve is a planar member in which liquid crystals are hermetically sealed, and allows the transmission of light in an almost parallel direction and selectively scattering undesired light. On a rear surface of the light valve is disposed a light guide tube which contains a plurality of minute apertures. Alternatively, one of the substrates which constitute the light valve may be made of a fiber plate. The fiber plate has a structure in which short optical fibers are stacked. The light guide tube or the fiber plate converges a luminous flux emitted from the light valve to improve the contrast of an image. A projection display apparatus is constituted of a light source, a light valve, either a light guide tube or a fiber plate, a lens, and a projection lens. A luminous flux emitted from either the light guide tube or the fiber plate is incident on the pupil of the projection lens by way of the lens, and the projection lens casts this luminous flux onto a screen, thus forming a projected image. The selectively scattered undesired light cannot pass through the light guide tube or file plate.

Projection display apparatus, and light guide tube/light valve for use

A projection cathode ray tube has an interference filter which is disposed at a boundary between a face plate and fluorescent layers. The interference filter is designed to be thinnest at the central area of the CRT and to become gradually thicker toward the peripheral area of the CRT, so that the CRT can produce a uniformly bright image over the central and peripheral areas. The fluorescent layers include a first layer composed of small fluorescent particles and a second layer composed of large fluorescent particles. With this first fluorescent layer, light beams emitted by the second fluorescent layer can be prevented from being reflected in multiple directions, thereby minimizing halo due to such multi-direction reflection of the light beams.

Projection cathode ray tube

An optical head device includes a tilt servo mechanism using photodetectors for detecting rays of light reflected from the recording surface of an optical disk. The rays of light are obtained from a laser diode used as a light source for information reproduction. According to one aspect; prisms are formed on the flange of a converging lens to refract peripheral portions of the light emitted from the laser diode for tilt detection. According to another aspect, secondary diffraction grating domains at the sides of the primary diffraction domain of a diffraction grating diffract peripheral portions of the emitted rays of light for tilt detection. According to another aspect, a mirror reflects peripheral portions of the emitted rays from the laser diode. According to a further aspect a mirror reflects the light from the laser diode passing through a beam splitter. Each photodetector receiving the light reflected from the recording surface of the disk may be partitioned into two detector cells, and a tilt signal is obtained as the differential output of the two cells.

Optical head with a tilt correction servo mechanism

An optical record and reproduction apparatus, in which a light beam generated by a light source is concentrated onto an information recording medium by a focusing device, and the light beam reflected by the information recording medium is detected by a light detector to obtain a tracking error signal. A liquid crystal panel having a transparent electrode aligned in a striped form and a polarizing plate or birefringent phase difference plate constitute a beam divider for obtaining a main beam and supplementary beams without any accompanying mechanical movement. The beam divider is arranged between the light source and the focusing device. By selectively applying a voltage to the transparent electrode, the liquid crystal panel is made to function in the same manner as a diffraction grating. Another transparent electrode aligned in a striped form at an inclined angle may also be provided.

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Nagaokakyo, Japan

Eiichi Toide