A polychromator system comprising: an optical element defining an aperture; a collimation mirror for receiving light via the aperture and reflecting substantially collimated light; at least a first dispersive optical component and a second dispersive optical component, each configured to disperse the substantially collimated light received from the collimation mirror by different amounts for different wavelengths and to provide cross-dispersed light having different wavelengths of light spaced along a first and second axis; and a focus mirror positioned to focus the cross-dispersed light onto a 2-D array detector to provide a plurality of aperture images of the aperture at a respective plurality of regions of the detector, each of the plurality of aperture images associated with a respective wavelength of the cross-dispersed light. Either one or both of the collimation mirror and the focus mirror is a freeform mirror having a reflective surface configured to mitigate effects of optical aberrations of the polychromator system over a plurality of the wavelengths of the cross-dispersed light along the first axis and the second axis and thereby optimise the resolution of the plurality of aperture images associated with the plurality of the wavelengths along the first axis and the second axis.

A head-mounted fixing device includes: a head frame including two side frame portions, and a front frame portion located between the two side frame portions and connected to the two side frame portions, and the two side frame portions and the front frame portion being made of rigid materials; an elastic piece including one end connected to the front frame portion; a headgear including an arc portion and a top portion, wherein two ends of the arc portion are respectively connected to the two side frame portions, one end of the top portion is connected to another end of the elastic piece, and another end of the top portion is connected to the arc portion; it is characterized in that the front frame portion is used to abut against a user's forehead to provide a fulcrum.

An optical receiving module may include: a light transmitting body configured to transmit light; a light incidence part through which light is incident into the light transmitting body; and a plurality of reflectors configured to reflect the light incident from the light incidence part a plurality of times, such that the light is incident toward a light receiver unit.

The disclosed optical beam expander may include (1) a monolithic structure including (a) a first nonplanar mirror that receives a first collimated optical beam having a first width and reflects the first collimated optical beam to generate a noncollimated optical beam and (b) a second nonplanar mirror that receives a diverging optical beam and reflects the diverging optical beam to generate a second collimated optical beam having a second width greater than the first width, where the first nonplanar mirror and the second nonplanar mirror are fixed in orientation and position relative to each other and (2) a planar mirror that reflects the noncollimated optical beam from the first nonplanar mirror to provide the diverging optical beam to the second nonplanar mirror. Various other devices, systems, and methods are also disclosed.

A flat-plate lens and an optical imaging system are provided. The flat-plate lens, includes a first face and a second face, the first face includes a ring-shaped light-transmitting region and a first reflective region surrounded by the ring-shaped light-transmitting region, and the second face includes an imaging region and a second reflective region surrounding the imaging region. The second reflective region is configured to reflect light to the first reflective region, and the first reflective region is configured to reflect light to the imaging region; the second reflective region includes a first mirror. The first mirror is one selected from the group consisting of a free-form curved mirror, an aspheric mirror and a spherical mirror, and the first reflective region includes at least one selected from the group consisting of a free-form curved mirror, an aspheric mirror, a spherical mirror and a plane mirror.

A light irradiation apparatus that splits white light into light rays of a plurality of wavelengths to apply the light ray includes a white light source, a diffraction grating that splits white light emitted by the white light source into light rays of a plurality of wavelengths, and a light selector that selects a light ray of a specified wavelength from the light rays of the plurality of wavelengths split by the diffraction grating.

A virtual image display system includes: a light source for projecting an image; a first beamsplitter including a first free-form curved surface; and a second beamsplitter including a second free-form curved surface facing the first free-form surface of the first beamsplitter, in which the first free-form curved surface is separated from the second-free form curved surface of the second beamsplitter by free space, and in which the first beamsplitter and the second beamsplitter are arranged to redirect light emitted from the light source toward a user to form a virtual image.

A fundus imaging system comprises: a first reflection mirror that reflects a light beam passing through a first focus of the first reflection mirror to pass through a second focus; a two-dimensional scanning unit that is disposed at a position of the first focus and reflects a light beam incident on the two-dimensional scanning unit so as to scan the retina with the light beam in two-dimensional directions; and a second reflection mirror that reflects a light beam passing through a third focus so as to cause the light beam to pass through a fourth focus, the second reflection mirror being disposed so that a position of the third focus coincides with a position of the second focus, wherein a position of the pupil of the subject is disposed so as to coincide with a position of the fourth focus.

A display system for a vehicle includes a head-up display unit operable to display, at a display area at a windshield of the vehicle, information that is viewable by a driver of the vehicle when the driver is normally operating the vehicle. The head-up display unit includes a Köhler illuminator having a light source and an optical element. A reconfigurable mask is backlit by Köhler illumination generated by the Köhler illuminator.

A multifocal rain sensor includes: at least one light emitting unit configured to output light; a first reflective plate corresponding to the at least one light emitting unit and disposed at a position spaced apart from the at least one light emitting unit by a predetermined distance; a glass part reflecting light after the light is reflected by the first reflective plate and forming a sensing region; a second reflective plate re-reflecting the light reflected by the glass part; and a light receiving unit configured to receive the light reflected by the second reflective plate. The second reflective plate includes a multifocal reflective plate having a plurality of focuses based on a vertical height of incident light that varies according to a change in thickness of the glass part.