Showing papers in "Opto-electronic Engineering in 2011"

An Improved Algorithm for Canny Edge Detection with Adaptive Threshold

Abstract: To overcome the difficulty of threshold selecting in Canny algorithm, an improved method based on Otsu algorithm is proposed to choose the threshold adaptively and simultaneously. Firstly, guided by the gradient histogram of the test image, all the pixels are divided into three classes. Secondly, based on the improved Otsu algorithm, an evaluation function is defined to describe the mean square error among the three classes. Finally, both the high and low thresholds are selected adaptively and independently by searching the maximum values of the evaluation function. Artificial parameter setting is not necessary in this method. Compared with the results from traditional Canny method and Direct Otsu method, the method shows great advantage in extracting the real edges from different images, especially low contrast ones.

Research of UAV Aerial Image Mosaic Based on SIFT

Abstract: The matching effect of conventional methods is poor,sometimes even not matching due to the instability of Unmanned Aerial Vehicle(UAV) air gesture and the defects such as the existence of its tilted capture images,uneven exposure.SIFT algorithm has a good adaptability for image geometric distortion,resolution differences and rotation,etc.The SIFT algorithm is introduced to extract the feature points of UAV images,and the least-squares algorithm is used to match the images precisely.Moreover,the block splicing method is proposed to reduce the error spread in the process of stitching.The experimental results show that SIFT image matching algorithm has a good adaptability in matching UAV images.The matching error can be eliminated effectively to introduce the least-squares algorithm in the matching process.What is more,the time and space complexity can be obviously reduced.

Camshift Ship Tracking Algorithm Based on Multi-feature Adaptive Fusion

Abstract: Multi-target tracking based on vessel image sequences monitored on waterway is the premise of carrying out the vessel active warning and improving bridge-area ship navigation safety. Accurate tracking results are unable to be obtained by traditional Camshift tracking only based on color histogram under complex weather conditions. For this reason, a Camshift ship tracking algorithm based on color, shape and texture multi-feature adaptive fusion is proposed. In this method, the target model is realized by multi-feature adaptive fusion, which increases the reliability of observation and improves the robustness of observation model. When tracking targets, the target model based on fusion is included in the Camshift tracking algorithm. The experimental results show that the proposed tracking algorithm can provide higher correctness and stability than traditional Camshift algorithm.

The Development of a New Atmosphere Transmittance Meter

Abstract: An atmosphere transmittance meter is developed.With transmitting a beam light and detecting it,the atmosphere extinction coefficient is obtained and various weather condition can be forecasted.Prototype machine is developed and field test is done.Experiment results demonstrate the correction of test principle and technique approach.The actual measure error of atmosphere transmittance meter is approximate 10%,which is close to that of product of VAISALA in Finland.Therefore,this transmittance could meet the demand of practical application.

Lane Coordination Detection Based on Hough Transformation and Least Square Fitting

Abstract: To improve the real time performance and robustness,lane coordination detection is executed,which detects the lane parameter by adopting the global extraction based on Hough transformation and the local windows extraction with the help of the lane parameter confidence interval and the Kalman filter.Image preprocessing is conducted including the improved fast median filter,the lane feature filter,the gradient angular histogram selection,and the lane connectivity analysis to cut the computational expense and enhance the lane edge feature after the lane region of interest is defined.Real vehicle experiments show that the proposed method can run at an average speed of 25 frames per second on a Pentium (R) D 2.00 GHz CPU,and the accuracy can reach 97.2%.Meanwhile,it can robustly detect the lane even if there are some interference factors in the road such as shadow,vehicle and landmark etc.,as well as fuzzy lane boundaries and relatively weak contrast.

