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Issue 3 ， 2002
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Research on the field corrector design for the R-C system of the large telescope Cassegrain focus
Abstract：The R-C system of Cassegrain focus needs a corrector for extending the effective field with good image quality. The restuls of optimization sensitively depends on the focal ratio of the primary mirror of the telescope. Four sets of correctors were designed for various F/# of the primary mirror of a 2-meter telescope:F/3,F/2.5,F/2 and F/1.5. The optimized spots of each corrector are:0.29, 0.418, 0.934 and 1 784 arcsec, respectively. The conclusion is that for the F/3 primary it is very easy to design the field corrector, but if the primary F/# goes down to F/2.5, the corrector should be more complicated than to use two elements.Keywords：Cassegrain focus;R-C system;field corrector;focal ratio(F/#)- 54
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Published：2020-08-12 -
Diagnostic method for laser plasma soft X-ray source
Abstract：Laser plasma soft X-ray source is a kind of pulsed light source. There are several diagnostic methods for this kind of light source. This paper discusses a new and practical way to measure the spectrum of the laser plasma soft X-ray source. A low noise channel electron multiplier(CEM) is used for detecting nanosecond pulsed light signals generated by the laser plasma source, CEM's output signal is fed to a low-noise and fast responsive charge-sensitive preamplifier for further amplification.Output charges from the preamplifier are proportional to the peak of its input pulse. And the spectra from the laser plasma soft X-ray source with copper target and O2,Kr gas target are measured in 8～30nm region, respectively by means of the above-mentioned way.Keywords：laser plasma;soft X-ray diagnosis;gas target;soft X-ray source- 54
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Published：2020-08-12 -
Automatic animal fibre measurement system based on image analysis
Abstract：Diameter measurement of animal fibres is one of the most important physical parameters to evaluate the quality of fibres. An automatic image analysis system for measurement of animal fibres is introduced in the article.The system is mainly based on the technology of image analysis as well as image recognition by computer, which can simultaneously achieve both the automatic diameter measurement and data statistic of many fibres. So all of the data are managed and useful curves are drawn after the rapid and simple measurement process with reliable and accurate results. The system has standard variance σ of 0.135,relative precision value δof 0.66%, and stability of long time of 0.112μm,reaching the advanced level in the world.Keywords：animal fibre;diameter measurement;image analysis- 42
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Published：2020-08-12 -
Study of information hiding algorithm based on noise extraction
Abstract：Information hiding, a form of information processing, embeds data into trivial media for the purpose of concealing the secret communication. Provided that the change due to the above-mentioned process cannot to be detected by human vision system, only the two parties of communication know the covered channel within the traffic, thus it arouses less suspicion. In this paper the authors believe that information hiding combined with encryption techniques can provide a perfect scheme for high strength secure communications. Utilizing a new information hiding algorithm based on noise extraction, the above-mentioned scheme has been realized, to design the algorithm the factors including image quality,ability of whole bits restoration,security,performance of anti-detection have been taken into account. Finally, the experiment and analysis of anti-detection are given.Keywords：information hiding;noise extraction;secure communications- 50
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Published：2020-08-12 -
Adaptive blind watermarking algorithm based on wavelet transform
Abstract：A digital watermark is an invisible mark embedded in digital images,video or audio documents,which may be used for a number of different purposes including copyright protection,authentication and captioning.In this paper, an effective adaptive watermarking algorithm for still images is porposed.This is a blind watermark confirming the copyright without the original image, which is transformed using wavelet transform, and the watermark is embedded in the selected subband of frequency domain according to neighboring symbol’s mean value and odd-even adjugement rule. The experimental results and attack analysis show that the watermark algorithm is transparent and robust against some image processing operations, such as JPEG lossy compression,median filtering,additive noise,scaling, and incorporating attacks.Keywords：digital watermark;wavelet transform;neighboring symbol's mean value;odd-even adjudgement rule- 57
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Published：2020-08-12 -
Improved fragile watermark technique
