Abstract: 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.

Abstract: A retro-focus type lens is provided from a large conjugate side with a first lens group having a negative refracting power, a second lens group having a positive refracting power which is spaced away from the first lens group at an air interval D1, and a third lens group having a positive refracting power. The following conditions are satisfied when focal lengths of the first lens group, the second lens group, the third lens group, and a total lens system are assumed respectively as f1, f2, f3, and f:1.8<D1/f<3.01.1<f2/f3<1.61.5<.vertline.f1.vertline./f<2.3.A projection lens constructed by inserting a mirror in a lens system of thus constructed retro-focus type lens is used in a projection-type display apparatus.

Abstract: Disclosed is a condenser lens with large aperture, having a numerical aperture of 0.9 or larger, which consists of a bi-aspherical single lens having a first surface of convex form facing the larger conjugate side and a second surface facing the smaller conjugate side and whose outermost circular zone is formed concave, the condenser lens satisfying the following conditions (1) or (2). Also disclosed are a light source apparatus using such a condenser lens and a projection display apparatus using such a light source apparatus.(1) 0.42<r1/nf<0.45 18<.vertline.r2/nf.vertline. -0.39<K1<-0.25 0.11<.DELTA.2/f<0.14(2) 0.4<r1/nf<0.6 -0.5<r2/nf<-0.3 -0.6<K1<-0.2 -0.1<SG2/f<0.1wheref: focal length of the whole lens systemn: refractive index of the lensr1: radius of center curvature of the first surfacer2: radius of center curvature of the second surfaceK1: conic constant of the first surface.DELTA.

Abstract: A zoom lens system comprising, in order from a large conjugate side a first lens group having a negative refracting power and a second lens group having a positive refracting power. A focal length of the zoom lens system becomes longer, as a gap between the first lens group and the second lens group is reduced. The zoom lens system satisfies following relational expressions (1) to (4),0.9<.vertline.f.sub.1 .vertline./f.sub.w <1.2 (1)0.8<f.sub.2 /f.sub.w <1.2 (2)0.3<D.sub.12w /f.sub.w <0.5 (3)BF.sub.w /f.sub.w >1.5 (4)where a symbol f.sub.1 designates a focal length of the first lens group, a symbol f.sub.2 designates a focal length of the second lens group, a symbol f.sub.w designates a focal length of the zoom lens system at a minimum focal length state, a symbol D.sub.12w designates the gap between the first lens group and the second lens group at the minimum focal length state, and a symbol BF.sub.w designates a back focal length at the minimum focal length state.

Abstract: A projection-type display device comprises a pillar optical element having an injection end and an emitting end, a lamp, an elliptical mirror for condensing light emitted by the lamp in the vicinity of the injection end, a first lens for forming an image of the emitting end, a light valve for forming a picture image on a surface having an image display area, and a projection lens. The image of the emitting end of the pillar optical element is projected by the first lens on the image display area within the surface of the light valve. The projection lens magnifies and projects the picture image displayed by the light valve on the screen.

Abstract: A projection display device comprises: a diaphragm for the illuminating system disposed in the vicinity of a focal point of the light collected by the concave mirror; a collimation lens for rendering parallel the light passing through the aperture of the first diaphragm; a scattering-type liquid crystal light valve for forming forming image on its displaying surface; a field lens for converging the light rendered parallel by the collimation lens; a projection lens having an entrance pupil disposed in the vicinity of a focal point of the light converged by the field lens; and a second diaphragm having an aperture and provided in the projection lens. An aperture varying section of the first diaphragm varies the aperture diameter of the diaphragm of the illuminating system, and the other aperture varying section varies the aperture diameter of the diaphragm of the projection lens, thereby varying the diameter of an entrance pupil.

Abstract: A light source apparatus using a condenser lens satisfying either condition (1) or (2).(1) 0.42<r1/nf<0.45 (1)18<.vertline.r2/nf.vertline.-0.39<K1<-0.250.11<.DELTA.2/f<0.140.4<r1/nf<0.6 (2)-0.5<r2/nf<-0.3-0.6<K1<-0.2-0.1<SG2/f<0.1where f:f: focal length of the whole lens systemn: refractive index of the lensr1: radius of center curvature of the first surfacer2: radius of center curvature of the second surfaceK1: conic constant of the first surface.DELTA.2: axial difference between the aspherical face of the outermost circular zone within the effective diameter of the second surface and a reference spherical face having the radius of center curvature of r2SG2: axial difference of the aspherical face of the outermost circular zone within the effective diameter of the second surface with respect to the center of the second surface.

