Cat-eye Effect Research Articles

Jamming effect analysis and reticle parameter identification of infrared spin-scan seeker under dynamic engagement environment

The infrared jammer is a common countermeasure for escaping the missile’s attack, but a systemic analysis for jamming effectiveness in the target-missile engagement is absent. This paper analytically elaborates on the jamming effect for a spin-scan seeker with different parameters including jamming power, frequency, and phase. First, the mathematical expression of error signal for spin-scan seeker is derived, which provides the basis for constructing a missile guidance loop in which a target at arbitrary orientation employs a jammer. Next, the jamming effect of infrared jammer with different parameters is evaluated by the magnitude of miss distance. The simulation results and corresponding theoretical analysis indicate that a greater jamming power will increase the target survival probability and the range of jamming frequency and phase can be set more flexibly. Furthermore, the jamming will be valid if the jamming frequency is close to the reticle spin frequency under the condition of a greater jamming power, which forms the jamming strategy. Finally, a frequency identification method for a missile is designed by the cat-eye effect theory through signal processing and proved to be accurate, so the jamming strategy will be more utilizable in practice. The simulation results and analysis in the present paper will provide theoretical support for infrared jamming strategy.

Three-dimensional echo light field analysis for dual-band laser active detection of a cat-eye optical system.

Laser active detection technology utilizing the cat-eye effect provides rapid response, precise positioning, and long detection distances. However, current research mainly focuses on active detection within a single visible or near-infrared band, lacking quantitative analyses of the echo spot. In this paper, a four-interval theoretical model for dual band cat-eye target echo detection was constructed using matrix optics theory and Collins diffraction integration method. Dual-band echo detection experiments were conducted using 10.6 um far-infrared waves and 532 nm visible light waves, also the power, radius, and target-missing quantities of the echo spots were collected and quantitatively compared with the theoretical results. Results indicate that, due to the diffraction limit's effect on the distribution of the echo field, the echo power of far-infrared band detection is smaller than that of visible light band detection. The impact on the light spot caused by the positive and negative defocus values is asymmetric, with positive defocus having a lower impact on the echo spot than negative defocus at the same value. A weak positive defocus value that minimizes the radius of the echo spot and maximizes the echo power exists, with the value of weak positive defocus varying between detection bands. A linear relationship exists between the incident angle of the detection laser and the deviation of the echo spot. These findings provide a foundation for extracting working band details, predicting the motion trajectory of moving cat-eye targets, and achieving real-time tracking and detection recognition during laser active detection.

Three-dimensional echo distribution analysis of multi-band and oblique Gaussian beams propagating through cat-eye optical system

The cat-eye effect in optical systems enables active laser detection at long distances and high orientation precision. However, few studies focus on the influence of a multi-band laser with a large incident angle on the echo distribution. This study proposes a three-dimensional echo distribution calculation model of an obliquely incident multi-band laser based on the Collins diffraction integral formula and aperture function expansion as the sum of complex Gaussian functions. The echo distributions for different detection ranges are calculated by coupling the size of the detector in a cat-eye optical system into the model. In the numerical simulation, the influences of laser wavelength, incident angle, and target detector parameter are quantitatively analysed by introducing a target-missing quantity of echo spot and peak light intensity. The results show that the peak light intensity decreases with an increase in incident laser wavelength. When the incident angle increases to a particular value, the peak light intensity decreases sharply, and the target-missing quantity of the echo spot centroid is positively correlated with the incident angle. We can effectively extract important information, such as the working band and detector size, from the cat-eye target echo using this model and provide a trajectory prediction theory for the active detection of a cat-eye target moving at high speed.

