2019 Vol. 40, No. 3

Oe System and Engineering
Design of aerospace optical imaging system with high-resolution and ultra-low distortion
LI Li, ZHANG Kaidi
2019, 40(3): 363-368. doi: 10.5768/JAO201940.0301001
In space rendezvous, docking and other high-precision positioning applications, optical imaging system is required to have the characteristics of high resolution, ultra-low distortion and large field of view. Therefore, an aerospace objective which could meet the above requirements was designed. The complex double-Gaussian structure was used to design the quasi image space telecentric optical path. The system consisted of 9 lenses and used the radiation-resistant glass to reduce the corrosiveness of ionizing radiation.Moreover the filter was used to avoid the influence of short-wave radiation on the system, the aspheric surface was introduced to improve the imaging accuracy, and finally the tolerance analysis of the imaging objective was carried out. The focal length of the designed system is 24 mm, the relative aperture is F/2.2, the work waveband is 600 nm~800 nm, the full field of view(FOV) is 35°. The design results show that the modulation transfer funciton (MTF) of each FOV of the objective lens designed by this method is all above 0.3 at 128 lp/mm and the distortion value is 0.007 2%, which meets the design index requirements.
Design of optical imaging system for RGB three-channel diffraction telescope
LI Fei, WANG Keyi
2019, 40(3): 369-372. doi: 10.5768/JAO201940.0301002
Based on the large aperture diffraction telescope which is currently being studied, a scheme of optical system for diffraction telescope imaging in visible light range was proposed. The scheme solves the problem of narrow imaging spectrum existing in the current diffraction telescope and can obtain color images in the light range. The specific design methods are as follows: the diffraction elements are dividing into three channels along the radial direction, and the information of three color channels of R, G and B are imaged respectively, the imaging bandwidth of each channel is 40 nm; then by controlling the system parameters, the images of the three channels can coincide at the image plane and are acquired by the image sensor. A three-channel telescope optical system based on 25 m aperture diffraction primary mirror was designed and simulated. The simulation results agree with the design theory. The scheme can increase the spectral range of the system, and can get the same main lobe width as that of the single channel system.
Research progress and development trend of fast steering mirror
WANG Zhen, CHENG Xuemin
2019, 40(3): 373-379. doi: 10.5768/JAO201940.0301003
Fast steering mirror(FSM) with benefits of small dimension, high accuracy, high bandwidth, fast response speed is widely used in optoelectronic systems such as laser communication, image stabilized platform, dastronomical telescope. To facilitate FSM reseachers, operating principles of FSM are introduced briefly. Then classifying methods, technical characteristics and performance variation of FSM are introduced from several aspects. After that, several types of FSMs from home and abroad are introduced in terms of technical characteristics, performance indication and applications. Finally, several key technologies of fast mirrors are prospected, it is pointed out that high closed-loop bandwidth, high control precision and digital control are considered as the development trends of FSM.
Nighttime environment perception of driverless vehicles based on improved YOLOv3 network
PEI Jiaxin, SUN Shaoyuan, WANG Yulan, LI Dawei, HUANG Rong
2019, 40(3): 380-386. doi: 10.5768/JAO201940.0301004
Environmental perception is a key task of driverless vehicles at night. An improved YOLOv3 network was proposed to realize the detection of pedestrians and vehicles in infrared images captured by driverless vehicles at night. The problem of estimation of the moving direction of surrounding vehicles is transformed into the problem of estimation of the angle of the surrounding vehicle position. What's more, the network is fused with the depth estimation information to estimate the distance and speed of the surrounding vehicles. Therefore the driverless vehicles can obtain the driving intention of the surrounding vehicles at night. The network has the end-to-end advantage, in which an image is as the input, and the positions of the bounding boxes, the classes and the angle estimation results of the detecting targets are returned directly at the output layer. Moreover, the depth estimation information is combined with the above information to obtain the distance and speed of the surrounding vehicle. The experimental results show that the speed of target detection in the infrared images captured by driverless vehicle is 0.04 s/frame. The effect of angle and speed prediction is good, and the accuracy and real-time performance meet the requirements of practical application.
