198 results about "Phase drift" patented technology

Disclosed herein is a scanning ladar transmitter that employs an optical field splitter/inverter to improve the gaze characteristics of the ladar transmitter on desirable portions of a scan area. Also disclosed is the use of scan patterns such as Lissajous scan patterns for a scanning ladar transmitter where a phase drift is induced into the scanning to improve the gaze characteristics of the ladar transmitter on desirable portions of the scan area.

Disclosed herein is a scanning ladar transmitter that employs an optical field splitter/inverter to improve the gaze characteristics of the ladar transmitter on desirable portions of a scan area. Also disclosed is the use of scan patterns such as Lissajous scan patterns for a scanning ladar transmitter where a phase drift is induced into the scanning to improve the gaze characteristics of the ladar transmitter on desirable portions of the scan area.

The invention discloses a spectral measurement method based on optical frequency combs. The measurement method is characterized in that firstly, an annular laser resonant cavity based on a phase modulator is actively modulated by use of a first optical frequency comb controllable in time domain and frequency domain so that the annular laser resonant cavity is converted into a second optical frequency comb having tiny difference in repetition frequency with the first optical frequency comb, and spectrum detection is performed on the two optical frequency combs to obtain an interference signal carrying the information of a sample to be tested, and meanwhile, frequency beating is performed on the two optical frequency combs and continuous frequency stabilized laser, respectively, the difference frequency signal of two obtained beat frequency signals is mixed with the interference signal, and a signal obtained by virtue of detection mixing is taken as a spectral signal for Fourier analysis so as to reduce the optical information of the sample to be tested. The spectral measurement method has the advantages that the error of the spectral detection due to own phase drift of a dual-optical comb system can be eliminated, and therefore, the resolution and the detection accuracy of the spectral measurement can be improved.

The invention discloses a four-state quantum encoder and decoder for phase modulation polarization encoding and a quantum key distribution system. The encoder and the decoder have intrinsic stability, namely, the working stability is not influenced by the external environment or connecting optical fibers which can be common mono-mode optical fibers. The quantum encoder and decoder can be applied to the field of quantum key distribution, the whole system comprises a transmitting end and a receiving end, and the transmitting end and the receiving end are connected through a quantum channel to complete the key distribution process. The quantum encoder and decoder can achieve BB84 protocol four-state quantum key encoding and decoding with intrinsic stability. The common mono-mode optical fibers can be used as all the connecting optical fibers without using polarization-maintaining optical fibers, and interference with the phase drift and polarization change of the system from the external environment has no influence on the encoding or decoding process at all.

The invention discloses a two-node measuring equipment unrelated quantum key distribution system. Two independent laser devices and a measuring device Charlie are all placed on the same node, namely an Alice end or a Bob end to form the two-node bidirectional transmission quantum key distribution system. According to the system, a two-node structure is adopted, the Faraday conjugated rotation effect is utilized, and the same transmission path is designed; as a result, the problem that an existing three-node measuring equipment unrelated quantum key distribution system is poor in stability due to polarization change, phase drift, non-uniform phase reference systems, time jitter and other factors is effectively solved, the purposes of polarization self-compensation, phase drift self-compensation, calibration-free phase reference systems and easy synchronization are achieved, and an important basis is provided for practical application of the measuring equipment unrelated quantum key distribution system.

The invention relates to a method for online monitoring the content of gas in transformer oil and a system thereof. A gas optoacoustic spectroscopy is adopted to measure the gas dissolved in the transformer oil, namely, after the gas is sent into an opto-acoustic pond, a gas circuit valve is closed, laser sent by a laser is used for radiating sample gas in the opto-acoustic pond, sound wave is generated by the gas which passes through light-absorbing pulse, and the intensity of the sound wave is detected by a rheomicrophone; then, a signal is amplified by preposing and phase locking, and the data of the signal is collected by a high-accuracy digital-analog converter and a DSP data transmitter and stored; at the same time, opto-acoustic phase drift analysis is carried out by a lock-in amplifier, and the running quality or fault category and fault severity of an electrical power unit is exactly judged according to the sorts and the concentration of the gas, thus judging the running state or the property and degree of fault of the electrical power unit with high accuracy. The invention has simple structure and stable running, and can realize online monitoring for a long time.