Transient Temperature Field and Thermal Stress of High Power LED

Abstract: Thermal characterization of high-power Lighting Emitting Diode(LED) device was reported,utilizing finite element software ANSYS with thermal stress analysis based on the thermal stress theory,and the transient temperature and stress field were obtained.The thermal stress,displacement and shear stress distribution on the path which was parallel with X axis at the top of LED substrate were calculated.The simulation results indicated that the maximum von mises stress was at the corner of the thermal sink and die attach,and the maximum displacement was located at the edge between the lens and the thermal sink.The maximum shear stress was concentrated at the corner region.The numerical study that was carried out with LED base center to understand the temperature distribution by FEM technology was experimentally calibrated.Finally,variation of the maximum temperature and maximum thermal stress with thermal conductivity of various materials was considered.The results are of great importance to the high-power LED package.

Fish Motion Tracking Research Based on Video Algorithm

Abstract: Aiming at the problem of water environment protection using fish motion tracing,the fish motion monitor research is proposed based on the video algorithm.It can obtain trajectory and velocity of the fish by means of segmentation and tracing of the fish motion video,which lie a theory foundation for the fish to participate in the environment pollution research(through the comparison of some parameters of the fish motion in different polluted environment,to carry out quantitative analysis of the water pollution degree).The algorithm uses marker multi-scale watershed method for fish motion segmentation,then tracks the fish motion video with the improved weighted-Hausdorff.Finally,in order to accommodate the shape change of the fish in the moving process,introduce the Euclid norm into multi-value images as the restriction to accomplish the update of the tracing model.The experiment shows that the proposed method presents the state of stable tracking,the position shift in the tracking of the successive 100 frame is within a pixel,and the tracing velocity difference is within 0.12 pixels,which can segment and track the fish motion object fleetly and precisely.

An Applied Method for Reading Recognition of Index-instrument

Abstract: As to the identification and calibration of index-instrument,a novel method for reading recognition based on digital image processing is proposed.Firstly,preprocessing operation on images is done,including image segmentation,image filtering,image dilation and thinning etc,and a method of improved adaptive median filter is adopted to improve the image.Then,characteristic information of image is extracted with the improved dual thresholds Hough transformation,and the pointer reading is got using the linear relationship between scale and angle of instrument dial revolutionary.And as to the situation that pointer coincides with the whole tick,late correction has been done.The experiment results show that the algorithm is very valid for the pointer angle recognition,and has higher precision and real time.It has strong practical application value.

Method of Tolerance Sensitivity Reduction of Optical System Design

Abstract: A method by controlling the primary aberration of each surface in the system based on Seidel aberration theory is proposed for reducing system tolerance sensitivityFirst of all,it illustrates the principle of small aberrations balancing,and then the relation of the Seidel aberration theory and tolerance sensitivity is indicated by theoretical formulaAt last,we enumerate an example which is the optical design of objective lens of aerial camera and make tolerances analysis both on the compensation of big aberration and small aberrationThe results show looser tolerances distribution,better stability and great reduction of the cost on the compensation of small aberration

Phase-shift Extraction and Wave Reconstruction in Four-step Phase-shifting Interferometry

Abstract: An approach of unknown phase shifts extraction and complex wave reconstruction in generalized phase-shifting interferometry is proposed by the combination of least square methods and generalized four-step formulaeA much-simplified algorithm is suggested to extract reference phase and then reconstruct object wave-front by replacing the conventional least-square method in above process with our specially derived wave reconstruction formulae for generalized phase-shifting interferometryIn this method,only one least-square equation is needed for one iteration to retrieve the reference phase,and the object phase can be calculated simultaneouslyThe feasibility and effectiveness of this algorithm have been verified by computer simulationsThe results show that this innovation can keep the phase extraction errors mostly in 0004 rad and save computing time by about 10 times compared with previous four-step LSM algorithm while it still ensures its high precisionOptical experimental results are also satisfactory

Research of Opto-electronic Match in Long-distance Laser Ranging System Based on APD

Abstract: Aimed at active weak IR detection, how to get the stable high gain from Avalanche Photodiode (APD) circuits and its opto-electronic matching characters are researched. The methods are relation with APD exponent gain and linear noise with its reverse bias voltage. It gets closed to temperature coefficient by serial Zener diodes and always-stable bias voltage to APD near break voltage at real PN junction temperature, and is over 100 times gain with temperature complement circuits. Transistor cut-off frequency and its response are increased by NPN type transistor with an improved a.c. couple low noise and low voltage supplier negative feedback circuits. The system voltage gain enhances 2 to 3 times, and opto-electronic sensitivity rises over 23 dB. Because PN junction temperature of power LD changes causes wavelength drift, it is very difficult to match extremely narrow bandwidth interference filters. So the interference filter bandwidth between 10 and 15 nm is available for background radiation depression.

