39 results about "Coherence length" patented technology

The invention relates to the field of optical measurement, in particular to a reflective interference film thickness measurement method and system for eliminating back scattering of a transparent substrate, and the method comprises the following steps: transmitting a light beam through a low-coherence-length broadband light source, and forming linearly polarized light through polarization modulation; focusing the light beam to the surface of the film through a confocal optical system; collecting reflection interference signals of the upper surface and the lower surface of the film; spatial filtering, low-coherence gating and polarization control are used for cooperatively inhibiting back scattering of the substrate. And processing the acquired interference signal, and calculating to obtain film thickness information. According to the invention, triple inhibition mechanisms are adopted for synergistic effect, and the method comprises the following steps: spatial filtering: shielding out-of-focus back reflected light through a confocal small hole; low-coherence gating: using a short coherence length to naturally suppress a reflected signal beyond a coherence range; and polarization control: further weakening stray light interference through polarization state matching, and effectively suppressing back scattering of the substrate.

The invention relates to a method for measuring the coherence length of a Shell model correlation structure light beam, which belongs to the field of laser space coherence measurement, and comprises the following steps: S1, calculating the coherence lengths # imgabs0 # and # imgabs1 # in x and y directions by using the analytic relationship between the coherence length of the Shell model correlation structure light beam and the spatial coherence modulus; s2, a double-aperture mask is arranged on a light beam shaping transmission path of the laser processing system, the aperture positions are symmetrical, the distance d is adjustable, and after light beams are focused, intensity signals # imgabs2 are collected at a focal plane detector; and S3, extracting an intensity signal # imgabs3 # to obtain a double-aperture interferogram, performing Fourier transform on the interferogram, establishing a corresponding relation between a low-frequency component in a frequency spectrum and a characteristic frequency of an aperture spacing d, and calculating to obtain a spatial coherence modulus # imgabs4 #. According to the invention, based on partially coherent light dual-aperture interference and Fourier spectrum analysis, a direct analytical relationship between the spatial coherence degree and the coherence length is established, and a new way is provided for beam quality control in laser processing.

The embodiment of the invention discloses a preparation device and method of a volume holographic grating. The device comprises a coherent light source used for generating coherent light with the coherent length larger than the optical path difference of the grating recording device; the beam expanding and splitting device is used for expanding and splitting the coherent light into object light and reference light with the same polarization direction; the control unit is used for decomposing the volume holographic grating into a plurality of volume holographic sub-gratings related to the grating position; the light modulator unit is used for modulating complex amplitude distribution of an object light wave surface to obtain object light with certain complex amplitude distribution, and the object light with certain complex amplitude distribution and the reference light interfere to form stripes with light intensity distribution corresponding to the volume holographic sub-grating; a light transmission unit for transmitting the object light having a certain complex amplitude distribution and the reference light to a recording medium; and the spatial position adjusting unit is used for bearing the recording medium and adjusting the position of the recording medium according to the signal from the control unit, so that the recording medium records stripes corresponding to the position according to the position to obtain the volume holographic grating.

The present disclosure provides a free space optical communication system comprising a superluminescent light emitting diode (SLED) with an ultrashort coherence length configured to generate a broadband beam of light, a modulator configured to modulate the broadband beam of light to encode data and generate a modulated beam of light, a semiconductor optical amplifier (SOA) configured to amplify the modulated beam of light to generate an amplified beam of light, wherein the SOA has a bandwidth of at least 25, 50, or 100 nanometers, and an output configured to transmit the amplified beam of light through a variably refractive medium. The system enables high-bandwidth optical communication with improved performance in atmospheric turbulence.

The invention relates to the technical field of earphone control, and discloses a multi-scene adaptive wireless earphone dynamic control method, which comprises the following steps: identifying environmental noise through phonon entangled state density and phase coherence length by adopting a quantum sensor array; physiological signals of a user are collected through the anti-interference electroencephalogram electrode, and the auditory state is analyzed; a millimeter wave radar is used to construct an environmental acoustic model, and quantum-classical hybrid calculation is combined to realize rapid sound field simulation; establishing a multi-objective optimization function to dynamically adjust noise reduction, equalization and spatial sound effect parameters; and realizing smooth transition control based on scene change prediction. According to the invention, the control accuracy of the wireless earphone during multi-scene adaptation can be improved.

