
In order to detect motion object, a moving object detection method based on adaptive threshold and Principal Components Analysis (PCA) is presented. First, a set of images of the static environment without motion object is captured to obtain the transformation matrix that used in PCA. By means of this matrix, the successive images are projected in the transformation space. On the contrary, the transformed image can also be recovered using inverse transformation. By evaluating the Euclidean distance between the original and recovered images, the motion detection is performed. The image regions whose Euclidean distance is greater than a threshold is considered like belonging to motion objects. By dynamically adjusting threshold, the algorithm can obtain the adaptive threshold that compensates to a great extent, illumination and other environmental conditions variations. The experimental results show that, the method has better robustness and effectiveness.
Considering that the standard Cardinality Balanced Multi-Target Multi-Bernoulli (CBMeMBer) filter cannot track multiple maneuvering targets effectively in the clutter environment, a new tracking algorithm of maneuvering targets is proposed, which combines the CBMeMBer filter with the adaptive current statistical model. In the new algorithm, the dimension of the target state vector is augmented, the state transition matrix and the process noise covariance are adjusted, and the control matrix is attached. Then the targets’ acceleration can be adjusted adaptively. Finally, the new algorithm can adapt to the change of the targets’ moving state. Simulation results show that the proposed algorithm can track multiple maneuvering targets effectively, which has higher tracking accuracy in the maneuvering condition.
In order to extract the small moving target accurately in real time in the aerial video, we propose a fusion detection method for an improved ORB feature matching and differential multiplication algorithm. First of all, as the original ORB appears to be a large number of false matching problems, we describe feature points based on K nearest neighbor. After the description of the feature points in two consecutive frames by two-way matching, we further refine consistency by sequential sampling algorithm. Then, the purified matching points are used to calculate the background motion model, compensating background activity. Finally, the four consecutive frames difference multiplication and morphology processing are used to accurately segment the moving small target in the aerial video. Experimental results show that the match after purification method of accuracy up to 99.9%, the average time of which is 0.46 s, and processing speed is about 5 times of SURF feature matching algorithm, 25 times of the SIFT feature matching algorithm, so it can meet the requirements of aerial video real-time processing and has stronger ability to resist noise.
The photoelastic modulator can be affected by its heat dissipation, which induces the change of elasto optical crystal its temperature, natural frequency drift with the temperature caused photoelastic modulation instability and modulation efficiency is decreased. The frequency self tracking technology is presented. According to the effect of temperature on photoelastic modulation system, dynamic model of photoelastic modulation system is established to get the relation between the feedback signal and the high voltage drive signal that the minimum phase difference corresponding resonant frequency. Combined with multichannel Direct Digital Synthesis and Digital Phase Locked Loop technology based on FPGA design, the self frequency tracking system is completed. By experimental verification, the design can achieve the following on the frequency drift, and be able to automatically find elastic optical crystal resonance frequency and remain stable when the drive signal change or start the photoelastic modulator, which improves the stability and modulation efficiency of elastic light modulator.
A visible optical plasma diagnostic system is designed for EAST Tokamak facility. Due to the particularity of performance demand and working environment, an innovated optical structure was adopted, which satisfy the optical indexes, and minimize the radiation and stain at the same time. At last the wide-angle and high-speed visible plasma imaging system was designed, with 2.5 mm aperture diameter, 6 mm focal length, 60°×50°field of view, and 380 ~780 nm wavelength. Then the stray light was analyzed and the suppression method was implemented. After alignment, the optical performance was tested. The results show that all of the indexes satisfy the requirement of the system. Through the imaging experiment for the discharge process in the EAST Tokamak, the system was proved to achieving plasma imaging with wide-angle and high-speed.