Abstract：This paper firstly introduces the principle of watermark and summarizes the techniques of image watermark. Then an improved fragile watermark technique is presented, where Haar wavelet transform does not involve normalization, and quantization function is mended, watermark embedding equation is also improved. With these improvements, the watermark technique does work precisely. Using the error control code, fragile watermark detection can be done without original watermark.Keywords：discrete wavelet transform;fragile watermark;error control code;data security- 51
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Published：2020-08-12 -
Study of image segmentation based on improved Hough transform
Abstract：Hough transform has been widely used in pattern recognition and computer vision since its discovery,but it cannot detect the endpoints and length of a curve. Furthermore, high memory space is required in traditional Hough transform. In this paper, an improved Hough transform algorithm is proposed. According to the inverse transform of HT,it subdivides image space little by little and excludes the area without lines. With this algorithm,the memory space required is reduced, and high efficiency is available, besides the endpoint and length of a curve can be detected. It has been applied to the vehicle license plate recognition (LPR) system successfully.Keywords：Hough transform;image segmentation;edge detection- 80
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Published：2020-08-12 -
Study of the fuzzy control technique for the amplitude of the power ultrasonic instrument
Abstract：The effect of operation is directly determined by the vibration amplitude of the ultrasonic scalper, which is a key control parameter on the treatment for the patient by using the power ultrasonic medical instrument.Because the vibration amplitude of the scalper changes with multiple factors such as environmental temperature, time variance nonlinear load and static state press, a vibration amplitude control technique is needed for obtaining the stable vibration amplitude in the power ultrasonic medical system. This paper analyzes the equivalent electromechanical model of the ultrasonic vibration system made up of a longitudinal composite bar high-power transducer, a horn and a scalper, and presents the vibration amplitude control approach based on the self-modifying PID fuzzy controller for the power ultrasonic medical instrument.Compared with the PID controller,the self-modifying PID fuzzy controller has two merits: avoidance of the limit circle oscillation and elimination of the system residual error.Finally,it states the design procedure.The experiments show that the robustness and the control accuracy of the power ultrasonic system can be improved by using the self-modifying PID fazzy control technique.Keywords：ultrasonic aspirator;self-modifying PID fuzzy controller;robustness;power ultrasonic- 42
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Published：2020-08-12 -
Research on SU-8 resist photolithography process
Abstract：SU-8 resist is an epoxy-type,near-UV,negative photoresist based on EPON SU-8 resin.The resist has been specifically developed for the applications requiring high aspect ratios in very thick layers. However, this photoresist has proven very sensitive to process variations. The main process variations influencing the pattern such as pre-and postbake temperature and time, exposure time and development time have been studied. And the conclusion that prebake and development time are the main factors affecting the image’s resolution and aspect-ratio,has been drawn.After analyzing the experiment results,a proposed fabrication process for 200μm SU-8 application is given as follows:coating at a speed of 200μm/s,prebaking at 95°C for 1 hour,near-UV（400nm） contacting lithography,postbaking at 95°C for 30 min and development for 20 min. In addition,the main two problems involved in the experiment are researched.One is the bend of substrate,which can be resolved by the following solutions:decreasing the postbake temperature and increasing the postbake time,using thick wafer instead of thin one, dividing the thin wafer into 4～8 pieces and designing the mask reasonably.The other is the removal of SU-8,which can be resolved by the combination of marinating in hot acetone,ultrasonic cleanout,RIE and cineration at high temperature.Keywords：SU-8 resist;high aspect ratio;photolithography- 80
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Published：2020-08-12 -
Research on the structure design of a precision stage based on magnetic levitation technology and used in micro-electron manufacturing field
Abstract：A new kind of stage which can be positioned accurately and quickly is presented in this paper. Magnetic levitation (maglev.),linear drive and control technologies are applied in the stage. With a maglev system providing normal lift force and plane guiding force, the structure of the stage is simple and it can be controlled easily. By using linear synchronous motor, vibration caused by linear induction motor disappears, which benefits the maglev controlling system. Because of levitation and non-contact driving, there are no friction, wearing, metal particle, grease pollution and linking gap, and the total weight of the stage is lighter. All above improve its dynamic response frequency and the positioning accuracy. This stage meets the requirements of modern information industry to super-clean condition,high accuracy and high efficiency in micro-electron manufacturing field.Keywords：magnetic levitation;position stage;linear motors;non-contact drive;Hopf bifurcation- 42
