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Issue 9 ， 2007
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Neural network error modification method for three-axis photoelectric tracking system
Abstract：System errors seriously influence on the leading and measuring precisions of a three-axis photoelectric tracking system. As least square method has lower precision, and global-function system error modification method could not properly be used in three-axis photoelectric tracking system when azimuth axis runs continuously,a novel neural network error modification method is presented in this paper. The system errors of three-axis photoelectric tracking system locate on a curve composed of three angle values,and the neural network can fit precisely complicated curves or curved faces. Analysis and simulation prove that BP neural network system error modification method can be used in three-axis photoelectric tracking system when azimuth axis runs continuously and can reduce system errors by 72%.Keywords：three-axis gimbal;photoelectric tracking;system error;neural network- 42
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Published：2020-08-12 -
High-resolution Fourier transform lens
Abstract：According to the theory of geometrical optics and the requirements of a particle observation experiment, the systematic initial parameters were researched and a 532 nm Fourier transform lens was designed using ZEMAX. The opto-mechanical structure was designed according to the system feature. By using the software of finite element method, the influence of vacuum on optics spacing and mirror surface shape was analyzed. The analytical and experiment results indicate that the changes of optics spacing and mirror surface shape caused by vacuum can not affect on the imaging quality. The testing experiment using the visual microscope shows that the system resolution is 2.81 μm. After the alignment, the system can keep low-vacuum (lower than 100 Pa) 12 h. And the system has already been used in the particle observation experiment successfully.Keywords：Fourier transform lens;optical design;opto-mechanical structure- 69
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Published：2020-08-12 -
Novel packaging method for optical fiber collimator based on image processing
Abstract：On basis of the "measurability" conception and the Design For Test(DFT) method, a new packaging method for the collimator based on image processing technique was put forward.The compurter vision and digital image processing technique were used to ensure the optical fiber plug to a right phase, and then keep the plug phase intercalating into the stainless steel tube. At the same time, the optical fiber plug feed was moved to adjust the clearance between the plug and GRIN lens in the stainless steel tube to make the plug get to the best assemble place to ensure the optical fiber collimator outputs in maximum light power. The main parts of the system were CCD camera, image board, controlling system and image processing software, and the whole assembly process was controlled by computer. The experimental results show that the system is practical and effective, and the assembly angle tolerance can be controlled less ±3° to satisfy the demand of collimator assembly precision. The packaging method for collimator has been applied to production, which has increased productivity and the qualified rate greatly.Keywords：optical fiber collimator;computer vision;packaging;image processing;phase detecting- 44
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Published：2020-08-12 -
Influence of optical surface error on encircled energy
Abstract：In view of a optical transmitting system, the mathematical model between the Root-Mean-Square Gradient (GRMS) error of optical elements and Encircled Energy (EE) was established by assuming that the surface error is stationary Gaussian random process, and the numerical computation and actual surface profile data of the model was validated. It is found that EE declines in exponential form with the increasing of GRMS, and that the low and high-spatial frequency errors form the centre and the edge of the far-field intensity distribution respectively. The theoretical analysis matches numerical computation very well when GRMS is less than 7 nm/mm. The mathematical model agrees with the actual results well, which can be used to analyze the influence of GRMS on EE and can provide the support for the evaluation criterion of the surface profile of the optical elements.Keywords：optical transmitting system;surface error;encircled energy;phase error;Root-Mean-Square Gradient(GRMS)- 36
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Published：2020-08-12 -
Accurate measuring temperature with infrared thermal imager
Abstract：In order to measure the temperature accurately using infrared thermal imager the interpolation of true surface temperature and the influence factors were studied. Based on the principles of thermal radiation and temperature measurement with infrared thermal imager,a general formula for computing the true surface temperature of objects was given. The influence of emissivity on accurate temperature measurement was discussed mainly, the conditions of accurate temperature measurement with infrared thermal imager were analyzed, and the influence factors from the surroundings, the atmosphere and the thermal imager were investigated too. Finally, the theoretical curves of the various factors influencing on the accuracy of measuring temperature were given.The results show that when emissivity is 0.7, the true temperature is 50℃, as deflected emissivity is 0.1, the measuring result of true temperature fluctuating is 0.76~0.89℃ for a 3~5 μm thermal imager; and 1.56~1.87℃ for a 8~14 μm thermal imager.It is shown that proposed method can provide a feasibility for improving the accuracy of measuring temperatrue and surface emissivity and reducing measuring errors.Keywords：infrared thermal imager;temperature measurement;error analysis;emissivity- 80