To meet the requirement of wear eye protection and gas mask when using the military sighting telescope, the exit pupil distance of eyepiece is needed to be longer than the other. The optical characteristics and aberration characteristics of eyepiece with long exit pupil distance were analyzed, and the configuration of positive, positive, and negative three lens groups was proposed. According to the aberration theory, the optical power distribution formula was derived by analytical method. The eyepiece with long exit pupil distance was designed with optical design software ZEMAX, the focal length was 20 mm, exit pupil diameter was 5 mm, view angle was 40°, exit pupil distance was 40 mm, and relative eye clearance was 2. Designing results show that the MTF of every field above 0.2 in 40 lp/mm satisfy the application requirements of visual optical instrument.LI Li,WANG Xingbin,ZHANG Weiguo. A recognition method of “Cat-eye” effect target based on texture character [J]. Acta Photonica Sinica,2014,43(2):0210001-1-0210001-11.
With the development of microscopic imaging technology, the autofocus method has been adopted more widely. An innovative autofocus solution is presented based on liquid lens used in microscope imaging system through optical simulation and experiment. Firstly, two commercialized liquid lens are discussed on its principle and application, and Optotune lens was chosen as the autofocus device for microscopic imaging system. Secondly, the liquid lens is integrated into the system design and the optical performances are simulated. Finally, the experiment is carried out in order to evaluate the functionality and performance of the integrated system. Experiment results show that the depth of field of the system can be extended to 1mm while maintain good image quality. The autofocus technology based on liquid lens has the advantage of compact design, fast focusing, and low cost without compromising its optical performance.JIANG Decai. Design and Development of Auto-Controlled stage for bio-microsystem [D]. Jinan:Shandong Univeristy,2007: 10-19.
The lens surface figure precision of lithography objective lens is a key factor which influences the system imaging quality. In order to meet lens surface figure accuracy RMS better than 1~2 nm, this article introduces a lens support structure with multi point equal supporting which wholly has the radical freedom. Then, based on gravity deformation and thermal deformation, the structure optimization is finished. Finally, due to gravity and thermal load, the finite element analysis of lens deformation is done. Results are as follows: lens surface figure RMS of the upper surface causing by gravity is 0.429 nm, while the lower surface is 0.294 nm, and lens surface figure RMS of the upper surface causing by thermal load is 0.409 nm, while the lower surface is 0.063 nm. The results indicate that the lens supporting structure is of high precision, and can be satisfied with the lithography objective lens surface accuracy.
Aiming at the combination of the acquirement and display of the 3D image data, an integrated system to perform the real-time 3D acquisition and multiview true 3D display was proposed. This integration of input (acquisition) end to output (display) end provided vivid experience in 3D visualization of the objects according to human's natural way to view the realistic world. This paper focused on both the architecture design and the implementation of the hardware and software of the acquisition, transmission and display components in our system: the camera array performed the real-time 3D acquisition at the input end and sends the acquisition-aligned images to the output end, where the projector array renders the object or scenes at the anisotropic screen in multi-view true 3D way after the projection-alignment. Different parameters were compared showing that our prototype is able to render true 3D image using the acquired 3D data with proper parameters.
Double metal cladding waveguide can couple the light into the guiding layer to inspire the ultrahigh order modes, the incident waves overlap with the reflected waves to form standing waves in the guiding layer, and then a series of enhanced power points which are considered to be optical trapping points are formed. Based on this optical property, aiming at the shortcomings of the general optical reactor, we had designed a novel liquid-core waveguide optical reactor. Aqueous Fe2+/Fe3+ salt solutions in the hollow-core acted as the guiding layer of the reactor. Two hours after the light had coupled into the guiding layer under the special optical field, the synthetic products had been prepared. Depending on some analysis toward the products, it is sure that they are crystalline magnetite γ-Fe2O3.
For the current of the Gallium Arsenide optical fiber temperature sensing technology not described in detail and have low demodulation precision, based on the relationship of absorption spectrum of the Gallium Arsenide fiber optic temperature sensor varying with temperature, a new data processing flow is proposed, and a temperature demodulation method is researched based on the spectral analysis of Arsenide fiber absorption optical fiber temperature sensing technology. This article used standard temperature measurement system to verify the reasonableness of the demodulation method and data processing procedure. The results show that in the range of 25℃~70℃, the measurement accuracy is less than ±0.1℃, and in the range of 70℃~250℃, the measurement accuracy is less than ±0.7℃.