Moving Object Detection Algorithm Based on Three-frame-difference of Moving Background and Edge Information

Abstract: Adopting the moving object detection algorithm of moving background,an improved three-step search algorithm is proposed.The proposed algorithm can effectively accelerate motion-vectors search and reduce computational complexity while keeping up high search accuracy.Firstly,the same background of three continuous images are fixed to the same position of the same image through the global motion compensation.Secondly,three continuous edge images information are obtained by edge extracting,and the motion information is detected by three-frame-difference operation.Finally,morphologic close-algorithm and morphologic fill-algorithm are used to extract the moving objects.Experimental results demonstrate that this method can accurately extract moving objects,and has strong robustness.

An Adaptive Denoising Method for Salt and Pepper Noise Detected by Neural Network

Abstract: To remove impulse noise from image before some other process, an adaptive switching filter based-on neural network noise detector is proposed. This method describes each pixel with pixel value and its neighborhood characteristics and takes these as inputs of the neural network to identify pixels which are likely to be contaminated by noise with the trained neural network automatically. According to the idea of switching filter, the noisy pixels detected are processed by mean filter with adaptive window size, and only noise-free pixels of the window are involved in the average computation. Compared with some other common filters, the experimental result shows that this BP neural network has high accuracy of salt and pepper noise detection. Besides, this filtering process is superior in denoising effect, details preserving and time consuming reduction without manual intervention.

The Influence and Control of Wind Loading on the One Meter Solar Telescope Servosystem

Abstract: The performance of one meter solar telescope position control servosystem was influenced seriously by wind disturbances,because of its special optic and mechanical structure and open observation mode.Therefore its servosystem was required to achieve good disturbance rejection.At first,the telescope's optic and mechanical properties were described,and then mathematical model and numerical simulation of its soversystem was presented.Furthermore,the rate and position controllers' abilities to minimise the effect of wind disturbance were analysed in depth.On the premise of servosystem's stabilisation,to improve servosystem's stiffness by increasing servosystem's gain can meet the demand of the telescope working normally under the condition.of moderate breeze disturbance.In the end,experiment results about servosystem performances and short time tracking accuracy were provided.The results show that the servosystem can achieve the tracking precision required of the telescope's scientific goals and terminal instruments.

A Extracting Scheme for Targets of Interest in High Resolution Remote Sensing Imagery

Abstract: During the analysis and interpretation of remote sensing image,it can greatly relieve the processing system of the heavy computing burden to extract targets of interest rapidly and correctlyAccording to the attention mechanism of human,a detection algorithm for targets of interest based on visual attention mechanism was proposedFirstly a saliency map was computed by analyzing the spectral residual,and then salient target can be extracted without a priori knowledge by searching through the saliency map with a control mechanism of win-take-all competing and inhibition-of-returnA majority of salient regions were discarded by using the possible bound of size and shape for target of interestOtherwise the focused regions were projected to the target feature subspace,and the difference in the projection coefficients can be used to determine whether the region is of interest or notThe proposed scheme is tested using an amount of high resolution remote sensing images,and the results show that it is effective

An Adaptive Autofocus Method Using No-reference Structural Sharpness

Abstract: An adaptive mountain-climb searching strategy based on No-Reference Structural Sharpness(NRSS) of single image is proposed for autofocus systemThis new method utilizes the prior knowledge on defocusing amount provided by NRSSIf the imaging system is greatly defocused,a large step-size is used to approach the focusing position quickly;otherwise,a small step-size is used to locate the focusing position accuratelyThis method has the same focusing accuracy to mountain-climb strategy,and it greatly decreases the number of images and the number of decision makings that are requiredThe experimental results indicate that the proposed method improves the speed of autofocus about 50%

