2010 Vol. 31, No. 2
Optical tracking device is one of the major ground based measurement instument in target field mapping system. Its main function is to stably track various targets such as flying object and spacecraft. The insturment can accurately measure and record these tracks and flight attitude. Since the instrument is a precise optical device, its technical specifications such as tracking performance, angle measurement accuracy and image quality have a great impact on the successful completion of the measurement. In order to timely detect problems in the device and ensure the effective monitoring, we have developed a dynamic testing device. This paper introduces the basic principle of dynamic testing in laboratory conditions, and the simulation results are provided. The analysis and calculation for the actual accuracy of the detection device are carried out based on engineering design. Finally, It is concluded that the target angle error better than 5（RMS,1）is achieved and the new design can meet high-precision dynamic testing requirement in laboratory conditions.
In order to overcome the weaknesses of observation and detection systems in tanks, such as inefficiency and inaccuracy, the design of the panoramic optical systems based on the distributed aperture concept was performed, whose principle is to implement the real-time collection of the panoramic image information covering 360space in utilizing four objectives of aperture greater than 90, integrate the collected four-path images into one path by the internal relay system, receive the image information by a CCD camera, provide the images spliced with the accurate and uniform panoramic images, estimate under ideal situation the parameters such as detection distance, recognition distance and blind spots, and then estimate the invalid detecting distance by the aid of ray tracing. Panoramic optical systems can realize the all-dimensional real-time observation and detection at the working distance of 57m～6.45km.
The paper puts forward a solution of plesiochronous data multiplexer for a free space optical (FSO) system, which makes full use of the capability of digital multiplexer by expanding the transfer capacity, the method takes majority decision measures and uses filter modules which greatly improved the reliability of the whole system. The system was designed by taking TOP DOWN method. All of the functional modules were described in VHDL. The whole system was accomplished by FPGA chip EP1C3T100C6. Taking the multiplexing of three plesiochronous digital as example, the result of simulation agrees with the experiment result. It is concluded that the solution can greatly reduce interference signals and transfer plesiochronous data signal in FSO accurately and reliably.
In order to improve the printing quality, a high precision system for measuring the surface position deviation of the printer cylinder at high revolution speed is presented. The design concept, structure, function and software design of the system are introduced. The design of the barcode and the method for measuring the position deviation of the surface with phase locking circuit are discussed. The experimental results show that the system can identify the position deviation down to 10m and measurement error is less than 3m.
s-polarization and p-polarization will separate when thin-film filters are used in tilted incidence. Central wavelengths of the two polarization beams do not coincide with each other and pass-band width of s-polarization is less than that of p-polarization. However, the polarization characteristics of the two polarization components in incidence angle can be coincided by adopting film system architecture meeting specific conditions with more than two kinds of materials. Above all, two equations on the polarization componentsreflectivity are given based on theoretical analysis. Requirements for depolarization can be found from the expressions. Then, the refractive index of the materials can be obtained. Thus, we can design depolarization film system architecture. Finally, the simulation calculations of a filter design composed of 129 layers for three cavities prove that the method is feasible.
A new optimized design of large aperture mirror is presented, the optimum mirror size is obtained by using Design Of Experiment, optimization module embedded in Isight which integrates with SolidWorks and ANSYS. Subjected to deformation of gravity and 60℃/-40℃ as well as first order natural frequency, design target is to minimize the mass of oval mirror, the weight is reduced to 51％. The deformed node of mirror is fitted to Zernike polynomial, imported into codeⅤ. Then the spot diagram of optical system dependent on temperature and gravity is obtained, and the deformed mirror effect on optical performance is achieved.
An electro-optical monitoring system based on PLC and wireless sensor networks was built to overcome the deficiencies of traditional monitoring system. We analyzed the components of the optical monitoring system and its working principle，discussed the implementation of optical wireless sensor-networks based on remote sensing technology and investigated the feasibility of the software and hardware implementation of the ABB PLC as well as the development risk of Fame View software．This paper takes AC500 PLC produced by the ABB Company as the main control device, polling the wireless sensor nodes by the order address through the Modbus protocol to collect the data and dealing with the data accordingly, and the final result is passed to the host computer. The received data is used to generate monitor screen by FameView configuration software for real-time detection and monitoring of the operation site．The Monitoring is flexible and effective, and data collection is more efficient, and the system can be upgraded easily. The new optical monitoring system can find its application in production, the battlefield environment, and many other military and civilian fields.
