10 results about "Quadratic phase" patented technology

The present application relates to a kind of Hartmann wavefront measurement dynamic range extension method based on quadratic phase control, belong to wavefront measurement technical field.For the problem that the measurable slope interval is limited in the limited detection displacement range in traditional Hartmann wavefront measurement, at least the sub-aperture phase distribution containing reference focusing phase and quadratic phase term is constructed in super surface phase control, and the displacement of each sub-aperture corresponding light spot on the detection surface and the local average slope of the sub-aperture satisfy the preset monotone reversible nonlinear mapping relationship in design working interval by combining theoretical modeling, numerical optimization and / or experimental calibration.The present application can reconstruct the slope-displacement encoding rule of traditional Hartmann under the premise of keeping local average slope reversible and wavefront reconstructable, extend the encodable slope range in given displacement range, so as to improve the dynamic range of Hartmann wavefront measurement, especially suitable for the measurement scene of strong non-uniform, large dynamic range wavefront.

The invention discloses a large-view-field polarization detection super lens based on an instrument matrix, and relates to the technical field of micro-nano optics and polarization detection. Comprising four sub-lens structures. A secondary phase distribution and global optimal phase screening strategy is adopted in the structural design, and a calibration method based on an instrument matrix is provided. According to the structure, different polarization components are spatially separated and focused, and polarization response of a system at different incident angles is accurately calibrated by using an instrument matrix, so that polarization detection in a large view field range of 120 degrees is realized. The invention has the characteristics of super compactness and high precision, and can be used for designing polarization detection, polarization imaging and the like in a large view field range.

This invention proposes a low-noise holographic 3D display method based on a fractional Fourier transform algorithm. The method includes the following steps: First, setting the signal and noise intervals of the recorded object to obtain a preprocessed image RD(X,Y); Second, superimposing the image RD(X,Y) with a quadratic phase generator to produce a corresponding complex amplitude distribution D0(X,Y) on the object plane; then, performing a fractional Fourier transform based on the complex amplitude distribution D0(X,Y) on the object plane to obtain a complex amplitude distribution D1(X,Y) on the holographic plane; extracting the phase information of D1(X,Y) and... The complex amplitude distribution D2(X,Y) of the object plane is obtained through fractional-order inverse Fourier transform. A double constraint of amplitude and second-order phase is applied to the signal interval of D2(X,Y) to obtain the complex amplitude distribution D3(X,Y) of the object plane, completing the first iteration. The complex amplitude distribution D3(X,Y) is then used to replace D0(X,Y) to start the next loop, continuing until the phase converges to the optimal solution. In the third step, the phase distribution of the optimal solution is extracted to generate a pure phase hologram. By superimposing pure phase holograms of different depths, the final pure phase hologram of the 3D object is obtained. Low-noise holographic 3D display is achieved by illuminating the pure phase hologram of the 3D object with coherent light.

The invention provides a performance evaluation method and device for non-line-of-sight free space quantum key distribution, and belongs to the technical field of quantum communication and free space optical communication, and the method comprises the steps: constructing a three-dimensional light beam propagation model which comprises light beam drift, light beam broadening and light spot distortion caused by light beam diffraction and atmospheric turbulence; the method comprises the following steps: generating random turbulent flow phase distribution based on a sparse spectrum phase screen method, carrying out numerical simulation on a laser transmission process in combination with a step-by-step propagation algorithm, obtaining a transmissivity sample sequence in which geometric mismatch loss and a turbulent flow fading coupling effect are jointly considered under linear phase shift and secondary phase shift design, and further constructing end-to-end transmissivity probability distribution; and performing weighted evaluation on the key rate of the discrete variable and continuous variable quantum key distribution protocol by using the transmissivity probability distribution to avoid channel fluctuation distortion. The method is suitable for parameters of different turbulence intensities, wavelengths, receiving apertures and channel lengths, and can provide a basis for design and optimization of a non-line-of-sight quantum communication link.

The application discloses a GEO SAR time-varying ionosphere error compensation method based on maximum contrast self-focusing, and belongs to the technical field of GEO SAR (Geosynchronous Earth Orbit Synthetic Aperture Radar). The method selects distance line signals from a GEO SAR image, the distance line signals are the signals with the same distance time in the azimuth direction, the average power of each distance line signal in the image is calculated, a part of the distance line signals are selected, then the contrast of the SAR image is used to iteratively estimate the quadratic phase error coefficient, the cubic phase error coefficient is iteratively estimated based on the quadratic phase error coefficient, and finally the obtained quadratic and cubic phase error coefficients are used for phase compensation of the original SAR image, so that the SAR image affected by the time-varying ionosphere is accurately compensated. Experiments prove that the contrast of the compensated SAR image is improved by the method, and the compensated image is good, and is close to the image not affected by the time-varying ionosphere.