The present invention discloses a multi-path atmospheric coherence length measurement method and system for satellite-to-ground laser communication. The system consists of a binocular image acquisition module, a control module, a data processing module, and a storage module. The binocular image acquisition module is used to acquire paired star spot images, the control module is used to control the binocular image acquisition module to effectively acquire images, the data processing module is used to extract the centroid of the star spot from the two frames of synchronously acquired images, and use the differential image motion method to calculate the atmospheric optical turbulence intensity on the path where the spot is located; the storage module saves the data results. In the specific measurement method, the photon flux density method is used to calculate the detection capability of the measurement system; the number of detectable star spots and their probability are determined based on the field of view of the equipment; the optical flow method is used to realize the estimation of pixel motion and the tracking of star point trajectories; the atmospheric coherence length and seeing are calculated based on the variance of the centroid motion of the star spot, revealing the intensity of atmospheric optical turbulence at different positions.

The invention relates to the field of non-imaging optical design, and discloses a beam shaping reflector with a decoherence effect, the reflector comprises a plurality of first-level sub-surfaces, a plurality of beam propagation channels are formed, each first-level sub-surface is composed of a plurality of ellipsoid surface elements, and light distribution of light beams in a single channel is realized; the first-stage sub-surfaces are arranged in a preferable form, so that the optical path difference between light beams of each channel is greater than the coherence length of a light source, and a de-coherence function is realized; multi-channel light distribution is carried out on the light source, high-uniformity light spot shaping is achieved, meanwhile, the adaptability to the light source with energy distribution fluctuation is good, and high stability is provided for practical application of light beam shaping; besides, light beam shaping and de-coherence are completed only through one free-form surface, the size is small, the light path can be adjusted to the maximum extent according to actual requirements, and high practical value and application prospects are achieved.

The invention relates to the technical field of optical detection, and provides a wavefront error detection method of a phase-shifting interferometer, which realizes phase shifting through voltage regulation and control of an electro-optical crystal, replaces a mechanical driving mode of a traditional piezoelectric crystal, avoids the problems of shifting distance drift and linearity distortion caused by internal heating of the electro-optical crystal, and improves the detection accuracy of the wavefront error of the phase-shifting interferometer. An error source caused by mechanical motion is eliminated in principle, so that the phase shifting process is more stable, and the detection repeatability is improved; by adjusting the optical path difference of a coherent optical path, the optical path difference of reflected light of the first semi-transparent and semi-reflecting mirror and the first beam expanding lens is only enabled to be smaller than the coherent length of short coherent light, and only target interference fringes are ensured to be generated; meanwhile, the optical path difference of other non-target optical paths exceeds the coherence length, stray light interference is effectively eliminated, the signal-to-noise ratio and purity of an interferogram are improved, and reliable data are provided for wavefront error calculation.

The invention provides a long-range high-precision frequency-modulated continuous wave ranging system with an optical switch capable of rapidly switching optical paths, and relates to the technical field of interference ranging. According to the system, a flight time infrared distance measurement module and a semiconductor optical switch switching module are added on the basis of an existing frequency modulation interference distance measurement system; the flight time infrared distance measurement module measures rough distances between different parts of the to-be-measured workpiece and the distance measurement module; the semiconductor optical switch switching module switches the optical path of a reference light beam to different optical path difference delay lines according to the distance measured by the flight time infrared distance measurement module when the interference distance measurement module measures a beat frequency signal, and matches the optical path of a measurement path and the optical path of a reference path, so that the measurement path and the reference path are kept at a coherence length. Therefore, the measurement precision is not deteriorated along with the increase of the distance; and finally, adding the interference distance and the optical path difference transmitted by the semiconductor optical switch switching module, and finally demodulating the distance of the to-be-measured workpiece according to the ratio of the optical path difference to the actual optical path, thereby completing distance measurement.