The Cat's Eye Effect Target Recognition Method Based on Visual Attention

The Cat's eye effect target recognition method based on visual attention (CTRVA) is proposed. The difference image can be processed by a designed second-directional derivative filter at eight directional channels. Morphological method is employed to deal with the filtered image in all directions, which ensures that target can be easily distinguished from background. The salient maps for each channel where the potential targets exist are calculated through the spectral residual approach, and the target-saliency map is computed by a designed saliency fusing method. The coarse detection is performed by the adaptive threshold to extract candidate targets from the target-saliency map. The real target region is identified by the characteristics of the cat's eye effect target. Experimental results show that the proposed method is efficient and has an outstanding performance for cat's eye effect target detection.

Cause analysis of chatoyancy of sapphires from Shandong, China.

Chatoyancy, that is, the cat's eye effect, has attracted many scholars' attention as a special optical effect. However, there are very few studies on the cat's eye effect of sapphire. The gemological features and formation mechanism of the chatoyancy of sapphires obtained from Shandong, China, were investigated by gemological microscopy, polarizing microscopy, scanning electron microscopy, infrared spectroscopy, X-ray fluorescence spectroscopy, UV-Vis spectroscopy, and Raman spectroscopy. Parallel orientations of the fracture surfaces were observed; light reflected on them, and an bright light band was formed perpendicular to them. No solid inclusions were detected under polarized light, and no absorption peaks of the solid inclusions were measured by Raman spectroscopy. In contrast, needle inclusions resulted in chatoyancy in other gemstones; parallel fracture surfaces with fluid inclusions above cause chatoyancy in sapphires. In this study, the origin of the cat's eye effect of sapphire was analyzed innovatively, and its phenomena were characterized concretely. In addition, this study provides a novel strategy to explain the mechanism of chatoyancy in the field of gemology and will be helpful for sapphire classification and quality evaluation.

Active laser detection system for recognizing surveillance devices

In recent years, we have seen proliferation in the presence of surveillance devices such as cameras and commercial unmanned aircraft vehicles (UAVs). These devices have posed ever-increasing security threats. This paper proposes an active laser detection system to counter surveillance components by exploiting cat-eye effect. We first establish a cat-eye target detection model and the calculation results show that our proposals are capable of achieving results comparable to those generated by thermal detection systems but more cost effective. We also investigate the properties of reflected spots generated by cat-eye targets, and formulate corresponding recognition criteria. Using our hardware platform and the proposed algorithms, our experiments produce the recognition of static cat-eye targets at a wide range of operating distances, as well as the real-time identification of moving cat-eye targets. These results have not been achieved before, to the best of our knowledge. The entire system can be applied not only for the detection of a wide categories of stationary monitoring targets with cat-eye configurations including cameras and optical sights, but also for tracking and confronting moving surveillance devices such as UAVs.

Freeform lens design to eliminate retroreflection for optical systems.

This paper presents an effective approach to alleviate the cat-eye effect by inserting a freeform single lens into the original optical system. By shifting the image of the given optical system transversely on the original image plane, the reflected beams originating from the sensor are subsequently blocked by the optical aperture, substantially eliminating retroreflections from the system. The influence of incident angle on retroreflected beams is analyzed in detail, and the optimal image translation distance for completely eliminating the cat-eye effect is also proposed via numerical simulations. According to the translation requirement, a freeform single lens comprised of two different freeform surfaces is designed for the given system as the only translation element. The design recipe is elaborated on the basis of phase pupil function. Furthermore, a design example is demonstrated to verify the feasibility of our proposal. After optimization with optical design software, the modulation transfer function (MTF) of the modified system after translation is close to the diffraction limit, and the cat-eye reflected beam could be eliminated thoroughly.

Design of laser active detection circuit based on accumulative detection technology

The cat eye effect of photoelectric system makes laser active detection possible. In order to detect the weak echo signal, a special circuit for extracting weak echo signal of ultrashort pulse laser is designed based on the accumulative detection technology. Based on the analyzing of the technology principle, the feasibility of the accumulative detection technology is simulated and summarized. Furthermore, the function and composition of the hardware system are designed. At last, ultrashort pulse laser is used as analog echo signal, and the detecting capability of the hardware system is checked up. The experimental results show that the accumulative detection technology is capable for weak laser signal detection. The minimum power of echo signal that the circuit system can identify is 3 uw. So, the validity and feasibility of the exploited circuit and accumulative detection technology are proved.

