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 display device according to the present invention includes, along an optical path of image light emitted from an image light generating device, a first optical unit having positive power, a second optical unit having positive power and including a first diffraction element of a reflective type, a third optical unit having positive power, and a fourth optical unit having positive power and including a second diffraction element of a reflective type. The second optical unit includes a first light-transmitting member having optical power and provided at a first surface of the first diffraction element, and a light shielding member provided at a second surface of the first diffraction element.

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.

Provided is an optical device that involves a simple attachment operation without the need for an adjustment process. The optical device includes a transparent body portion having a plurality of curved faces on its outer peripheral surface; and a blind-spot-side outward facing curved reflecting mirror, a blind-spot-side inward facing curved reflecting mirror, an eve-point-side inward facing curved reflecting mirror, and an eye-point-side outward facing curved reflecting mirror, which are integrally formed with the body portion. The body portion has formed therein an optical path that allows a light beam reflected by the blind-spot-side outward facing curved reflecting mirror to be sequentially reflected by the blind-spot-side inward facing curved reflecting mirror and the eye-point-side inward facing curved reflecting minor and then reach the eye-point-side outward facing curved reflecting mirror.

An optical system (L0) that forms an image of an object and that includes an aperture stop (SP), a first reflection surface (R2), and a second reflection surface (R3) which are disposed in order from an enlargement side to a reduction side, an area of the first reflection surface is larger than an area of the second reflection surface, a reference axis is a path of a reference ray that passes through an opening center of the aperture stop to reach a center of a reduction plane, and an angle QPR (deg) between a line segment PQ connecting the opening center P and an intersection Q of the reference axis and the first reflection surface, and a line segment PR connecting the opening center P and an intersection R of the reference axis and the second reflection surface satisfies a predetermined condition.

An imaging optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first mirror as a convex mirror, a first lens unit, a second mirror as a concave mirror, a third mirror as a concave mirror, and a second lens unit. The imaging optical system is configured to form a first intermediate real image and a second intermediate real image located at a position different from that of the first intermediate real image between the first mirror and a reduction side conjugate plane.

A method for generating high resolution multi-spectral light fields is disclosed. The method may include capturing a multi-perspective spectral image which includes a plurality of sub-view images; aligning and warping the sub-view images to obtain low resolution multi-spectral light fields; obtaining a high resolution dictionary and a low resolution dictionary; obtaining a sparse representation based on the low resolution multi-spectral light fields and the low resolution dictionary; and generating high resolution multi-spectral light fields with the sparse representation and the high resolution directory. Each sub-view image is captured with a different perspective and a different spectral range. The multi-perspective spectral image is obtain with one exposure.

In a method for three-dimensionally measuring a 3D aerial image in the region around an image plane during the imaging of a lithography mask, which is arranged in an object plane, a selectable imaging scale ratio in mutually perpendicular directions (x, y) is taken into account. For this purpose, an electromagnetic wavefront of imaging light is reconstructed after interaction thereof with the lithography mask. An influencing variable that corresponds to the imaging scale ratio is included. Finally, the 3D aerial image measured with the inclusion of the influencing variable is output. This results in a measuring method with which lithography masks that are optimized for being used with an anamorphic projection optical unit during projection exposure can also be measured.

A method for generating high resolution multi-spectral light fields is disclosed. The method may include capturing a multi-perspective spectral image which includes a plurality of sub-view images; aligning and warping the sub-view images to obtain low resolution multi-spectral light fields; obtaining a high resolution dictionary and a low resolution dictionary; obtaining a sparse representation based on the low resolution multi-spectral light fields and the low resolution dictionary; and generating high resolution multi-spectral light fields with the sparse representation and the high resolution directory. Each sub-view image is captured with a different perspective and a different spectral range. The multi-perspective spectral image is obtain with one exposure.

An imaging optical unit serves within a metrology system for examining a lithography mask. The lithography mask can be arranged in an object field of the imaging optical unit. The object field is defined by two mutually perpendicular object field coordinates. The imaging optical unit has an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1. This results in an imaging optical unit which can be used for the examination of lithography masks that are designed for projection exposure with an anamorphic projection optical unit.