Abstract: A light source apparatus of reduced thickness and high extinction ratio employs a series of columnar component elements of rhomboidal cross section. Incident and emergent surfaces are formed in periodic folds with each fold arranged for light incidence at and angle equal to or greater than the Brewster angle. At the Brewster angle, P-polarized light is transmitted without loss. For incidence at an angle greater than the Brewster angle, the transmittance of the S-polarized light is decreased with a slight decrease in transmittance of the P-polarized light, for a net increase in the extinction ratio. By using a multilayer structure, the extinction ratio is further increased. By inclusion of an ultraviolet/infrared cut-off filter and forced cooling, deterioration and deformation of the polarizing element are reduced. Arrangement of the layers with spacers and air layers prevents a decrease in extinction ratio due to multiple reflections.

Abstract: 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.

Abstract: 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.

Abstract: A retrofocus projection lens comprises a first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power. The first to third lens groups are arranged in this order from a large conjugate side. The first lens group includes a convex negative meniscus lens on the large conjugate side, the second lens group includes a biconvex positive lens, and the third lens group includes, in order from the large conjugate side, a biconcave negative lens, a convex positive meniscus lens on a small conjugate side and a biconvex positive lens. The first to third lens groups satisfy the following relations (1) to (3):0.25<D.sub.1 /f<0.55 (1)0.05<f.sub.2 /f.sub.3 <0.4 (2)0.8<.vertline.f.sub.1.vertline./ f<1.2 (3)where D.sub.1 is air gap between the first lens group and the second lens group, f.sub.1 is focal length of the first lens group, f.sub.2 is focal length of the second lens group, f.sub.

Abstract: Disclosed is a condenser lens with large aperture, having a numerical aperture of 0.9 or larger, which consists of a bi-aspherical single lens having a first surface of convex form facing the larger conjugate side and a second surface facing the smaller conjugate side and whose outermost circular zone is formed concave, the condenser lens satisfying the following conditions (1) or (2). Also disclosed are a light source apparatus using such a condenser lens and a projection display apparatus using such a light source apparatus.(1) 0.42<r1/nf<0.45 18<.vertline.r2/nf.vertline.-0.39<K1<-0.25 0.11<.DELTA.2/f<0.14(2) 0.4<r1/nf<0.6 -0.5<r2/nf<-0.3 -0.6<K1<-0.2 -0.1<SG2/f<0.1wheref: focal length of the whole lens systemn: refractive index of the lensr1: radius of center curvature of the first surfacer2: radius of center curvature of the second surfaceK1: conic constant of the first surface.DELTA.

Abstract: 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.

Abstract: A projection display device capable of selectively operating in a front projection mode and a rear projection mode, comprises a projector (300) disposed in a cabinet, a rear projection screen formed in a wall of the cabinet, and a front projection screen disposed outside the cabinet. To permit selection between the front and rear projections, the projector may be detachably mounted on the cabinet: when it is mounted the image rays (110) are introduced into the cabinet for the rear projection, while when it is detached it can be used for the front projection. In another embodiment, a selective light guide directs the image rays either to the rear projection screen or to the front projection screen. In a further embodiment, the rear projection screen can change between transparent and translucent states. When it is transparent, the image rays are passed therethrough to the front projection screen.

Abstract: A projection type display apparatus for displaying an enlarged composite image being composed of images each of which is produced upon a plurality of light valves upon a screen in every independent primary color. A correcting lens which corrects a projection magnification factor of the image formed by the light valve is disposed in the vicinity of at least one light valve on the projecting lens system side. The correcting lens adjusts the projection magnification factor of the image in each primary color to a predetermined factor. With this result, the disparity of pixels among the primary colors due to the chromatic aberration of magnification is corrected, and it becomes possible to obtain a high quality projection image.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.