1104 results about "Diffraction efficiency" patented technology

An optical relay comprises a light-transmissive substrate having a plurality of diffractive optical elements, where at least one diffractive optical element is characterized by nonuniform diffraction efficiency. The substrate and diffractive optical elements are designed and constructed to relay at least a portion of a light beam emanating from an object to at least one predetermined eye-box in a manner such that for each point of the object, there is a set of parallel outgoing light rays originating from the point and arriving to the eye-box. The color difference between any two parallel light rays of the set is less than 50 ΔE* units.

Lightwave diffraction device formed of a dielectric layer (4), a mirror (12) arranged at the lower face (10) of said layer, a semi-reflective structure (13) arranged at the upper face (100) of said layer, and a diffractive structure (8) arranged in said layer or on its faces. The height (H) of the layer is chosen so as to substantially satisfy the resonance condition for at least one leaky mode propagating in said layer for at least one given incident wave having a determined wavelengthλ and a determined incidence angle θ_c. Next, the diffractive structure is arranged so that there is no propagating positive diffracted order, and so that all negative orders other than the −1^st propagating order have zero or a relatively small diffraction efficiency, the reflected −1^st order propagating in a direction non-parallel to the incident wave. This diffraction device allows a high diffraction efficiency of up to 100% for the −1^st order.

A new photopolymerizable material allows single-step, fast recording of volume holograms with properties that can be electrically controlled. Polymer-dispersed liquid crystals (PDLCs) in accordance with the invention preferably comprise a homogeneous mixture of a nematic liquid crystal and a multifunctional pentaacrylate monomer in combination with photoinitiator, coinitiator and cross-linking agent. Optionally, a surfactant such as octancic acid may also be added. The PDLC material is exposed to coherent light to produce an interference pattern inside the material. Photopolymerization of the new PDLC material produces a hologram of clearly separated liquid crystal domains and cured polymer domains. Volume transmission gratings made with the new PDLC material can be electrically switched between nearly 100% diffraction efficiency and nearly 0% diffraction efficiency. By increasing the frequency of the switching voltage, switching voltages in the range of 50 Vrms can be achieved. The optional use of a surfactant allows low switching voltages at lower frequencies than without a surfactant. In an alternative embodiment, a PDLC material in accordance with the invention can be utilized to form reflection gratings, including switchable reflection gratings. In still further embodiments, a PDLC material in accordance with the invention can be used to form switchable subwavelength gratings. By further processing, static transmission, reflection, and subwavelength PDLC materials can be formed. In addition, PDLC materials in accordance with the present invention can be used to form switchable slanted transmission gratings suitable for switchable optical coupling and reconfigurable optical interconnects.

The method for controlling layers alignment in a multi-layer sample (10), such a semiconductors wafer based on detecting a diffraction efficiency of radiation diffracted from the patterned structures (12, 14) located one above the other in two different layers of the sample.

Described herein are the materials, mechanisms and procedures for optimizing various performance parameters of HPDLC optical devices in order to meet differing performance requirements. These optimization tailoring techniques include control and independent optimization of switchable HPDLC optical devices to meet the demanding requirements of anticipated applications for, inter alia, the telecommunications and display industries. These techniques include optimization of diffraction efficiency, i.e., index modulation, polarization dependence control, haze, cosmetic quality, control of response and relaxation time, voltage driving for on and off switching, and material uniformity. This control and independent optimization tailors properties of switchable HPDLC optical devices according to the specific requirements of the application of the switchable HPDLC optical device. The invention disclosed herein retains the desirable attributes of the multi-functional acrylate system for forming HPDLC optical devices, but adds new materials to the acrylate system and/or new process control to the recording to optimize performance parameters as may be needed for specific applications. This results in high optical quality switchable holograms with good diffraction efficiency and low, stable switching voltage.

The objective of the present invention is providing a method for fabricating high quality diffractive waveplates and their arrays that exhibit high diffraction efficiency over large area, the method being capable of inexpensive large volume production. The method uses a polarization converter for converting the polarization of generally non-monochromatic and partially coherent input light beam into a pattern of periodic spatial modulation at the output of said polarization converter. A substrate carrying a photoalignment layer is exposed to said polarization modulation pattern and is coated subsequently with a liquid crystalline material. The high quality diffractive waveplates of the present invention are obtained when the exposure time of said photoalignment layer exceeds by generally an order of magnitude the time period that would be sufficient for producing homogeneous orientation of liquid crystalline materials brought in contact with said photoalignment layer. Compared to holographic techniques, the method is robust with respect to mechanical noises, ambient conditions, and allows inexpensive production via printing while also allowing to double the spatial frequency of optical axis modulation of diffractive waveplates.

In a transmission grating as a dispersive element, diffraction efficiency is enhanced and manufacturing costs are considerably reduced. A dispersive element includes resin members for forming a diffraction grating, being composed of a plurality of diffraction grating members having a cross-sectional shape respectively surrounded by two straight lines such as a triangular shape, and metal members as light-shielding members each being formed on corresponding one of the diffraction grating members at one side of the diffraction grating member along any of the straight line and the curved line of the cross-sectional shape of the diffraction grating member formed by the resin member. The metal members are configured to reduce zero-order transmitted light with respect to incident light, and to enhance diffraction efficiency of first-order transmitted light.

