Calibration Method of Liquid-Crystal Spatial Light Modulator Based on a 1-D Phase Retrieval Algorithm

Liquid crystal spatial light modulators for precise dynamic manipulation of coherent light fields, used in diffractive optoelectronic optical data processing systems, are considered. This paper presents the results of a study of the temporal dynamics of the HoloEye PLUTO-2 VIS-016 liquid crystal spatial light modulator for analysis of light fields rate modulation. Experiments using binary phase computer generated holograms and binary focusing phase diffractive optical elements were conducted. Based on experimental data, the time characteristics of the modulator response were determined. It was found that when the rise time of the diffraction efficiency was 146 ms after the hologram displaying onto the SLM, and when switching to a new hologram, the decay time was 97 ms. These results allowed the dynamic generation of an alternating holograms at a refresh rate of 2 Hz with an interference level of –16 dB. Increasing the frequency of fringe pattern updates increases the level of interframe noise in the generated holograms, and when updated at the specification frequency, the generated distributions cannot be separated. Determining the actual frame rate based on the rise and decay times of the diffraction efficiency makes it possible to correctly calculate the minimum operating time of an information optical system containing a liquid crystal spatial light modulator.

The goal of this research is to build optical connectionist machines (OCM’s) capable of interconnecting many input units to output units via two-dimensional liquid crystal spatial light modulators (SLM’s). Liquid crystals SLM's are chosen because of their low optical absorption and power dissipation, moderate switching speeds, potential for high extinction ratios and resolution. In addition, these materials are birefringent and can easily implement a polarization-based optical associative memory. Previously, we presented results on connecting five input units to five output units [1], and eight input units to eight output units [2] with the OCM. The number of interconnections was limited by the low extinction ratio of the two-dimensional SLM used as the OCM connection matrix (The Radio Shack Pocketvision Model 5 extinction is 5:1). In this paper we present results of using higher contrast computer controlled SEIKO liquid crystal pocket television model LVD.012 and optically addressable ferroelectric liquid crystal SLM’s to hetero-associate pairs of 32 bit long input and output vectors. This association is performed using the least mean square algorithm (LMS), implemented with polarization encoding to represent both positive and negative weights.

A calibration method based on convex optimization (CVX) and neural networks is proposed for the large planar arrays of phased array three-dimensional imaging sonar systems. The method only needs an acoustic calibration source at an unknown position in the far field, and the direction of arrival (DOA) and gain and phase error are jointly estimated. The method uses a CVX algorithm to solve an optimization problem and initially estimates the DOA of the calibration source robustly. Subsequently, according to the estimation results, a neural network is used for fitting to obtain off-grid DOA estimation of the calibration source. Thereafter, spatial matched filtering is performed to obtain the gain and phase residual estimations. The root mean square error (RMSE) of the beam pattern calibrated by the method for uniform planar arrays can reach a value of 4.9542 × 10−5. The experimental results demonstrate the efficiency of the proposed method for gain and phase calibration.

The liquid crystal spatial light modulator (LC-SLM) is able to provide flexible wave front control, whereas its phase response distortions will influence the modulation accuracy. In this paper, we will provide a novel sub-regional phase response calibration method for minimizing these distortions. In our calibration method, the entire panel is divided into several local regions based on the similarity of phase response characteristic. Liquid crystal cells in one sub-region show the same phase response. The calibration method is theoretical analyzed and experimentally verified. For the entire Jasper 4K SLM panel, when three local regions are built, the root mean error of linear phase shifts is reduced to approximate 0.1 rad. The calibrated SLM is applied for holographic display and the structural similarity index of the assessment shows the improvement ratios reach 30.6p, 62.5p, and 43.6p for R, G, and B reconstructed components respectively. It also could be used for the calibration of various SLMs in the future.

The hydraulic shock absorber of a certain tractor suspension system is analyzed to determine the influence of the cross-sectional area ratio of the throttling holes of the restoration valve and the compression valve on the vibration damping performance of the whole vehicle, using a new method of machine-hydraulic co-simulation. First, the AMESim model of the hydraulic shock absorber is established, and the Kriging model is used to approximate the parameters of the AMESim hydraulic shock absorber model; the multi-island genetic algorithm and the gradient descent algorithm are used to obtain the three scenarios in which the cross-sectional area ratios of the throttle orifices of the same equivalent damping coefficients are greater than, equal to, or less than one. Then, a co-simulation model of 1/4 vehicle Recurdyn/AMESim and a co-simulation model of the whole vehicle with 162 degrees of freedom were established. The result show that, compared with the traditional method, this machine-hydraulic co-simulation method improves the calculation accuracy, calculation speed, and co-simulation model parameter accuracy. For low-speed conditions, when the throttle orifice area ratio equals 0.32, the minimum vehicle body center acceleration (root mean square value equal to 1.78 m/s2) is achieved. For high-speed driving conditions, when the throttle orifice area ratio is approximately 3.1, the minimum vehicle body center acceleration (root mean square value equal to 3.52 m/s2) is achieved.

Force and vibration generated in apical direction by three endodontic files of different kinematics during simulated canal preparation: An in vitro analytical study.

Focusing and imaging optics can be characterized by evaluating the wavefront error of the focused beam. We have bean developing a ptychographic phase retrieval method using a visible laser to measure the wavefront error. In this study, the measurement accuracy of the method is increased by improving both the phase retrieval algorithm and the experimental setup. The system is applied to the characterization of an ellipsoidal mirror used for the focusing of soft X-rays. The posture of the mirror can be measured with a resolution of 1.4 μrad. The wavefront error originating from the surface profile error can be detected with an accuracy of 0.01λ (root mean square).