A Robust Adaptive Zero-watermarking Algorithm in DWT-DCT Domain

Abstract: In order to overcome the limitation of the watermarked image quality degradation due to the some changes of the original image data when embedding watermark in the traditional digital watermarking schemes, a robust adaptive zero-watermarking algorithm based on the combined transforms of the Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) is proposed First, the original digital image is decomposed into the appropriate levels of DWT, and the DCT is applied to the obtained wavelet approximation sub-image, and then the DCT AC coefficients are selected adaptively in orders according to the size of the embedded digital watermark and the coefficient difference value Finally, after the combination of the original binary character watermark and the binary key image which is obtained from comparing the selected DCT AC coefficients, the embedding of zero-watermark is realized by registering to the center of authentication The results demonstrate that the proposed zero-watermarking algorithm not only ensures the watermarked image quality without distortion, but also has very good robustness against the conventional treatments (for example: noise addition, filtering, JPEG compression, rotation) , and is better than the some reported zero-watermarking algorithms

Absolute Distance Measurement Based on the Optical Frequency Comb of a Femtosecond Laser

Abstract: The method of measuring absolute distance with the optical frequency comb of a femtosecond laser was proposed.A femtosecond laser was used as the light source of performing absolute distance measurement.A Michelson type interferometer structure was built.Exploiting the principle of the dispersive interference,the spectrum was analyzed.Then,the phase difference which was caused by the optical path difference of optical interference was obtained.Finally,the optical path length difference was measured.The experiment result shows that our length measurement method has high accuracy with the resolution of nanometer level.The minimum measurable distance is 9 μm,and the non-ambiguity range of length measurement is 5.75 mm.Compared to the limited measuring range of traditional white light interferometry,the maximum distance can be extended to arbitrary length.

An Improved Randomized Algorithm for Detecting Circles Based on Least Square Approach

Abstract: An improved randomized circle detection algorithm based on least square approach was proposed. Because of the incorrect selection of threshold, a circle is divided into some circles. This algorithm can solve the problem perfectly. First, a randomized algorithm for detecting circles randomly picked four edge pixels each time and calculated circle parameters. The set of pixels belonging to the circle were obtained. Second, these pixels can calculate new circle parameters, and new pixels belonging to these parameters were obtained. Third, until no new pixel was added, it returned these pixels into the set. At last, we checked whether or not the set of these pixels was real circle. Compared with the original algorithm, the proposed algorithm enhances the stability and accuracy of circles detection.

Multi-focus Image Fusion Using Dual-tree Contourlet and Compressed Sensing

Abstract: In order to expand the capability of Compressed Sensing(CS),a fusion method for multi-focus image using Dual-tree Contourlet(DT-Contourlet) and CS is proposedFirst,the source images are decomposed using DT-Contourlet for extracting multiscale and direction information while overcoming the limitation of traditional contourlet which is lack of shift invarianceThen,in DT-Contourlet domain,the decomposition coefficients are treated as containing two components,ie,dense and sparse componentsThe dense components are fused using selection method by introducing neighborhood gradient as clarity index to indicate the characteristics of defocusThe sparse components are fused under the framework of CS via fussing a few linear measurements by solving the problem of L1 norm minimization which is based on a two-step iterative shrinkage/threshold reconstruction algorithmThe experiments demonstrate that the convergence rate of reconstruction is faster than that of orthogonal matching pursuitMeanwhile,the proposed method provides more satisfactory fusion results in terms of visual quality and quantitative criterion

Simulation Analysis of Absolute Measurement for Rotationally Asymmetric Surface Error

