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Issue 6 ， 2005
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Design of tunable optical filter using ladder-interference-type structure
Abstract：Based on the interference principle of Mach-Zehnder interferometer and the transfer matrix of multimode interference (MMI) coupler, the expression of the optical field at the output port was derived and the performance of the ladder-interference-type structure based tunable optical filter (LTOF) was investigated. The results show that there is an optimum splitting ratio of the MMI coupler for different stages obtained by algorithm. The increment in number of ladders for the LTOF will lead to the reducting peak power and narrowing 3 dB bandwidth. According to the effect of the diffraction order and the length of electrodes on the tuning performance, it is proposed to prolong the length of electrode by 40% to realize the continuous tuning. An example is given to verify the availability of this method.Keywords：guided wave optics;tunable optical filter;ladder-interference-type structure;splitting ratio;continuous tuning- 45
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Published：2020-08-12 -
Fabrication of Bragg grating in a highly nonlinear photonic crystal fiber
Abstract：Fabrication of the Bragg grating in a highly nonlinear photonic crystal fiber was investigated experimentally by phase mask method. Nonlinear coefficient and mode-area diameter of the highly nonlinear photonic crystal fiber are 12 W－1km－1 and 2.4 mm respectively. The evolution of reflectivity of the Bragg grating against irradiation pulse number was analyzed. The reflectivity entered into a saturated phase with increasing the irradiation pulse number, and it began to decrease with further increasing exposure. Bragg grating with the reflectivity of 44.4% in the highly nonlinear photonic crystal fiber was demonstrated, which paved the way for studying the nonlinear effects of fiber Bragg grating and their applications. The factors affecting writing efficiency Bragg grating in the highly nonlinear fiber were discussed.Keywords：photonic crystal fiber;Bragg grating;nonlinearity- 40
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Published：2020-08-12 -
A new mini-fiber-spectrometer adopting micro-silicon-slit
Abstract：A new mini-fiber-spectrometer was developed with micro-silicon-slit instead of traditional mechanical slit. By calculating the impact of nonlinearity MEMS-based slit on the resolution of the mini-fiber-spectrometer and measuring the resolution of the system, it finds that using micro-silicon slit is efficient. Meantime, a theory for wavelength-pixel calibrating was brought forward after analyzing the resolution of pixel and FWHM, which was validated by analyzing data of the experiments of measuring the mercury-arc and fine calculating through the tool of MATLAB system. The results show that the new mini-fiber-spectrometer with micro-silicon-slit is worked out, its FWHM is 0.85 nm, the precision of the wavelength calibration is less than 0.2 nm and the volume is 50 mm×46 mm×14 mm.Keywords：micro-silicon slit;mini-fiber-spectrometer;MOEMS;resolution;formula for wavelength calibration- 63
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Published：2020-08-12 -
Analysis of the influence of fabrication errors on the efficiency of X-ray zone plates by summing up the wavelets
Abstract：The influence of random zone position error, width error, interdiffusion and roughness on the efficiency of X-ray zone plates (ZP) was analyzed by summing up the wavelets of every pair of rings. Strehl ratio was used to quantify and evaluate the performance of the zone plates deviating from perfect ones. The tolerances of the 4 errors mentioned above were gained by using Strehl limit in two examples. The influence of random zone position and width error on the efficiencies of a Ni soft X-ray zone plate was calculated, and the influence of interdiffusion and roughness on the efficiencies of a SiO2/Ni hard X-ray sputtered sliced zone plate was analyzed. It is showed that the efficiency of the main focus decrease with increasing the four errors. The root-mean-square of random zone position and width error of the first zone plate need to be less than about 20% of the outmost zone width to generate a Strehl ratio higher than Strehl limit; the width of random interdiffusion region and the root-mean-square roughness of the second zone plate need to be less than about 90% and 60% of the outmost zone width to generate a Strehl ratio higher than Strehl limit respectively.Keywords：X-ray zone plate;zone position error;zone width error;interdiffusion;roughness- 45
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Published：2020-08-12 -
Measurement of piezoelectric properties of PZT films by laser Doppler technique
Abstract：Laser Doppler technique was used to measure the piezoelectric properties of PZT(Pb(Zr,Ti)O3) thin films. The measurement of piezoelectric properties on commercial PZT bulk indicated that the introduction of lock-in technique, which offered excellent noise rejection, raised the displacement resolution up to picometer order. Then experiments were performed on PZT films derived by sol-gel method and Electrical Spray Deposition (ESD) method. The obtained results show that the piezoelectric coefficients (d33) of the two films are 218.7 pC/N and 215.8 pC/N respectively, with 5 V dc bias, and the corresponding standard deviations are 12.7 and 28.6.Keywords：PZT thin film;laser Doppler technique;digital lock-in- 29
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Published：2020-08-12 -
Design of high sensitive shadowgraph system for internal wave visualization
Abstract：A shadowgraph system with a to-and-fro light-reflecting structure was designed and implemented. The system can reduce overall dimensions and improve visualizing sensitivity. A CCD direct imaging approach was introduced to reduce the system noise and realize full automation. The experimental results show that this system can visualize 1.0×10－6 g/cm5 variations in density gradient, and can be used to visualize experimental simulated internal waves in the study of ocean internal wave dynamics, and can meet the requirement of internal wave visualization with large wave field scale in limited laboratory space.Keywords：internal wave;shadowgraph;flow visualization;image processing- 24
