Provided are a diffraction grating structure (100), an imaging device (1000), and a wearable apparatus (2000). The diffraction grating structure (100) includes a waveguide sheet (10), a couple-in grating (20), a couple-out grating (30), and a functional layer (40). The couple-in grating (20) is configured to couple light in the waveguide sheet (10). Each of the waveguide sheet (10) and the couple-out grating (30) is configured to couple the light out to the functional layer (40). The functional layer (40) is configured to refract the light to an ambient environment and increase a light-outcoupling rate of the couple-out grating (30).

A laser beam combining device includes an emission optical system that emits a plurality of circular laser beams propagated coaxially and having mutually different wavelengths, and a diffractive optical element that is concentric and diffracts the plurality of circular laser beams. The diffractive optical element diffracts the plurality of circular laser beams in accordance with the wavelengths of the circular laser beams, such that local diffraction angles of diffracted light of the plurality of circular laser beams incident at mutually different local incidence angles are equal to each other.

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.

A method for designing a phase-typed diffraction suppressing optical device (12) for a transparent display screen(11) is disclosed, which comprises: acquiring a light field complex amplitude distribution U(x2,y2,d)=A(x2,y2,d)exp(iφ20(x2,y2,d)) on a plane with a distance d from the transparent display screen (12) after a plane wave is transmitted through the screen; and designing the diffraction suppressing optical device (12), so that it has a transmittance function t2 (x2,y2)=exp(iφ21(x2,y2)) and satisfies φ20 (x2,y2,d)+φ21 (x2,y2)=C, where C is a constant. A diffraction suppressing optical device (12) and an under-screen camera apparatus (1) comprising the same are disclosed. The phase-typed diffraction suppressing optical device (12) suppresses the diffraction effect in the under-screen camera apparatus (1) by providing phase modulation, thereby improving the quality of under-screen imaging.

An optical element may include a substrate. The optical element may include a first anti-reflectance structure for a particular wavelength range formed on the substrate. The optical element may include at least one layer disposed on a portion of the first anti-reflectance structure. The optical element may include a second anti-reflectance structure for the particular wavelength range formed on the at least one layer. A depth between a first surface of the first anti-reflectance structure and a second surface of the second anti-reflectance structure, a first index of refraction of the first anti-reflectance structure, a second index of refraction of the second anti-reflectance structure, and a third index of refraction of the at least one layer may be selected to form a diffractive optical element associated with a particular phase delay for the particular wavelength.

A diffractive optical element includes: a first material layer that has a diffractive grating shape; and a second material layer that is laminated on the first material layer, the diffractive grating shape forming a plurality of concentric annular ring zones in a plan view from a lamination direction of the first material layer and the second material layer, and a radius of an innermost first ring zone among the plurality of ring zones is less than any one of distances between the ring zones.

A diffraction optical element is disclosed. The diffraction optical element includes a substrate and multiple grating units. The grating units are disposed above the substrate. The grating units diffract incident light to generate diffracted light being passing through the substrate. A refractive index of the substrate is substantially below 1.45.

A security device includes a diffractive structure, including grating elements and having a first area, the grating elements within a region have a constant pitch or spacing; the first area regions pitches or spacings increase from one region to the next between a first region having a grating element pitch or spacing of less than or equal to 0.6 microns and an end region having a grating element pitch or spacing of greater than or equal to 5 microns; upon illumination and viewing along a first viewing direction substantially orthogonal to the first axis, the device exhibits a first optical effect in that at least one region exhibits a diffractive colour; each region has at least first and second sub-regions having different grating element orientations within the plane of the device such that the first optical effect is exhibited at more than one angle of tilt about the second axis.

A quantitative phase microscopy (QPM) system and methods are provided for sample imaging and metrology in both transmissive and reflective modes. The QPM system includes a first illuminating beam propagating along a transmission-mode path and a second illuminating beam propagating along a reflection-mode path, a microscope objective lens disposed in the reflection-mode path, and a common-path interferometer comprising a diffraction grating, a Fourier lens, a pinhole, and a 2f system lens to collimate the reference beam and the imaging beam such that the collimated reference beam and imaging beam interfere with each other to form an interferogram at a final image plane.

Provided are an optical anti-counterfeiting element and an anti-counterfeiting product, the optical anti-counterfeiting element comprises: a substrate (1); and a plurality of Fresnel structures (2) with preset lateral dimensions formed on the substrate (1), the plurality of Fresnel structures (2), when illuminated by a preset light source, being used to form preset graphic information in the transmission direction, and to present the preset graphic information with a relief effect in the reflection direction. The optical anti-counterfeiting element, when illuminated, reproduces a preset pattern from the transmission direction, and presents a relief effect from the reflection direction. The element improves anti-counterfeiting ability and recognition, and has a simple identification process.