Abstract: To meet the high accuracy optical testing requirement, the absolute measurement technologies instead of traditional testing techniques are more and more used in optical testing. However, the traditional absolute measurement technology has its own scope and complexity of the experimental process which required experimental equipment with high precision. In the filed of only rotationally asymmetric surface error required, rotating average method is a simple absolute measurement technology. Rotating average method is applied to rotationally asymmetric surface error testing of plane, spherical and aspheric. The principle of rotation averaging method was introduced. Then optical design software was used to simulate the testing process of rotation averaging method. By simulation test, the shape of the rotation asymmetric error and the kNθ rotation error were analyzed, simulation results in good agreement with theoretical results. Simulation experiment results show that rotating average method can effectively improve the testing precision of rotational asymmetric surface shape and the experimental simulation model can effectively simulate the actual testing process.

Planar Hyper Lens with Demagnification for Nanolithography

Abstract: Nanolithography using hyperlens in planar form and i-line mercury lamp is presented. To obtain patterns with high quality at the imaging plane of hyperlens, lens-photoresist-silver layer structure is employed to avoid the blurring of electric field intensity distribution delivered by the transversal magnetic polarization features of hyperlens. Moreover,the specific design of mask is employed for compensating aberration of magnification non-uniformity of hyperlens. Numerical simulations demonstrate the ability of nanolithography by this method. About 35nm line width with high contrast is obtained in the light distribution and the geometrical parameters influence is also discussed.

A Watermarking Algorithm for Print Forgery Prevention Based on Comparison between Norm and Mean of Norm

Abstract: At present,those existing watermarking algorithms for print forgery prevention always embed watermarks into original images,and their invisibility needed to be improved.Moreover,they had never studied their robustness against dual print-and-scan process.A watermarking algorithm for print forgery prevention was proposed to overcome those problems based on the comparison of numerical relationship between norm and mean of norm.It conducted discreet wavelet transformation on the original image,split its low frequency band into non-overlapping blocks,and conducted singular value decomposition on each block.The zero-watermark sequence was derived from judging the numerical relationship between singular matrix's norm from each block and mean of singular matrix's norm form all blocks.It has perfect visibility due to no alteration made to the original image.The experimental results show that it has the ability to resist both single print-and-scan process and dual print-and-scan process.

An Improved Evaluation Method for Converted Statistics in Converted Measurement Kalman Filtering Algorithm

Abstract: To improve the performance of Converted Measurement Kalman Filter (CMKF), a more accurate evaluation method for converted measurement error statistics (means and covariance) was presented. There were two sets of information that could be used to evaluate the converted measurement error statistics, i. e., measurements of the target and a priori state estimate of the filter. Firstly, the proposed procedure in this work derived the means and covariance of the filter's a priori spherical state estimation errors. Secondly, a more accurate evaluation of the converted measurement error statistics was obtained according to the a priori spherical state estimate of the filter instead of measurements. Finally, the improved evaluation method for converted measurement error statistics was utilized to implement the CMKF algorithm for a target tracking scenario. The simulation results show that the proposed method can provide superior performance in terms of convergence and estimation accuracy, especially in the case of significant measurement noises.

Sampling Technology on Video Signal of Spaceborne High Speed TDICCD Camera

Abstract: In order to improve the image quality of a high speed airborne Time Delay and Integration Charge Coupled Device(TDICCD) camera,a method to precisely adjust the Correlated Double Sample(CDS) signals is proposed.Moreover,a method to compensate the temperature excursion of the driver is proposed.First,the principle of CDS is introduced,and the influence of sample position on a TDICCD camera is analyzed.Then,a method is proposed to adjust the sample signals precisely,which is based on the MUXCY in FPGA.At the same time,the effect of temperature excursion of the driver on TDICCD signal is analyzed,and an adaptive method is proposed to compensate the temperature excursion,which could satisfy the sample timing relationship.Experiments were made from two aspects,which were based on the TDICCD imaging system in our project.One is aimed to the effect of the precision of sample position on imaging quality,and the other is aimed to temperature.Experiment results show that the methods proposed can adjust the sample position precisely,which can improve the dynamic range of an image,and adapt the temperature excursion of the driver.Before compensation,the signal and noise ratio of the image acquired at-36℃ is 37.4 dB.After compensation,the signal and noise ratio of the image acquired at-36℃ is 51 dB.

