2008 Vol. 29, No. supp
On the basis of adjustment experiment of optoelectronic products, it is pointed out that the drift of optical axes and the reliability of systems are main problems affecting product quality. It is very important for adjustment of the systems and improvement of the product quality to solve the above problems.
The test methods of the target identification and location for reconnaissance vehicles are elaborated systematically aiming at the trend that most of the modern reconnaissance vehicles are equipped with the advanced reconnaissance systems, such as visible CCD imaging system, infrared imaging system, laser rangefinder, inertial navigation system and satellite location system. The methods refer to the test methods of testing field, recognition range, laser rangefinding, orientation/location and the method of data processing. The synthetic performance of reconnaissance vehicles can be assessed and the vehicles can be accepted according to the test methods.
The imaging principle and characteristic of the synthetic aperture are analyzed. The model of the detecting system was established in combination with synthetic aperture and theodolite. The influence of the random vibration of the detector on imaging quality was analyzed. The random vibration experiment was implemented for the tracking process. The random vibration signal of the detector was tested for the tracking process of the turret. It is pointed out that the MTF of the synthetic aperture imaging system as an evaluation index for the imaging quality can prove whether the established system can be applied to the spatial imaging after the calculation and simulation analysis.
The two-dimensional rotation platform is one of the important subassemblies of a certain reliability test equipment. The azimuthal and pitching movement of the moving target can be simulated by two-dimensional rotating of the reflector fixed on the rotation platform. The design of the two-dimensional rotation platform is offered, and its CAD diagram is drawn. The stable design of closedloop servo system was carried out to match its parameters of the mechanical system based on the design of two-dimensional rotation of the reflector. By the characteristic analysis for the movement of the two-dimensional rotation platform, the load torque corresponding with its construction was derived to select the appropriate operating motor and achieve its stable design of the closedloop servo system.
Since the crystal ZnSe is soft and low transparent, a thin-film coating must be deposited on its surface to increase its transparence and machine strength. A method of depositing anti-reflection film on the surface of ZnSe substrate is introduced, which adopts ion source to deposit zinc sulfide (ZnS) as a combinative layer of crystal zinc selenide (ZnSe). The two kinds of different fluoride material were evaporated as a low refractive index and protective layer by using the total evaporation technology. A film system which meets the standard of environment and rigidity was prepared. Besides, its average transmissivity attains to 98% at the range of 3μm～5μm.
Based on PID control method and SMC arithmetic, a double-mode APR applied to nonlinear position servo system is investigated. The simulation results indicate that the PID method and the SMC arithmetic can help the servo system to behave a better performance.
The principle and method of ultraviolet detection are briefly introduced. The application prospect of the ultraviolet detection technology in military is predicted by analysis of the performances of the ultraviolet detection elements and imaging devices.
Alkaline and acidic solutions are used respectively in textures of monocrystalline and multicrystal silicon solar cells due to anisotropic etching of alkaline solutions and isotropic etching of acidic solutions. Two different textures on the surfaces of monocrystalline silicon are fabricated by using two solutions. According to the analysis of the performance of monocrystalline silicon solar cells with different texturing structures, the feasibility of substituting acidic solution instead of alkaline one is discussed.
Transparent conductive thin films are widely used as semi-conductor optoelectronic materials. Indium tin oxide (ITO) transparent conductive thin films have some characteristics, for instance, rare reserve, high preparation cost, inherent low stability, toxicity, and complex preparation techniques. Compared with the ITO films, the aluminum-doped zinc (ZAO) films have many advantages such as lower manufacturing cost, simple preparation techniques, non-toxicity and higher stability. The ITO films will be replaced by the ZAO films. The ZAO films have a brilliant prospect of development and application. The recent progress in research on ZAO films is reviewed.
The photon-counting imaging technique, which can detect and intensify the faint signal under the low-light-level condition, has beeb widely used in the military, astronomy, physics, chemical, biology etc.fields with the development of LLL image intensification technology and weaklight imaging elements. Introduced The working principle , characteristic and application of the photon-counting imaging are introduced. The effect of the niose on the photon-counting imaging quality is discussed.
More and more attention has been paid to the application and research of infrared image in recent years because of the uniqueness of infrared images. But its application has been restricted greatly due to the inherent defects, such as bad contrast, fuzzy edge and weak veins etc. And the relevant reports of the research are seldom. The preliminary research in the aspect was made. Two infrared pictures taken from two proper angles with Ti30 infrared instrument were processed through two methods: contrast self-adaptive histogram equalization and edge enhancement. At last, stereogram pair by the principle of two eyes fusion was observed. Experiment results show that the distinct space geometry distribution of every object can be obtained through observing the stereogram pair.