Optical image encryption is one of the most promising technologies being investigated in the field of data communication and information technology. In this paper, a novel image encryption system based on virtual optical technique, Fourier transform phase retrieval algorithm and RSA public key exchange is proposed. In this strategy, a gray-level image is captured using a digital camera and encrypted using a linear grating superposed on the reflected intensity map of the object. A speckle mask is simulated and used as a secret key in both transmission and reception ends so that the receiver can identify the authenticity of the ciphertext by using the speckle pattern in the decryption process. The decryption method is performed to recover the phase of the deformed grating pattern. Towards this, Fourier transform based phase retrieval and sequential line scan phase unwrapping algorithm is utilized. The simulation results demonstrate the validity of the encryption method and the high robustness against potential attacks. To determines the accuracy of the information retrieved by the proposed technique, root mean square error is calculated between the original image and retrieved image. The proposed technique is also applicable for the information authentication.

Adaptive beam shaping for improving the power coupling of a two-Cassegrain-telescope

Three-Dimensional Quantitative Comparative Analysis of Trapezial-Metacarpal Joint Surface Curvatures in Human Populations

The aim of the present research is to calculate the Relative Accuracy (R.A) and Root Mean Square Error (RMSE) for the location of Technical Institute, Mosul in Nineveh Governorate, Iraq. at the northern part of Mosul city by using surveying Instruments (GPS 1230 , Total Station 06 & Level NAK2), to calculate the coordinates and elevations of (16) Ground Control Points which covered the study area. The field data, remote sensing techniques and GIS software (Arc Map GIS10.3) are used to check the digital map of study area that helped the administrator to take the correct decision, determining positions of the future expansionist for buildings, roads, measuring lengths, areas and there coordinates, directions as well as the total costs estimation needed for any development from the final map. The gradient percentage between the highest and lowest points is calculated to be (9.954%). Relative accuracy for the based measured points (R.A) = 1:60000), and Root Mean Square error in Easting coordinates (RMSE) = ± 0.102m, in Northing coordinates (RMSN) = ± 0.096m, the Root Mean Square for the resultant (RMSR) = ± 0.099m, and Root Mean Square for Elevations ( RMSRL)= ± 0.005m. We Matched and correlated (10) measured points from study area with their graphic data positions on the aerial photo, determining the offsets for position and elevations as follows: (RMSE = ± 0.076m), (RMSN = ± 0.125m), (RMSR = ± 0.088m), and (Root Mean Square for Elevations = RMSRL= ± 0.045m). This research enable us after checking the results to produce new maps from Aerial photograph or Digital Image to use it for land uses and future extensions in whole study area.

Radar antennas in the open air are affected by dynamic wind loading during azimuthal scanning. In this state, the acquisition and prediction of the aerodynamic load is the focus of the structure design for the antenna. We performed wind tunnel force tests on flat plate antennas with different aspect ratios. The changes in mean, maximum, and root mean square values of the aerodynamic coefficients relative to the antenna aspect ratio and reduced frequency are given for the first time. The effects of the antenna aspect ratio and reduced frequency on aerodynamic characteristics are analyzed. The experimental results indicate that the magnitude of the azimuthal moment is related to the antenna aspect ratio and the reduced frequency. It is worth noting that the antenna aspect ratio has a significant impact on the mean, maximum, and root mean square values of dynamic aerodynamic coefficients. The mean, maximum, and root mean square values of the rolling moment coefficient, azimuth moment coefficient, and pitching moment coefficient monotonously decrease with the increase in aspect ratio. In addition, the influence of reduced frequency on the dynamic aerodynamic coefficient is closely related to the antenna aspect ratio. Under the same antenna aspect ratio, increasing the reduced frequency will increase the mean, maximum, and root mean square values of the aerodynamic coefficient. For flat plate antennas with different aspect ratios, at the condition of increasing the aspect ratios, the mean, maximum, and root mean square values of aerodynamic coefficients do not change significantly with the change of reduced frequency.

Soil Roughness Measuring System Combined With Image Processing

The vibration-based pavement roughness measurement method has garnered significant attention in recent years due to the development of low-cost sensors. The vehicle calibration process is necessary before field measurement due to the effect of changeable vehicle dynamics, restricting the large-scale implementation of pavement roughness measurement. This paper proposes a novel calibration method for vibration-based pavement roughness measurement. It can quickly calibrate vehicle dynamic parameters through a few controlled impact tests. The model updating technique is employed to estimate vehicle dynamic parameters, resulting in the development of a full-car numerical model that accurately simulates the vibration of the test vehicle. A road-vehicle coupled simulation system is introduced, incorporating randomly generated road profiles and the calibrated full-car model. This system can simulate vibration responses under various conditions. A linear relationship between IRI (International Roughness Index) and vehicle vibration indices (e.g., RMS – Root Mean Square of vertical acceleration) is estimated based on simulated results. The efficiency and accuracy of the calibration method are validated on actual roads in Shanghai, China. The average IRI difference between the ground truth and test data reached 0.5 m/km in a 100 m road section, demonstrating the reliability and practicality of this fast calibration method.

Fast and non-destructive determination of histamine in tuna fish by ATR-FTIR spectroscopy combined with PLS calibration method