Hitachi, Ltd.

Tsutomu Nakashima

Masahiko Yatsu

Satoshi Ouchi

Taro Imahase

Koji Hirata

Nobuyuki Kimura

Tomohiro Miyoshi

Kazuo Shikita

Nobuo Masuoka

Satoshi Nakayama

Hidehiro Ikeda

Futoshi Yamasaki

Shuji Kato

Takuya Shiaki

Eiji Yamaguchi

A technique according to the present invention allows a projection-type image display system to suppress the temperature rise of the polarization split devices and secure high image quality. Polarization split means has a polarization split device arranged in a medium with a refractive index larger than 1. The polarization split device has a polarization split surface on which a diffractive grating structure is formed to polarize and split light. An air layer is formed in contact with the polarization split surface. In a projection type image display apparatus or an optical unit using this apparatus, light fluxes are polarized and split by the polarization split means before irradiated to light valves and after modulated by the light valves and color composition is made from the polarized and split light fluxes before enlarged and projected by a projection lens unit.

Optical unit and projection-type image display apparatus using the same

A compact, light projection type image display apparatus based on reflection image display devices which provide high brightness without contrast deterioration caused by light leakage associated with black image display. The apparatus uses, as polarizers/analyzers for reflection image display devices, reflection polarizing plates which function as polarizing plates by their grating function only in a specific direction. In each light path, the reflection polarizing plate is located just before/after the reflection image display device.

Projection type image display apparatus using reflective image display elements, reflective polarizing plates and auxiliary analyzers

An optical unit includes a light source, a color separator, reflection-type image display elements, a color synthesizer, a reflection-type polarization plate, and an optical chassis. The optical chassis holds the reflection-type polarization plate and the reflection-type image display elements thereon, and has a translucent window on an incident light side of the reflection-type polarization plate while an exiting light side of the reflection-type polarization plate is sealed with an incident surface of the color synthesizer. A hermetically sealed space is defined by the optical chassis, the reflection-type image display elements and the incident surface of the color synthesizer, and within the hermetically sealed space is disposed a translucent liquid having a refraction index from 1.2 to 1.9.

Optical unit and projection type image display unit using it

The present invention provides a projection type image display device capable of affording a bright display of a high saturation and capable of ensuring a high reliability of optical parts. The projection type image display device is provided with a color synthesizer for color-synthesizing modulated and polarized light of red light, green light, and blue light, outputted from an image display element. The color synthesizer has an optical characteristic such that the transmittance including reflection by a reflecting film in the interior of the color synthesizer becomes highest for the polarized light of blue light out of the modulated and polarized light of red light, that of green light, and that of blue light. The color synthesizer also has an optical characteristic such that the quantity of the polarized light of blue light outputted becomes largest out of the modulated and polarized light of red light, green light, and blue light.

Projection type image display device, rear projection type image display device, optical unit, and screen unit

The present invention provides a projection image display technology capable of correcting astigmatism due to use of a polarized-beam splitter, thus ensuring high-resolution projection images. A wire-grid polarized-beam splitter (or the like) of a flat-plate-like structure is used as a polarized-beam splitter, and an astigmatism correction element, such as a cylindrical lens, is provided between the polarized-beam splitter and a projection lens unit.

Optical unit and a projection image display apparatus using the same

In a projection type image display apparatus, a projector optical unit for projecting an image onto a screen while magnifying a size of the image to be projected with respect to an original size of the image displayed by an image forming element, has a group of lenses for magnifying the size of the image with respect to the original size thereof, and an optical path extending from the image forming element to the screen to transmit the image along the optical path.

Projector optical unit, projection type image display apparatus, and rear projection type image display apparatus

Projection type image display apparatus

A quarter wavelength plate for reducing the dependence of a retardation value on an incident beam angle in optically anisotropic crystals. The quarter wavelength plate is formed of optically anisotropic crystals in a thickness of 0.1 mm to 0.5 mm. The quarter wavelength plate can contribute to a reduction in the dependence of the retardation value on the angle at which a light beam impinges on the quarter wavelength plate, and to a reduction in color shading caused by a rise in temperature. A reflection type liquid crystal display device which employs the quarter wavelength plate can enhance the luminance and contrast.

Quarter wavelength plate and projection type video display device using the same

Disclosed is a compact, light, inexpensive reflection type liquid crystal projector optical unit or reflection type liquid crystal projector which provides high brightness without contrast deterioration caused by light leakage associated with black image display. The unit or projector uses, as a polarizer/analyzer for a reflection liquid crystal panel, a reflection polarizing plate which functions as a polarizing plate by its grating function only in a specific direction. It also uses an auxiliary polarizer and an absorption auxiliary analyzer. Their reflection axis or absorption axis is adjusted according to the characteristic of the reflection liquid crystal panel so as to minimize light leakage associated with black image display.

Quarter wavelength plate and projection type video display device using same

A projection display according to the present invention reduces the size of a light beam in the optical path of an illumination optics from the periphery to change the amount of light incident on a video display device and the angle of such incidence, thereby making a plurality of image brightness/contrast combinations selectable. Further, the present invention changes the revolving speed of a projection display cooling fan and the adjustment value settings for the video display device's electrical characteristics in accordance with the aperture.

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Yokohama, Japan

Tsutomu Nakashima