13 results about "Faraday rotation angle" patented technology

This application relates to a polarization-maintaining isolator and optical device. The polarization-maintaining isolator includes a first collimator, a first polarizer, a Faraday rotator, a second polarizer, and a second collimator arranged sequentially along the optical path. The transmission axis of the first polarizer is along a first target polarization direction; the Faraday rotation angle of the Faraday rotator is equal to the target angle; the transmission axis of the second polarizer is along a second target polarization direction; the first target polarization direction, after being rotated by the target angle, is aligned with the second target polarization direction; and the second target polarization direction, after being rotated by the target angle, is perpendicular to the first target polarization direction. This application simplifies the device structure and reduces the space occupied by the device, achieving a compact design for the optical isolator.

The application discloses a temperature measuring method and device based on a Faraday magneto-optical effect of magnetic nanoparticles, and belongs to the technical field of nano material testing. The method comprises the following steps: placing a magnetic nanoparticle sample in a target area, and making the magnetic nanoparticles generate a magnetization response through an applied direct current excitation magnetic field; adopting a polarized light to irradiate the magnetic nanoparticles in the coaxial direction of the magnetic field, so that the Faraday magneto-optical effect occurs between the magnetic nanoparticles and the sample; taking a sample without adding magnetic nanoparticles as a control group, applying an excitation magnetic field with the same amplitude and opposite direction to the applied direct current excitation magnetic field to the sample, and detecting the emergent light; calculating the Faraday rotation angle generated by the magnetic nanoparticles according to the detected emergent light; and performing nonlinear fitting on the Faraday rotation angle generated by the magnetic nanoparticles and the applied direct current excitation magnetic field by using a Lenz function, so as to obtain the temperature of the magnetic nanoparticles in the target area. The application can realize remote and non-invasive in-vivo temperature measurement.

The invention provides a signal-to-noise ratio-based adaptive noise reduction processing method and system for a spaceborne full-polarization radar Faraday rotation angle estimator signal. The method comprises the steps of reading a linear polarization scattering matrix and converting the linear polarization scattering matrix to a circular polarization basis; calculating a complex conjugate product of the cross circular polarization channel sum; dividing the window into sliding windows which are overlapped with each other; calculating a signal-to-noise ratio (SNR); calculating filtering parameters in each sliding window; converting to a frequency domain; carrying out Goldstein filtering on the frequency spectrum corresponding to each sliding window; transforming the frequency spectrum back to a spatial domain; and calculating a Faraday rotation angle. According to the method, the estimation precision of the Faraday rotation angle can be effectively improved.

The application provides a dual-baseline spaceborne SAR Faraday rotation angle estimation method and belongs to the field of SAR ionospheric effect compensation.The method is based on the dual-baseline spaceborne SAR in a ping-pong working mode, Faraday rotation angle estimation is realized by using full polarization data, a measurement scattering matrix calculation model affected by the Faraday rotation effect is established under the condition that two satellites are respectively taken as a transmitting side and a receiving side, then intermediate parameters are obtained by adding and subtracting the measurement scattering matrix elements, complex parameters are constructed, the complex parameters are conjugated and multiplied, two Faraday rotation angles are estimated after mean filtering and noise reduction of the calculation results, and the Faraday rotation effect compensation is used.The method realizes the Faraday rotation angle estimation of the dual-baseline SAR, the estimation result is relatively accurate, and the estimation error does not change much under different signal-to-noise ratios.

According to the optical path integrated packaging module and the current measuring device provided by the invention, the polarization unit, the non-polarization beam splitting unit and the polarization beam splitting detection unit are integrated and packaged in the shell of which the surface is provided with the plurality of optical fiber interfaces, and a spatial optical path transmission scheme is designed; reflected light containing Faraday rotation angle information is returned to the polarization beam splitting detection unit along an original path, so that the influence of environmental interference and crosstalk of optical devices on a light polarization state can be effectively avoided, the sensitivity of traditional optical fiber connection to environmental vibration and polarization state drift is overcome, all the advantages of the traditional optical fiber connection are reserved, and the reliability of the optical fiber connection is improved. And meanwhile, a fragile spatial light path is converted into a stable integrated structure, so that the plug and play of the device is realized, the stability and reliability of light path transmission are improved, and finally, the module has high performance and high reliability, and meets the precision requirements on polarization state modulation and detection in scenes such as to-be-detected current detection and the like.

This invention discloses a method for compensating for ionospheric polarization dispersion errors in spaceborne P-band broadband SAR, relating to the field of synthetic aperture radar ionospheric effect error compensation. Specifically, firstly, a range-to-Fourier transform is performed on a two-dimensional SAR image affected by polarization dispersion to obtain a four-channel frequency domain image. Then, the image is transformed from a linear polarization basis to a circular polarization basis and processed to obtain image Z. By summing all azimuth points in each range direction of image Z, a one-dimensional complex array is obtained. The phase is extracted from each point in the array, and phase unwrapping and deblurring are performed to obtain the Faraday rotation angle. Finally, polarization dispersion compensation and a range-to-inverse Fourier transform are performed to obtain a time-domain image. This invention utilizes the SAR image itself to estimate the Faraday rotation angle, enabling accurate compensation for polarization dispersion even when errors exist in the Earth's magnetic field strength.

