In a projection optical system for use in an image projection apparatus illuminating an image display panel forming an image in accordance with a modulating signal with illumination light from a light source, the projection optical system includes first and second optical systems arranged along an optical path defining an upstream-downstream direction in the order described from upstream to downstream on the downstream side of the image display panel. The first optical system includes at least one dioptric system and has positive power. The second optical system includes at least one reflecting surface having power and has positive power. The image formed by the image display panel is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.

A projection optical system includes an eyepiece optical system configured to refract and reflect a light emitted from an image forming unit for forming image information to display a virtual image, wherein the eyepiece optical system includes at least a concave lens, a folding mirror, and a concave mirror which are successively placed in order from the image forming unit including a liquid crystal display panel. The projection optical system configured as above is provided on a head-up display.

A head-up display is configured to project an image on a transparent reflection member to cause an observer to visually recognize a virtual image, and includes a display device configured to display the image, and a projection optical system configured to project the image displayed by the display device as the virtual image for the observer. The projection optical system is configured to form the image as an intermediate image, and includes a first optical element configured to condense light, a first lens configured to condense light, and a second optical element configured to diffuse light. The first optical element, the first lens, and the second optical element are disposed in this order along an optical path from the display device.

A display device has a display, operable to generate a real image, and an optical system. In the optical system are at least two free-form reflective surfaces, S I and S2. At least one of the reflective surfaces is convex in one direction at substantially all points of its optically active area. Light rays from the display are reflected on SI before they are reflected on S2. The reflective surfaces SI and S2 are arranged to generate a virtual image from the real image on the display, by projecting light from the display to an eye position. The field of view occupied by the virtual image as seen from the eye position is greater than 50 degrees in at least one direction, preferably the direction linking the two eyes of an intended user.

A lens system includes a curved primary mirror and an aspheric secondary mirror. The aspheric secondary mirror has a diameter smaller than that of the primary mirror and shares an optical axis with the primary mirror. The aspheric secondary mirror and the primary mirror are rotationally symmetric with respect to the optical axis. A support member, which may be transparent over an operating wavelength of the lens system, is disposed on the aspheric secondary mirror.

A display device has a display, operable to generate a real image, and an optical system with one or more lenslets arranged to generate a virtual sub-image from a respective partial real image on the display, by each lenslet projecting light from the display to an eye position. The sub-images combine to form a virtual image viewable from the eye position. A radial focal length distribution of the optical system decreases with increasing radial angle at radial angles greater than 20 from the frontward direction.

The imaging optical system consists of, in order from a magnification side: a catoptric system; and a dioptric system that includes a plurality of lenses. The dioptric system forms a first intermediate image between the dioptric system and the catoptric system on an optical path and at a position conjugate to a reduction side imaging surface, and the catoptric system re-forms the first intermediate image on a magnification side imaging surface. The catoptric system consists of a first reflective surface, a second reflective surface, and a third reflective surface in order along the optical path from the magnification side. The first reflective surface and the third reflective surface are formed on one member and have the same surface shapes.

A display device has a display, operable to generate a real image, and an optical system, comprising one or more lenslets, arranged to generate a virtual sub-image from a partial real image on the display, by each lenslet projecting light from the display to an eye position. The sub-images combine to form a virtual image viewable from the eye position. At least one lenslet is symmetric with respect to a plane, and the display surface is cylindrical with its axis perpendicular to that plane.

An image projection device projects an image to a projection surface, and includes an image forming element, a refractive optical unit, and a reflective optical unit. The image forming element forms an image to be projected to the projection surface based on an image signal. The refractive optical unit has a refractive optical system including a plurality of lenses guiding light of the image toward the projection surface, the image being formed by the image forming element. The reflective optical unit includes a reflective optical system having a first mirror reflecting the light guided by the refractive optical system and a second mirror reflecting the light reflected by the first mirror toward the projection surface; and a blocking section including a blocking surface disposed at a position of blocking part of light generated in the refractive optical unit and passing through between the first mirror and the second mirror.

A laser system includes: A. a solid-state laser apparatus configured to output a pulse laser beam having light intensity distribution in a Gaussian shape that is rotationally symmetric about an optical path axis; B. an amplifier including a pair of discharge electrodes and configured to amplify the pulse laser beam in a discharge space between the pair of discharge electrodes; and C. a conversion optical system configured to convert the light intensity distribution of the pulse laser beam output from the amplifier into a top hat shape in each of a discharge direction of the pair of discharge electrodes and a direction orthogonal to the discharge direction.