Abstract: In the optical apparatus, the projection lens has a first lens group and a second lens group, the color synthesizing optical system has a transparent plate, dichroic mirrors and a plane mirror, the second lens group is disposed between the color synthesizing optical system and the polarization beam splitters, and the plane including the normal line of the plane of the transparent plate, the color synthesizing planes of the dichroic mirrors and the optical axis of the projection lens is perpendicular to the plane including the normal line of the polarizing and splitting planes of the polarization beam splitters and the optical axis of the projection lens.

Abstract: In an optical system phase device such as .lambda./2 plate or a .lambda./4 plate is used to convert S polarization to P polarization and vice versa. In the projection display, a white light emitted from a light source is separated by a color separation optical system, including dichroic mirrors or a dichroic prism, into three primary colors which are modulated by optical modulation elements. Then, the modulated lights are synthesized by a color synthesis optical system and projected by a projection element onto a screen. When appropriate plates are inserted appropriately in the optical system of the projection display, the conversion between S and P polarization occurs and an optical bandwidth becomes narrow, and color purity can be improved. A thick transparent plate is preferably adhered to the optical modulation element. A light absorption film is applied to an ineffective plane of the transparent plate.

Abstract: A projection lens includes sequentially from a screen side a first lens group which has a negative power, a second lens group which has a weaker power than that of the first lens group, a third lens group which has a positive power, a fourth lens group which has a positive power, and at least one transparent prism, wherein the fourth lens group is placed on the third lens group side of the transparent prism so as to be close to or in contact with the transparent prism. In the projection lens, a back focus of the main lens group is much longer compared with a focal length. A projection display apparatus using this projection lens is composed of one main lens group, three auxiliary lenses, and three polarizer-beam splitters, and a color combining optical system for combining three primary color components of red, green, and blue into one light beam is placed between the main lens group and the auxiliary lens.

Abstract: A light valve includes a light valve layer for forming an optical image as variations in its ability to scatter light, and two substrates between which the light valve layer is sandwiched and at least one of which is transparent. The light valve satisfies the following condition: ##EQU1## where t denotes a central thickness of the at least one of the substrates, n denotes a refractive index of the at least one of the substrates and d denotes a maximum diameter of an effective display area of the light valve layer. Alternatively, a transparent plate can be optically coupled to one of the substrates by a transparent body. In this case, the same condition is satisfied except that the thickness refers to a central thickness from a face of the transparent plate remote from the transparent body to the light valve layer.

Abstract: A light valve apparatus in which a first lens array, a second lens array, and a light valve are arranged sequentially from an incident light side, and a focal length of each of the microlens elements for the first lens array is set shorter than a focal length of each of the microlens elements for the second lens array. The respective microlens elements of the second lens array are adapted to form a real image, corresponding to an imaginary object on a focal point of the respective microlens elements of the first lens array, on corresponding pixels of the light valve. A plurality of very small light source images corresponding to the light source are formed by the first lens array, and light emitted from the plurality of very small light source images are incident upon the respective microlens elements of the second lens array such that the images are projected onto the pixels of the light valve.

Abstract: A polarization plane rotator, for executing rotation of the plane of polarization of linearly polarized light that is incident thereon with a predetermined angle of incidence, is formed of a transparent prism or an array of such prisms, each prism having a triangular cross-sectional shape, with first, second and third surfaces having respective lines of intersection that are mutually parallel. The linearly polarized light is incident on the first surface, to be reflected twice in succession at the second and third surfaces, to be emitted from the first surface with the plane of polarization rotated by 90.degree. and the direction of propagation altered. An optical thin film is formed on the second and third surfaces, for substantially reducing an amount of phase difference between the P and S polarization components which results from reflection, thereby ensuring that the emitted light is substantially completely linearly polarized.

