A diffractive optical element exerts a diffractive action on a display light that is emitted from a display unit. A folding mirror is provided on the opposite side of the diffractive optical element from the display unit to reflect the display light. The diffractive optical element includes a transmissive action part and a diffractive and reflective action part. The transmissive action part exerts a transmissive action to transmit therethrough the display light, which is incident from the display unit and is in a first polarization state, toward the folding mirror. The diffractive and reflective action part exerts a diffractive and reflective action to diffract and reflect the display light, which is reflected by the folding mirror and is in a second polarization state opposite to the first polarization state, toward the projection portion on an optical path.

A holographic display system for a motor vehicle includes a coherent light source for generating a beam of coherent light and a spatial light modulator (SLM) having a two-dimensional pixel array, which is encoded with a hologram for modulating a phase of the coherent light. The SLM generates a first diffracted beam associated with a main image and a second diffracted beam associated with a conjugate image, where the first and second diffracted beams are angularly spaced from one another by a first angle. The system further includes an optical component for angularly spacing the first and second diffracted beams from one another by a second angle that is larger than the first angle. The system further includes a display surface receiving the first diffracted beam from the optical component to display the main image, with the display surface being free of the second diffracted beam.

Moiré is an appealing visual effect observable when two or more repetitive patterns are superposed. We introduce a method for designing and fabricating level-line moirés on curved surfaces. These moiré shapes are obtained by superposing a partly absorbing or partly light deviating curved base layer and a curved revealing layer formed by a grating of transparent lines or cylindrical lenses. The distances between base layer and revealing layer are adapted to the locally varying distances between successive transparent lines or cylindrical lenses of the curved revealing layer grating. We demonstrate the quality of our method by rendered simulations and by fabrication. The resulting level-line moiré display devices can be manufactured using different fabrication techniques, from multi-material 3D printing to molding.

An optical device includes a stack of multiple grating structures, each of which includes a plurality of sublayers of liquid crystal material. Each sublayer of liquid crystal material includes laterally extending repeating units, each formed of a plurality of liquid crystal molecules. The repeating units of the liquid crystal layers are lateral offset from one another, and defined a tilt angle. The grating structures forming the stack of grating structure have tilt angles of different magnitudes. The grating structures may be configured to redirect light of visible or infrared wavelengths. Advantageously, the different tilt angles of the stack of grating structures allows for highly efficient diffraction of light incident on the grating structures at a wide range of incident angles.

An optical device for a head-mounted display device includes a first partial reflector and a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light. At least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector. At least one of the first partial reflector or the second partial reflector includes a reflective holographic element.

An electronic device may include a housing and a display mounted to the housing. The housing may have a rear wall, a front wall that forms a display cover layer, and sidewalls. A coating may be formed on a portion of the housing. The coating may include a diffractive layer having a textured surface that diffracts incoming light to form at least part of a spectral rainbow on an outer surface of the housing. The textured surface may have pits and bumps in any suitable shape and pattern. The coating may include a thin-film interference layer that increases an intensity of the spectral rainbow. The thin-film interference layer may be interposed between an ink layer and the diffractive layer. The diffractive layer may be a reflective diffractive layer that reflects ambient light or a transmissive diffractive layer that transmits light from a light source in the electronic device.

In a virtual image display apparatus, as viewed from an exit pupil, a first emission diffraction grating and a second emission diffraction grating overlap, and a region, of the first emission diffraction grating, emitting first image light is different from a region, of the second emission diffraction grating, emitting second image light. As a result, an optical path from the first display element to the first emission diffraction grating can be prevented from being largely different from an optical path from a second display element to the second emission diffraction grating. Thus, unevenness in luminance in a virtual image displayed due to an increased difference in luminance between the first image light emitted from the first emission diffraction grating and the second image light emitted from the second emission diffraction grating can be suppressed.

A 3D grating and a 3D display apparatus are provided. The 3D grating comprises a first refraction layer and a second refraction layer that are stacked, wherein refractive indexes of the first refraction layer and the second refraction layer are different; and an anti-reflection layer is arranged at least on a joint surface of the first refraction layer and the second refraction layer, or an end surface, away from the second refraction layer, of the first refraction layer. The 3D grating improves a transmittance of the 3D display apparatus.

Disclosed is an improved diffraction structure for 3D display systems. The improved diffraction structure includes an intermediate layer that resides between a waveguide substrate and a top grating surface. The top grating surface comprises a first material that corresponds to a first refractive index value, the underlayer comprises a second material that corresponds to a second refractive index value, and the substrate comprises a third material that corresponds to a third refractive index value.

Diffraction gratings provide optical elements in head-mounted display systems to, e.g., incouple light into or out-couple light out of a waveguide. These diffraction gratings may be configured to have reduced polarization sensitivity. Such gratings may, for example, incouple or outcouple light of different polarizations with similar level of efficiency. The diffraction gratings and waveguides may include a transmissive layer and a metal layer. The diffraction grating may comprises a blazed grating.