Abstract: An image display apparatus for a viewer to view a two-dimensional image demonstrated on an image display device as an enlarged virtual image by a virtual-image optical system. The image display apparatus includes a prism and a reflective transmitting surface for reflecting or transmitting image light incident from an incident optical surface. The image display apparatus also includes a reflective optical component for reflecting image light reflected from the reflective transmitting surface and radiated from a first planar optical surface towards the reflective transmitting surface as a collimated light beam and a phase difference optical component arranged on a light path between the first planar optical surface and the reflective optical component to the state of polarization of the image light.

Abstract: Disclosed is an image display apparatus for a viewer to view a two-dimensional image, demonstrated on an image display device, as an enlarged virtual image by a virtual-image optical system. The image display apparatus includes a prism (15), provided with a second planar optical surface (15c), arranged parallel to a first planar optical surface (15b) on a side towards an optical pupil (19), and with a reflective transmitting surface (16) for reflecting or transmitting image light incident from an incident optical surface (15a), which has an optical axis with an angle of tilt not less than 30 degrees and less than 90 degrees relative to a normal to the first planar optical surface or to the second planar optical surface, and on which is incident image light, demonstrated on an image display device (11) and relayed by a relaying optical system.

Abstract: A projection lens of the retrofocus type that has a long back focus and that can project with a high contrast, exhibits small aberrations and converts a light path inside the lens. A first lens set having a negative refractive power, a light path converter, and an iris and a second lens set having a positive refractive power and an aspheric lens are disposed in order from the screen side. The first lens set includes a lens set having a negative refractive power and one or more aspheric lenses, a bending mirror serving as the light path converter, and a lens set having a positive refractive power. The lenses in the first lens set have an outer shape with a portion thereof cut outside an effective light ray in a direction of the light path conversion, and the direction of the light path conversion is a direction of a shorter side of rectangular image formation element.

Abstract: A projection lens of the retrofocus type which has a long back focus, can project with a high contrast, exhibits small aberrations such as a distortion aberration and converts a light path in the inside thereof. A first lens set (0) having a negative refractive power and having light path conversion means built therein, an iris (400) and a second lens set (300) having a positive refractive power and including an aspheric lens are disposed in order from the screen side. The first lens set (0) includes a first A lens set (100) having a negative refractive power and including one or more aspheric lenses, a bending mirror (M) serving as the light path conversion means, and a first B lens set (200) having a positive refractive power. The lenses in the first A lens set have an outer shape with a portion thereof cut outside an effective light ray in a direction of the light path conversion, and the direction of the light path conversion is a direction of a shorter side of the rectangular image formation element.

Abstract: A video display apparatus which exhibits high utilization efficiency of a luminous flux from a light source and can provide a uniform video. The video display apparatus includes a light source unit including a plurality of coupling optical elements for converting light emitted from a plurality of light sources into a substantially parallel luminous flux and operable to condense light having passed through the coupling optical elements at a predetermined position, an optical integrator for equalizing the intensity distribution of the condensed light, and a light valve.

Abstract: A projection lens including a first lens group, a diaphragm, and a second lens group, which are disposed in that order from a screen to an image source. The first lens group includes an aspherical lens and at least one positive lens, and has a positive refractive power. The second lens group includes at least one set of combined lenses and an aspherical lens, and has a positive refractive power. A lens gap in the first lens group is moved to perform a focusing operation. It is possible to provide a wide-angle projection lens which uses few lenses and has a long back focus and focal length when BF/F is greater than 1.87, and HF2/F2 is greater than 0.22 but less than 0.57, where F denotes the focal length of the projection lens, BF denotes the distance in air from a last lens surface of the second lens group to the image source, F2 denotes the focal length of the second lens group, and HF2 denotes the location of a front principal point of the second lens group.

Abstract: A video display apparatus is disclosed which exhibits high utilization efficiency of a luminous flux from a light source and can provide a uniform video. The video display apparatus includes a light source unit including a plurality of coupling optical elements for converting light emitted from a plurality of light sources into a substantially parallel luminous flux and operable to condense light having passed through the coupling optical elements at a predetermined position, an optical integrator for uniformizing the intensity distribution of the condensed light, and a light valve.

Abstract: A projection lens which has a wide angle view, a short projection distance and telecentricity, and in which the projection can be performed with high contrast, various aberrations such as a distortion aberration are reduced and the optical path is converted by providing a first lens group having negative refractive power and second and third lens groups having positive refractive power are arranged from a longer conjugate side. Representing a back focus at a projection distance of an infinite point by BF; the composite focus distance of the entire system by F; a center distance between said first lens group and said second lens group by GD1; the composite focus distance of said first lens group by F1; the composite focus distance of said second lens group and said third lens group by F23; and the center distance between said second lens group and said third lens group by GD2, the following relationships are satisfied:[2.8<BF/F],[3.0<GD1/F<4.50],[0.40<-F1/F23<0.48],and[0.40<GD2/F23<0.8].