The passive and active infrared thermal imaging technologies were analyzed based on the Stephen-Boltzmann law（W=εσT4）. The passive infrared imaging technology adopts a thermal camera to receive the infrared radiation of an object, and the active infrared imaging technology, based on the equation of heat exchange, researches the interaction of variation thermal sources with medium material and geometrical structure. The active infrared imaging technology obtains the information of material homogeneity and the structure under its surface to implement the non-destructive testing and inspection by monitoring the temperature variation of material surface through flashing light, ultrasonic wave, laser, THz wave, hot blast, electric current or mechanical vibration. The applications of both technologies are compared according to their principles.
With the rapid development of infrared technologies, optical systems with dual FOVs have been applied in all kinds of fields. The system with dual FOVs belongs to the simple zoom optical systems. The realization modes of zooming comprise of the independent zooming, rotary zooming, insert zooming, axial zooming and so on. Based on the analysis of zoom modes, a new mode of zoom optical system has been developed, which realizes the dual FOV optical system by sharing secondary imaging lenses. By the mode, the FTM value of the dual FOVs can be made to approach to the diffraction limit, and the accuracy of the optical axis can be improved. It decreased the moving mechanisms and reduced the difficulty of the system assembly.
The wavelet transform is a major way to process the optical information. A filter designed according to the wavelet function is put on the Fourier plane in an optical 4f system, the way which is an usual solution to implement optical wavelet transform. A grating was taken as the filter of the system to implement the optical wavelet transform. The grating and the whole system were designed according to the relationship between the grating parameters and the wavelet threshold function, and by the aid of ZEMAX software. The simulation result shows that the wavelet transform can be implemented with the grating as the filter of the 4f system, and the grating can character the wavelet functon.
Based on biological vision system, the variable focus liquid lens without any mechanical moving unit has lots of advantages, compared with conventional zoom systems, such as smooth zoom, little volume, light weight, simple fabrication and low cost. Therefore, it will have many potential applications in many fields. The variable focus liquid lens can be realized with three ways. The mechanically-actuated variable focus liquid lens, whose liquid surface curvature is controlled by a stepping motor, was designed and tested. The tested result shows that the variance of the focal length is accordance with the analitical result of CODE V. By putting the liquid lens in front of a fix-focus digital camera, the defocussing range of the system can be adjusted, and the zoom imaging can be realized. Finally the liquid lens has shown a satisfactory effect of imaging.
Distortion is the aberration of the principal ray ( when the chief rays from image and object are not parallel, the point of intersection of image chief ray and ideal image plane are not coincident with the point of the ideal image). Since the lens distortion impact directly on the image quality of cameras, it is essential to measure the lens distortion. The distortion of a panoramic camera lens was measured with the equipments available. The measurement results are presented.
The relative attitude of the return cabin and parachute is an important factor for the landing of the return cabin, and is an important basis for designing and improving the space vehicle. since the size limitation of the return cabin,the measurement accuracy of traditional multi-view intersection method could not satisfy the need of the project. A new method, collinear restrict method, is proposed for solving the problem. With the new method, the camera on the top of return cabin acquires the images of the parachute, and then adds the restrain information for acquiring the relative attitude. The simulation results show that the new mathod has great capability in accuracy and antijamming.
Aiming at the problems difficult to operate the measurement system and calibrate a system in conventional 3-D outline measurement, a new method to measure 3-D outline of an object based on projected fringe patterns is proposed. The measurement principle of the system is presented. The calibration method of CCD camera and calibration process of the projector are discussed. An idea to solve the spatial coordinates with phase matching is proposed. The restraint of parallelism and perpendicularity of conventional structures was eliminated. The system calibration and measurement process are simple, and easy to be realized in engineering. Theoretical analysis and measurement results show that the technology is robust and available.
The entangled photon pair in quantum communication experiments is produced by laser pumping nonlinear crystal. In the experiments, it is necessary to adjust the optical axe of uniaxial crystal to the vertical plane. Usually, the optical axe direction is determined by polarizer, but this method can only give the two engine directions of the crystal. The relation between the direction of the optical axe and the trend of the interference fringes was analyzed. The experimental method and results for calibrating the optical axe direction of uniaxial crystal are offered. The experiment results show that the optical axe direction is perpendicular to the trend of interference fringes.
In order to implement the effective anti-reconnaissance to unmanned aerial vehicles (UAV), the feasibility of effective monitor for UAV by a laser detecting system was analyzed, the model of laser transmittingreceiving system and optoelectronic imaging system of UAV was established, and the characteristics of specular scattering light of the UAV imaging lens and reflecting light of focal plane were simulated. Taking a UAV at the altitude of 10,000m as an example, the application feasibility of the detecting system with two kinds of reflecting light was analyzed, and the available incident angle range of laser detection was obtained. The characteristics of light distribution on the photosensitive face of the detecting system and reflecting light change when the detecting laser was dynamically scanning were analyzed. The results show that the intensity of the focal plane reflecting light from imaging lens is much higher than that of the specular scattering light, and it has a very good characteristic of returning to the original path. And also it can detect and locate the target (UAV) by the aid of the reflecting light from the focal plane at the FOV coverage range of the imaging system on UAV.