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Published：2020-08-12 -
Approach to estimate infrared point-target detection range against sky background based on contrast
Abstract：This paper investigates the approach to estimate the maximum detection range of an infrared point-target against sky background based on the minimum resolved contrast(MRC)criteria. Firstly, the characteristics of radiation propagation and attenuation in the atmosphere, and the power response of a contrast-limited optoelectic system are analyzed, the apparent contrast model of a target is developed, and the detection range equation dependent on the aerosol extinction coefficient and range parameter are derived. Secondly, other parameters such as temperature difference and emissivity of target and sky, molecular absorptive transmittance, instantaneous field of view (IFOV), contrast threshold and radiant wavelength are discussed in detail. Finally,the numerical simulations related to infrared point-target detection range are executed using typical atmospheric data output form LOWTRAN7 code.Keywords：Infrared;point-target;detection range;Contrast;instantaneous field of view- 73
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Published：2020-08-12 -
Method for improving precision in noncontact measurement by linear CCD
Abstract：To measure work pieces by CCD sensor is a common way in the noncontact measurement field,but the precision can only reach μm because of the size of CCD cells,which restricts the wide use of this kind of measurement system.This paper gives a method to improve CCD precision by arithmetic aspect. The experiment demonstrates that this method can improve the measurement precision by one order of magnitude.Keywords：Charge Coupled Devices;dimension measurement;edge detection;grads- 63
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Published：2020-08-12 -
Measurement of the line-density of a varied-line-space grating by Moir? fringe
Abstract：Varied-line-space gratings are very useful in synchrotron radiation devices and laser inertial confinement fusion devices, but there are no good ways to measure and manufacture them.In this paper the line-density of a varied-line-space grating is outlined, which is expressed by power series. In comparison with other methods, the Moir? fringe method is introduced, Moir? and Moir? interferometry discussed. The Moir? is used to check the gratings with very low density; while the Moir? interferometry is used in the gratings with high density. The density of Moir? fringes shows the line density of a grating. If it is very high, the coordinates can not be surveyed exactly, the line-density of a grating can be achieved by counting the number of Moir? fringes. Some formulae are deduced, and the data processing method is given. Finally, the author explains the optical alignment of Moir? interferometry.Keywords：varied-line-space grating;line-density;Moir? fringe- 91
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Published：2020-08-12 -
Research on the measurement of motor's torque and rotational speed
Abstract：The torque ancd rotational speed of a motor are the most important two parameters ,their measurement must be accurate.According to the requirements to the measurement aviation motor by the user,this paper analyzes the measurement principles of torque and rotational speed,and points out that the measuring apparatus composed of optoelectric sensors is more suitable for measuring heavy torque and high rotational speed. Through analysis the reasons influencing measuring stability have been found out, which are the flexure strain and structure resonance produced by the transmission axle under the function of the gearing-in force of the reduction gear.This paper,through accurate calculation,takes account of the effects of the mechanical structure on the measuring stability and gives the basic principles and method of choosing the torque sensor and rotational speed sensor.Besides,the measuring accuracy of the apparatus has been considerably increased, the size made smaller, and weight lost,so that they are fit for a viation use.Keywords：torque and rotational speed;sensors;reduction gears;measuring stability;measuring accuracy- 71
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Published：2020-08-12 -
Investigation of the LD pumped all solid-state blue laser
Abstract：Research on the all-solid-state blue laser has become a focus point in the laser field because of its applications in many fields and potential value of commerce. This paper introduces the developing history and conditions of the LD-pumped all solid-state blue laser,discusses gain media, frequency-doubled crystals, Q-switched crystals and configurations of the cavities, which are linear , "v"-shaped and "z"-shaped. The "blue noise problem" and coating technology are reported. And the developing direction of high power and compactness is pointed out.Keywords：LD pump;solid-state blue laser;gain medium;frequency-doubled crystal;"blue noise problem- 81