Research and implementation of virtual assemble system based on CPS under environment of augmented reality
HAN Feng, ZHANG Heng, ZHU Lei, LIU Hu
2019, 40(3): 387-392. doi: 10.5768/JAO201940.0301005
Based on the principle of binocular vision, a virtual assembly system of cyber-physical systems (CPS) in augmented reality environment was developed by using Unity3D game engine. The registration relationship between virtual model and real assembly unit was established by studying the fast location algorithm through identifying the feature marker points. The virtual assembly simulation was realized by fusing the projection image of virtual model and the real assembly image, and the real-time output was displayed by the video glasses. The experimental results show that the system meets the requirements of real-time CPS, stability and integration of information world and physical world.
Design of four-channel visible-spectral camera
FENG Shan, ZENG Xiangzhong
2019, 40(3): 393-398. doi: 10.5768/JAO201940.0301006
With the development of spectroscopy technology, multi-spectral cameras have been widely used in agriculture, medical, machine vision, remote sensing and other fields. This paper proposes a miniaturized four-channel visible-waveband multi-spectral camera with a size of 107 mm×110 mm×74 mm and a mass of 1 043 g, which is especially suitable for remote sensing detection on a miniaturized drone. The camera system adopts a prism beam splitting optical path design scheme to avoid optical path difference and optical axis shift. The specially designed four-channel multi-spectral camera in visible light uses an field-programmable gate array (FPGA) controller to simultaneously drive 4 image sensors to realize four-channel pixel-level synchronous acquisition, and the exposure is exactly the same.The test results show that at the 3 specific bands of red, green and blue and the full band, the camera can output images in real time, which can output a specific band image (60 fps) or 4 band images (15 fps) at the same time, which is beneficial to the synchronous acquisition of multi-band images and the research on multi-spectral images fusion.
Error analysis and correction of circular grating angle measurement system
ZHANG Wenying, ZHU Haoran
2019, 40(3): 399-403. doi: 10.5768/JAO201940.0301007
In order to improve the measurement accuracy of the angle measuring system, based on the characteristics and form of the error, the corresponding mathematical models of the scoring error, photoelectric signal error, eccentricity error, tilt error and the error caused by the deformation in the angle measuring system were established from the harmonic angle aspect, and the eccentricity error and tilt error were analyzed. Furthermore, a metal circular grating angle measuring system was built, and the error in the system was analyzed and corrected. The experimental results show that the angle measurement error of the angle measuring system is 134.2″, and the corrected error is 32.23″. The error analysis of the circular grating angle measurement system provides a theoretical basis for the subsequent error compensation.
Research on preparation method of mold of diffractive optical element based on computer generated holography
WU Yaoxia, ZHANG Jin, SUN Guobin, JIANG Shilei, MI Qian, LI Shijie, YANG Pengfei, WANG Yujin
2019, 40(3): 404-410. doi: 10.5768/JAO201940.0301008
The preparation method of mold based on computer generated holography(CGH) of asymmetric multi-step diffractive optical element was introduced, the working principle and design method of phase-type CGH were studied, the corresponding optical system and the diffracted light wave model were established and the algorithm flow chart for obtaining phase-type mold microstructure was designed. Taking a folded heart pattern as an example, the phase information and surface microstructure morphology of 2-step, 4-step, 8-step and 16-step diffractive optical element were simulated by MATLAB, and the quality of the reconstructed image was compared on the basis of theoretical analysis. It is found that the more the number of steps is, the better the quality of the reproduced images will be. After obtaining the height data of the die space and the distribution of the surface structure, the 2-step and 4-step molds with the 6 mm×6 mm element size and the smallest characteristic size 30 um were respectively obtained by the fast knife processing method and the single-point diamond turning technology, and the step contour curve and surface structure contour of actual processing were obtained. Finally, the ultraviolet(UV)-curing nanoimprint technology was used to realize the replication process of the 4-step mold, and the image of replicated samples were produced. The results show that the method can be used for the mold preparation of asymmetric low-step diffractive optical elements.
