72 results about "Liquid crystal tunable filter" patented technology

A hyper-spectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers forming interference filters. The retarders can include tunable birefringent elements such as liquid crystals controlled in unison, fixed retarders and / or combined tunable and fixed birefringences. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging.

A wavelength locker operates with a reference tunable liquid crystal filter having integrated photodetectors deposited on the front and backside of the liquid crystal cell to track power intensity of the accepted passband signal and its rejected signal compliment at a 50% power point where the two signals cross on the side of the filter transmission peak. The tunable filter is tuned by an offset wavelength from the laser wavelength such that 50% power is transmitted through the filter at the center wavelength of the laser. The wavelength locker may be configured with a liquid crystal tunable etalon or a liquid crystal tunable bandpass filter. A method for locking an optical signal to a desired frequency is also included and provides a substantially linear feedback signal computed by dividing the rejected signal power by the accepted signal power and passing it to laser transmitter to enable it to correct for frequency drift. Optional features of the present invention include an integrated thermal sensor and heater and temperature compensation control schemes.

A temperature compensation mechanism and associated methodology to provide compensation for temperature-induced drifts in the peak transmission wavelength of a liquid crystal (LC)-based tunable optical filter stage. The filter-staged based methodology uses a simple, empirical mathematical relationship that represents thermal effects on a liquid crystal-based filter stage by taking into account a relationship among the LC material's actual temperature coefficient (of thermal expansion), the operating temperature variation, and wavelength drift attributable to the temperature variation. In one embodiment, a control channel based mechanism is used to provides appropriate temperature compensation to a liquid crystal-based tunable optical filter by accurately calculating LC driving voltage values needed for temperature compensation and then supplying the calculated drive voltage to drive various LC components in the filter.

A near-infrared spectrum imaging system for diagnosis of the depth and the area of burn skin necrosis comprises a spectrum imager and a computer controlled system. The spectrum imaging system comprises a light source (101), an optical lens (102), a filter (103), a driving controller (105a, 105b, 104), and a CCD camera (106). The filter (103) uses a wide-spectrum liquid crystal tunable filter (LCTF) or an acousto-optic tunable filter (AOTF) that obtain 1100-2500 nm waveband spectral signals of burn skin necrosis tissue of a target region. A compute controlled system is internally provided with a universal module, a data module, a spectrum correction module, a spectrum matching module, and a burn wound three-dimensional synthesizing module. The spectrum imager obtains spectral image data of burn skin necrosis tissue of a target region and inputs the data into the computer controlled system, and the computer controlled system performs image analysis and processing of the data; the depth and the area of burn of the target region can be obtained by means of spectral matching and recognition on a spectral reflectance curve corresponding to each image pixel in an spectral image and a standard spectral reflectance curve in a burn skin necrosis spectral database in a data module, and the data is synthesized into a three-dimensional image for display.

The invention discloses a full-wave-band achromatism filter type spectral camera, belongs to a filter type spectral camera in the technical field of spectral cameras, and aims to provide a full-wave-band achromatism filter type spectral camera capable of eliminating the aberration of any wave band. The full-wave-band achromatism filter type spectral camera comprises an optical lens, a liquid crystal adjustable light filter (LCTF), an area-array camera and a controller, wherein the optical lens is fixedly connected with the LCTF; the LCTF is separated from the area-array camera; an electric control translation mechanism is arranged below the area-array camera; a translation platform of the electric control translation mechanism is connected with the area-array camera; the controller is electrically connected with the LCTF and the electric control translation mechanism; the electric control translation mechanism can drive the translation platform and the area-array camera to move together along the optical axis direction; the distance between the LCTF and the area-array camera can be adjusted, so that a clear sample image can be recorded on the area-array camera, and full-wave-band achromatism is realized.

A hyper-spectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers forming interference filters. The retarders can include tunable birefringent elements such as liquid crystals controlled in unison, fixed retarders and / or combined tunable and fixed birefringences. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging.

The invention discloses a method for improving spectrum reconstruction precision and resolution of a liquid crystal tunable filter. The method utilizes devices comprising an imaging target (1), a collimation system (2), the liquid crystal tunable filter (LCTF) (3), an imaging lens (4) and a detector array (5). The method comprises the steps of: 1) setting a wavelength of non-uniform sampling points of the liquid crystal tunable filter; 2) acquiring imaging spectrum data of the liquid crystal tunable filter, and preprocessing the imaging spectrum data; 3) establishing a spectra aliasing function model for of the non-uniform sampling points of the liquid crystal tunable filter; 4) and conducting spectrum reconstruction by combining with a Richardson-Lucy algorithm. The method discloses by the invention effectively improves the resolution of spectra, and the position precision and the amplitude precision of the spectral characteristic peaks.

A SWIR hyperspectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers. The retarders can include active retarders such as tunable liquid crystal birefringent elements, passive retarders such as fixed retarders, and / or combinations thereof. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging. The filter may be configured to provide faster switching speed and increased angle of acceptance and may operate in the rage of approximately 850-1700 nm.