The invention relates to a method and a device for measuring harmonic impedance. Aiming at the main error source in an 'incremental method' of the method for measuring the harmonic impedance, namely the problem of the synchronization of frequency deviation and two different time signal phase angles, the invention discloses a 'bisynchronous incremental method', and develops a corresponding testing instrument, wherein the first synchronization is that a reference phase is synchronized with the system cycle to solve the drifting problem of the reference phase; and the second synchronization is that the sampling frequency is synchronized with the system frequency by tracking the changes of the system frequency by a hardware phase lock circuit and generating the sampling frequency by the phase lock circuit. The device for measuring the harmonic impedance comprises a synchronous circuit of the sampling frequency and the system frequency and a synchronous circuit of the phase and the system cycle. The 'bisynchronous incremental method' solves the error problems caused by benchmark reference phases, system frequency fluctuations and the like in the 'incremental method'; the device has a simple principle and is easy to implement; and the method and the device reach the engineering application level and solve the problem of measuring the harmonic impedance in the generation of electricity.

The invention provides a method for correcting near-field test phases of a millimeter wave plane. The method comprises the steps that step 1, a set XY plane is scanned and four points in a zone with strong signals are selected to serve as phase sampling points; step 2, preset periods are set, plane scanning is conducted on the four points, and collection moments, collection data and collection positions of the four points in each period are determined; step 3, according to data variable quantity of the selected four points, the phase of each point in the scanned plane is corrected; step 4, Fourier transform is conducted on the corrected data of the whole scanned plane, far-field data are calculated through near-field data, and the near-field far-field transformation formula is . According to the technical scheme, a function relationship, corresponding to the sampling points, of phase drift and time is established through the method that the positions of the appointed sampling points on the scanned plane and the sampling data in the positions are recorded, phase compensation of the data of the whole scanned plane is achieved through the interpolation mode, and therefore the measurement accuracy of a near-field measurement system under a millimeter wave frequency band is improved.

The invention discloses an interferometric optical fiber sensor and the digital closed-loop method of controlling action spots of the interferometric optical fiber sensor. A square wave phase modulation signal is introduced between two beams of interference light waves of an interferometer so as to enable the output signal of the interferometer to be changed into a square wave error signal from a cosine response signal; the square wave error signal is demodulated by adopting digital correlation detection technology, and the size of low frequency phase drift is obtained; the demodulated low frequency phase drift generates compensating phase shift and sends the compensating phase shift back to a light path for counteracting the low frequency phase drift, and after the process is repeated many times, the interferometer is caused to be at an orthogonal action spot. The invention has the advantages that the low frequency phase drift generated from environmental disturbance is compensated and the orthogonal action spot of the interferometer is stabilized so that a system can work in a most sensitive area always and the stability of the system is enhanced.

A laser interference lithography system with a pattern locking function comprises a laser, a reflector, a beam splitter, a substrate stage, a substrate and a pattern locking device. A laser beam emitted by the laser is split into an exposure beam and a reference beam by a spectroscope; the exposure beam passes through the beam splitter, and is reflected to the substrate on the substrate stage by the reflector to realize interference; the interference patterns can realize pattern record transfer by exposing the substrate; and the patterns are locked by the pattern locking device to prevent pattern drift during exposure. The pattern locking device includes a null phase meter, an electronic signal processing component, a controller, a driver and a phase modulation executing, wherein the null phase meter is used for measuring pattern phase drift; the pattern phase drift is fed back to the controller through the signal processing component; and the controller controls the phase modulation executer to realize phase locking through the driver. The laser interference lithography system provided by the invention has the advantages of simple structure, high pattern locking accuracy and the like, and is a key system for realizing large-area high-accuracy grating fabrication.

The invention relates to a digital array radar amplitude-phase monitoring and calibration method based on an optical fiber delay system. The method mainly includes the steps that a radar array front array element and an array front monitoring coupled array element are utilized to collect amplitude-phase data of all uplink channels and all downlink channels of the radar array front array element in a mutual coupling mode, amplitude-phase monitoring of all the uplinks and the downlinks of a radar array front is finished, when amplitude-phase correction and calibration need to be conducted on the array front, the difference value between the amplitude-phase data and factory data is acquired through amplitude-phase monitoring, and then amplitude-phase calibration of the uplinks and the downlinks of the array front is finished after the difference value is corrected. According to the method, the optical fiber delay system is introduced to separate transmitting time from receiving time, within a transmitting monitoring operation time sequence, the monitored channels work in a deep blanking state, optical fiber amplitude-phase drifting self-calibration is finished, and accuracy of monitored data is guaranteed. The method has the advantages of being good in real-time performance, convenient and quick to operate, and good in cost performance. The presentation and engineering realization of the method have high practical application value in the field of digital array radar monitoring and calibration.