Since the existing optical fiber evanescent wave sensor sensitivity is not high, not easy to be encapsulated and other issues, the long segmented structure optic fiber sensor is proposed. The waveguide modes of the segmented structure and straight are simulated and analyzed by using Beam Propagation Method (BPM). The effect of the same core diameters, the different structures and the concentration of solution on the sensitivity of the sensors are investigated. The sensors of different structure parameters are fabricated with chemical corrosion method, and the sensitivity tested by using different concentrations of the methylene blue solution. The experimental results show that in the case of fixed corrosion depth, increasing the length of optical fiber sensing and segmented number can effectively improve the sensitivity and detection limit of the sensor, and the lowest concentration of the methylene blue solution can be detected up to the order of 10-6 mol/L. The sensor has the advantages of high sensitivity, simple structure, easy fabricated, low cost, which is suitable for materials spectrum measurements.
An insulator-metal-insulator filter based on Surface Plasmon Resonance (SPR) and photorefractive (PR) grating in Lithium niobate (LiNbO3) is designed. Through numerical simulation by using two-dimensional finite element method, incident angle of 46.399 5° for stimulating SPR was calculated at a fixed wavelength 656 nm. On the basis of definition of complex refractive index, sensitivity of SPR wavelength to half angle of dual beam was theoretically derived. Finally, under different grating periods in LiNbO3, reflection spectrum of SPR stimulated from a broadband light source was studied. The results show wavelengths corresponding to SPR are filtered and the SPR wavelengths shift when the period of PR grating is changed. The designed device is expectable for tunable filtering.作者简介:张明(1975-),男(汉族),河北唐山人。博士,副教授,主要从事光通信器件和光电
It is significant to study the effect of irradiation on the Charge Coupled Device (CCD) in order to correctly use it in irradiation environment. In this paper, we choose the ICX285 array CCD as the experimental sample. To satisfy the ionizing radiation effects experiments specifications, an off-line array CCD test system is presented to meet the demand of ionizing irradiation measurement, which contains a radiation circuit card and a test device for this array CCD. The system has two special functions: programmable integral time and overscanning dummy pixels controlling. It has been applied for the experiments of ionizing radiation effects on array CCDs with an 60Co-γ ray source, and has played an important role in understanding of the dark signal changes of array CCD after ionizing radiation damage.作者简介:罗通顶(1984-),男(侗族),湖南邵阳人。工程师
Manual retrieval of key frames from an Intravascular Ultrasound (IVUS) pullback sequence is a tedious and time-consuming task. The retrieval results are subjective and highly depend on clinical experiences and professional knowledge of the operator. In this paper, two methods for automatically retrieving key frames in an IVUS image sequence are proposed. One is based on the description of the vascular morphology. First, the morphological profiles of vessel are extracted. Then, the sequences of cross-sectional areas in each frame are coded with the symbolic aggregate approximation (SAX) algorithm. Finally, key frames are selected through comparing the Euclidean distances between the coded area sequences of successive frames with a properly selected threshold. The other is based on the histograms of IVUS images. The key frames are retrieved through comparing the Bhattacharyya distances between histograms of successive frames with a properly selected threshold. The validity of both methods has been validated in vivo image data and the accuracy was quantitatively evaluated. The results show that a higher compression ratio, lower redundancy and higher precision can be obtained with the morphological description method than the histogram method. However, its efficiency is relatively lower than the histogram method.
This paper describes the dispersion encoded sparse signal reconstruction algorithm based on k-domain extraction to suppress the complex conjugate mirror term in frequency domain Optical Coherence Tomography (OCT). This algorithm uses the numerical dispersion compensation to acquire the unmatched dispersion phase, meanwhile adopts the sparse signal reconstruction algorithm to extract the frequency spectrum of the peak and its corresponding mirror iteratively. This algorithm reduces the numbers of the FFT per iteration and cancels the complex conjugate mirror term. The experiment result demonstrated that the algorithm can suppress the complex conjugates effectively, and computational velocity improves 46.1%.