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Published：2020-08-12 -
Precise center location algorithm for circle target in CCD laser dual axis autocollimator
Abstract：A precise circle target center location algorithm was proposed and the multiscale generalized mathematical morphological filtering method with multiple structuring elements was utilized for eliminating noise in the image. The subpixel position of circle target was obtained by Zernike moment contour subpixel location algorithm,and the circle target center position was acquired ultimately and accurately using circle fitting method based on least square method. The experiment results show that the method is stable and accurate located for measuring 2D small angle, and the measuring uncertainty of this modified instrument is better than 0.3″ within ±2' range, with the measuring resolution increased by 10 times. The results also show that the measuring resolution and accuracy of the autocollimator can be improved effectively.Keywords：autocollimator;multiscale and multiple structuring element morphological filtering;Zernike moment;subpixel location- 60
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Published：2020-08-12 -
A temperature sensor array based on flexible MEMS skin technology
Abstract：A 8×8 array platinum film resistor temperature sensor on polyimide flexible substrate was successfully fabricated based on MEMS skin technology. The flexible polyimide substrate were formed by spin-coating liquid polyimide on a thermally oxidized silicon wafer. The wafer was used as a mechanical carrier for the flexible substrate during device fabrication. The finished flexible devices were finally separated from the carrier by wet etching. The test results show that the platinum film resistor temperature sensors on polyimide substrates exhibit excellent linearity and the temperature coefficient of resistance is close to 0.0023/℃. The spin-coated liquid polyimide solves two major problems comparing with the solid polyimide sheets as a flexible substrate. First, flatness of the flexible substrate is maintained with no air bubbles between the interface of ployimide and silicon. Second,the thermal expansion of the flexible substrates during the fabrication process due to thermal cycling is reduced greatly. The flexible skin with a temperature sensor array can be easily attached on a highly curved surface to detect temperature distribution inside a small area.Keywords：skin technology;polyimide;flexible substrate;platinum film resistor;temperature sensor- 48
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Published：2020-08-12 -
A high speed camera calibration method in coordinate measurement of bomb-fall and its precision analysis
Abstract：For the application environment and the necessary precision in vision coordinate measurement of bomb-fall, a corresponding method was proposed which just calibrate two key camera parameters: the focal length and the horizontal angle of the optical axis. By analyzing the coordinate calculation model, a linear calibration equation was presented,in which multiple vision sensors can derive their parameters at one time when getting two known coordinate points (target). Through analysis of precision, the optimum location of the target was given. The total errors were synthesized and the theoretical error values were obtained on every point in the measuring area. At last, the experimental results were given. The results show that the method is practical and simple for algorithm analysis, and is suitable for wide-range vision measurement, especially for field application. In the application of inspecting a f400 m area from 1 200 m away, the method can ensure that the coordinate measuring error is less than 0.3 m.Keywords：Vision coordinate measurement;camera parameter;camera calibration;precision analysis- 39
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Published：2020-08-12 -
Study of measurement system for rough surface accuracy
Abstract：A system for measuring rough surface accuracy was designed. A line edge laser trianglulation method was used to realize subpixed measurement and a threshold value method was utilized to improved measuring image algorithms. At the same time, a morphological filtering was used to process the surface image of a quizzee. The results show that the system can improve the accuracy better and obtain the satisfied image ledge and the accuracy survey of 5 m.The measurement system can be used in a wide scope and can also realize the measurement of the thickness and uniformity of coating layer on battery electrodes with rough surface.Keywords：thickness measurement;rough surface;subpixel;threshold value method;laser trianglulation measurement;line edge method;morphological filtering- 39
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Published：2020-08-12 -
Research of micro-driven table based on PZT and its control system
Abstract：The high-speed high-precision robot based on error compensation was presented. The micro-driven table was designed by means of ANSYS. The table consisted of a parallel board framework and direct-driven by PZT which integrated high-resolution strain transducer. Experiments demonstrate that the steady time of the micro-driven table has been shortened significantly by adopting the fuzzy PI controller, and the motion performance index of robot is improved by using the micro-driven table to compensate the swing displacementKeywords：micro-driven;PZT;error compensation;finite element analysis;robot- 35
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Published：2020-08-12 -
Research of vibration locator mass adjustment based on laser technology