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Published：2020-08-12 -
Application of fiber optic displacement sensor to measuring suspension micro-displacement of superconducting rotor in cryogenic instrument
Abstract：A Compensated Fiber Optic Displacement Sensor (CFODS) was introduced and its transmission properties at room temperature (293 K) and liquid nitrogen temperature (77 K) were analyzed comparatively. The analysis shows that this sensor can effectively eliminate environment effects, so it can be used to measure displacement at a large temperature range. The results of measuring suspension micro-displacement of superconducting rotor at liquid helium temperature (4.2 K) demonstrate that it is feasible to measure micro-displacement of objects using the CFODS with measuring resolution about 10 μm at low temperature, which gives some useful reference for the application of the CFODS to cryogenic environment.Keywords：fiber optic sensor;Micro-displacement measurement;cryogenics;superconductor- 61
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Published：2020-08-12 -
Aberration correction of a large aperture optical imaging system by holography
Abstract：Based on the principle of holography,the working mechanism and holographic correction method of an aberrated optical imaging system was described and analyzed in detail. An experimental system was established for the aberration correction in an optical system with a low quality and 500 mm diameter spherical mirror for finite object imaging. By comparing the interferograms and images obtained before and after correction, the feasibility of the correction method was verified. The experimental results show diffraction-limited performance of the system and residual aberration is about λ/8.Keywords：Holography;optical imaging system;large aperture mirror;aberration correction- 30
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Published：2020-08-12 -
Non-uniformity correction of key device ICCD in ultraviolet imager
Abstract：The mechanism of optoelectronic non-uniformity characteristic in Image Intensified Charge Coupled Device(ICCD) was analyzed, and then a response characteristic mathematic model was proposed. Base on the two-point multi-section method, a non-uniformity equation of ICCD in ultraviolet imager was given and correction coefficients were obtained in specific experiment condition. In the experiments, it is found that the "snow like flicker" (mainly composed of the shot noises of detector) and blind pixels are the main factors of the non-uniformity improvement,which can be compensated by the response values under corresponding illumination. The results show that the compensated and corrected image has effectively reduced the measurement error brought by non-uniformity of the detector and the uniformity decreases by 37.1%. Proposed method and experiment can reduce the intrinsic pattern noise brought by the physical characteristics of ICCD and fabrication defects in certain degree.Keywords：ultraviolet imager;Image Intensified Charge Coupled Device(ICCD);non-uniformity;linearity correction;two-point multi-section correction method;noise compensation- 40
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Published：2020-08-12 -
Experimental study of bending silicon chip with
Abstract：The experiment of silicon chip bending by a millisecond pulse width Nd:YAG laser was done,and the energy threshold of silicon bending was given. Meanwhile, using the Nd:YAG long pulse laser,the influence of pulse frequency and pulse width on the bending angle was mainly investigated,which could be transformed to the influence of scan velocity and power intensity on the bending angle. The pulse duty cycle was also used to describe the influence of the energy’s time distribution on bending. The experimental results indicate that the silicon chip could be bent an angle more than 20° using the Nd:YAG long pulse laser.Keywords：laser bending;silicon chip;pulse frequency;pulse width;pulse duty cycle- 34
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Published：2020-08-12 -
Speckle contrast reduction in laser display
Abstract：In order to weaken the influence of speckle on laser display system, a novel speckle reduction method utilizing pure phase pattern optical element was presented based on the theoretic analysis of speckle contrast. Then, by using green laser as source, the laser beam passed through the Diffractive Optical Element(DOE) in experiment. The changes of speckle contrast and light intensity on screen were obtained with the help of CCD camera and image processor. The experimental results indicate that the contrast of laser speckle is reduced to 3.7%, which meets the requirement of laser display. Proposed method has many advantages in simple practice, low cost and good manufacture in industry.Keywords：laser display;speckle;Contrast- 35
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Published：2020-08-12
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