Oe Information Acquisition and Processing
Research on distribution of aperture position error in multi-beam coherent imaging and its impact on image quality
ZHANG Yu, LUO Xiujuan, LIU Hui, CHEN Minglai, CHENG Zhiyuan, LAN Fuyang
2019, 40(3): 411-415. doi: 10.5768/JAO201940.0302001
As the research of coherent imaging (Fourier telescopy) in the procedure from laboratory experiments to the real system, there are many factors that may impact on the realization. However, among the factors and analysis, there has not been a theoretical support for calibrating the aperture position error distribution and the error range. In this article, based on the optical transportation theory, the aperture position error distribution and its impact on image quality were analyzed. The paper also proposed the error range and carried out the experimental setups. The results demonstrate that the relative position error should be controlled less than 5%. To sum up, this article provide a theoretical method to analyze the design and the configuration of the real Fourier telescopy.
Visible light imaging system through frosted glass
LI Chengyong, YING Chunxia, HU Jingjing
2019, 40(3): 416-421. doi: 10.5768/JAO201940.0302002
The ability to obtain fine information of object images through complex media is a major difficulty in photoelectric image acquisition and processing. The complementary metal oxide semiconductor (CMOS) photoelectric image sensor was adopted to design a CMOS imaging system and a back-end reading and processing circuit, the target object was imaged through the frosted glass, and the acquired image information is transmitted to the computer for processing.The system was fabricated according to the principle of camera optical imaging system. The circuit was completed by the general CMOS image sensor chip, and the image was acquired by infrared laser-assisted illumination shooting. The same target was imaged at far and near distances respectively, and the iterative image enhancement algorithm was optimized for the target image. It can solve the problem of non-uniformity of frosted glass, greatly improve the reconstruction precision of the light source, and obtain a clear outline of the visible light image. Compared with the general CCD imaging system, the recognition rate is over 95%, which is much larger than the general imaging system, and the imaging performance is good.
Research on three-dimensional detection of microscopy using nonparallel light interference illumination
PAN Hui, QU Yufu
2019, 40(3): 422-428. doi: 10.5768/JAO201940.0302003
In order to realize rapid and simple measurement on micro-topography, an optical detection method using interference illumination of nonparallel light was proposed. In this method, a spatial light modulator is used to diffract the laser beam, and two diffracted beams with similar intensity are selected to pass through the objective. Fringe which has accurate phase and period approximately equal to resolution can be obtained by dual-beam interference. The surface topography is detected by calculating four fringe images with equal phase difference. This method neither need interferometric objective to produce fringes nor axial scanning device to record fringe changes, therefore the phase adjustment is accurate, and the imaging is intuitive. In addition, because the phase varies linearly with the pixel coordinates, the fringe period does not need to be modified. The adjustment path of fringe parameters is separated from imaging path, hence the system is simple and easy to adjust. To verify the accuracy of the proposed micro-topography method, a module (Ra=100 nm) and a silicon wafer were used as the samples for three-dimensional reconstruction experiments. The results show that the proposed method can achieve a repeatability measurement accuracy of 8.6 nm (2σ) in axial direction.
Research on HgCdTe focal plane arrays for ultra-spectrumdetection in Vis/NIR
ZHANG Shan, SHEN Yiming, LIU Dan, ZHONG Yanhong, WEI Yanfeng, LIAO Qingjun, CHEN Honglei, LIN Chun, DING Ruijun, HE Li
2019, 40(3): 429-434. doi: 10.5768/JAO201940.0202004
To meet the requirement of high-resolution and high-sensitivity observation in visible-near infrared, the HgCdTe focal plane arrays(FPAs) with high signal-to-noise ratio was fabricated based on the large-array low-noise HgCdTe detector manufacture technology and low-damage substrate removal technology. The response of short-wave infrared detector was extended to 400 nm~2 600 nm by the ZnCdTe substrate removed with mechanical thinning and chemical wet etching technology. After the fabrication of the Vis/NIR 640×512 pixel 25 m FPAs, the performance was evaluated with a certain quantity of radiation. The results indicate that the quantum efficiency is approximately 88.4% at 2.32 μm waveband, the effective pixel rate is 98% and the signal-to-noise ratio is 287, the clear imaging quality in Vis/NIR waveband can be obtained.
