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 luminaire including: at least one light source (2), and an optical system (10, 11, 12a, 12b) for directing and/or distributing the light (5) emitted by the source(s) (2) into a desired output light distribution pattern (7); wherein the optical system comprises one or more optical elements (10, 11, 12a, 12b), the or each said optical element (10, 11, 12a, 12b) comprising a thin foil or sheet substrate having at least one optically functional surface or surface layer thereon or on a portion thereof, and wherein: (i) at least a portion of the at least one optically functional surface or surface layer on the substrate of at least one of the one or more optical elements (10, 11, 12a, 12b) has an at least partially diffractive optical function, and/or (ii) at least a portion of the at least one of the one or more optical elements (10, 11, 12a, 12b) is shaped such that its substrate is configured so as to have a non-flat or non-planar shape in three dimensions.

An optical device of the present disclosure includes a first light guide body including a first light-incident portion provided with a first incidence-side diffraction element, and a second light guide body including a second light-incident portion provided with a second incidence-side diffraction element, wherein the second light guide body, when light is caused to enter the first light-incident portion, is disposed at a position at which a part of the light passing through the first light guide body enters the second light-incident portion, and the second incidence-side diffraction element is an element that diffracts light of monochromatic color at a smaller angle than the first incidence-side diffraction element does, when the light of monochromatic color is caused to enter at a same angle.

An all-optical hologram reconstruction system and method is disclosed that can instantly retrieve the image of an unknown object from its in-line hologram and eliminate twin-image artifacts without using a digital processor or a computer. Multiple transmissive diffractive layers are trained using deep learning so that the diffracted light from an arbitrary input hologram is processed all-optically to reconstruct the image of an unknown object at the speed of light propagation and without the need for any external power. This passive diffractive optical network, which successfully generalizes to reconstruct in-line holograms of unknown, new objects and exhibits improved diffraction efficiency as well as extended depth-of-field at the hologram recording distance. The system and method can find numerous applications in coherent imaging and holographic display-related applications owing to its major advantages in terms of image reconstruction speed and computer-free operation.

A method includes receiving collimated light from an optical imaging system and dividing the received light into multiple bands of wavelength. Each band is refocused onto a corresponding diffraction grating having an amplitude function matched to a point spread function (PSF) of the optical imaging system. The light that is not filtered out by the diffraction grating is transmitted onto a corresponding pixel array. An image is reconstructed from data provided by the pixel arrays for each band. The intensity of light scattered by each diffraction grating may be detected, with the image being reconstructed as a function of an average value of detected intensity of scattered light used to scale the known zero-order mode profile, which is added to the image on the pixel array.

An all-optical Diffractive Deep Neural Network (D.sup.2NN) architecture learns to implement various functions or tasks after deep learning-based design of the passive diffractive or reflective substrate layers that work collectively to perform the desired function or task. This architecture was successfully confirmed experimentally by creating 3D-printed D.sup.2NNs that learned to implement handwritten classifications and lens function at the terahertz spectrum. This all-optical deep learning framework can perform, at the speed of light, various complex functions and tasks that computer-based neural networks can implement, and will find applications in all-optical image analysis, feature detection and object classification, also enabling new camera designs and optical components that can learn to perform unique tasks using D.sup.2NNs. In alternative embodiments, the all-optical D.sup.2NN is used as a front-end in conjunction with a trained, digital neural network back-end.

An optical waveguide device for use in a head up display. The waveguide device provides pupil expansion in two dimensions. The waveguide device comprises a primary waveguide and a secondary waveguide, the secondary waveguide being positioned on a face of the primary waveguide. The secondary waveguide has a diffraction grating on a face opposite to the face which contacts the primary waveguide. The diffraction grating diffracts light into more than one diffraction order. Rays diffracted into a non-zero order are trapped in the secondary waveguide by total internal reflection.

An apparatus including a first substrate including a first incoupling diffractive optical element configured to couple light into the first substrate, and a first outcoupling diffractive optical element configured to output, from the first substrate, light that has been coupled into the first substrate; and a second substrate including a second incoupling diffractive optical element configured to couple light into the second substrate, and a second outcoupling diffractive optical element configured to output, from the second substrate, light that has been coupled into the second substrate; wherein the first and second incoupling diffractive optical elements are substantially inverse of each other and the first and second outcoupling diffractive optical elements are substantially inverse of each other.

A system includes: a light source; first and second gratings; and at least one reflective component that in a first position forms a first light path originating at the light source and extending to the first grating and thereafter to a subsequent component in the system, and that in a second position forms a second light path originating at the light source and extending to the second grating and thereafter to the subsequent component.

A method includes selecting a period for a volume Bragg grating (VBG) such that a spectral selectivity of the VBG is at least as wide as a spectral width of a broadband light beam that is to be spatially transformed, selecting a desired beam transformation for the broadband light beam, passing a first light beam from a recording light source through an optical device to a volume holographic recording medium where the optical device is configured to induce the desired beam transformation, directing a second light beam from the recording light source to the recording medium, and converging the first light beam and the second beam at a recording angle such that a spatial refractive index modulation profile is recorded in the recording medium that provides the VBG with the selected period, and a phase profile is embedded in the VBG that induces the desired beam transformation for each spectral component within a spectral width of the VBG.