This invention discloses a method for measuring the wavelength of low-coherence lasers using a synthetic Fizeau interferometer cavity. The method involves acquiring the interference fringes and extracting the initial phase of each actual Fizeau interferometer cavity with different free spectral ranges (FSRs) that meet the coherence length requirements of the low-coherence laser to be measured. Based on the FSRs and initial phases of each actual cavity, a synthetic Fizeau interferometer cavity with a FSR smaller than that of the physical cavities is constructed to obtain the synthetic free spectral range and synthetic initial phase. The interference order of the synthetic cavity is then determined by combining the input estimated wavelength or frequency, and wavelength refinement is performed to finally obtain the measurement wavelength. This invention does not limit the specific optical path structure or detector arrangement, and can effectively overcome the limitation of low-coherence laser coherence length on the accuracy of Fizeau wavelength measurement without increasing the optical path difference of the actual Fizeau interferometer cavity or reducing the fringe signal-to-noise ratio.

The application discloses a kind of based on the principle of OFDR's double-pulse long-distance distributed vibration detection device, including narrow linewidth laser light source and to-be-measured interferometer, and the application also includes auxiliary interferometer and phase noise demodulation and elimination mechanism, narrow linewidth laser light source includes NLL laser and first fiber coupler, the first output channel and the second output channel of first fiber coupler are connected with to-be-measured interferometer and auxiliary interferometer respectively, and to-be-measured interferometer and auxiliary interferometer are connected with phase noise demodulation and elimination mechanism.The application uses the above structure based on the principle of OFDR's double-pulse long-distance distributed vibration detection device, utilizes two homologous pulses to carry out Rayleigh scattering detection, mixes with auxiliary interferometer, realizes the elimination of phase noise, breaks through the limit of coherence length to range, realizes long range, frequency response high vibration signal detection, and only needs to mix in optical path twice, demodulation algorithm is simple, and phase correction speed is fast.

The invention relates to the technical field of image degradation processing, in particular to a method for evaluating the degradation degree of optical system imaging caused by atmospheric factors. According to the method, a systematic evaluation system for the influence of atmospheric factors on optical imaging is constructed, the modeling processes of the fog aerosol MTF and the long exposure turbulence MTF are integrated, the Nyquist frequency is used as a bridge, the atmospheric coherence length when the fog aerosol MTF and the long exposure turbulence MTF are equivalent is solved, and a breakthrough from independent factor analysis to synergistic effect quantification is achieved. An evaluation model is constructed by fusing multiple parameters such as optical thickness, atmospheric coherence length, wavelength, spatial angular frequency and the like, and a complete technical chain of modeling-simulation-evaluation is formed by combining Fourier transform image simulation with evaluation indexes such as peak signal-to-noise ratio, structural similarity index and the like. And a solution with theoretical preciseness and engineering practicability is provided for predicting the degradation degree of the optical imaging system in a complex atmospheric environment.

A system configured to perform the DCS-type measurements with the use of low-coherence continuous-wave (CW) light source at levels of light intensities that are substantially lower and with pathlengths through the tissue that are substantially longer than those afforded by the use of conventional methods. The method includes utilizing the optical detection system to producing signals representing interference between the portion of CW light arriving through reference arm of interferometer and the sample CW light potion that has traversed the sample arm including different paths through the target tissue while switching between first and second of said different paths only by adjusting a delay in the delay line. The spatial resolution of different pathlengths of sample light through tissue is defined by coherence length of CW light.

The invention discloses a terahertz wave decoherence method, a terahertz wave decoherence system and an imaging system. The terahertz wave decoherence method comprises the following steps: carrying out active phase modulation on coherent terahertz waves by adopting a reconfigurable phased array comprising a plurality of array elements with independent terahertz wave phase regulation freedom degrees, and regulating and controlling the number of effective array elements of the reconfigurable phased array and / or the phase regulation and control change rate of the effective array elements, and the first-order coherence function modulus value of the terahertz wave is reduced, so that the terahertz wave decoherence is realized, and the intrinsic time coherence length of the terahertz source is not changed. The reconfigurable phased array is used for performing decoherence modulation, and the variable capacitance characteristic of the SBD is used, so that the phased array receives different voltages to cause the change of junction capacitance, thereby causing the change of the resonance mode of the terahertz antenna, realizing terahertz phase modulation, particularly realizing active and controllable terahertz decoherence operation, and further optimizing the terahertz imaging effect.