To improve the detection performance and location finding accuracy of the conventional sniper detection, an active laser detecting method was designed based on cat eye effect theory. The device takes a semiconductor laser as light source and a linear array CCD as laser echo detector. The specific reception field of view was matched with 2160 elements of linear CCD by using proper optics system, and its detection accuracy reached the level of mrad. Operation timer of CCD was created by FPGA and the program could be compiled on line and modified conveniently, which could improve the speed of design greatly. The system is simple and portable, and it has its own power management system. The detection distance reaches 250 meter after minimizing noise by frame-subtract and threshold comparing algorithm.
The dichroic beam-splitting mirror of cubic prism is an important element to realize multispectrum in one channel. Due to polarization effect, the dichroic beam-splitting mirror of cubic prism produces a high reflection peak at the high-order doubling frequency, which influences the transmittance in short wavelength seriously. A dichroic beam-splitting mirror of cubic prism, which has high transmittance in the range of 400nm～900nm and high reflectivity at 1064nm, was designed with the dummy layer concept. A valid method to remove the frequency-doubled reflection peak is presented. A sample with good optical performance was fabricated successfully. The film system is easy to be prepared, since its structure is simple, layer number is fewer, material alternatives and process requirement are less strict.
A new metal grid anode made of silver, copper and nickel is reported. Using it as anode, P3HT(poly(3-hexylthiophene)): PCBM(［6,6］-phenylC61butyricacidmeth-ylester) layer as active layer，flexible polymer solar cells were manufactured by spin-coating. Five different structures of solar cell devices were made by using the traditional Indium tin oxide（ITO）anode material or the new anode material. After comparison, it is found that the performances of the new anode material device is greatly improved, open circuit voltage of 0.54V, short circuit current density of 5.39mA/cm2, and power conversion efficiency (PCE) of 2.060% are achieved under 50mw/cm2 illumination.
People with poor vision have difficulty in using their mobile phones because of the relatively small size of the screens. In order to help them to see more clearly, we designed several magnification lens for mobile phones with ZEMAX. After analyzing the features of the magnification lens used in mobile phones, we found that the aspheric lens could reduce the thickness of the lens and achieve better image quality on the periphery. At last, we designed several mechanisms for coupling the lens with the mobile phones and overcame the drawbacks of the current magnification lenses for mobile phones.
According to noise characteristics of aerial image, this paper proposes a kind of wavelet transformation denosing method based on medium filtering for aerial image. The medium filter is applied to reduce image random noise, and wavelet transformation is made on filtered image. Compared to given threshold, the wavelet coefficients that could be judged as signal or noise obviously are processed, other coefficients are processed before running down in multi scale of wavelet. Experiments prove that this method improves image signal to noise ratio objectivley, and makes denoised image more clearly and suitable for human visual observation, which is good for analysis and judgement of aerial images.
The imaging quality can be easily degraded by stray light in some space imaging optical systems, so measures are taken to handle it. An optomechanical model of conformal optical system was established in stray light analysis software. And we tried to find out the systems critical surfaces in collecting out of field stray light by backwards ray tracing method. There were three baffles used in this system to block stray lights, and the simulation result proved the blocking effect of the baffles.
In order to meet the requirements of high space resolution, high spectral resolution, high time resolution, small volume and light weight for the remote sensing of pilotless planes, the off-axis three-mirror anastigmatic optical system is adopted. The asynchronous working mode is proposed for two cameras. The integration of data from the asynchronous cameras and the synchronous real-time output were realized by FPGA. The structure of the entire asynchronous image data acquisition system is introduced. The time sequence simulation was carried out with Modelsim 6.1 in the environment of Xilinx ISE7.1, and then the actual testing was performed. The experimental results show that the system is stable and reliable. Its focal length is f=70mm, relative aperture is D/f=1/6, angle of FOV is 2w=65and total weight is 6kg.
To evaluate the quality of grating, it is desirable to have a ray tracing map of the designed grating. A method of ray tracing for mechanically ruled gratings is developed. Based on Fermats principle and light path function, it gets the spectral distribution of the incident rays, and it can get the ray tracing map through a matrix method. The method is applicable to plane, spherical and aspheric gratings with variable spacing. The groove spacing can vary in arbitrary forms, and the image surface can be chosen as a plane or a conicoid. The ray tracing map of a concave grating ruled on toroidal surface proves the feasibility of the method.
