Mitsubishi Denki Kabushiki Kaisha

Mitsushige Kondo

Shinsuke Shikama

Eiichi Toide

Hiroshi Kida

Masahiro Usui

Kazuo Okada

Teruo Fujita

Keizo Kono

Kazuo Hirasawa

Eiichi Tiode

The present invention provides a color projector utilizing three liquid crystal display elements. The natural light is separated into illuminating rays of red, green and blue colors by a dichroic mirror, each of these illuminating rays being used to illuminate the corresponding one of the liquid crystal display elements. Each of the liquid crystal display elements is controlled by a desired image signal with respect to its transmittance at each pixel. After passed through the liquid crystal display elements, three kinds of colored illuminating rays are again synthesized by the other dichroic mirror to form a light beam which in turn is enlarged and projected by a projecting lens on a screen. By providing light source means including means for converting the natural light into the linearly polarized beam, the illuminating rays may have their polarizing angles coincide with each other without any loss of light. As the linearly polarized beam is reflected by the mirror system, the illuminating rays of red, green and blue colors are changed with respect to their polarizing angels. Depending on the changed polarizing angles, the polarizing angle of the light rays incident on each of the liquid crystal display elements may be adjusted to remove any loss of light.

Color projection type display apparatus having three liquid displays of

Color projection type display apparatus having three liquid crystal

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

The projection-type display device has a light source emitting a parallel luminous flux, a liquid crystal light valve disposed on the luminous flux and outputs a rectangular two-dimensional image to be projected on a screen, and a projection lens magnifying the rectangular two-dimensional image output. The light source has a first concave mirror (parabolic mirror) the reflective surface of which is oriented in the direction of emission of the luminous flux, a lamp laced in front of the first concave mirror, and a second concave mirror (parabolic mirror or spherical mirror), the reflective surface of which is oriented toward the first concave mirror. In the second concave mirror is formed an aperture window, which is a rectangle of substantially similar to that of the liquid crystal light valve and emits a rectangular luminous flux. The beam from the lamp is reflected by the first concave mirror, and one or more times by the second concave mirror, becoming a parallel beam oriented in the direction of the optical axis. The parallel light beam is made into a luminous flux of rectangular cross section by the rectangular aperture window. Accordingly, luminous flux is not blocked wastefully, but serves to increase the brightness of the projected image.

Projection-type display device having light source means including a

Projection cathode ray tube having an interference filter

Three light fluxes are modulated by corresponding light valves so as to project a color image on a screen. An interference filter for selectively transmitting a light flux which is emitted in a direction perpendicular to a light emitting surface of the interference filter is disposed on the light-emitting portion so as to increase the intensity of light fluxes which are emitted in the forward direction. A light-flux-emitting portion of a light source and the light valve have approximately the same configuration so that the intensity of the light fluxes to be projected on the light valves is increased.

Projection color display apparatus

In a projection display device having an illumination optical system which converts the light emitted from a point light source into a substantially parallel luminous flux, a light valve which modulates the light flux, and an optical projection system which projects images on the light valve onto a screen, the illumination optical system converts the light into a substantially parallel luminous flux having a cross section of substantially the same size and shape, e.g., rectangular shape, as the shape of the frame of the light valve.

Projection display device

An optical head device comprises a semiconductor laser beam source, a diffraction grating for deflecting a laser beam emitted from the laser beam source at an angle of about 90.degree., a beam splitter placed between the laser beam source and the diffraction grating, and an objective for converging the laser beam deflected by the diffraction grating on an optical disc.

Optical head device having deflection means including means for reducing

In an optical type head device comprising a light source for emitting a light beam, a beam splitter, a condensor lens and a light detector for receiving said light beam for photoelectric conversion wherein a diffraction grating is provided to separate the light beam into a plurality of subbeams consisting of a zero-order subbeam and other subbeams so that a focussing error of the spot of the zero-order subbeam on an optical type data storing medium is detected by the fact that the light spot of the zero-order subbeam is deformed on the light detector, and a positional error of the spot of the zero-order subbeam with respect to a data track on the optical type data storing medium is detected depending on the position of the spots of the other subbeams.

Optical head utilizing diffraction grating

An optical type head device comprises a laser beam source for emitting a laser beam, a light focussing means for converging the laser beam on a data storing surface of an optical type data storing medium, a laser beam detecting means which receives the laser beam reflected by the optical type data storing medium and modulated by data held by the same, and converts the data into electric signals, a driving current supplying means for supplying a driving current to the laser beam source. The driving current supplying means comprises a high frequency current generator which supplys to the laser beam source a high frequency current having a waveform ranging from the lower part of the threshold value at which the laser beam source starts emission of the laser beam to the higher part of the thresheld value, and the frequency of the high frequency current is at least twice as high as the maximum frequency component of information which is contained in the data storing medium.

Optical head with laser having particular source of driving current

Optical head device having positionally adjustable parts

An optical head assembly for recording information on an optical disc or for taking out information already recorded, the optical head assembly including a semiconductor substrate and a dielectric light conducting layer formed on the substrate, the light conducting layer being internally formed with optical elements for converging laser beam from a laser beam source onto the optical disc and directing the reflected beam from the optical disc surface toward a photo detector. Output signal from the photo detector is used for reading information and also for allowing the optical head assembly to trace a track on the optical disc.

Head assembly for optical disc

A focusing error detecting device used in a head assembly for recording information to a recording surface of an optical disc or reading out information already recorded, the focusing error detecting device including a diffraction grating for focusing light which has been introduced from a light source into a thin-film waveguide layer, onto the recording surface, and two light receiving diffraction gratings for conducting the light reflected by the recording surface again into the waveguide layer. The two light receiving diffraction gratings have optical characteristics which differ from each other, depending the position of a focused spot of the light focused on the recording surface by the focusing diffraction grating. Therefore, by comparing the intensity of light from one light receiving diffraction grating with that from the other light receiving diffraction grating, there can be seen a positional relationship between the focused spot and the recording surface.

Focusing error detecting device in head assembly for optical disc

An optical signal reproducing system uses laser light reflected from a recording disc track 12 to recover signals stored in pits 13 separated by lands. The differential output of the reflected light only when the focused beam is incident on pits is used to control lateral tracking offset correction in a negative feedback mode, thereby immunizing the system from false tracking correction due to light reflected from lands when the disc is tilted from the optical axis.

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Nagaokakyo, Japan

Mitsushige Kondo