The application provides a microwave interference optical fiber sensing system for measuring Faraday rotation angle, comprising an optical carrier microwave generating device, a magneto-optical crystal, a polariscope and a photoelectric detector, the optical carrier microwave generating device is used for generating two routes of orthogonal but incoherent linearly polarized light, each route of linearly polarized light is loaded with a microwave, thereby forming two routes of optical carrier microwave, the two routes of optical carrier microwave are transmitted to the polariscope through the magneto-optical crystal, the magneto-optical crystal is placed in a corresponding intensity magnetic field, after the two routes of optical carrier microwave pass through the magneto-optical crystal, the polarization direction changes, at the polariscope, only microwave interference occurs to the two routes of optical carrier microwave, thereby generating an optical signal carrying a microwave interference signal; the photoelectric detector converts the optical signal into an electrical signal; according to the intensity of the microwave interference signal in the electrical signal, the Faraday rotation angle under the corresponding intensity magnetic field is calculated. The application has better stability, higher measurement accuracy and better anti-interference performance.

A method for correcting time-varying ionospheric error in high-orbit SAR based on Faraday rotation estimation is proposed. The method first performs zero-padding of the azimuth signal, then calculates the azimuth decompression phase, reconstructs the azimuth echo, estimates the time-varying ionospheric error phase, performs time-varying ionospheric error correction, acquires the corrected full image data, and finally obtains the final corrected image data. This invention utilizes the Faraday rotation error caused by the time-varying ionosphere in the fully circularly polarized signal wave of high-orbit SAR. By employing azimuth echo reconstruction and Faraday rotation angle estimation inversion, it can achieve high-precision correction of the time-varying ionospheric error in high-orbit SAR images. Its phase correction accuracy is better than 0.01 rad, and the correlation between the corrected image and the original image is as high as 99%. The system is simple and low-cost.

The invention discloses a brightness temperature correction method based on improved ocean target transformation. A sea area reference area is selected; extracting data snapshots in the defined longitude and latitude range of the reference area; for pixel points in each extracted data snapshot, screening effective pixel points by taking a wind speed, a Faraday rotation angle and a polarization rotation angle as constraint conditions, and determining an effective data snapshot according to a screening result; for each effective data snapshot, acquiring the brightness temperature of an observation point and corresponding sea-land surface physical parameters, calculating a simulated brightness temperature by using a forward model, and performing pixel-by-pixel subtraction on the simulated brightness temperature and the brightness temperature of the observation point to generate a brightness temperature deviation field; dividing an antenna space cosine coordinate system into grids, and interpolating the brightness temperature deviation into the grids; the brightness temperature deviation values in the effective grids are accumulated, the median in each grid is taken, the grid data quality is evaluated, a deviation field OTT is generated, the OTT correction value is mapped to a global measurement point, and the corrected brightness temperature is generated.

The application relates to the technical field of satellite remote sensing imaging, in particular to a channel error estimation method and device of a satellite-borne synthetic aperture radar. The method comprises the following steps: obtaining a measurement matrix of a plurality of calibrators under full polarization channels of the satellite-borne synthetic aperture radar and a feature matrix of each calibrator; determining an estimated value of a Faraday rotation angle based on a double-angle formula, the measurement matrix and the feature matrix corresponding to each calibrator; determining an initial estimated value of a channel error based on the estimated value of the Faraday rotation angle; and determining a target estimated value of the channel error under consideration of calibrator errors and system thermal noise based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, a least square method and the measurement matrix and the feature matrix corresponding to each calibrator. The scheme considers the system thermal noise and the calibrator errors, and can improve the precision of the target estimated value of the channel error.

The invention belongs to the technical field of magneto-optical crystal preparation, and relates to a bismuth-doped europium yttrium iron garnet magneto-optical crystal and a preparation method and application thereof. According to the preparation method, a magneto-optical crystal with a chemical formula of Eu < 3-x-y-z > Bi < x > Y < y > Tb < z > Fe < 5-w > Ga < w > O < 12 > is grown by adopting a top seed crystal method, wherein x ranges from 0.30 to 0.43, y ranges from 1.20 to 2.06, z ranges from 0.08 to 0.17, and w ranges from 0.09 to 0.17. The method has the advantages of high crystal growth speed, simple process and the like, and can be used for preparing centimeter-level single crystals. A Bi2O3-Fe2O3 self-service solvent is used for crystal growth, and compared with a Pb-containing cosolvent system, the Bi2O3-Fe2O3 self-service solvent is more environmentally friendly, and harm to a human body and pollution to the environment can be reduced. The Faraday rotation angle of the garnet crystal can be increased by doping Bi in a proper amount.

The utility model discloses a quantum random number generator which comprises a laser module, an alkali metal atom gas chamber, a detection module and a post-processing module, the output end of the laser module is connected with the input end of the alkali metal atom gas chamber, the output end of the alkali metal atom gas chamber is connected with the input end of the detection module, and the output end of the detection module is connected with the input end of the post-processing module. The utility model discloses a quantum random number generator, which can improve the generation rate of random bits without being limited by the autocorrelation time of a single-photon detector by generating noise in a paramagnetic Faraday rotation angle of a detection light beam output by a laser module through spontaneous spin noise of alkali metal vapor in an alkali metal atom gas chamber.

The invention discloses a compact polarimetric SAR calibration method and device based on an active calibrator, and belongs to the technical field of signal processing. The method comprises the following steps: establishing a calibration model of a compact polarimetric SAR system based on a Freeman model; substituting the three active scaler characteristic matrixes with different polarization characteristics into the system model, and respectively analyzing and calculating the receiving channel imbalance, the receiving channel crosstalk, the transmitting channel crosstalk and the Faraday rotation angle; and a rough Faraday rotation angle is calculated by using ionosphere total electron quantity data provided by a global navigation satellite system, and defuzzification is carried out on the Faraday rotation angle with phase ambiguity. According to the method, only three active calibrators are needed, analytical calculation and GNSS auxiliary ambiguity resolution are combined, calibration of the CTLR mode compact polarimetric SAR system with high precision, low equipment quantity and simplified process is achieved, and the method has high noise resistance and calibrator error resistance.