Abstract: A rear projection screen for use in a rear projection display apparatus contains a Fresnel lens sheet, a horizontal lenticular lens sheet capable of horizontally refracting the incident light, and a vertical lenticular lens sheet capable of vertically refracting the incident light, in this order from the incident side of the incident light, in which the lens center of the Fresnel lens sheet is arranged upward with respect to the mechanical center of the screen, and, in relation to this arrangement, black stripes of the vertical lenticular lens sheet are shifted with respect to the vertical lenticular lens.

Abstract: A liquid crystal display device has a liquid crystal cell, a liquid crystalline substance layer, a pair of polarizers, and an optical compensation element. The twist angle of the liquid crystal cell is set to 180 to 270 degrees. The optical compensation element has a twisted structure twisted in the opposite direction to that of the liquid crystal cell. The difference in the absolute values of the twist angles between the liquid crystal cell and the optical compensation element is from 40 to 100 degrees. The difference in retardation at a wavelength ?=550 nm between the liquid crystal cell and the optical compensation element is from 100 to 250 nm. When the absolute values of the differences in retardation at wavelengths ? of 400 nm and 550 nm between the liquid crystal cell and the optical compensation element are represented by ?R(400) and ?R(550), respectively, and the ratio D therebetween is represented by D=?R(400)/?R(550), D is within the range of 0.5 to 1.0.

Abstract: An object of the invention is to provide a rear projection screen that has a high contrast and produces high-quality images. The object is achieved by a rear projection screen and rear projection display apparatus having the same. This rear projection screen contains a vertical lenticular lens sheet on the viewer side, and the vertical lenticular lens sheet includes a lenticular lens capable of vertically refracting the incident light on its incident surface, black stripes in the vicinity of the focus of the lenticular lens in portions where the incident light does not pass through, and a flat surface on its viewer side.

Abstract: A liquid crystal display device comprises a liquid crystal cell, polarizers disposed on both sides of the liquid crystal cell, and an optical compensation element disposed on at least one side of the liquid crystal cell between the liquid crystal cell and the polarizers, wherein the twist angle of the liquid crystal layer in the liquid crystal cell is set to from 180 to 270 degrees; the optical compensating element has a twisted structure twisted in the opposite direction to that of the liquid crystal layer; the difference in the absolute values of the twist angles between the liquid crystal cell and the optical compensation element is from 40 to 100 degrees; the difference in retardation at a wavelength &lgr;=550 nm between the liquid crystal cell and the optical compensation element is from 100 to 250 nm; and the ratio of the absolute values of the differences in retardation at wavelengths &lgr; of 400 nm and 550 nm between the liquid crystal cell and the optical compensation element is within the ra

Abstract: A rear projection screen for use in a rear projection display apparatus contains a Fresnel lens sheet, a horizontal lenticular lens sheet capable of horizontally refracting the incident light, and a vertical lenticular lens sheet capable of vertically refracting the incident light, in this order from the incident side of the incident light, in which the lens center of the Fresnel lens sheet is arranged upward with respect to the mechanical center of the screen, and, in relation to this arrangement, black stripes of the vertical lenticular lens sheet are shifted with respect to the vertical lenticular lens.

Abstract: A complex diffraction device, which is excellent in designability, easy in setting the diffraction angle, adaptable to size increase, and easy to handle by adding a diffraction function resulting from an uneven pattern to the diffraction device comprising a liquid crystalline layer where the helical orientation of the smectic liquid crystal phase having a helical structure is maintained.

Abstract: A transflective liquid crystal display providing a bright displayed image of high contrast in the transmission mode with less dependence on the viewing angle by combining a polarizer with an optically anisotropic element having a liquid crystal film in which a twisted nematic alignment stricture is secured to produce a circular polarizer and disposing the circular polarizer on the rear side of a transflector in the transflective liquid crystal display.

Abstract: A transflective liquid crystal display providing a bright displayed image of high contrast in the transmission mode with less dependence on the viewing angle by combining a polarizer with an optically anisotropic element having a liquid crystal film in which a twisted nematic alignment stricture is secured to produce a circular polarizer and disposing the circular polarizer on the rear side of a transflector in the transflective liquid crystal display.

Abstract: A complex diffraction device, which is excellent in designability, easy in setting the diffraction angle, adaptable to size increase, and easy to handle by adding a diffraction function resulting from an uneven pattern to the diffraction device comprising a liquid crystalline layer where the helical orientation of the smectic liquid crystal phase having a helical structure is maintained.

Abstract: A laminated transparent structure for a reflective display which is used, for example, as a head-up display of an automotive vehicle. The laminated transparent structure comprises a glass plate. A transparent layer is bonded to the glass plate. An optical rotation film is disposed between the glass plate and the transparent layer. Additionally, a hot-melt adhesive is disposed between the optical rotation film and the glass plate to bond the optical rotation film to the glass plate.

Abstract: A rear projection screen is used for a projection optical system where projected lights perpendicularly enter the screen from the rear face of the screen includes a Fresnel lens sheet incorporating a prism and a lenticular lens sheet that horizontally disperses lights emitted from the Fresnel lens sheet incorporating a prism. The Fresnel lens sheet incorporating a prism has a linear prism, which acts as a linear Fresnel lens for converging image lights in the screen height direction, at the projection light source side, and has a circular Fresnel lens, which acts to converge image lights in the direction of the screen center, at the observer side. According to the rear projection screen, the peak screen gain is increased and the peripheral luminance ratio is improved without degrading light utilization efficiency.