Optical detection algorithm for seafloor roughness and its experimental study
GAO Sunpei, XU Jian, ZOU Bo
2019, 40(3): 435-439. doi: 10.5768/JAO201940.0302005

As an important physical property of seafloor sediments, the seafloor micro-topography roughness is of great significance to marine engineering and scientific investigation. How to measure seafloor micro-topography roughness by optical method has been a hot topic in this field in recent years. Based on the shape from shading (SFS) algorithm in optics, a fast seafloor micro-topography roughness algorithm was put forward. While constructing the model, the absorption and attenuation model of underwater light propagation was considered, and the seafloor micro-topography roughness was measured and the parameters were fitted according to the power law form. Simulation results prove that the algorithm has 95% confidence, it is suitable for seafloor micro-topography roughness measurement, and its validity and correctness are proved by experiments.

Image denoising algorithm based on information preservation network
CHEN Qingjiang, SHI Xiaohan, CHAI Yuzhou
2019, 40(3): 440-446. doi: 10.5768/JAO201940.0302006
Due to various factors such as imaging equipment, the image will be disturbed by noise during imaging or sensing. Image denoising aims to reduce or eliminate the influence of noise on the image, which often leads to the loss of high-frequency information. In order to protect the edge information and texture details of the image while removing image noise, a convolution neural network with information preservation blocks with relatively low computational complexity is proposed to denoise the noisy image directly. The information preservation block extracts the mixed feature information of the local long path and the local short path by residual learning. Peak signal to noise ratio (PSNR/dB) and structural similarity index method (SSIM) are used to quantify the experimental results. The larger the two indexes, the better the denoising effect. Experiments show that the mean values of PSNR and SSIM can reach 30.36 dB and 0.828 0. Compared with other denoising algorithms, the two evaluation indexes are improved by 2.15 dB and 0.072 9 respectively. The proposed algorithm has good denoising effect for different kinds and different levels of noise, and the speed is better than the general algorithms compared, which contributes to the further development of the denoising based on convolutional neural networks.
Adaptive linear transmission estimation dehazing algorithm
YANG Yan, LI Yifei, YUE Hui
2019, 40(3): 447-453. doi: 10.5768/JAO201940.0302007
In order to effectively restore the degraded images in hazy weather, an adaptive linear transmission estimation dehazing algorithm was proposed. Firstly, we created a linear transformation model between the hazy image and the dehazing image minimum channel. Secondly, the adaptive parameters were obtained by using the mixed channel of the hazy image, and the transmission was estimated by combining the adaptive parameter and the linear transformation model. Then, a Gaussian function was constructed by the minimum channel of the hazy image to compensate the estimated transmission of the bright region, and the accuracy of the transmission of this region was improved, and the cross-bilateral filter was used to eliminate the texture effect to obtain the optimized transmission. Finally, a dehazing image was restored in combination with the atmospheric scattering model. The experimental results show that the method can effectively reduce the time complexity, and the restored image has obvious details and appropriate brightness.
Detection performance of underwater laser light screen based on Monte Carlo method
YANG Tong, WANG Fan, NI Jinping, ZENG Hui
2019, 40(3): 454-460. doi: 10.5768/JAO201940.0302008
In order to improve the detection performance of underwater laser screen, the underwater laser light screen detection model was established according to the underwater beam propagation law. The detection performance of underwater laser light screen was analyzed based on Monte Carlo simulation method. The simulations were carried out based on the above underwater laser light screen detection model using MATLAB software to analyze the influence of attenuation coefficient of seawater, initial power and transmission distance on the underwater laser light screen transmission. The simulation results show that the smaller the attenuation coefficient of seawater, the smaller the impact of the transmission rate of the underwater laser light screen. When the seawater parameters and transmission distance are fixed, the initial power can only affect the final power reaching the detection end, but it has little effect on the transmission rate of the underwater laser light screen. When the seawater parameter is fixed and the transmission distance is 1m, the transmission rate is about 15% and is stable. When the transmission distance is increased to 30 m, the transmission rate is below 5%.