Optimized phase mask to realize retro-reflection reduction for optical systems

Aiming at the threats to the active laser detection systems of electro-optical devices due to the cat-eye effect, a novel solution is put forward to realize retro-reflection reduction in this paper. According to the demands of both cat-eye effect reduction and the image quality maintenance of electro-optical devices, a symmetric phase mask is achieved from a stationary phase method and a fast Fourier transform algorithm. Then, based on a comparison of peak normalized cross-correlation (PNCC) between the different defocus parameters, the optimal imaging position can be obtained. After modification with the designed phase mask, the cat-eye effect peak intensity can be reduced by two orders of magnitude while maintaining good image quality and high modulation transfer function (MTF). Furthermore, a practical design example is introduced to demonstrate the feasibility of our proposed approach.

Periodicity analysis on cat-eye reflected beam profiles of optical detectors

The cat-eye effect reflected beam profiles of most optical detectors have a certain characteristic of periodicity, which is caused by array arrangement of sensors at their optical focal planes. It is the first time to find and prove that the reflected beam profile becomes several periodic spots at the reflected propagation distance corresponding to half the imaging distance of a CCD camera. Furthermore, the spatial cycle of these spots is approximately constant, independent of the CCD camera’s imaging distance, which is related only to the focal length and pixel size of the CCD sensor. Thus, we can obtain the imaging distance and intrinsic parameters of the optical detector by analyzing its cat-eye reflected beam profiles. This conclusion can be applied in the field of non-cooperative cat-eye target recognition.

A Fast Recognition Algorithm for Photoelectric Peeping Equipment

The spreading use of concealed miniature photoelectric devices threatens the information security of interior activities. Information leaking from interior environments like meeting room, drama theatre, technical lab and private space may cause serious social problems or commercial losses. To solve the critical problem, this study proposed a practical system based on the “cat-eye effect” to detect the interior optical targets in real time. The proposed method reduces false positives based on strength of the echo signals and shape of the laser cross section. A morphological criterion is presented to determine the true target. Laboratory experiments have been performed repeatedly with different kinds of interference and background of different complexity to validate the proposed method. The results indicated that the true target was recognized accurately and rapidly. Moreover, the recognition results were demonstrated not influenced by external light illumination conditions. The average runtime was 67ms which is superior to the recent methods in the literature.

Cat-eye effect reflected beam profiles of an optical system with sensor array.

In this paper, we propose an applicable propagation model for Gaussian beams passing through any cat-eye target instead of traditional simplification consisting of only a mirror placed at the focal plane of a lens. According to the model, the cat-eye effect of CCD cameras affected by defocus is numerically simulated. An excellent agreement of experiment results with theoretical analysis is obtained. It is found that the reflectivity distribution at the focal plane of the cat-eye optical lens has great influence on the results, while the cat-eye effect reflected beam profiles of CCD cameras show obvious periodicity.

Stereo-based bokeh effects for photography

Bokeh, a sought-after photo rendering style of out-of-focus blur, typically aims at an esthetic quality which is not available to low-end consumer-grade cameras due to the lens design. We present a bokeh simulation method using stereo-vision techniques. We refine a depth map obtained by stereo matching, also using some minor user interaction. Overexposed regions are recovered according to depth information. A depth-aware bokeh effect is then applied with user-adjustable apertures sizes or shapes. We also simulate swirly bokeh, also known as cat-eye effect. Our method mainly aims at the visual quality of the bokeh effect rather than (so far) at time efficiency. Experiments show that our results are natural looking and that they can be comparable to bokeh effects achieved with expensive real-world bokeh-capable camera systems.

