To provide a projection optical system that can cover a wide range of magnification changes with a focus lens group in which the number of constituted lenses is decreased, and a projector including the projection optical system. A 1-2nd lens group as the focus lens group includes an F1 lens group configured of one positive lens, an F2 lens group configured of one positive lens and one negative lens, and an F3 lens group configured of one negative lens. At least the F2 lens group is caused to move when focusing is performed in response to a magnification change.

An optical relay system that is capable of re-imaging an image or a pupil from a shared location to two or more optical systems, or from two or more optical systems to a shared location is disclosed.

A projection optical system (2) projects from a DMD (7) on a reducing side onto a screen (9) on an enlargement side, and includes: a first refractive optical system (10) that forms a first intermediate image (51) on the enlargement side using light incident from the reducing side; a second refractive optical system (20) that forms the first intermediate image (51) on the reducing side into a second intermediate image (52) on the enlargement side; and a first reflective optical system (30) including a first reflective surface (31a) with positive refractive power that is positioned on the enlargement side of the second intermediate image (52), wherein the second refractive optical system (20) includes a first focus lens group (61) that moves when focusing is carried out, and the first focus lens group (61) includes at least one lens (L13) included in the second refractive optical system (20).

Eye-tracked head-mounted displays are provide which, in one aspect, may utilize the same optics for eyetracking and image viewing, with a selected portion of the optics used for an eyetracking optical path and a selected portion of the display optics used for an image viewing optical path.

A beam delivery system may include: beam adjusters configured to adjust a divergence angle of a pulse laser beam; a beam sampler configured to separate a part of the pulse laser beam outputted from a first beam adjuster provided at the most downstream among the beam adjusters to acquire a sample beam; a beam monitor configured to receive the sample beam and output a monitored diameter; and a beam delivery controller configured to control the beam adjusters based on the monitored diameter. The beam delivery controller may adjust each of beam adjusters other than the first beam adjuster selected one after another from the most upstream so that the monitored diameter at the beam monitor becomes a predetermined value specific to the beam adjuster, and adjust the first beam adjuster so that the pulse laser beam becomes focused at a position downstream of a target position.

Optical systems, such as 2-D and 3-D projection systems, may be configured to have a compact back focal length to allow for more compact projection lenses, lower throw ratios, improved contrast, or any combination thereof. In an embodiment, an optical system may include a relay element configured to form an intermediate image having a focal point proximate to a projection lens.

A compact, uniaxially-aligned series of lenses are shaped and coated to allow coaxial viewing of two different fields of view on the same focal-plane array by selecting a type of light. The selection can be, for example, by spectrum or polarization. Zonal coatings on the lens surfaces permit for a catadioptric narrow field-of-view light path. The lens assembly accomplishes simultaneous dual field-of-view in a durable package without respective motion of optical elements, without substantial gaps between the lenses, and at lower cost than other assemblies.

A front projection display device is provided including an image-generating source configured to generate an image, a wide angle lens system adapted to receive the image, and a screen. The wide angle lens system may be configured to increase distortion of the image in a first stage and decrease distortion of the image in a second stage. The screen may be configured to receive the image from the wide angle lens system on a first side and reflect the image back to a viewer on the first side. In another embodiment, a screen is provided for a front projection system, the screen may be configured to receive light from a steep angle and may include any number of surface topographies configured to reflect light back to the viewer along a desired viewing plane.

A variable magnification optical system includes, in order from the object side along the optical path, a first group that has a positive power, a second group that has a positive power, a third group that has a negative power, a stop, a fourth group that has a positive power, and a fifth group that has a positive power. The first group includes two mirrors. An intermediate image is formed in the optical path between the first group and the second group. The second group, the third group, and the fourth group are refractive optical systems. During changing magnification, the two mirrors of the first group, the second group, the stop, and the fifth group are immovable, the third group moves to the image side, and the fourth group moves to the object side.

A projection objective for microlithography for imaging an object field onto an image field includes: a first partial objective for imaging the object field onto a first real intermediate image; a second partial objective for imaging the first intermediate image onto a second real intermediate image; a third partial objective for imaging the second intermediate image onto the image field, the third partial objective including an aperture; and a first folding mirror for deflecting radiation toward a concave mirror and a second folding mirror for deflecting the radiation from the concave mirror toward the image plane; in which the projection objective is an immersion projection objective in which during operation an immersion liquid is situated between a last lens surface and an image plane, and at least one surface of at least one lens in the second partial objective has an antireflection coating including at least six layers.