A detector (110) for determining a position of at least one object is proposed. The detector (110) comprises: at least one angle dependent optical element (130) adapted to generate at least one lightbeam (131) having at least one beam profile depending on an angle of incidence of an incident light beam (116) propagating from the object (112) towards the detector (110) and illuminating the angle dependent optical element (130), wherein the angle dependent optical element (130) comprises at least one optical element selected from the group consisting of: at least one optical fiber, in particular at least one multifurcated optical fiber, in particular at least one bifurcated optical fiber; at least one diffractive optical element; at least one angle dependent reflective element, at least onediffractive grating element, in particular a blaze grating element; at least one aperture stop; at least one prism; at least one lens; at least one lens array, in particular at least one microlens array; at least one optical filter; at least one polarization filter; at least one bandpass filter; at least one liquid crystal filter, in particular a liquid crystal tunable filter; at least one short-pass filter; at least one long-pass filter; at least one notch filter; at least one interference filter; at least one transmission grating; at least one nonlinear optical element, in particular one birfringent optical element; at least two optical sensors (113), wherein each optical sensor (113) has at least one light sensitive area (121), wherein each optical sensor (113) is designed to generateat least one sensor signal in response to an illumination of its respective light-sensitive area by the light beam (131) generated by the angle dependent optical element (130); at least one evaluationdevice (133) being configured for determining at least one longitudinal coordinate z of the object (112) by evaluating a combined signal Q from the sensor signals.

A SWIR hyperspectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers. The retarders can include active retarders such as tunable liquid crystal birefringent elements, passive retarders such as fixed retarders, and / or combinations thereof. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging. The filter may be configured to provide faster switching speed and increased angle of acceptance and may operate in the rage of approximately 850-1700 nm.

A VIS-NIR hyperspectral imaging filter has serial stages along an optical signal path with angularly distributed birefringent retarders and polarizers. The retarders can include active retarders such as tunable liquid crystal birefringent elements, passive retarders such as fixed retarders, and / or combinations thereof. Distinctly different periodic transmission spectra are provided by different filter stages, each having multiple retarders, in particular with some stages having broad bandpass peaks at wide spectral spacing and other stages have very narrow closely spaced peaks. The respective spectra include at least one tunably selectable band at which the transmission spectra of the filter stages coincide, whereby the salutary narrow bandpass and wide spectral spacing ranges of different stages apply together, resulting in a high finesse wavelength filter suitable for spectral imaging. The filter may be configured to provide faster switching speed and increased angle of acceptance and may operate in the rage of approximately 400-1100 nm.

The invention provides a rapid spectrum scanning liquid crystal electric control adjustable optical filter which comprises a liquid crystal adjustable optical filter body and a drive controller. The liquid crystal adjustable optical filter body is of a multistage cascade structure, polarizing films, electric control liquid crystal wave plates and fixed phase retardation films are sequentially and mutually arrayed in parallel and are stacked at intervals to form multiple stages, and the fixed phase retardation films can be arranged or cannot be arranged in the first stage. The transmission polarized light directions of all the polarizing films are mutually in parallel, and an angle of 45 degrees is formed between the fast axis directions of all the electric control liquid crystal wave plates and the transmission polarized light directions of all the polarizing films. In the structure of each stage, the electric control liquid crystal wave plates are controlled by the drive controller, and alternating current overvoltage drive signals of different amplitudes are loaded. The liquid crystal electric control adjustable optical filter has the advantages that rapid spectrum scanning and imaging can be achieved, the spectrum scanning speed can be effectively increased, the spectral imaging frame frequency can be effectively improved, and the applied range of the liquid crystal electric control adjustable optical filter is greatly expanded in the fields of remote sensing detection, medical diagnosis, environmental monitoring, agricultural and forestry general investigation and the like.

The invention is a system and method for obtaining interference and optical coherence tomography images from an object. The system comprises a wideband source, an optical mask for extending the depth of field, a a liquid crystal tunable filter and a phase modulator all of which are uniquely integrated in a Linnik interferometer microscope. The system has several imaging modes: in the time domain mode the device may operate either with wideband illumination or with quasi monochromatic illumination. The monochromatic illumination can be varied in wavelength along a wide spectral region thus allowing true spectroscopic imaging in high resolution and with high speed. Due to the liquid crystal tunable filter and the optical mask, the frequency domain mode is also accessible. The method of obtaining the optical coherence tomography images, both in the time and in the frequency domains, using the liquid crystal retarder is described in detail.

An external-cavity tunable laser with a flexible wavelength grid tuning function comprises a resonant cavity, collimating lenses, an optical isolator, and an output optical fiber. The resonant cavity comprises a semiconductor gain chip, a beam expander collimating lens, a combined liquid crystal tunable filter assembly, and a reflecting mirror. A current injected to the semiconductor gain chip is converted to broadband spontaneously radiating photons through electrical-to-optical conversion, and the photons are spread along a waveguide toward two sides. A part of photons with special frequencies go back and forth multiple times in the resonant cavity to form a laser after a threshold condition is met. The laser is collimated by the collimating lens, passes through the optical isolator, is coupled by the collimating lens, and enters the output optical fiber.