Optical Metrology and Measurement
Novel algorithm for analysis of cellular fluorescence spectrum based on optimization iteration
DU Yue, MENG Xiaochen, ZHU Lianqing
2019, 40(3): 461-467. doi: 10.5768/JAO201940.0303001
When using the spectral measurement method for multi-color fluorescence analysis of cells, the emission spectrum can produce partial spectral overlap, which poses certain difficulties for qualitative and quantitative analysis. Aiming at the problem, a novel algorithm was developed to effectively decompose the overlapped spectral peaks based on optimization iteration. First, the separation model of overlapped peak was built up to obtain the peak vertex of overlapping peaks. And then, according to the size of each constructed peak area, the structure of the constructed peak was re-determined, and finally the vertex and area information of the simulated peak was obtained.Moreover, the algorithm was used to analyze the overlapping peaks formed by the superposition of Gaussian functions, and compared with the conventional methods. The results show that the analytical error of the optimized iterative algorithm is stable within 0.15%, while it can be stabilized within 0.85% after adding random noise, which are all better that the other two algorithms. In addition, the iterative efficiency under the algorithm was calculated, and the results show that the algorithm is 32.2% higher than the conventional method.
Shape-based infrared image leakage gas detection method
LIU Lumingen, ZHANG Yaozong, LUAN Lin, HONG Hanyu
2019, 40(3): 468-472. doi: 10.5768/JAO201940.0303002
Aiming at the explosion and fire caused by leakage gas in industrial production, an infrared image leakage gas detection method based on shape and support vector machine(SVM) is proposed. The SVM classifier is trained by using the shape features of the infrared image sample of the leaking gas and the interfering object. The candidate target region is obtained by using the background difference-based motion detection for the infrared image sequence, and then the shape feature is extracted from the candidate target region, and finally the SVM classifier is used to obtain the final detection result. Experiments were carried out using ethylene gas leakage simulation data, and the detection rate was up to 98%. The results show that this method can effectively detect the leakage gas, which greatly reduces the false detection caused by the interference.
Method of thin film thickness measurement based on laser heterodyne interferometry
SHI Kai, SU Junhong, QI Yuan
2019, 40(3): 473-477. doi: 10.5768/JAO201940.0303003
For the difficulty of measuring the thin film thickness, a method of thin film thickness measurement based on laser heterodyne interferometry was proposed. Using the classical Michelson interference optical path, the heterodyne interference principle was used to convert the film thickness difference into the optical path difference, and the precise displacement table was used as the scanning mechanism to realize the progressive scanning measurement of the film thickness. Results show that the shift of the measurement system within 20 min under constant temperature experimental conditions does not exceed 8 nm, and the average deviation of the measurement results is less than 1 nm. Comparing with the measurement results of the ellipsometer, the measurement difference is 12.97 nm, indicating the feasibility of the method.
Research on near-UV to near-IR spectroradiometer and its calibration method
YUAN Linguang, FAN Jihong, ZHOU Xiaoguang, ZHAN Chunlian, LU Fei, LI Yan, ZHANG Boni, CHEN Juan, YOU Yue
2019, 40(3): 478-482. doi: 10.5768/JAO201940.0303004
In order to realize high precision measurement of spectral radiance, a kind of small field near ultraviolet(UV) to near infrared(IR) spectroradiometer was developed with a wavelength range of 300 nm~ 2 000 nm and a spectral radiance measurement range of 50μW/cm2·nm·sr~1 000μW/cm2·nm·sr. First the design principle and critical components of the near-UV to near-IR spectroradiometer were described. Then the direct method based on tungsten strip lamp was used to realize the spectral radiance absolute calibration of this spectroradiometer. Finally, the spectral radiance of the standard integrated sphere source was measured. The results show that the deviation between measured and standard values is less than 0.5%.
