Optical systems including an image surface, a stop surface, a partial reflector disposed between the image surface and the stop surface, a reflective polarizer disposed between the stop surface and the partial reflector, and a quarter wave retarder disposed between the reflective polarizer and the partial reflector are described. The reflective polarizer is convex along two orthogonal axes. The reflective polarizer may be a thermoformed multilayer reflective polarizer.

Optical systems including first and second optical stacks and adapted to provide an adjustable dioptric correction are described. The first optical stack includes a first optical lens and a partial reflector. The second optical stack is convex along orthogonal first and second axes and includes a second optical lens and a reflective polarizer. The reflective polarizer has at least one first location having a radial distance r1 from an optical axis of the second optical stack and a displacement s1 from a plane perpendicular to the optical axis at an apex of the reflective polarizer, where s1/r1 is at least 0.1. A quarter wave retarder is disposed between the second optical stack and the first optical stack.

There is disclosed an optical device, including a light-transmitting substrate having an input aperture, an output aperture, at least two major surfaces and edges, an optical element for coupling light waves into the substrate by total internal reflection, at least one partially reflecting surface located between the two major surfaces of the light-transmitting substrate for partially reflecting light waves out of the substrate, a first transparent plate, having at least two major surfaces, one of the major surfaces of the transparent plate being optically attached to a major surface of the light-transmitting substrate defining an interface plane, and a beam-splitting coating applied at the interface plane between the substrate and the transparent plate, wherein light waves coupled inside the light-transmitting substrate are partially reflected from the interface plane and partially pass therethrough.

A beam diameter expanding device includes a first optical element and a second optical element. The first optical element expands a beam diameter of a light beam entering through a first incident face by expanding in a first direction, and emits the expanded light beam from a first emission face. The second optical element expands a beam diameter of the light beam that entered through a second incident face in a state expanded in beam diameter in the first direction by the first optical element, by expanding in a second direction, and emits the expanded light beam from a second emission face. A width of the first incident face in the second direction (the direction of beam diameter expansion by the second optical element) is narrower than a width of the second incident face in the first direction (the direction of beam diameter expansion by the first optical element).

Embodiments of the present invention are directed to autofocus subsystems within optical instruments that continuously monitor the focus of the optical instruments and adjust distances within the optical instrument along the optical axis in order to maintain a precise and stable optical-instrument focus at a particular point or surface on, within, or near a sample. Certain embodiments of the present invention operate asynchronously with respect to operation of other components and subsystems of the optical instrument in which they are embedded. In one embodiment the autofocus detector comprises a beam splitter arranged to split the autofocus light beam into a plurality (n) of down-stream light beams and a photodetector arrangement for registering the intensity of each one of the down-stream light beams.

A head-mounted display including a first optical system is provided. The first optical system includes an image surface, a stop surface, a first optical stack disposed between the image surface and the stop surface and a second optical stack disposed between the first optical stack and the stop surface. The first optical stack includes a first optical lens and a partial reflector. The second optical stack includes a second optical lens and a curved multilayer reflective polarizer. A quarter wave retarder is disposed between the multilayer reflective polarizer and the partial reflector. The multilayer reflective polarizer and the partial reflector may be convex toward the image surface along orthogonal first and second axes.

A light beam measurement device includes: a polarization measurement unit including a first measurement beam splitter provided on an optical path of a laser beam and configured to measure a polarization state of the laser beam having been partially reflected by the first measurement beam splitter; a beam profile measurement unit including a second measurement beam splitter provided on the optical path of the laser beam and configured to measure a beam profile of the laser beam having been partially reflected by the second measurement beam splitter; and a laser beam-directional stability measurement unit configured to measure a stability in a traveling direction of the laser beam, while the first measurement beam splitter and the second measurement beam splitter are made of a material containing CaF.sub.2.

There is disclosed an optical device, including a light-transmitting substrate having an input aperture, an output aperture, at least two major surfaces and edges, an optical element for coupling light waves into the substrate by total internal reflection, at least one partially reflecting surface located between the two major surfaces of the light-transmitting substrate for partially reflect ing light waves out of the substrate, a first transparent plate, having at least two major surfaces, one of the major surfaces of the transparent plate being optically attached to a major surface of the light-transmitting substrate defining an interface plane, and a beam-splitting coating applied at the interface plane between the substrate and the transparent plate, wherein light waves coupled in side the light-transmitting substrate are partially reflected from the interface plane and partially pass therethrough.

An optical system and a magnifying device including the optical system are described. The optical system includes an exit pupil, a reflective polarizer proximate the exit pupil, a partial reflector disposed adjacent the reflective polarizer opposite the exit pupil, and a quarter wave retarder disposed between the reflective polarizer and the partial reflector. The reflective polarizer is curved about two orthogonal axes and the partial reflector is spaced apart from the reflective polarizer.

A three-plate image projecting optical system that has a compact and simple configuration and achieves enhanced luminance efficiency and reduction of light quantity loss on the dichroic coating, and a projector equipped with the optical system. The optical system includes a color separating/combining prism having a first/second dichroic coatings, and a first to third digital micromirror devices. A first plane including an illumination light axis and a projection light axis on an image display surface of the third digital micromirror device and a second plane including a surface normal of the first/second dichroic coatings and a surface normal of a center of the third digital micromirror device are relatively rotated with respect to each other from orthogonal states toward a direction in which an incident angle of the illumination light axis with respect to the first dichroic coating or the second dichroic coating is decreased.