The application provides a full-field OCT system based on orthogonal double liquid crystal phase compensation, an imaging method, equipment and a medium, and comprises the following steps: a broadband light source module is used to provide broadband illumination light with a low coherence length; a light splitting module is used to make the broadband illumination light enter a reference arm and a sample arm according to a predetermined proportion; the reference arm is sequentially provided with a first liquid crystal phase modulation component, a first wave plate, a first microscope objective and a fixed reference mirror; the sample arm is sequentially provided with a second liquid crystal phase modulation component, a second wave plate, a second microscope objective and a sample to be measured; a detection module is used to receive an interference signal of the reference arm reflected light and the sample arm backscattered light and to perform photoelectric conversion; and a control module is used to apply a differential driving voltage to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component and to synchronously control a face array camera to collect, so as to solve the problems of stability and defocusing caused by mechanical phase shifting in the FFOCT system and low light energy utilization and dispersion mismatch caused by liquid crystal polarization dependence.

The application discloses an interference distance measurement signal enhancement method and device based on reference optical path segmentation matching, and belongs to the technical field of weak coherent interference measurement. The method comprises the following steps: controlling a reference arm reflector to move, performing coarse positioning on a reflection characteristic peak of a front surface of a ball lens in a sample arm, and making the reflection characteristic peak enter a coherence length range; performing fine scanning near the coarse positioning position, extracting an interference envelope, and determining accurate coordinates of a zero optical path difference position; offsetting the reflector by a preset optical path amount according to a working distance of the ball lens, and making the zero optical path difference move to a focal point; in a probe moving process, A-scan signals are collected at preset time intervals, and an offset amount of an actual depth of the reflection characteristic peak relative to a reference depth is calculated; when the offset amount exceeds a tolerance threshold, the reflector is reversely driven to move by a compensation distance, and the zero optical path difference moves along with the focal point. The application does not need to reform the probe, adopts a translation type optical path adjustment to avoid optical path mismatch, realizes real-time following of the zero optical path difference position in a probe dynamic moving process, and enhances an interference signal.

The application provides a backscattering measurement system and method based on low-coherence interference, wherein, during measurement, the system is first built, for backscattering light of each backscattering angle, a backscatterer is uniformly moved to provide a continuously changing optical path difference; two groups of interference lights are respectively subjected to real-time photoelectric conversion by using a balanced detector module, and an output voltage V is calculated by using a preset backscattering alternating current signal mathematical model to acquire an electric signal in real time; the electric signal is input into a central processing unit module in real time and is analyzed and processed to complete measurement of the backscattering light; the application uses the characteristics of a wide spectrum and a short coherence length of a low-coherence light source, controls the optical path difference, thereby filters out a concerned stray light source, removes the influence of other non-target stray lights, and can distinguish different stray light sources; in addition, the application uses an interference method to perform measurement, which is closer to the actual working condition of a telescope, and improves the sensitivity and accuracy of measurement.

This invention discloses a method for measuring the atmospheric coherence length of a free-space optical communication link. The method includes: firstly, within the framework of Kolmogorov's atmospheric turbulence theory, expressing the time average of the variance of the optical signal wavefront phase fluctuation caused by atmospheric turbulence in the free-space optical communication link using the time average of the phase structure function; then, establishing an analytical expression for the relationship between the time average of the variance of the optical signal wavefront phase fluctuation and the atmospheric coherence length based on the relationship between the phase structure function and the atmospheric coherence length, thereby indirectly measuring the atmospheric coherence length using the information on the optical signal wavefront phase fluctuation caused by atmospheric turbulence in the free-space optical communication link.