Measurement method of response time consistency for sky screens vertical target
TIAN Ya'nan, TIAN Hui, YUAN Yun
2019, 40(3): 483-488. doi: 10.5768/JAO201940.0303005
In order to verify whether the response time of 6 light screens is consistent while the projectile passing through the sky screens vertical target, and to improve the velocity measurement accuracy of test equipment, a measurement method for detecting the response time consistency of sky screens vertical target was proposed, and a test device based on this method of signal source for simulating projectile over-screen was designed. The device controls the two light source intervals to change lightly and darkly by digital-analog(DA) conversion, by calling the projectile contour data stored in the ROM, which is used to simulate the instantaneous change of light energy while projectile passing through the light screen. The test was completed by comparing the difference value between the time interval of two output signals collected synchronously by the signal acquisition and processing instrument with the delay time interval by the device. The test results show that the difference value between the output signal time and the set delay time is both less than 1 μs, which satisfies the technical requirements of the response time consistency of 6 light screens, the test device and the measurement method can be used for the measurement of response time consistency for the sky screens vertical target.
Laser Technology
Research on 200 mJ semiconductor end-pumped MOPA Laser
XIONG Bo, YU Cailiang, CHU Zhaohua, ZHAO Chong, KAO Xiaomei, WU Jiakai, CUI Ying, MAO Mingfeng, XIN Chao, WEI Xiaoyu
2019, 40(3): 489-492. doi: 10.5768/JAO201940.0307001
Using the high-power laser diode array (LDA) end-pumped Nd:YAG laser bar method, combined with the design of the convex-concave unstable cavity, the average energy of the small beam divergence laser output was achieved about 83 mJ under 20 Hz operating conditions. Then taking the laser as the oscillation source, the same method of the LDA end-pumped Nd:YAG laser rod was used for energy amplification to form an LDA end-pumped master oscillator-power amplification (MOPA) laser, which finally obtained the pulsed laser output with a repetitive frequency of 20 Hz, an average energy of >200 mJ, a divergence angle < 2.1 mrad and an energy fluctuation < ±2.5%. The laser has a optical-to-optical conversion efficiency of about 14.6%, a volume of 175×91×49 mm3, a mass of < 1 kg, and a divergence angle of < 0.3 mrad after transmitted through an 8× transmission antenna.
Research on path optimization method of laser scanning projection based on improved Fleury algorithm
HOU Maosheng, SUN Mingli, YANG Fan, LI Lijuan, ZHU Yundong, FAN Chengbo
2019, 40(3): 493-499. doi: 10.5768/JAO201940.0307002
In order to improve the serious flickering problem of the laser scanning projection system caused by the scanning frequency much smaller than 20 Hz when scanning complex graphics, we applied the Fleury algorithm to the laser scanning projection path planning based on the graph theory, and proposed a novel improved Fleury algorithm for the limitations that the previous algorithm could not optimize the non-Eulerian paths.We simulated and analyzed the scanning path optimization effects of the above algorithm by MATLAB, and applied it to the existing laser scanning projection system for experiment furthermore.Experiments results show that, the laser scanning projection path optimization technology based on the improved Fleury algorithm can increase the frequency to around 20 Hz, effectively solve the flickering problem, it can also improve the quality of the drawn graphics, thus enhancing the practical application value of the self-developed laser scanning projection instrument.
Tunable multi-wavelength holmium-doped fiber laser operating at 2.1μm
YU Xiuming, DING Yunfei, MA Wanzhuo, ZHAO Desheng, LIU Runmin, WANG Tianshu
2019, 40(3): 500-504. doi: 10.5768/JAO201940.0307003
In order to generate the multi-wavelength fiber laser at 2.1 μm band, a tunable multi-wavelength Ho3+-doped ring fiber laser based on all-fiber Sagnac interferometer was designed. A 3 m long Ho3+-doped silica fiber was pumped by a Tm3+-doped fiber laser, and then the spontaneous radiation at 2.1 μm band was amplified. In the annular cavity, the Sagnac fiber interferometer consisted of an 8 m long polarization maintain fiber (PMF) and a polarization controller (PC), and the output wavelength at 2.1 μm waveband can be period tuned by the Sagnac interferometer. In experiment, a multi-wavelength laser at 2.1 μm waveband can be got, the output power can be tuned from 1 mW to 15 mW, and up to 6 wavelengths of laser output can be observed. By adjusting the PC in annular cavity, the output tunable wavelength number can be realized from 1 to 6 at 2.1 μm band.