The short coherence digital holography based on LED was studied. The time coherence and spatial coherence of the LED were studied respectively. Although the time coherence of the LED is very short, the spatial coherent of the LED can be further improved by decreasing the area of the light source. The noise in digital holography could be suppressed by utilizing the short coherence and the quality of the retrieved field is enhanced. The digital holography by means of laser and LED was carried out respectively，then the quality of the reconstructed fields were compared. The results show that the speckle noise and multiple reflections, which are introduced by laser source, are completely eliminated in the digital holography based on LED. Consequently, the quality of the reconstructed object field, including amplitude and phase distribution, is greatly improved. However，owing to the short coherence of LED，the application is confined to in-line digital holography, the thickness of the object to be measured should be no longer than tens of microns.
A new method for the acceleration of Richardson-Lucy（R-L）iterative image restoration algorithms is given, which is based on the damped RL algorithm and polynomial extrapolation. By storing the latest several (n) results of damped R-L algorithm, a polynomial function is used to analyze these results, and to approximate the relationship among them. Then, this polynomial function is utilized to predict the later results in the iterative process. This method can simplify calculation and accelerate the image restoration algorithms. The method can offer nearly perfect reconstructed image, and is applicable to other relevant algorithms.
To improve the use of the Chan-Vese method in the segmentation of the three-phase and to reduce its computational complexity, an improved ChanVese method is used to realize infrared image segmentation. The improved Chan-Vese method uses progressive processing and the reversion of gray value to achieve Chan-Vese multiphase object segmentation. The improved Chan-Vese method can realize the three-phase infrared image segmentation. The experiment result demonstrated the efficiency and effectiveness of the improved method.
As an IR target radiation source, portable IR target simulator is widely used in field to evaluate the performance of defense electro-optical system. Since IR target simulator in field couldnt be calibrated accurately, a new method which uses standard IR extended source blackbody and Fourier spectroradiometer to make calibration is presented. The spectral radiance for IR simulator was measured at a given temperature. Then the integral radiance was calculated in the interested wave band. Finally, based on the radiant area of IR simulator, the radiant intensity was calculated at various given temperatures. Experimental results show that the measured radiance curve is consistent with the theory curve in the interested wave band, and the measurement method is proved.
system used for testing transmissivity uniformity of high-absorption filters was developed. Its hardware consists of three major parts, including optical system, photoelectric conversion system and signal acquisition system. Its modularized software was designed based on LabVIEW 8.0. The real-time transmissivity measurement of multi-point distribution based on transmissivity of standard attenuators was computed through moving testing filters controlled by two-dimensional turntable, and the transmissivity error of central point was analyzed. The dynamic range of the system is from 0.001% to 1%, and the relative error is less than 0.1%.
This paper discussed the effect of GaAs semiconductor material thickness on the device sensitivity, and a new method for measuring the thickness of multilayer semiconductor material such as GaAs by spectrophotometer is put forward. According to the theory of wave interference, the value of wave hollow reflectivity was put into JAVA program and the thickness of multilayer semiconductor material was obtained directly. This method has many merits such as high efficiency, no damage and good repeatability. This method provides the sample semiconductor material thickness error of less than 9%, which meets the test requirement. It is an effective method for analyzing epitaxial material and improving the process of photocathode.
With laser beam directly radiated to the test surface, a CCD was used to pick up the fringes before and after its deformation due to speckle interference. These fringes were translated into the displacement and deformation components and its off surface displacement was obtained. In the optimized algorithm, phase shift technology was adopted to obtain the fringe image of another shift, which separated surface displacement with off surface displacement, the zero order component was removed and projection grating was move by a half period. A three-dimension space model was established through Matlab and four step phase algorithm. The experiment data indicated this solution could measure the three dimension deformation of the object accurately.
Based on Mie theory and HITRAN2008 data, the scattering efficiency and phase function of H2SO4 aerosol at 10m and 0.87m wavelengths were analyzed when the aerosol radius was 2m and 5m. The results show that the cooling effect of H2SO4 particle is stronger at 10m wavelength with higher temperature under same H2SO4/H2O, while there is almost no effect at 0.87m wavelength. The results also show that the cooling effect of H2SO4 particle is weaker when the scattering angles are larger than 173 degree at 0.87m wavelength with higher H2SO4/H2O under the same temperature.