Provided are wafer scale lenses having a diffraction surface as well as a refractive surface, and an optical system having the same. The wafer scale lens includes a lens substrate, a first lens element formed on the object side of the lens substrate, having a positive refractive power, a second lens element formed on the image side of the lens substrate, having a diffraction surface, and a third lens element deposited on the diffraction surface of the second lens element, having a negative refractive power. The invention allows miniaturized optical system and efficient calibration of angle of view, reducing the angle of light incident onto the diffractive surface, thereby increasing diffraction efficiency and eliminating high order diffraction light to improve picture quality.

High efficiency reflective volume Bragg gratings with chirped gratings recorded in photo-thermo-refractive glass having an absolute diffraction efficiency exceeding 95% in transmitting and reflecting modes are used to stretch and/or compress ultrashort laser pulses with high efficiency. Robustness, compactness, thermal and laser stability along with placement of multiple elements in the same space provides femtosecond laser system with high efficiency of stretching and re-compression of femtosecond pulses.

A direct light type backlight unit and a liquid crystal panel employing the same. The backlight unit includes a plurality of light emitting devices disposed at a predetermined angle on a substrate; and a grating which diffracts incident light from the light emitting devices at different diffraction angles to separate the incident light into a plurality of colored light beams. The backlight unit and the liquid crystal display include direct light type light sources emitting light at an optimal angle to provide maximum diffraction efficiency of the grating, which allows color image realization without the use of a color filter.

The light directed from a light source to a concave mirror and the light directed from a display device to an eyepiece optical system are intersected by each other in a layout. This allows the light source, the concave mirror, and the display device to be arranged in compactness adjacent to the eyepiece optical system without increasing the optical power of an illumination optical system. As the result, the apparatus can easily be minimized in the thickness or the overall size. A hologram optical element is provided where the relationship between the wavelength range Δλ1 at half of the diffraction efficiency of each of the three primary colors of the light in the hologram optical element and the wavelength range Δλ2 at half of the intensity of each of the three primary colors of the light emitted from the light source is defined by Δλ1<Δλ2. Accordingly, a component at desired wavelengths of each of the R, G, and B colors of the light emitted from the light source can be diffracted by the action of the hologram optical element and then directed to the pupil of the viewer. This allows the image to be increased in the color reproduction area and improved in the quality regardless of the display device actuated in a time-division mode.

A grating structure with a dielectric coating is disclosed that operates efficiently away from the blaze angle in low order with a high diffraction efficiency and high wavelength dispersion. Such grating structure can be employed in Littrow configuration to provide, for example, cavity feedback in excimer lasers.

The invention provides in particular for an achromatic diffractive diffuser comprising a surface relief diffractive device arranged such that, under illumination by ambient light, the diffractive effect serves to provide a uniform achromatic diffuser reflection into a defined viewing zone for observation by an observer, and also such that the achromatic diffractive replay of the device has a non-symmetric distribution of diffractive light intensity between positive and negative diffractive order such that the diffractive efficiency in the desired diffractive order is enhanced over that of the undesired order to provide an enhanced brightness achromatic device.

An optical element of which diffraction efficiency hardly varies with wavelength is provided by using an optical material satisfying the conditions that n_d>−6.667×10⁻³v^d+1.70 and θ_g,F≦−2×10⁻³ν_d+0.59 where n_d is a refractive index at d-line, ν_d is an Abbe number at the d-line, and θ_g,F is a second order dispersion at d-line, whereby diffraction efficiency is improved in any working visible wavelength region and more precise chromatic aberration correction is obtained.

An optical diffraction grating includes a substrate and a diffraction surface comprising, for example, diffraction grooves. The diffraction grating has a spatially varying diffraction efficiency which increases or decreases as a function of distance from a reference location at which an incident light beam is received at the grating. Spatially varying the diffraction efficiency of the grating may be accomplished by selectively changing or modifying one or more grating design parameters such as the shape, size, depth, profile, pitch, and optical properties of the diffraction grooves at predetermined locations on the grating.

A diffraction device having, on a transparent substrate plate, a diffraction pattern composed of periodically alternating array of first and second phase control zones. Each one of the first and second phase control zones is provided with an infinitesimal ruled structure in a pitch of the order of sub-wavelength, i.e., in a pitch smaller than the shortest wavelength of incident light, thereby to control phase shifts to the same angle in a plural number of wave ranges. The infinitesimal ruled structure in the first and second phase control zones are disposed in perpendicularly intersecting relation with each other. Thus, the diffraction device can diffract incident light with a diffraction efficiency free from dependency on wavelength and give a performance not dependent on the direction of polarization of incident light.

According to the present invention, the method for designing a diffraction grating structure (1), the grating period (d) of the structure comprising at least two grating lines each consisting of a pair of adjacent pillars (2) and grooves (3), comprises the steps of—determining desired diffraction efficiencies η_d of the diffraction orders, and—dimensioning the pillars (2) and grooves (3) so that when calculating for each pillar, on the basis of the effective refractive index n_eff for the fundamental wave mode propagating along that pillar, the phase shift Φ experienced by light propagated through the grating structure, the differences in the calculated phase shifts between adjacent pillars corresponds to the phase profile Φ_r required by the desired diffraction efficiencies.