Fiber Sensing and Optical Communication
Two-step stage optimized CMA algorithm in super-high coherent optical telecommunications
ZHONG Kun, YANG Huaidong
2019, 40(3): 505-510. doi: 10.5768/JAO201940.0308001
In ultra-high coherent optical telecommunications, constant modulus algorithm (CMA) is usually adopted for compensation of impairment of polarization demultiplexing and polarization mode dispersion (PMD). Standard CMA has a function of self-adapt dynamic equalizer, with coefficient signal constantly updating according to input signal. It is a popular blind-equalizing algorithm at present. In CMA algorithm, the value of step-size usually severely influences the performance evaluation of algorithm convergence, error vector magnitude (EVM), and bit error ratio (BER). This paper presents an optimized CMA algorithm of two-step size coefficients, which is capable of labeling stable span of error vector function curve. The verification of calculation shows, the optimized CMA algorithm can improve the demodulation performance, decrease the EVM of X and Y polarization state, validating its preferable applicability.
Side-grinding U-shaped gold sputter plastic fiber SPR sensor
HOU Jianqiao, JING Ning, WANG Zhibin, LI Kewu
2019, 40(3): 511-516. doi: 10.5768/JAO201940.0308002
In order to measure the change of the refractive index of solution, the three layers structure of fiber core-gold layer-liquid on the surface of plastic optical fiber core was studied.A surface plasmon resonance(SPR) sensor using U-shaped structure combined with side polishing method was developed. First, a segment of plastic fiber was bent into a U shape, and the curvature of the segment was fixed at higher temperatures in the oven. The outer surface of the curved part was then polished to expose the plastic fiber core layer at the position and to sputter the gold nano-film layer on it. Finally, the prepared sensor was immersed in the liquid with different refractive indices, and the movement of the spectrum was observed using a spectral analyzer. The experimental results show that when the plastic optical fiber SPR sensor measures the liquid with the refractive index variation range of 1.333~1.406, it can be observed through the spectrum that with the increase of the liquid refractive index, the plasma resonance absorption peak position is also moving towards the direction of wavelength increase, and there is a linear relationship between the two, and its sensitivity is 7.5×10-4 RIU/nm. The sensor probe has the characteristics of miniaturization, easy preparation and low cost.
Research on extraction of true random numbers based on turbulence-induced optical scintillation
KANG Liming, YAO Haifeng, CHEN Chunyi, LIU Zhonghui, XIANG Lei
2019, 40(3): 517-524. doi: 10.5768/JAO201940.0308003
Aiming at the generation of true random numbers, a true random number extraction method based on light scintillation images in atmospheric turbulence was proposed. First, we used a camera to obtain the light spot images of the laser with a wavelength of 532 nm propagating through atmospheric turbulence. Then, according to its scintillation characteristic, we selected the light spot images by fixed-interval selection and multiple-step selection, respectively, the fixed interval was selected as 50 frames, the multiple steps were selected as 30 frames, 70 frames and 100 frames. The correlation of the obtained light spot images was weak, and the correlation coefficient was less than 0.3. Because of the influence of the turbulence effect, the pixels in the image changed irregularly. We calculated the combination of pixels to extract the random sequences. Finally, we tested the extracted random sequences by the national institute of science and technology(NIST) randomness test method. Experimental results show that the random effect of random sequence with the fixed-interval selection is general and the test results have the P value less than 0.01, while the P value obtained by multiple-step selection are all greater than 0.01 and the random sequence can pass the randomness test.
2019, 40(3)