The invention provides a light beam shaping device and an optical system, the light beam shaping device comprises a first optical module, and the first optical module comprises a light splitting unit, a delay unit and an imaging unit; the light splitting unit is used for splitting the first light beam into N first split light beams in a first plane and emitting the first split light beams in parallel; the delay unit is arranged on the light emitting side of the light splitting unit and used for enabling the first split light beams to be emitted through different propagation lengths, and the minimum delay value between the emitted first split light beams is larger than or equal to the coherence length of the first light beams; the imaging unit is arranged on the light emitting side of the delay unit and used for imaging the first split light beams emitted through the different propagation lengths, the difference of the longitudinal positions of real images of the first split light beams is smaller than one time of the Rayleigh length, and the transverse positions of the real images of the first split light beams are overlapped. Through the light beam shaping device and the optical system provided by the invention, the problem that the existing Gaussian laser beam is not suitable for thin film processing is particularly solved.

The present disclosure provides a free space optical communication system comprising a superluminescent light emitting diode (SLED) with an ultrashort coherence length configured to generate a broadband beam of light, a modulator configured to modulate the broadband beam of light to encode data and generate a modulated beam of light, a semiconductor optical amplifier (SOA) configured to amplify the modulated beam of light to generate an amplified beam of light, wherein the SOA has a bandwidth of at least 25, 50, or 100 nanometers, and an output configured to transmit the amplified beam of light through a variably refractive medium. The system enables high-bandwidth optical communication with improved performance in atmospheric turbulence.

A method for producing a quantum device comprising forming a superconductive layer, forming a mask on the superconductive layer, the mask comprising masking patterns and at least two openings alternately in a direction, the at least two openings) being separated from one another by a separation distance, and further each having a width, such as the separation distance and the width are less than a coherence length of a Cooper pair in said superconductive material, and modifying, through the at least two openings, of the exposed portions of the superconductive layer, so as to form at least two barriers of width di separating the superconductive regions.

A temperature monitoring device according to the invention comprises a control system (100) adapted to generate a substantially periodic control waveform applied to a control input of a light source (111) with a tunable wavelength connected to a fiber interferometer (112), wherein a measuring fiber (120) is connected in an arm of one of the fiber interferometers (112) and the interferometer (111) output is connected to a detector (113), the output of the detector (113) being connected to a signal processing module (101) adapted to identify temperature changes as a function of the fiber length, characterized in that the coherence length of the light source (111) is longer than 0.5 m and the period of the periodic waveform is shorter than or equal to 20 s, the difference between the minimum and maximum wavelengths is higher than 3 pm, and the fiber is adapted to be placed near an energy-discharging device in a vehicle during its operation. A temperature monitoring method according to the invention is characterized in that the temperature is determined by cumulatively taking into account changes detected at measurement points on the measuring fiber of the device using the device according to the invention. A temperature monitoring system according to the invention is characterized in that the measuring fiber of the device according to the invention is placed near an energy-discharging device in a vehicle.

The invention provides a waveguide sheet, and relates to the technical field of optics, and the waveguide sheet comprises an optical region which is internally provided with a plurality of beam splitting surfaces; coupling-in light rays of the incident optical area are divided into turning light rays incident into a plurality of turning light paths after passing through the plurality of beam splitting surfaces. The multiple turning light paths comprise at least part of first turning light paths, the reflection times of turning light rays in the first turning light paths are smaller than a preset value, the different first turning light paths are not overlapped, and the optical path difference of the turning light rays in the different first turning light paths is larger than the coherence length. In the prior art, the turning light rays are reflected by different turning light paths and then are converged at one point on the same beam splitting surface, so that the illumination intensity of the point is too high, the optical path difference of the turning light rays in different first turning light paths is larger than the coherence length, the frequency of interference of different turning light rays is reduced, and the display effect is optimized.

The invention provides a method for establishing an amount of displacement between a first and a second object, in particular a displacement in the order of tens of nanometres, more in particular in the order of nanometres, comprising generating a phase-synchronised radio-frequency signal which is phase-synchronised using a clock signal having an accuracy of at least 10-10-th of a second, in particular at least 10-11-th of a second, more in particular at least 10-12-th of a second, providing an optical laser beam having a coherence length of less than 100 mm, in particular less than 10 mm, more in particular less than 1 mm, adding said phase-synchronised radio-frequency signal to said optical laser beam, transmitting said optical laser beam into an optical resonance cavity which has one end fixed to the first object and another end to the second object, extracting said optical laser beam from said optical resonance cavity, extracting a resonated radio-frequency signal from said resonated laser beam, determining a cavity length change from the resonated radio-frequency signal, and determining from said resonance cavity length change said amount of displacement.