Impact of defocus on divergence of reflected light beam in cat-eye effect

平行光束或者激光束在光轴方向上照射焦平面成像系统时会产生猫眼效应，焦平面探测器安装的正交性与离焦量直接影响猫眼回波的光学特性，进而影响基于猫眼效应的探测系统的性能。针对猫眼效应中离焦量与后向反射光束发散角之间关系，利用物理光学进行分析，建立理论模型，对焦距为0.18 m的焦平面探测成像系统进行数值计算得到：在离焦量为0.16 mm时，发散角最小（0.019 mrad）。搭建实验系统，测试离焦量与猫眼回波发散角，测得离焦量在0.15 mm附近存在最小的发散角为0.025 mrad，与计算结果0.019 mrad基本吻合。研究表明：1） 负离焦对发散角的影响大于正离焦；2） 猫眼回波发散角基本上随着离焦量绝对值的增加而变大，但是变化曲线并不关于零离焦量点对称，而是在某个正离焦处存在一个最小发散角。

基于矩阵光学的猫眼效应回波特性模型

基于矩阵光学的猫眼效应回波特性模型

Cat-eye effect target recognition with single-pixel detectors

A prototype of cat-eye effect target recognition with single-pixel detectors is proposed. Based on the framework of compressive sensing, it is possible to recognize cat-eye effect targets by projecting a series of known random patterns and measuring the backscattered light with three single-pixel detectors in different locations. The prototype only requires simpler, less expensive detectors and extends well beyond the visible spectrum. The simulations are accomplished to evaluate the feasibility of the proposed prototype. We compared our results to that obtained from conventional cat-eye effect target recognition methods using area array sensor. The experimental results show that this method is feasible and superior to the conventional method in dynamic and complicated backgrounds.

Cat-eye target recognition with image registration of dual-CCD

With the development of optoelectronic surveillance, tracking and optical communication technology, high efficient and reliable target recognition algorithm, especially cat-eye effect target recognition algorithm, becomes more and more important. However, the accuracy and efficiency have been difficult to guarantee. To solve these problems, a cat-eye effect target recognition method based on image registration (CEIR) of dual-CCD is proposed. In this method, before difference operation, image registration is applied to correct corresponding mismatching points. Besides, in the CEIR, an improved algorithm for the exhaustive algorithm is proposed to shorten the running time and improve the correctness of the exhaustive algorithm. Experimental results show that the CEIR is capable of recognizing cat-eye effect targets in static and dynamic background. The CEIR can remove dynamic background distraction and extract cat-eye effect targets with only one pair of images. The CEIR is more efficient in the running time than the shape-frequency dual criterions (SFDC) method.

Fast cat-eye effect target recognition based on saliency extraction

Background complexity is a main reason that results in false detection in cat-eye target recognition. Human vision has selective attention property which can help search the salient target from complex unknown scenes quickly and precisely. In the paper, we propose a novel cat-eye effect target recognition method named Multi-channel Saliency Processing before Fusion (MSPF). This method combines traditional cat-eye target recognition with the selective characters of visual attention. Furthermore, parallel processing enables it to achieve fast recognition. Experimental results show that the proposed method performs better in accuracy, robustness and speed compared to other methods.

Real-time detection system of cat-eye effect target based on embedded platform

In order to solve the problem of finding the sniper quickly in security, a system using the cat-eye effect principle of sniper scope to find a target is designed. The system is different from that of traditional design of lighting source. It is a system based on semiconductor modulated laser, which replaces CW laser source, and works with modulated signal to scan the field. A CCD is used to capture the active and passive echo image. According to the target echoes image at different distance, the algorithm can be implemented in embedded DSP high-speed processing platform for the near and far targets respectively. The results, obtained in the field experimental, showed that the new system increases the detection rate, and reduces the incidence of false alarms. The system accurately detected the target of 300m and 800m in distance with a real-time processing speed of 10 fps.

基于嵌入式平台的猫眼效应目标实时探测系统研究

基于嵌入式平台的猫眼效应目标实时探测系统研究