Abstract: Provided is an optical device through which the angle of light passing and going out has little wavelength dependency and which is well applicable to Fresnel lenses with little coloration of light passing through it. The optical device has a diffraction grating formed on one surface and capable of diffracting rays of light incident thereon, and has a refracting member (e.g., a Fresnel lens) formed on the other surface opposite to the diffraction grating and capable of refracting the diffracted rays of light from the diffraction grating to make the refracted rays of light go out of it, in which the wavelength dependency of the diffractive angle of the main rays diffracted by the diffraction grating compensates for the wavelength dependency of the refractive angle thereof refracted by the refracting member, or that is, the former wavelength dependency is opposite to and cancels out the latter one.

Abstract: A novel optical film capable of readily vitrifying the tendency and state of liquid crystal alignment, excellent in the ability to retain the alignment state, and suitable for the application to optical elements. The film is produced from a liquid-crystal material containing as the essential ingredient a liquid-crystal polyester having structural units (A) and (B) as the essential unit, exhibiting a vitrified state at a temperature lower than the liquid-crystal transition point, and having a logarithmic viscosity number (&eegr;) of 0.04-0.4 dl/g as measured at 30° C. in a phenol/tetrachloroethane solvent (60/40 by weight), wherein each X represents independently O or C═O; each Y represents independently a group selected from among F, Cl, Br and 1-4C alkyls; and n is 0 or 1.

Abstract: The object of the present invention is to provide an optical pulse generator which very stably generates for a long period of time a high cycling frequency optical pulse chain. In order to obtain this object, in a ring type resonator R, the present invention provides an optical path length regulator 14 which performs high precision optical path length adjustment and an optical path length regulator 60 which performs wide range optical path length adjustment, and extracts a clock signal by converting an optical pulse emitted from the ring type resonator R to an electrical signal by a clock extractor 42, detects the frequency difference between a base frequency signal output form a synthesizer 52 by a frequency difference detector 50, and controls said optical path length regulator 14 and said optical path length regulator 60.

Abstract: According to the present invention, damage to a photo-detector disposed in clock signal extractor by means of an optical pulse having an optical power exceeding a rated value is prevented. A ring resonator generates a repetitive, high-frequency optical pulse. Optical branching circuit branches a portion of the optical pulse circulating through ring resonator, while optical branching circuit further branches a portion thereof to protective device. Pumping source generates an excitation light for exciting a rare-earth doped optical fiber. Optical multiplexer couples the optical pulse branched by optical branching circuit, and the excitation light. Upon excitation by means of the excitation light, rare-earth doped optical fiber amplifies and emits the incoming optical pulse. The optical power of the excitation light is adjusted such that the output of rare-earth doped optical fiber reaches a saturation power.

Abstract: A double-faced lenticular lens sheet including at least one incident side lens formed on a first face of the double-faced lenticular lens sheet; and at least one corresponding emergent side lens formed on a second opposite face of the double-faced lenticular lens sheet; wherein light rays incident on the at least one incident side lens parallel to an optical axis thereof pass through the lenticular lens sheet and emerge from the at least one emergent side lens; an angle of refraction .theta.1 is formed by a straight line parallel to an optical axis of the at last one incident side lens and a light ray refracted by an incident plane passing through the lenticular lens sheet; an angle of refraction .theta.2 is formed by a straight line parallel to an optical axis of the at least one emergent side lens and the light ray refracted by and emitted from an emergent plane; .DELTA..theta.1 is an absolute value of the angle of refraction .theta.1 on the incident plane; .DELTA..theta.

Abstract: The present invention provides a novel liquid crystalline polyester comprising structural units represented by the following general formulae A, B, C and D: ##STR1## where X and Y are each independently H, Cl, Br or an alkyl group having 1 to 4 carbon atoms, the molar ratio of A/B is in the range from 49/1 to 20/30 and that of C/D is in the range from 10/40 to 45/5.

Abstract: In a rear-projection screen comprising a Fresnel lens and a light-diffusing member such as a lenticular lens sheet, a rise angle in a central region of the Fresnel lens is smaller than a rise angle in an intermediate region thereof (e.g., the former is not larger than 3.degree. and the latter is larger than 3.degree. ). The rise angles may preferably gradually increase from the central region of the Fresnel lens toward the intermediate region thereof. The central region of the Fresnel lens may preferably be a region extending within the range of from 1/4 to 1/3 from the middle point of a diagonal of the rear-projection screen. Such a Fresnel lens is effective for improving white uniformity in the intermediate region of the rear-projection screen and eliminating color corn in the central region thereof.

Abstract: A hydraulically actuated tensioner of a toothed belt. A piston slidable with clearance in a cylinder forms front and rear oil-filled chambers communicating through a passage in the piston with a check valve for restricting flow in one direction. A piston rod extending from one end of the piston is urged by a spring, through the front chamber, against a roller to impart tension on the belt. An oil reservoir communicating with the front chamber is enclosed by a spring-biased diaphragm for maintaining the oil pressure in the chambers above atmospheric pressure at all times.

Abstract: Novel 2-oxopyrrolidine compounds represented by the formula ##STR1## wherein R.sup.1 and R.sup.2 are hydrogen or alkyl group, respectively, A is alkylene group or phenyl substituted alkylene group, and B is alkylene group,or a salt thereof, a process for the preparation thereof, and a pharmaceutical agent comprising the compound or salt as an effective component.