An embodiment of the present disclosure provides a holographic optical element and a manufacturing method of a holographic optical element including holographic gratings, the manufacturing method including: a step (a) of forming a photosensitive substrate by coating one surface of a substrate with a photosensitive resin; and a step (b) of recording the holographic gratings by irradiating each of one surface and the other surface of the photosensitive substrate with laser light, wherein in the step (a), the photosensitive resin is applied so that a height of a photosensitive resin coating layer varies along a predetermined direction.

An illumination device for illuminating a spatial light modulator device. Sub-holograms are used for encoding a hologram into the spatial light modulator device. The Illumination device includes at least one light source for emitting light for illuminating the spatial light modulator device and a beam shaping unit. The beam shaping unit provides a flat-top plateau-type distribution of an absolute value of a complex degree of mutual coherence of the light in a plane of the spatial light modulator device to be illuminated. The flat-top plateau-type distribution of the absolute value of the complex degree of mutual coherence has a shape that is at least similar to a shape of the largest sub-hologram used for encoding of object points into the spatial light modulator device.

A projection system projects images onto a projection surface in, for example, a computer game head-mounted display (HMD). The light is projected through a spatial light modulator that contains a phase-only image of a Freeform Fourier Lens that is a combination of a Fresnel lens, an X-phase grating, a Y-phase grating, and a radial grating. The freeform lens is a condensing freeform lens that causes the gradual shrinking of portions of the laser-projected image, decreasing the perceived pixel pitch in at least one foveal area on the projection surface compared to a non-modulated laser image. The center positions of the Fresnel lens and radial grating can be changed in the X and Y axes, moving the condensed foveal areas in accordance with eye tracking of the user. In effect, the system projects a Foveated image that contains variable pixel pitch such that a user perceives a higher visual acuity in his gaze direction to the projected surface.

A holographic display apparatus includes a light source disposed on a printed circuit board, a display panel diffracting light transferred from the light source, and an optical system disposed between the light source and the display panel. The optical system converts the light incident from the light source into a surface light source.

A polarization diffraction element comprising a film including a liquid crystalline material having photosensitivity, the film having at least one hologram recorded therein, and thereby having a property as a fork-shaped polarization grating having an anisotropic structure in which an optical axis continuously rotates toward a direction of a grating vector.

In described examples, a system (e.g., a projection system) can include a diffractive optical element adapted to be illuminated by at least one coherent light beam. A lens array is coupled to receive a diffracted beam of light from the diffractive optical element. The lens array includes a first and a second array lens. The first array lens is coupled to receive a first sector of a pattern of illumination of the diffracted beam of light, and the second array lens is coupled to receive a second sector of the pattern of illumination of the diffracted beam of light. A spatial light modulator is coupled to receive overlapping diffracted beams of light from the first and second array lenses to form an image beam.

A hologram recording device for producing a hologram that diffracts incident light includes: a laser light source; a first half-wave plate that controls a polarization direction of a light beam emitted from the laser light source; a polarizing beam splitter that reflects S-polarized light to emit the S-polarized light as an A light ray and transmits P-polarized light to emit the P-polarized light as a B light ray with respect to the light beam passing through the first half-wave plate, and splits the light beam in two directions; a first wedge prism mirror that reflects the A light ray; a second half-wave plate that polarizes the B light ray into S-polarized light; a second wedge prism mirror that reflects the S-polarized light polarized by the second half-wave plate; and a recording medium irradiated with light rays reflected by the first wedge prism mirror and the second wedge prism mirror.

A projection system projects images onto a projection surface in, for example, a computer game head-mounted display (HMD). The light is projected through a spatial light modulator that contains a phase-only image of a Freeform Fourier Lens that is a combination of a Fresnel lens, an X-phase grating, a Y-phase grating, and a radial grating. The freeform lens is a condensing freeform lens that causes the gradual shrinking of portions of the laser-projected image, decreasing the perceived pixel pitch in at least one foveal area on the projection surface compared to a non-modulated laser image. The center positions of the Fresnel lens and radial grating can be changed in the X and Y axes, moving the condensed foveal areas in accordance with eye tracking of the user. In effect, the system projects a Foveated image that contains variable pixel pitch such that a user perceives a higher visual acuity in his gaze direction to the projected surface.

A device in holographic imaging comprises: at least two light sources, wherein each of the at least two light sources is arranged to output light of a unique wavelength; and at least one holographic optical element, wherein the at least two light sources and the at least one holographic optical element are arranged in relation to each other such that light from the at least two light sources incident on the at least one holographic optical element interacts with the at least one holographic optical element to form wavefronts of similar shape for light from the different light sources.

Some embodiments are directed to a system for measuring vibrations of a surface of a mechanical part, by digital holography. The system includes a source of radiation emitting in a predetermined range of frequencies, a first separator element configured to define a first incident ray and a reference ray, a module for shaping a second incident ray from the first incident ray, and an optical element configured to make the reference ray and a radiation produced by a reflection of the incident ray on the surface of the mechanical part interfere. The module for shaping the second incident ray includes diffracting optical elements having a diffraction structure to diffract the incident radiation. The structure is from a polymer, sol-gel or photoresin material resting against a glass substrate, the structure including elements etched in a plane parallel and/or orthogonal to the substrate, with dimensions from 100 nanometres to 100 micrometres.