Abstract: The invention provides an optical visual apparatus which eliminates ghost light and is small in size and light in weight so that observation for a long time does not tire the eyes of a user and the user does not suffer from displacement of the apparatus on the head. A half mirror for reflecting image light from a two-dimensional display element is formed in a wedge-shaped profile having a varying thickness such that an opposing surface opposing to a half-coated surface is inclined with respect to the half-coated surface. The inclination angle of the opposing inclined surface and the Abbe's number of the half mirror are so set that ghost light and regular light are overlapped with each other at the position of an eye-ball of the user or the ghost light is reflected to the outside of the field of view of the user so that the ghost light may not be observed by the user.

Abstract: A fast lens system is provided which includes a front lens group having a negative power, a diaphragm, and a rear lens group having a positive power, arranged in this order from a side of an object of the lens system. The lens system satisfies the following conditions:-0.5<f/f,<-0.2; (1)1.0<.SIGMA.d.sub.F+S /f<3.0; (2)ana1.5<.SIGMA.d.sub.R /f<3.0, (3)wherein f represents a focal length of the entire lens system, f.sub.F represents a focal length of the front lens group, .SIGMA.d.sub.F+S represents a sum of the thickness of the front lens group and the distance between the front lens group and the rear lens group, and .SIGMA.d.sub.R represents a thickness of the rear lens group.

Abstract: A fast aspherical lens system is provided which includes a front lens group having a negative power, a diaphragm, and a rear lens group having a positive power, arranged in this order from the side of an object to be photographed. The rear lens group is provided with at least one lens having a diverging aspherical surface and satisfies the following conditions:-0.6<f/f.sub.F,<-0.2;tm (1)3.0<.SIGMA.d.sub.F+S /f<8.0; (2)3.0<.SIGMA.d.sub.R /f<6.0; (3)-0.9<.DELTA.I.sub.ASP <-0.1; (4)where f represents a focal length of the entire lens system, f.sub.F represents a focal length of the front lens group, .SIGMA.d.sub.F+S represents a sum of the thickness of the front lens group and a distance between the front lens group and the rear lens group, and .SIGMA.d.sub.r represents a thickness of the rear lens group, and .DELTA.I.sub.ASP represents an aberration factor of the aspherical surface term of the third-order spherical aberration factor of the aspherical lens.

Abstract: A fast ultra-wide angle lens system is provided which includes a front lens group having a negative power, a diaphragm, and a rear lens group having a positive power, arranged in this order from a side of an object to be photographed. The lens system satisfies the following conditions:-0.5<f/f.sub.F <-0.2; (1)7.0<.SIGMA.d.sub.F+S /f<12.0; and (2)5.0<.SIGMA.d.sub.R /f<10.0, (3)wherein f represents a focal length of the entire lens system, f.sub.F represents a focal length of the front lens group, .SIGMA.d.sub.F+S represents a sum of the length of the front lens group and a distance between the front lens group and the rear lens group, and .SIGMA.d.sub.R represents a length of the rear lens group.

Abstract: A zoom lens system includes, in order from the object side, a first lens unit that remains fixed during zooming and which has a positive power, a second lens unit that has a zooming capability, that moves during zooming and that has a negative power, a third lens unit that has a capability of compensating for the position of the focal point, that moves during zooming and that has a negative power, and a fourth lens unit that has an imaging capability, that remains fixed during zooming and that has a positive power, said fourth lens unit comprising a first sub-unit that comprises, in order from the object side, a positive lens element, a positive lens element and a negative lens element and that has a positive overall power, and a second sub-unit that comprises, in order from the object side, a positive lens element, a negative lens element and a positive lens element and that has a positive overall power. The zoom lens system satisfies the specified conditions.

Abstract: An image display apparatus for a viewer to view a two-dimensional image demonstrated on an image display device as an enlarged virtual image by a virtual-image optical system. The image display apparatus includes a prism and a reflective transmitting surface for reflecting or transmitting image light incident from an incident optical surface. The image display apparatus also includes a reflective optical component for reflecting image light reflected from the reflective transmitting surface and radiated from a first planar optical surface towards the reflective transmitting surface as a collimated light beam and a phase difference optical component arranged on a light path between the first planar optical surface and the reflective optical component to the state of polarization of the image light.