A new method is proposed for detecting the concentration of benzene quickly and accurately with Raman spectrum. Based on the theoretical analysis of benzenes Raman spectrum, the experiments proved that the Raman spectrum peak value of benzene was proportional to the concentration of benzene, which could be obtained by substituting the strongest peak value of 561.4nm into the linear regression equation, with the detection limit of 0.3%.
This paper introduced a spectral imaging detection system which is based on a liquid crystal tunable filter. The system can get the samplesspectral image continuously. Its spectral resolution is up to 0.5nm. We processed and analyzed the image with Matlab software. The system was used to carry out in vivo test of Panacis quinquefolii and its pseudo products Platycodi. We obtained the fluorescence spectra image between 400nm～680nm. By comparing their characteristic spectral curve and calculating the correlation coefficient, we could differentiate the American ginseng and its counterfeit effectively. It provides a method for identifying the authenticity of Panacis quinquefolii.
In the case of neglecting the loss and diffusion process, the effects of temperature on the evolution and stability of a separate screening bright-dark soliton pair formed in a serial two-photon photorefractive crystal circuit are investigated with numerical method. The result shows that a steady-state bright-dark soliton pair are taken shape in a crystal circuit at given temperature, the soliton supported by the other crystal evolves into another steady-state soliton if the temperature change of one crystal is quite small, whereas it becomes unstable and experience lager cycles of compression or break up into beam filaments if the temperature different is big enough. The dark soliton is more sensitive to the temperature change than the bright one in the separate screening spatial soliton pair.
A method of detecting liquid surface wave based on laser diffraction was proposed. A He-Ne laser beam was obliquely incident upon liquid surface wave directly, the wave intensity was controlled by an electromagnetic type exciter and the frequency of the liquid wave was controlled by a signal generator, the laser diffraction patterns from liquid surface waves were collected by a charge-coupled device. The dependence of the diffracted field on the surface waves was derived by theory of wave optics. The experiment result indicates that the proposed method has the advantages of high sensitivity, high speed and non-destructive.
The performance of microchannel plate (MCP) is very important for the resolution of image intensifier. In order to analyze the impact of MCP parameters on the resolution of image intensifier, the transverse scattering of electrons from the output surface of MCP and the elastic scattering of electrons from the non-open surface of MCP were investigated by using electron scattering theory. The results show that the resolution of image intensifier can be improved by reducing channel distance, using multilayer electrodes, increasing the depth of output electrode and increasing open area ratio.
By discussing the effect of light source illumination on measuring modulated transfer function (MTF) of image intensifier, the light intensity through slit used in MTF testing system was analyzed. By adjusting the illumination on slits surface, measuring MTF in different illuminations and comparing it to the maximum output brigtness, it is concluded that the relationship between incident light illumination and MTF of the 3rd low-light-level image intensifier agrees with parabola distribution, there is a maximum value of MTF which restricted by the automatic brightness control (ABC) of image intensifier. The suitable incident light illumination can be specified by this method, which ensures enough signal to noise ratio in tested image intensifier and does not cause image intensifer to saturate.
Free space optical communications have potential applications in the future global communication network. However, performance of free space optical communication is degraded by atmospheric turbulence. Adaptive optics technique can be used to solve this problem of turbulent atmosphere. In this paper, the performance of communication system through gamma-gamma atmospheric turbulence using adaptive optics was analyzed; the simulation results of laser uplink and downlink propagation were presented. The results indicate that the performance can be improved significantly using adaptive optics error compensation technique, and low-order Zernike mode compensation can have good correction.
A bandpass filter based on resonant tunneling phenomenon in three-core photonic crystal fibers (PCFs) is presented. Resonance will occur if the effective refractive indices of the fundamental modes of three-core PCFs match at the same wavelength. By choosing the proper parameters of PCFs, all the three modes could meet the resonant condition. The effective refractive indices of the three-cores match only at the wavelength of 1.55m. As a result, wavelength-selective coupling is achieved. Full-vector beam propagation method (BPM) is employed to analyze the performance of the filter. Numerical investigation demonstrates that the coupling length is 22.8mm, and the bandwidth of the bandpass filter is 8.9nm with the loss of -3dB at 1.55m.
