18 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 present invention discloses a double-layer metasurface wide-angle imaging lens with quadratic phase modulation and monochromatic aberration elimination. The double-layer wide-angle imaging lens comprises: a substrate L1, a nano-cylinder array structure layer M1 arranged on the upper surface of L1, and a nano-cylinder array structure layer M2 on the lower surface. M1 is established according to the binary optical surface 2 formula of ZEMAX and has the function of correcting spherical aberration; M2 is modulated by the quadratic phase formula and can eliminate the coma generated after the angled light source is incident and focused. When the imaging lens is working, the angled light source is incident from the dielectric cylinder array structure layer on the top surface of the substrate, passes through L1 and M2, and focuses the light onto the sensor. The present invention uses a nano-cylinder array structure layer, which can be used to focus incident light at a large angle, and can minimize the volume and weight of the system, thereby improving the practical application effect of the imaging lens.

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 present disclosure relates to electronic devices with a quadratic phase generation circuit. An electronic device can include wireless circuitry. The wireless circuitry can include a quadratic phase generator for an outputting a full interpolated constant amplitude zero autocorrelation (CAZAC) sequence for a transmit path. The quadratic phase generator can include a numerically controlled oscillator, a switch controlled based on a value output from the numerically controlled oscillator, a first integrator stage, and a second integrator stage connected in series with the first integrator stage. The numerically controlled oscillator can receive a chirp count and a word length as inputs. The switch can be configured to switchably feed back one of two input values as a function of the chirp count and the word length to the first integrator stage. The quadratic phase generator can output a full bandwidth chirp or a reduced bandwidth chirp. Bandwidth reduction can be achieved by scaling the two input values of the switch.

The invention discloses a stable image bias self-focusing method and device for a video SAR (Synthetic Aperture Radar), and the method comprises the steps: carrying out the inter-frame drift error modeling of an echo signal collected by the video SAR, and obtaining an echo signal containing a slope distance error and each frame of echo signal containing a phase error; forming a first signal sub-segment and a second signal sub-segment according to the echo signal containing the slope distance error; constructing an objective function according to the correlation between the first signal sub-segment and the second signal sub-segment; performing global optimization search based on the target function to obtain an optimal secondary phase error coefficient; constructing a motion error function of each frame of echo signal according to the optimal quadratic phase error coefficient; and performing inter-frame drift error compensation and defocusing phase compensation on each frame of echo signal containing the phase error according to the motion error function of each frame of echo signal to obtain each frame of compensated echo signal, and forming a video SAR image sequence. According to the invention, compensation of the inter-frame drift error of the video SAR image can be realized.

The invention discloses a clutter Doppler sharpening method under range ambiguity of space-based double-station detection. The clutter Doppler sharpening method comprises the following steps: determining a squint angle change range in a beam detection area according to system parameters of a space-based double-station radar; dividing a beam detection area into a strong space-variant area and a weak space-variant area based on the squint angle variation range; constructing a partition compensation function for the strong space-variant region and the weak space-variant region to compensate the distance linear walking of the clutter signal to obtain a compensated clutter signal; fitting based on the compensated clutter signal to obtain a clutter equivalent energy center; and constructing a secondary phase compensation function by using the clutter equivalent energy center, and performing secondary phase compensation on the compensated clutter signal through the secondary phase compensation function. According to the clutter Doppler sharpening method, the compensation precision is high, compensation failure is avoided, and clutter energy diffusion caused by distance ambiguity component secondary phase compensation deviation can be avoided.

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.

There is described a system for determining a modal property of a quantum state. The system generally has a quantum light source generating an optical pulse having a given frequency, a pulse time duration and a quantum state with a modal property; a local pulse generator having: a laser source generating a local optical signal having a frequency associated to the given frequency; an optical modulator modulating the local optical signal; and an arbitrary wave generator supplying electrical waveforms to the optical modulator for said modulating, said modulating including forming local optical pulses from the local optical signal, the local optical pulses being distributed within the pulse time duration; and a homodyne detector optically coupled to the quantum light source and to the local pulse generator for performing two-time correlation measurements being indicative of the modal property of the quantum state of the given optical pulse.

The application discloses an unmanned aerial vehicle ISAR imaging method based on improved PGCPF parameter estimation, and relates to the technical field of inverse synthetic aperture radar imaging. The method comprises the following steps: performing distance compression, slant compensation and translational compensation on received echo signals to obtain processed data; performing reconstruction on the processed data through a weighted PGCPF optimization algorithm based on differential evolution to obtain reconstructed signals; and finally performing two-dimensional ISAR imaging on the reconstructed signals. The application introduces a weight factor in a PGCPF estimation multi-component linear frequency modulated (LFM) signal method, improves the accuracy of estimated quadratic phase term and linear phase term coefficients, reduces error accumulation in subsequent estimation, and optimizes parameter selection in the estimation process through a differential evolution algorithm. The application takes the ISAR image entropy as an evaluation function, finds the best parameter combination, and obtains the optimal echo signal. The reconstructed echo signal of the estimated multi-component linear frequency modulated signal can effectively improve the imaging effect of a rotor unmanned aerial vehicle in non-stationary motion and improve the imaging quality.

The invention relates to a terahertz video SAR (Synthetic Aperture Radar) imaging method and device for secondary phase error compensation, and the method comprises the steps: obtaining low-resolution imaging through an improved image displacement algorithm according to the imaging characteristics of a terahertz video SAR and a secondary phase error appearing in the imaging process, and then obtaining low-resolution imaging through a minimum image entropy criterion. And constructing a quadratic phase error function related to the vertical distance of the route, and accurately compensating the residual quadratic phase error of the image to obtain a fine high-resolution image. The quadratic phase error function constructed by the method considers the influence of the vertical distances between different distance units and the route on imaging, and the influence of the spatial-variant characteristics of the distance units on imaging can be reduced. According to the method, through minimum image entropy processing, a Doppler frequency modulation rate and a quadratic phase error function which are more accurate than those of an image displacement algorithm are obtained, and the influence of a quadratic phase error on imaging is compensated, so that a fine high-quality image is obtained.

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.

The application relates to a kind of secondary phase error compensation terahertz video SAR imaging method and device, by the characteristics of terahertz video SAR imaging and the secondary phase error that appears in the imaging process, first by improved image displacement algorithm, obtain low resolution imaging, again with minimum image entropy criterion, construct the secondary phase error function related to the vertical distance of flight line, accurately compensate the residual secondary phase error of image, obtain fine high-resolution image.The secondary phase error function constructed by the application considers the influence of the vertical distance of different distance units and flight line on imaging, and can reduce the influence of the range dependence of distance unit on imaging.The method obtains more accurate Doppler frequency and secondary phase error function than image displacement algorithm by minimum image entropy processing, compensates the influence of secondary phase error on imaging, so as to obtain fine high-quality image.