Abstract: A light valve apparatus in which a first lens array, a second lens array, and a light valve are arranged sequentially from an incident light side, and a focal length of each of microlens elements for the first lens array is set to be shorter than a focal length of each of microlens elements for the second lens array, and the respective microlens elements of the second lens array are adapted to form real image corresponding to an imaginary object on a focal point of the respective microlens elements of the first lens array, on corresponding pixels of the light valve. By the first lens array, a plurality of very small light source images corresponding to the light source are formed, and light emitted from the plurality of very small light source images are incident upon the respective microlens elements of the second lens array so as to be projected onto the pixels of the light valve.

Abstract: A polarization separation mirror is made by evaporation-depositing a first multi-layers thin film and a second multi-layers thin film respectively on both surfaces of a transparent substrate, the mirror acts as a polarization beam splitter by cementing it between two transparent prism bodies. By shifting the relative film thicknesses of the first multi-layers thin film and of the second multi-layers thin film, reflecting wavelength range for the S-polarization component is changed.

Abstract: A liquid crystal displaying apparatus, a projection displaying apparatus, and a view finder apparatus using the liquid crystal displaying apparatus, are disclosed. Polarizing plates are disposed on the incident side and the outgoing side of a liquid crystal cell so that a twisted nematic liquid crystal is arranged to become approximately 90.degree. in twist angle between two transparent substrates having a picture element electrode. A direction of a phase advancing axis of the phase difference plate with respect to the polarized light axis of the polarizing plate on the incident side is set so that the transmission index of the optical head from the polarizing plate on the incident side to the polarizing plate on the outgoing side may become minimum when a given voltage for black displaying operation is applied on the liquid crystal cell and the light is inputted from the given direction.

Abstract: A picture display apparatus which converts an input optical image into a projected picture using a photoelectric effect. The picture display apparatus includes an image transfer device having a plurality of graded index lenses which are bundled in parallel to an optical axis. The image transfer device is provided between an electro-optical device and a picture display device so that an input optical image on the picture display device is transferred in equisize onto the photoconductive layer of the electro-optical device.

Abstract: An optical system of a projection display apparatus includes a projection lens assembly having a first lens group having a negative power, a second lens group having a negative power and a third lens group having a positive power, all arranged in this order from a side of a screen. An air space is provided between the first and second lens groups and also between the second and third lens groups. Each air space is longer than the entire length of the second lens group as taken along the optical axis of the assembly.

Abstract: A viewfinder suited for use in a video camera, wherein rays of light emitted at a large solid angle from a minute light emitting area of a light emitting element are converted by a condenser lens into a bundle of generally parallel rays of light having a narrow directionality before they enter a liquid crystal display. The liquid crystal display modulates the rays of light emerging from the condenser lens according to a video signal to effect an image display. The displayed image is magnified by a magnifying lens. The liquid crystal display is of a type wherein an optical image is formed as a function of a change in state of light scattering and may be a polymer dispersed liquid crystal display, a liquid crystal panel utilizing a dynamic scattering mode, a ferro-electric liquid crystal panel using a scattering mode or a display panel utilizing PLZT.

Abstract: A polarizer comprising; a substrate transparent to a light of actual use and optical thin films of a higher refractive index than that of said substrate deposited on both surfaces of said substrate. The substrate is arranged so as to receive the incident light obliquely thereto. When the incident angle and the thickness of the optical thin film are optimally selected, the transmittance for the P polarized light can be made approximately 100%, while that for the S polarized light very small. The polarizer can extract a substantially linearly polarized light from natural light, A projection image display system has the polarizer as its pre-polarizer. The polarizer is also useful for infrared radiation.

Abstract: A polarization beam splitter which includes a first prism, a second prism, and a dielectric multilayer film which is sandwiched between the first and second prisms is disclosed. The dielectric multilayer film comprising: a plurality of high refractive index layers having a refractive index higher than refractive indices of the first and second prisms; a plurality of intermediate refractive index layers having a refractive index lower than the refractive index of the high refractive index layers; and a plurality of low refractive index layers having a refractive index lower than the refractive index of the intermediate refractive index layers, a reference incident angle .theta..sub.0 of light which is incident on the dielectric multilayer film through the first or second prism being within a range of the following expression:.theta..sub.1 <.theta..sub.0 <.theta..sub.2where ##EQU1## where n.sub.H indicates the refractive index of the high refractive index layers, n.sub.

