Based on the Mie scattering theory and the gamma
size distribution model, the scattering extinction parameter
of spherical fog-drop is calculated. For the transmission
attenuation of the laser in the fog, a Monte Carlo simulation
model is established, and the impact of attenuation ratio on
visibility and field angle is computed and analysed using the
program developed by MATLAB language. The results of
the Monte Carlo method in this paper are compared with
the results of single scattering method. The results show
that the influence of multiple scattering need to be
considered when the visibility is low, and single scattering
calculations have larger errors. The phenomenon of
multiple scattering can be interpreted more better when the
Monte Carlo is used to calculate the attenuation ratio of the
laser transmitting in the fog.
In this paper a kind of optoelectronic hybrid joint transform correlator for recognition of gray images has been proposed. In order to remove low frequency components, the input gray image is preprocessed by edge enhancement using the Gauss-Laplace algorithm. The joint transform power spectrum of object and referenced image is obtained by Fourier transform with optical apparatus. The power spectrum is captured by CCD and input into computer for process. First, the joint power spectrum is modified by subtracted the power spectrum of the object image and of the reference image being only respectively. The subtracted power spectrum is filtered by Butterworth high-pass filter to further intensify high frequency components and restrain low frequency components. Then the filtered power spectrum is replicated into N copies to form a power spectrum array displayed on the Electronic-Addressing Spatial Light Modulator (EA-SLM). The N output correlation signal addition is obtained by inverse Fourier transform of the power spectrum array with optical lens. The theoretical analysis and computer simulation indicate that the correlator can make full use of the areas of the SLM, improve the light efficiency, sharpen the correlation peak effectively and eliminate the central zero-order component in correlation place.
A new optical encryption technique based on computer-generated hologram (CGH) and fractional Fourier transform (FRT) is presented. And the algorithm of making asymmetry FRT CGH is provided in this paper. In this method, the fractional Fourier transform of the input image is performed by two one-dimensional FRT with different orders in the <i>x</i> and <i>y</i> directions in cascade. With Lohmann III detour phase encoding method and computer plotting program, the transformed image is encoded and fabricated into CGH on the computer. Then a piece of asymmetry fractional Fourier transform CGH (AFRTCGH) of original input image is obtained. In order to reconstruct the encoded image, a special fractional Fourier transform systems with two special cylinder lens’ are needed. Namely, only when the transform order in each direction is respectively matched with that of the asymmetry fractional Fourier transform CGH, can the encoded image be reconstructed exactly. Because of its particularity of image reconstruction, it is regarded as a new optical security system and can be used in anti-counterfeiting. When it is used to encrypt image or to anti-Counterfeit, anti-counterfeiting intensity can be improved greatly. So it has very high applying value.
A new kind of optoelectronic hybrid joint transform correlator is proposed in this paper, it fulfills edge enhancement preprocessing for the input images in the spatial field and subtraction modifying and exponential filtering for the joint power spectrum in frequency field with electronic method. The influence of different edge enhancement operators (Log, Roberts, Sobel and Prewitt) and exponential parameters value on correlation result is studied. When the values of two exponential parameters are matched, the correlator can produce excellent correlation output. Computer simulation results show that the proposed correlator can eliminate the strong zero-order component in the output plane, enhance and sharpen the auto-correlation peak and restrain cross-correlations between each input targets. So the correlation recognition ability of this hybrid system is quite better than the classical joint transform correlator, it can be used for multi-object recognition.
In this paper, a convolute structure optoelectronic hybrid processing system for cruise missile scene matching guidance based on Joint Transform Correlator was proposed. An electrically addressed liquid crystal displays (EALCD) controlled by computer was used as spatial light modulator (SLM) was placed on input plane, on which reference image and target image were juxtaposed to display; in addition, CCD camera as a square law detector was placed in frequently spectrum plane recorded joint transform power spectrum and correlation result. Owing to detected the joint power spectrum and correlation result by CCD camera, the system could achieve sharper correlation peak and location accuracy by using edge detection input image and binaryzation of joint power spectrum. It was very advantageous to meet the demand of further improving performance, speed, strike accuracy of the cruise missile. Computer simulation and optical experiments showed that even in noisy background, the system can achieve excellent recognition and location performances with max speed: 16frames/s, recognition probability greater than 94%, and location accuracy better than a pixel.
In this paper the four-channel real-time joint transform correlator (JTC) for fingerprint verification is proposed which is consists of right-angle prism, 4f system, liquid crystal light valve, hololens array and CCD. Fingerprint image is inputted real-timely using a right-angle prism and processed by 4f system optically to insure the higher contrast. To avoid refusal phenomenon owing to fingerprint images distortion, the single channel correlation identification is changed to four-channel correlation recognition using hololens array. A little different reference fingerprint images from an identical finger are placed in different channels. When a object fingerprint image is inputted, four kinds of correlation results are presented. Not only the recognition accuracy is increased but the processing speed and capability of the system is enhanced. The experimental results are given in this paper.
In this paper a multi-channel real-time hybrid joint transform correlator is proposed. In this correlator, the computer control is used to divide the screen into several equal size windows, reference images of the windows are all the same one and object images are adopted from different frames of image sequences by CCD, twice Fourier transforms of every channel images are realized by using hololens array. Areas of LCLV and the output light energy can be used effectively. The correlation performance can be improved.