The invention relates to an optical signal receiving method, an optical signal receiving device and an optical transmission system; the method comprises the following steps: receiving a 16QAM optical signal and local oscillator light, carrying out coherent detection to the signal and the light to obtain a 16QAM signal; according to the nonlinear phase shift factor and the drift phase error make-up corresponding to a previous 16QAM signal, pre-compensating for the phase of a current 16QAM signal, calculating the nonlinear phase shift factor and the shift phase error corresponding to the current 16QAM and takes the same as the nonlinear phase shift factor and the shift phase error required by compensating for a next 16QAM signal. The realization of the embodiment of the invention not only can effectively compensate for the shift phase error caused by frequency shift and phase shift between optical carrier and the local oscillator light, but also can compensate for the nonlinear phase shift of the 16QAM optical signal when transmitted in an optical fiber caused by nonlinear effect, thereby greatly reducing the error rate of the system and not producing format effect.

Various implementations of the invention compensate for “phase wandering” in tunable laser sources. Phase wandering may negatively impact a performance of a lidar system that employ such laser sources, typically by reducing a coherence length/range of the lidar system, an effective bandwidth of the lidar system, a sensitivity of the lidar system, etc. Some implementations of the invention compensate for phase wandering near the laser source and before the output of the laser is directed toward a target. Some implementations of the invention compensate for phase wandering in the target signal (i.e., the output of the laser that is incident on and reflected back from the target). Some implementations of the invention compensate for phase wandering at the laser source and in the target signal.

The invention, which belongs to the signal processing technology field, discloses an optimization method based on traditional phase difference measurement and a circuit. According to the method, two sinusoidal signals with different frequencies or a same frequencies pass through a signal collection circuit, an amplification circuit, and a comparison circuit as well as two paths of rectangular wave signals pass through an OR gate circuit so as to obtain a needed pulse signal; AD sampling is carried out so as to obtain a pulse width and a time difference of signal zero crossing, so that a phase difference is calculated. According to the invention, because a special circuit design is employed, phase drift generated by hardwares of a traditional zero cross detection circuit itself can be substantially changed, so that correlated subsequent processing of the phase difference on software becomes easier; therefore, the strong practicality is realized.

Methods for recovering high-resolution images from an analog video interface by autonomously correcting for phase errors between a synchronized clock signal to a sampling analog-to-digital converter and the input video signal. A global phase adjustment first detects video transitions in the sampled video data stream in order to determine and then select the optimum clock phase over entire video frames for rendering the pixels of the video input. This corrects for long-term phase errors, such as those from timing tolerances in circuit components and timing tolerances in the video input. A local phase adjustment selects the samples used for rendering individual pixels according to an algorithm that avoids the selection of samples that may be located within video transition regions. This corrects for short-term phase errors, such as those from jitter and phase drift on the sample clock.

The invention relates to a motion compensation method and system in three-dimensional imaging of a dynamic object. The motion compensation method comprises the following steps: firstly, carrying out primary estimation on a motion error; then, reestimating the motion error of each pixel of which the root-mean-square error is greater than a set threshold; calculating a correction estimation value of a phase of each pixel of which the root-mean-square error is greater than the set threshold according to the reestimated motion error and fixed phase drift and original deforming bar chart data of the system; replacing an initial estimation value of the phase of the corresponding pixel with the correction estimation value to form a wrapped phase diagram subjected to motion compensation; reestablishing a depth phase subjected to motion compensation by using the wrapped phase diagram subjected to motion compensation. The motion compensation method and system disclosed by the invention have relatively high reliability and relatively good compensation effect on the errors caused by motion, so that the dynamic surface measurement precision is greatly improved and the dynamic range of system measurement is expanded. The motion compensation method and system are applicable to a three-dimensional measurement system consisting of a projector and a single camera or two cameras, or motion error compensation of an absolute phase diagram subjected to phase unwrapping.