Abstract: A liquid-crystal light valve unit and a projection display system using same are provided. The liquid-crystal light valve includes a light valve having openings defining pixels in a matrix arrangement, first light-reflecting layer for reflecting light projected from a light source entering out of the openings of the light valve, a second light-reflecting layer, including openings in a matrix arrangement, located between the light source and the first light-reflecting layer, for directing the light reflected from the first light-reflecting layer toward the light valve while allowing the light from the light source to be propagated through the openings to the light valve, and a lens array including a plurality of positive lens elements in a matrix arrangement for directing the light from the light source to the second light-reflecting layer, a focal point of each of the positive lens elements being defined on a given area in the vicinity of each of the openings of the second light-reflecting layer.

Abstract: An optical system of a projection display apparatus includes a projection lens assembly having a first lens group having a negative power, a second lens group having a negative power and a third lens group having a positive power, all arranged in this order from a side of a screen. An air space is provided between the first and second lens groups and also between the second and third lens groups. Each air space is longer than the entire length of the second lens group as taken along the optical axis of the assembly.

Abstract: A light valve image projection apparatus includes a light source, field lens, liquid crystal panel, a projection lens assembly, and projection screen. The projection lens has a stop forming an aperture of the lens assembly decentered from the optical axis of the lenses of the projection lens assembly in the vertical scanning direction of the liquid crystal panel. Principal rays are approximately parallel to each other within the effective field angle on the side of the liquid crystal cell. In the light valve image projection apparatus principal rays, parallel to each other, are irradiated on the liquid crystal panel at an angle resulting in the highest contrast ratio to produce a projected image having uniformity and high contrast.

Abstract: A polarizer comprising; a substrate transparent to a light of actual use and optical thin films of a higher refractive index than that of said substrate deposited on both surfaces of said substrate. The substrate is arranged so as to receive the incident light obliquely thereto. When the incident angle and the thickness of the optical thin film are optimally selected, the transmittance for the P polarized light can be made approximately 100%, while that for the S polarized light very small. The polarizer can extract a substantially linearly polarized light from natural light. A projection image display system has the polarizer as its pre-polarizer. The polarizer is also useful for infrared radiation.

Abstract: A polarizing beam splitter apparatus of a light valve image projection system includes a polarizing beam splitter commonly usable as a polarizer and an analyzer, and a quarter wave plate in combination. In the polarizing beam splitter apparatus, a quarter wave plate is arranged in a light path along which a light passes out from and passes back again to the polarizing beam splitter in such a manner that either a fast axis or a slow axis of the quarter wave plate is perpendicular to a plane containing both a first optical axis and a second optical axis of the polarizing beam splitter, so that the angular range of a light to be used can be increased. In the light valve image projection system, a light outputted from a light source is incident through a polarizing beam splitter apparatus to a light valve, and an effective component of the light reflected from the light valve is projected through the polarizing beam splitter apparatus and a projection lens on a projection screen.

Abstract: A projection system comprises a light source, a dichroic mirror for separating white light into blue, green and red color light beams, a halfwave plate for converting the direction of polarization, three light valves for forming optical images depending on a picture signal, and three projection lenses for projecting the optical images on the light valves onto a screen. By using the halfwave plate, the color light of p-polarized light component or s-polarized light component emitted from the dichroic mirror is entered into the liquid crystal panel. The gradient width of the spectral distribution of the color light entering the liquid crystal panel is smaller, and the color nonuniformity of projected image by changes of spectral transmittance characteristic of the dichroic mirror with respect to the incident angle is reduced.