A kind of shore-to-ship receiving high frequency ground wave radar group target distance domain resolution method, including the construction of shore-to-ship receiving HFSWR group target echo geometric model;From the time domain echo signal of shore-to-ship receiving sub-target, derive motion compensation factor and distance scaling factor;According to the radial velocity and radial acceleration estimated by minimum entropy criterion, establish the motion compensation factor expressed in phase;The estimated rotational angular velocity is obtained by using the quadratic coefficient estimation method based on the quadratic phase cancellation to estimate the quadratic coefficient;The motion compensation factor is used to motion compensation group target time domain echo signal to obtain the Doppler spectrum after removing ambiguity;The estimated rotational angular velocity is brought into the radial distance scaling factor, and the Doppler spectrum after removing ambiguity is converted from Doppler frequency to radial distance domain by the radial distance scaling factor, to realize the resolution of group target in distance domain.The present application solves the problem that HFSWR is difficult to distinguish group target, and improves the resolution ability of shore-to-ship receiving HFSWR group target in distance domain.

The invention discloses an ultra-high-speed target imaging method and system based on double-step frequency phase cancellation. According to the method, the characteristic that two groups of stepping frequency signals with different repetition periods can be converted to a frequency domain on a slow time axis is utilized, and the stepping frequency signals are combined with a phase cancellation operator constructed by the frequency domain, so that a primary phase term and a secondary phase term caused by motion can be eliminated on the premise of keeping system parameters consistent; meanwhile, sampling envelope walking under the high-speed condition can be effectively restrained, so that stable correction is still achieved under the high-speed scene, the energy focusing capacity is improved, and the high-performance imaging method based on the frequency domain phase cancellation technology is obtained. According to the method, range image offset, image waveform divergence and sampling envelope walking can be effectively inhibited under the condition of ultra-high-speed motion, the speed application range of double-pulse-group stepping frequency imaging is expanded, and the target imaging focusing performance and the positioning precision are improved.

This invention discloses a robust detection method and system for high-speed, highly maneuverable targets based on Radon-LVD transform, belonging to the field of radar signal processing. The method estimates the target's velocity and acceleration from the pulse-compressed echo signal using Radon-LVD transform; constructs a slow-time-range frequency domain quadratic phase compensation function using the velocity and acceleration estimates; performs migration compensation on the slow-time-range frequency domain of the echo signal; and then performs moving target detection in the range-Doppler domain. The two searches during this process improve the accuracy of target parameter estimation. This invention combines Radon transform and LVD transform, which can compensate for range migration and Doppler migration respectively, achieving coherent accumulation of energy in the echo signal of a uniformly accelerated target.

The invention discloses a shore-launch ship high-frequency ground wave radar group target distance domain distinguishing method. The method comprises the following steps: constructing a shore-launch ship HFSWR group target echo receiving geometric model; receiving a sub-target time domain echo signal by a shore-transmitting ship, and deriving a motion compensation factor and a distance calibration factor; establishing a motion compensation factor represented by a phase according to the radial speed and the radial acceleration estimated by the minimum entropy criterion; estimating a quadratic term coefficient by using a quadratic term coefficient estimation method based on primary phase cancellation to obtain an estimated rotation angular velocity; performing motion compensation on the group target time domain echo signal by using the motion compensation factor to obtain a Doppler spectrogram after deblurring; and the estimated rotation angular velocity is substituted into a radial distance calibration factor, and the Doppler frequency of the deblurred Doppler spectrogram is converted to a radial distance domain through the radial distance calibration factor, so that the resolution of the group target in the distance domain is realized. According to the method, the problem that the HFSWR is difficult to distinguish the group target is solved, and the distance domain distinguishing capability of the shore-launched ship receiving the HFSWR group target is improved.

This invention belongs to the field of laser shaping technology and provides a three-channel parallel ultrafast laser shaping system and method based on spatiotemporal compensation. By setting a pre-dispersion compensation module, this invention introduces controlled negative dispersion in advance, thereby precisely offsetting the pulse broadening induced by digital micromirror array diffraction and thick glass elements in subsequent branches, ensuring that the pulse width of each shaping branch at the focal plane remains in a fidelity state. The beam is distributed to three functionally complementary shaping branches, and a digital virtual focal length is generated by superimposing a specific quadratic phase function. This allows for dynamic compensation of focal position deviations between branches without moving any mechanical components, achieving instantaneous drift-free alignment of multimodal coaxial focal points. This invention not only achieves multi-dimensional flexible customization of the processed morphology but also ensures high consistency of processing thresholds and high fidelity of spatiotemporal pulses during high-speed switching of modes.