Lidar is a high-tech which combined laser technology with traditional radar technology. As lidar has the advantages of narrow beam, high measurement precision, high resolution, high anti-jamming capability, and can measure target attitude and image the target, it has been widely used in proving ground abroad. Its application prospect is analyzed based on the characteristic of lidar technology and its superiority of performance compared with traditional optical measurement equipments.
Because of the absorption and scattering effect of water, it is always very difficult to explore under water with common light source. With advantages of the characteristics of laser, the absorption and scattering effect of water is reduced. Taking He-Ne laser as the light source, the reflection coefficients of the objects were detected in the air and underwater to make sure the feasibility of underwater exploration with laser. It is found that the experiment result is good after comparing the detected results with the reference data.
The incoherent combination of several pulsed YAG lasers is studied in the paper. The methods to obtain high peak power laser by the incoherent combination and the fields of their application are discussed. The method of the laser pulse precision time-domain synchronization combination, computer simulation results, experiment data and the blinding effect of laser on CCD sensors in engineering applications are presented.
The ablation damage caused by laser beam to targets is investigated. The laser disturbance and ablation damage principles are analyzed by the aid of the isochronal irradiation at different power, laser irradiation at different incident angle and solar cell destructive tests. The variation of the solar cell output power with the laser irradiation time is related with the power density of incident beam. The power density inferior to the threshold may leads a decline of solar cell output, which is restorable and temporary. The consequential ablation damage is caused by heat effect of laser. In contrast, the power density in great magnitude may lead a serious ablation damage that is not restorable.
Since the birth, the FOG has been put into application in many ways, for its many advantages such as simple structure, stability, low cost, small volume and low weight. But with the effect of much noise, the stability of the FOG is still not good. In order to improve the stability, the data of IFOG are analyzed with Allan variance method and each error coefficient is identified. Furthermore, a random drift error model for IFOG was built by the aid of the time sequence analysis and the error model of the FOG′s drift is expressed as ARMA(2,1). At last, onestep predict curve of data is assessed. The adaptability of the error model is discussed. The conclusion provides supports for error compensation of IFOG.
The wavelength demodulation of the measurement signal is one of the key technologies for fiber Bragg grating sensors, especially for the dynamic signal measurement. A Bragg grating dynamic strain sensor taking a long period grating as the linear edgedfilter for demodulating the wavelength signal was developed. The meaasurement system has the advantages of simple structure and good measuring repeatability, and can carry out reltime distortionless measurement, whose dynamic strain range is 0～5000με and the strain resolution reaches 3nε/Hz. The design method of the prob of the fiber grating sensor and the method for gluing the fiber Bragg grating with the strain field are analyzed.The dynamic characteristics of the strain sensor are tested with a PZT.
The principle of closed-loop FOG detection of triangular waveform phase compensation and a new detection method are analyzed. For the measurement of rotation velocity on the triangular waveform phase modulation, the expressions of rotation rate and rotated angleθ were deduced. Then the multiperiodic rotation rate measurement was carried out. Through the expansion for the dynamic range, the measurement method was obtained when the rotation rate was at high or extremely low range. The influence of the parameters on the rotation velocity was analyzed. With theory analysis, a new design was implemented by using MCU to realize the signal detection. The design is simple and the cost is low. The flow chart of the circuit is presented. The factors which affect the system measurement precision are also analyzed, and then the solution is given.
Since the ring fiber bundle has the advantages of coaxial illumination, uniformly emitted light and shadowlessness, it has been widely used in machine vision, optical instruments, image processing and so on. Proceeding from the illumination mode of ring fiber bundles, the fiber bundles of single ring, double rings, multi rings, small obliquity (0°～30°), large obliquity（30°～60°）and axial direction in direct illumination mode, and the fiber bundles of dome-lick structure, diffused structure and leaky structure in indirect illumination mode are elaborated. The characteristic of the structures and applications of the ring fiber bundles are summarized and the notes in manufacturing the ring fiber bundles are presented.
Bragg condition equation is one of the most important fundamental theories for FBG sensor, and has important value for the study of the mechanism of FBG sensors. The reflection spectrum characteristics of FBG were studied and the Bragg condition equation was obtained by the aid of the light interference principle. The analysis shows that the result derived by the light interference principle is consistent with the one deduced by the coupled-mode theory.