Experimental Study of Detecting "Cat-eye" Target Based on CCD

Abstract: The most distinguished advantage of an active laser detection system based on CCD detection device is the capability of acquiring the straightforward vision of "cat-eye" targets. The active laser detection theory based on "cat-eye" effect was discussed according to the model for echo power ratio of "cat-eye" target and diffuse reflection target. The key components of this detection system were described and the wavelength matching problem of CCD device and laser source was analyzed. The detection experiments were made by using typical "cat-eye" target at different distances, such as 300 m and 2 500 m. The experimental result shows that the "cat-eye" target can be easily found from background at a certain detection distance, so the validity of the active laser detection system is proved.

An Efficient Two-stage Enhancement Algorithm of X-ray Carry-on Luggage Images

Abstract: Aiming at the problem of high false alarm rate or high leakage alarm rate caused by poor quality of low-contrast x-ray carry-on luggage images in airport security, an efficient two-stage x-ray image enhancement scheme is proposed in this paper. First, low and high energy images are fused with Discrete Wavelet Transform (DWT) and Independent Component Analysis (ICA) to implement the first stage enhancement. Then, the proposed Adaptive Sine Gray Level Transform (ASGT) is applied to achieve the second-stage enhancement. Experimental results demonstrate that the proposed algorithm can improve image quality effectively and outperforms other enhancement methods discussed in this paper.

Target Tracking Using ESM with Bearing and Doppler Frequency Measurements

Abstract: Aiming at the feature of Electronic Support Measures (ESM) detecting the bearings and Doppler frequencies simultaneously,a target tracking algorithms is proposed which uses ESM’s Doppler frequency and bearing measurements based on Modified Gain Extended Kalman Filter (DB-MGEKF). Compared with bearings-only target tracking algorithm,DB-MGEKF increases the Doppler frequencies measurement and introduces the MGEKF which can handle the nonlinear system preferably. The method improves the accuracy of target estimates as well as the stability of the filtering. Moreover, the observer’s maneuvering can be avoided. Monte-Carlo simulations with result analysis further illustrate the effectiveness of the algorithm.

The Transfer and Contrast Analysis of Radiometric Temperature for Indoor Millimeter-wave Imaging

Abstract: When the Millimeter-wave (MMW) radiometric imaging is carried out indoors, the radiometric temperature contrast between the target and the background decreases sharply, which leads to degradation of MMW radiometric images and difficulty in recognizing targets. Based on the realistic problem of MMW radiometric imaging for detecting contraband concealed on personnel indoors, the radiometric temperature transfer model was put forward. At the same time, both the apparent temperature distribution and radiometric temperature contrast between target and human body were deduced. Combined with the specific parameters of some typical targets, the reason for low indoor radiometric temperature contrast was analyzed. Then, the method of noise illumination was adopted in the application of indoor radiometric imaging, and the contribution of this method to the improvement of indoor radiometric temperature contrast was emphatically investigated. Moreover, from the perspective of radiation power density, it was proved that noise illumination was safe to human body. Both the theory analysis and simulation results are presented to demonstrate the feasibility and significance of noise illumination.

Compensation for Error of Diamond Tool\'s Cutting Edge in Single Diamond Turning

Abstract: 超精密车削中的金刚石刀具刃口误差的补偿问题一直是制约高精度非球面车削直接成形的瓶颈技术,尤其对于大相对口径,深度非球面的车削,金刚石刀具刃口误差对最终的面形的影响非常大.传统补偿方法是根据轮廓仪的测量结果对刀具刃口误差进行修正,但是该方法存在测量时间长,高频误差大,加工效率低的缺点,本文最先提出利用车削表面面形误差拟合后的泽尼克多项式系数对刀具刃口误差进行加工补偿,首先对该补偿方法进行了详细的理论...