An optical parametric device (OPD), which is selected from an optical parametric oscillator (OPO) or optical parametric generator (OPG), is configured with a nonlinear optical element (NOE) which converts an incoupled pump radiation at first frequency into output signal and idler radiations at one second frequency or different second frequencies, which is / are lower than the first frequency, by utilizing nonlinear interaction via a random quasi-phase matching process (RQPM-NOE). The NOE is made from a nonlinear optical material selected from optical ceramics, polycrystals, micro and nanocrystals, colloids of micro and nanocrystals, and composites of micro and nanocrystals in polymer or glassy matrices. The nonlinear optical material is prepared by modifying a microstructure of the initial sample of the NOE such that an average grain size is of the order of a coherence length of the three-wave interaction which enables the highest parametric gain achievable via the RQPM process.

The application relates to a transformer rapid explosion suppression and fire prevention method, and belongs to the technical field of power equipment safety, which specifically comprises the following steps: S1, collecting multi-physical field data in real time through a sensor network arranged in the transformer; S2, determining an electric-thermal instability index, a fractal dimension of a fire core growth, a maximum eigenvalue of an irradiance Hessian matrix, and a spectral coherence length decay rate based on the multi-physical field data; S3, combining the electric-thermal instability index, the fractal dimension of the fire core growth, the maximum eigenvalue, and the spectral coherence length decay rate to construct a feature vector; and S4, identifying a preliminary fault state based on the feature vector, correcting the preliminary fault state by using a preset physical model to obtain a final fault state, and triggering a hierarchical response strategy according to the final fault state. The application solves the problem that a single signal source is prone to failure under the interference of a complex electromagnetic and thermal environment, and provides a solid data foundation for subsequent accurate diagnosis.

The application discloses a time delay interference laser phase noise compensation method and device for optical frequency domain reflection, and comprises the following steps: obtaining a linear sweep signal light based on a signal source; obtaining a first heterodyne signal through a measurement interferometer, and obtaining a second heterodyne signal through a reference interferometer; and processing the first heterodyne signal and the second heterodyne signal by using a time delay interference algorithm, so that direct compensation of laser phase noise is realized; and obtaining a strain signal based on the direct compensation of the laser phase noise. Through compensation of the laser phase noise, high-precision measurement of the strain signal can be realized at a distance far beyond the coherence length of the light source.

The invention discloses an optical cable same-trench and same-cable detection method and system based on a related optical detection technology, belongs to the technical field of optical communication, and aims to solve the technical problem of analyzing whether a same-trench and same-cable routing hidden danger exists in an optical path in an optical transmission network. The method includes: acquiring light path data; acquiring bottom-layer basic layer data related to the geographic information; obtaining an oscillogram of coherent light through an optical frequency heterodyne detection principle, and calculating a coherence length based on the oscillogram; combining a plurality of continuous coherence lengths into a coherence event, and calculating the coherence length of each coherence event; carrying out screening based on a ratio between the length of the bearing section and the coherence length of the coherence event, and carrying out overlay analysis and marking on the bearing section based on the bottom layer basic layer data and the bearing section data; and matching the bearing section data with the light path data, and synchronously displaying the matched bearing section data on a map.

The present application relates to the field of laser, especially to the field of high-power single-frequency laser design. First, high-power single-frequency laser is generated by using high-power multi-end pump unidirectional circulation cavity, second, high-power single-frequency laser is used to generate single-frequency second and third harmonic laser output by intracavity frequency doubling, and finally, high-power single-frequency light and frequency is realized by designing coupling light path outside the circulation cavity, so as to generate high-power single-frequency five times frequency laser. The structure of the present application can easily obtain 1um laser band single-frequency five times frequency laser, and is widely used in the scene application requiring coherence length.