Optical apparatus includes a Fresnel lens (40), including an array of refractive bands (37) bordered by abrupt phase steps (39) of a height selected so as to focus light in different, first and second wavelength ranges from an object plane (35) toward an image plane (36) with a modulation transfer function (MTF) in excess of a predefined threshold, while focusing light in a third wavelength range, intermediate the first and second wavelength ranges, with MTF less than the predefined threshold. A display (32) is configured to generate, at the object plane of the Fresnel lens, an image including first and second pixel colors within the first and second wavelength ranges, respectively.

Structures for response shaping in frequency and time domain, include an optical response shaper and/or a modulator device with multiple injection. The device comprises a resonator having an enclosed geometric structure, for example a ring or racetrack structure, at least two injecting optical waveguides approaching the resonator to define at least two coupling regions between the resonator and the injecting waveguides, and may define at least two Free Spectral Range states.

One or both of the coupling regions has a coupling coefficient selected for a predetermined frequency or time response, and the coupling coefficient or other device parameters may be variable, in some case in real time to render the response programmably variable.

A method may include thinning a silicon wafer to a particular thickness. The particular thickness may be based on a passband frequency spectrum of an adjustable optical filter. The method may also include covering a surface of the silicon wafer with an optical coating. The optical coating may filter an optical signal and may be based on the passband frequency spectrum. The method may additionally include depositing a plurality of thermal tuning components on the coated silicon wafer. The plurality of thermal tuning components may adjust a passband frequency range of the adjustable optical filter by adjusting a temperature of the coated silicon wafer. The passband frequency range may be within the passband frequency spectrum. The method may include dividing the coated silicon wafer into a plurality of silicon wafer dies. Each silicon wafer die may include multiple thermal tuning components and may be the adjustable optical filter.

A tunable optical filter provides a narrow passband centered around the wavelength of the laser beam to limit ambient light noise impinging on a primary photodetector. As the wavelength changes due to temperature or other effects, the wavelength is indirectly measured and used to shift the passband of the filter to center it on the shifted wavelength. A portion of the emitted beam is diverted through the same tunable filter to a feedback photodetector. The output of the feedback photodetector will be at a maximum value when the tunable filter passband is centered on the laser beam wavelength. By controlling the passband of the tunable filter to maximize the feedback photodetector output, the passband remains centered on the laser wavelength. The tunable filter is a Liquid Crystal Tunable Filter (LCTF) or another tunable filter large enough to pass both reflected and feedback light to the primary and feedback photodetectors.

A film, in which a phase transition material is not applied on an entire surface thereof and a pattern form is provided so that the aesthetically superior film of which a color is not cloudy but bright may be obtained and which has a high visible light transmittance as well as superior thermochromic properties, and a smart window including the same.

A light modulation device and a single-channel spectrum detection system are provided. The light modulation device includes: a light guide plate; a dispersing component configured to disperse received light into light of different wavelengths and to diffract the light of different wavelengths into the light guide plate at different angles; and a dynamic filtering component configured to prevent light of a selected wavelength in the light guide plate from entering the dynamic filtering component such that the light of the selected wavelength emits out from the light guide plate, and to make light of non-selected wavelengths in the light guide plate enter the dynamic filtering component such that the light of the non-selected wavelengths is filtered out from the light guide plate.

An electronic device is disclosed herein that includes an infrared light source to emit infrared light, a rolling shutter sensor, and at least one processor. The at least one processor is to: cause the rolling shutter sensor to output a first signal corresponding to a first frame of image data during exposure to the infrared light, reset the rows of the rolling shutter sensor at a same time, cause the rolling shutter sensor to output a second signal corresponding to a second frame of image data without exposure to the infrared light from the infrared light source, determine a difference between the first signal and the second signal to generate an ambient infrared free frame, and recognize a face based on the ambient infrared free frame.

A reflective display apparatus includes three liquid crystal modules stacked in sequence for an incident light to enter from top to bottom sequentially. Each liquid crystal module includes a liquid crystal layer disposed between two substrates. A switchable electric field and a vertical alignment force are provided by the two substrates to the liquid crystal layer. The three liquid crystal modules are respectively: a blue light liquid crystal module located at a top layer, a green light liquid crystal module located in a middle layer and having the liquid crystal layer doped with a dichroic dye for absorbing a light within a blue light wavelength range, and a red light liquid crystal module located at a bottom layer and having the liquid crystal layer doped with a dichroic dye for absorbing a light within a green light wavelength range. A method for controlling the reflective display apparatus is also disclosed.

A display device includes: a color filter including a first transmissive filter, a second transmissive filter, and a third transmissive filter, the first, second and third transmissive filters being configured to transmit respective light beams having peak wavelengths different from each other; a first selective-wavelength-reflection layer adjacent to an optical-input surface of the first transmissive filter, the first selective-wavelength-reflection layer being configured to reflect light of a wavelength band that passes through the third transmissive filter; a second selective-wavelength-reflection layer adjacent to an optical-input surface of the second transmissive filter, the second selective-wavelength-reflection layer being configured to reflect light of a wavelength band that passes through the third transmissive filter, the second selective-wavelength-reflection layer being identical in composition to the first selective-wavelength-reflection layer; and a light emitter configured to emit light that travels toward the color filter.

An optical filter for a display includes a filter film with at least one optical filter layer. The filter layer blocks a band of optical wavelengths and is transparent for optical wavelengths outside the band. The filter film has a thickness within the range of 25 microns through 1 mm. The filter film may include one or more laminate layers that are optically transparent in the wavelengths of the band blocked by the filter layer. The filter film may include one or more layers of liquid crystal polymers in layered contact with one or more transparent electrode layers and one or more layers of polymers in layered contact with the one or more layers of liquid crystal polymers.