By the analysis of several common filtering methods, a filtering method of diffraction fringes is used based on the spin filtering with a thorough consideration of the special needs of light diffraction method to diffraction fringes. The filtering results of simulated diffraction patterns prove that the spin filtering with curve windows is effective in the noise filtering of diffraction patterns and keeps the available signal of patterns at the same time. It can improve the measurement accuracy of particle size.
In the process acquiring three-dimensional information from the twodimensional picture, the camera calibration is one of essential steps. Moreover, the result of the camera calibration will affect the performance of the machine vision system to a great extent. In the camera calibration process, the camera imaging relations are accurately described using the nonlinear camera model to gain the more accurate camera parameters for improving the performance of the machine vision systems. Finally, the simulation result of the nonlinear camera model calibration is given.
The virtual reality (VR) technology, based on computable information can generate an immersed interactive environment. The key issue of the VR technology is to precisely establish a model of the virtual objects and environment, simulate the 3D space environment with motion, sound, vision and tactile sense by the aid of the computer hardware and software techniques, and make the user to be affected by the simulated world, allowing him/her to directly view and interact with the varying virtual environment. The VR technology was compared with the computer simulation. The great significance of the application of computer simulation in VR technology is elaborated. The key points of the VR technology is discussed. Some view points about the VR technology are proposed.
The relation between sub-apertures configurations of optical sparse-aperture imaging systems and MTF is discussed. A new method, based on Monte Carlo inversion, for the aperture configuration optimization of sparse-aperture systems is proposed. The number of the aperture models under test is greatly reduced through discrete model space and optimization speed is improved through searching the model space by alternate random search and systematic search. The effectiveness of the new method was evaluated and analysed by computer simulation experiment. The optimality results of the three, four, five, six and seven sparse-aperture structures are accordance with the results of the other references. The optimization efficiency of the method was tested simultaneously. The test result shows that the method has higher optimization efficiency.
The stable and clear diffraction patterns were obtained by an experiment of laser diffraction from 1-D liquid surface acoustic wave (SAW) excited at low frequencies. When the incident direction of laser and the propagation direction of SAW are in same plane, it is observed that the distribution direction of the diffraction patterns is also located in this plane. However, when the incident direction of laser and the propagation direction of SAW are not in same plane, the distribution direction of the diffraction patterns is not located in the plane with the incident light. The formula of laser diffraction from one-dimensional SAW in oblique incidence was theoretically derived by the aid of the establishment of the proper coordinate system. Furthermore, the relation between the distribution direction of the diffraction pattern and the incidence angle of the laser was also achieved. The wavelength of SAW was obtained by the calculation of the data from the experiment and it agrees with the results obtained by the other methods.
The twisted nematic liquid crystal can be regarded as a congruence of multilayer birefringent wafers, and the optical axes of the adjacent wafers rotate consecutively a small degree. A reflective model of the linear polarized light in the twisted nematic liquid crystal is proposed. A mode which describing the light reflectance in this liquid crystal is presented to conveniently discuss the propagation of the transmitted wave through a liquid crystal. The method of the correct adding of the electronic field is used to investigate the light propagation property in the twisted nematic liquid crystal. The analog computation shows that if the linear polarized light is vertically emitted into the liquid crystal, the intensity of transmitted light depends on both the wavelength of light and the structure of this liquid crystal. The experimental results show that the intensity of the transmitted wave is different at different voltage. In other words, the intensity of the transmitted wave with different wavelength is related with the structure of liquid crystal.
In combination with the measurement technology of the stereo machine vision and the measurement principle of CCD, a new method to measure the sighting line parameters of the helmet-mounted sight is presented, the possible error source is analyzed, and the solution is proposed. Based on the mathematical model of bore-sighting measurement for helmet-mounted sight, the characteristic points on the helmet were constructed by means of machine vision to acquire the characteristic point coordinate, and then resolve the parameters of the boresighting. The structure of the system is simple. The measuring accuracy can satisfy the accuracy requirement of resolving the bore-sighting parameters for the helmet-mounted sight.
The coloration index Ra is one of the important aspects of evaluating performance of light source. A method of improving coloration index of white LED with complementary color is put forward. According to the calculated maximum of the coloration index, the main wavelength and light intensity of the complementary light can be confirmed. To make sure the possibility of this way, the complementary colour was carried out for a white LED called LE W E2A made in OSRAM. The result indicates that the coloration index of the LED is improved from 79.59 to 85.76 after adding the homogeneous light to one certain area, and the coloration index of compound light is improved to 93.01 after adding the homogeneous light to two claimed areas.
The linear propagation, law of refraction, law of reflection and lens imaging, described by the geometrical optics, are its most basic and classical contents. Some of the classical results in the geometrical optics were resolved through the ideal paraxial optical system by the matrixing, and the transformation matrix of the optical propagation for the five optical phenomena was derived.