Abstract：The vibration locator developed by precision work has excellent performance.It is an important key component of finding location or direction in the modern weapon system. The mass adjustment for a vibration locator is an importance step of processing the spherical vibration part. The vibration locator mass adjustment based on laser technology was put forward in this paper. The principle of the laser beam balance was introduced and the distribution, modality and construction of the vibration part processing defect-layer were discussed,and an arithmetic to eliminate the defect and confirm the laser beam time was given. The contract test results show that the vibration split frequency difference of the spherical vibration part is higher than 0.5 Hz, but the split frequency difference required by making locator should be 0.004 Hz. It is proved that the method is effective.Keywords：mass adjustment;Laser beam;vibration locator;spherical vibration part- 27
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Published：2020-08-12 -
Design of JPEG image file system in corona detection system
Abstract：An ultraviolet corona detecting system was proposed for detecting and locating corona, in which TMS320DM642 was used as primary processor. A visible camera and an ultraviolet camera were used for inputing in the system. Two cameras have same visual field, so the processor can compose those input videos, and then display the result on LCD for user easy to observe and locate the corona. The interested images can be captured and saved into the internal FLASH of the system before it is encoded to JPEG files. The images in the internal FLASH can be displayed on LCD or downloaded into PC using USB interface. A kind of JPEG image file system was designed for saving these images, and implementation of JPEG algorithm based on RF5 was discussed. The design of storage space, structure of directory area, and the implementations of basic operations such as initialization, reading and writing in the file system were particularly discussed. The experimental results show that it respectively spends 10.5 ms and 9.6 ms for JPEG encoding and decoding operations on the image of 720×576 resolution, and it spends about 4~6 s for capturing and saving operations, and 70 images can approximately be saved in the file system.Keywords：DSP;JPEG;file system;RF5;ultraviolet corona- 35
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Published：2020-08-12 -
Two-laser scanning confocal system for microarray analysis
Abstract：A dual-fluorescence microarray scanner based on laser confocal principle was constructed to detect the Cy3-protein or Cy5-protein dotted slides. The images were constructed according to the fluorescent intensity signals, and enhanced through adopting the technique of morphologic methods to meet the situation in which the fluorescent intensity was very low and the dynamic range of the data was wide relatively. The measuring ways of the signal-to-noise ratio and the sensitivity of the system were put forward, and the measurement result shows the sensitivity of the system is about 0.1 fluo/μm2.Keywords：biochip;confocal system;dual-fluorescence;morphology;sensitivity- 36
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Published：2020-08-12 -
Restoration of motion-blurred image based on Wiener filter and its application in aerial imaging system
Abstract：The mechanism of generation of motion-blurred image was given. A mathematics model of motion-blurred image was built up. In addition, A procedure for estimating Point Spread Function(PSF) of motion-blurred was provided. The aerial vehicle platform and related system were quickly moving relative to ground target during the image data collection.The image might become blurred. The motion-blurred images could be restored using restoration of image. In restoration methods, Wiener filter is less sensitive to noise than inverse filter for the restoration of motion-blurred images, however, there is a large edge-error. This paper presents the optimal window technique for the restoration of motion-blurred images. With these optimal windows, near-perfect restorations can be obtained if the images vary gradually in intensity near their edge.Keywords：aerial imaging;motion-blurr;Wiener filter;Point Spread Function (PSF)- 53
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Published：2020-08-12 -
An automatic recognition algorithm for bullet holes
Abstract：An algorithm to extract the bullet holes from a chest bitmap out of doors real-time was proposed. A gray projection algorithm was used to extract the chest bitmap from the target bitmap. The mathematical morphology was used to stress the character of bullet holes and to overcome the disturbance of figures. Using mathematical morphology could resolve the overlapping of the bullet holes, then the fuzzy theory was used to extract the target holes accurately. For recognising the bullet holes, the histogram of the target bitmap was used to gain a threshold to exclude the pixels which could not become bullet holes to reduce the complication of computation and a strategy judging the distribution of the pixels around the target holes was used to exclude the invalidation bullet holes. Experiment results show that the algorithm can extract bullet holes accurately and adapt to various circumstances. If the size of the bitmap is 648×480, it only needs 150 ms to complete this algorithm. The new algorithm can also overcome the overlapping of the target holes.Keywords：target bitmap;chest bitmap;mathematical morphology;membership degree;gray projection- 53
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Published：2020-08-12 -
Image denoising algorithm based on L-curvature flow filter
Abstract：Denoising algorithm of L-curvature flow filter was presented. The image noise was obviously removed according to SNR level in terms of the algorithm. L filter, multistage L filter, and the filter combined L filter with curvature flow filter through many iterations, could filter image noise of higher, middle, and lower SNR level respectively. Experiment results show that the lower the input image SNR is, the better the performance of developed algorithm is comparing with the average filter and mean filter. When input image SNR level is low, output image SNR of the algorithm is about 2.98 dB higher than average filter for images with Gaussian noise, and 11.09 dB higher than mean filter for images with impulse noise. The method is very efficient to decrease the image noise of different kinds of SNR and intensities.Keywords：L filter;curvature flow filter;image denoising- 40
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Published：2020-08-12
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