Since the wavelength feature of an optical filter is fixed once it is made, surface plasmon polarition on a flat metal-dielectric interface is used to make a modulated filter. When light beam is focused on the metal-dielectric interface, the surface plasmon polarition (SPP) of metal-dielectric will be changed to modulate the wavelength of the filter by modulating the dielectric index of the dielectric layer. A modulated optical filter is fabricated on an Au film with a set of sub-wavelength nanometer hole arrays. In the experiment, air, alcohol and oil are selected as dielectric layers to test the filter. Unlike the conventional optical filter, this filter can be modulated continuously and conveniently.
Several possible methods for the fabrication of integrated sensors were compared and a novel hybrid integration method was developed. To realize the hybrid integration of the pyroelectric detector with the signal readout circuit (ROIC), it is proposed to use the anisotropic conductive tape as the interconnection between the sensor and the ROIC. The method showed good compatibility for the fabrication of integrated multi-sensors. Single crystal LiTaO3 (LT) was used as the pyroelectric material for demonstration purpose. The LT wafer was thinned with mechanical grinding method. 3M z-axis adhesive film 5552R was used as the anisotropic conductive film to realize the interconnection between the sensor and the ROIC. Results showed that the LT thin film had similar pyroelectric properties as those of the single crystal wafer. The integrated pyroelectric detector showed good thermal isolation characteristics and high dynamic response.
According to the designed requirements of UV systems, a low-pass filter was studied and developed on K9 glass substrates with high reflectivity at 254nm and high transmittance in visible spectrum. According to the film designed theory, low-pass interference filter film was obtained by optimizing Needle method. The electron-beam evaporation materials of HfO2 and MgF2 were studied. The splash was solved and the absorption was decreased. By using Kaufman ion source, the film density was improved, the drift of spectral curves was solved and the quality of the film was improved by optimizing the process parameters.
In order to improve the sensitivity of single-photon detection systems, InGaAs/InP avalanche photodiode (InGaAs/InP APD) is used in the design of single photon detector of quantum communication. Single photon detector bias generation circuit in gate pulse mode, single-photon signal amplification circuit, single photon signal detection circuit and temperature control module were realized. By selecting high-precision OP37 preamplifier and precision comparator AD8561, quantum efficiency was increased to 18.3%, dark count was controlled within 4.1 10-6/ns.
A CCD, a computer and a traditional microscope are combined to realize the non-destructive microscope observation of specimens. The hardware and the software of the system are introduced, with focus on the assessment of image definition and the key algorithm of image reconstruction, and VC++ program is used to validate and implement. The definition evaluation function is specified by gray variance algorithm, and the definition of the image is indicated by gray variance. The non-destructive analysis instrument collects a lot of images of the specimen in different distances by moving the plate controlled by accurate mechanism. It finds the clear parts of the image by using definition evaluation function, and synthesizes them into a complete clear image.
Optical dither is introduced to improve lock-in for better performance of laser gyro. The influence of the back-scatter light on the lock-in of laser gyro was investigated, and the basic principle of back-scatter reduction and lock-in improvement with optical dither was expounded. Optical path variation under optical dithering was carried out by perturbation and the best theoretical amplitude of optical dither for lock-in was deduced. The experiments were done according to the concept. The result showed that the effect of optical dither was similar to mechanically dithered noise, which could improve the bias stability of gyro. Therefore, optical dither is suitable for laser gyro to improve the lock-in.
During the measurement of the dynamic laser goniometer(DLG), its very important to have a collimation device named null-indicator (NI) to establish an accurate zero point, the high speed response and the accuracy of NI are very important. This paper established an error equation of the output pulse, introduced the optical design of the auto-collimation NI and the interference NI, and obtained their errors. The accuracy of the interference NI is 0.05, the auto-collimation NI is 0.23. The interference NI can meet the precision requirement of the DLG.
During the laser surface texturing, the high intensity of the laser beam pulse on the metal material surface results in the negative heat effect. A new processing approach of single pulse one time, repeating at intervals is presented in this paper. The movement control card and self-developed Qswitch card were programmed for coordinated control between laser system and movement control system. The new processing process was realized by the coordinated control and the technique of acoustic-optic Q-switched and servo control. The system was controlled by industrial computer. With the new approach, the micro-dimple and groove can be easily fabricated and the negative thermal effect can be reduced. The required micro-structures can be produced on the surface of friction units.