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Published：2020-08-12 -
Effective methods for raising the measured distance of the pulse laser spots removed target in outfield
Abstract：A pre-estimation to open a CCD electronic shutter and image subtraction between the background image composed of a laser spot and the background are introduced in this paper. These techniques are effective to increase the tested distance of the pulse laser spots removed target in outfield during daytime. Manipulating the trigger pulses of a CCD electronic shutter, the shutter will be pre-opened. Therefore, the full energy of the laser spot lasting only several nano-seconds can be caught. Using the technique of the image subtraction, the bright background where a weak laser spot was merged, was eliminated and the image of the laser spot was emerged. The test results are also presented in this paper.Keywords：pre-estimation of electronic shutters;background subtraction;laser spot test- 51
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Published：2020-08-12 -
Design and manufacture of the intelligent precision platform for a laser processing system
Abstract：Laser processing has been widely used in industrial production. In order to develop the processing system, it is necessary to adopt computer technology and precision machinery transmission. An intelligent precision platform as a part of the processing system has been built. For promoting the quality and automation three problems were solved. They are: (1) the intelligent control of step motors and laser power; (2) the design and security of high precision machinery transmission; (3) the timely monitoring and testing of position and movement during processing.Keywords：laser processing;intelligent control;precision platform;pattern recognition- 50
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Published：2020-08-12 -
Integrative unitization of optical and mechanical design based on optical lens CAD software system
Abstract：This optical lens CAD software system has carried out the integrative unitization of optical and mechanical design based on the communicative technology of multi-database. So the traditional design of an optical lens with two stages of optical and mechanical method has been changed into one time design for the first time. The system can supply such program blocks as those for creating optical system,tracing rays,computing optical aberration,designing zoom lenses,evaluating image quality,and interconnecting systems,etc.All of them will accomplish optical system design,parameter computation,creation of the database for optical design and system parameters.After the database file parameters and optical system model are selected,the system control program runs the database program for the self-creating public function and the mathematical models of mechnnical components.Then the optical lens CAD software system automatically generates the mechanical graphics of components. In this way,the autodesign of an optical lens has been realized.Finally,the article illustrates the example of designing a zoom lens for professional TV camera.Keywords：optical lenses;integrative unitization of optical and mechanical design;CAD software system- 68
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Published：2020-08-12 -
Computing the pure vibrational and vibrational-rotational energy eigenvalues of 7Li2 by difference method
Abstract：The difference method for solving pure vibrational energy level and vibration-rotational energy level is proposed in this paper. Vibratioanal and vibrational-rotatioonal energy eigenvalues of 7Li 2 were calculated by means of introducing a difference method, and the computed results were compared with the results calculated by Ley-Koo, et al. In the process of solving the vibrational energy levels, the difference method is distinguished from other methods, in which wave functions do not need finding out, and vibrational energy levels can be found directly. Therefore it has the advantage of simplicity over other methods. It can be used to accurately determine both analytical and numerical potential functions of biatomic molecules. Furthermore, it can be employed to solve radiation problems such as quasi-molecular radiation.Keywords：diatomic molecule;vibrational energe;vibradional-rotational energe;difference method- 36
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Published：2020-08-12 -
Zernike polynomial fitting method and its application
Abstract：The items of Zernike polynomials have corresponding meanings of Seidel aberrations. The method of using Zernike polynomials to fit optical surfaces has been widely used in project, optical design software and interference check. So it is convenient and mature to use Zernike polynomials as the data transmission tool between optical and structural analysis programs. Here, Zernike polynomials and their fitting method, fitting process are outlined, and are used in the integrated analysis of a space camera, as an example.Keywords：Zernike polynomials;fitting;integrated analysis;finite element method;thermal-structural systems- 213
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Published：2020-08-12
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