2005 Vol. 26, No. 5
After investigations on the methods usually used in measuring the spatial light intensity of lamps, a new test method for spatial light intensity is proposed. A data model, which can automatically align the spatial light intensity of a lamp, has been established. The structure and principle of the system for automatically measuring the spatial light intensity are introduced. The threedimensional figures of spatial light intensity were drawn with a 2D scanning system and a dedicated test softwave (Matlab). With the technology we can rapidly derive the lightintensity distribution in x and y axes, and the divergence angle of the lamp. An example of measuring a projection lamp is given in details. The ideal results, among which the peak light intensity is 2634.4 cd and the divergence angle is 15.25°， are acquired in the experiment while a lamp is 5m away from the detector of the system.
A test equipment for boresighting the three optical axes of the groundbased observing and aiming system that consists of laser, day light, IR(or low level light) sensors is introduced. Its test principle and process to measure the optical axes boresight of the three sensors mentioned above are described in details. During the design of the line graticule, we did not use the ruling technique on glass, but selected Wwire to make the LOS and welded two electrodes at the two ends respectively. This design can avoid any possible error caused by the replacement of the crossline graticule observation when a multispectral optical system is tested. This equipment provides a foundation for precision adjustment by detecting and testing of the optical axis boresight in the multispectral optical systems, accordingly making the optical axis bore sight of the three optical sensors fulfill the boresight accuracy requirement of the system instrument and ensuring the direction consistence of observation aiming and rangefinding.
It is understood that the characteristics of the atmospheric attenuation materials (haze, smoke, dust or aerosol) are important factors for applications such as military conflict, environmental protection and prevention of forest fire. However, the current atmospheric attenuation measurement method for laser transmittance could not achieve accurate results because it does not take the fluctuation of the laser pulse energy into account. In order to overcome such problem, a new test scheme and data processing method is designed. To take the laser energy fluctuation into consideration, a beam splitter and a laser receiver are added to the traditional design for monitoring the change of laser energy. Therefore, the emitting energy of the laser pulse is monitored and it can be used for inverse data processing for far field reception energy. Finally, the measurement accuracy of the transmittance is significantly improved and reliable data are provided to decision makers.
A fluorescence spectrometer which can measure pesticide concentration is designed by using a xenon lamp as excitation lightsource，employing optical fibers to transmit and detect fluorescence and combining with CCD spectrumdetermination technology based on fluorescent characteristics of carbaryl that can emit fluorescence as it is excited by UV rays.Moreover,the rapid measurement of carbaryl residues in cucumbers is implemented with a steadystate fluorescent spectrograph and the new system respectively. The results indicate that the linear concentration range is 0.0～120.0μg／L for carbaryl, the detection limit (LOD) is 5×10-7μg／L，the linear correlation coefficient r is 0.9991 as the excitation wavelength is 319nm and the fluorescence emission wavelength is 647nm. The data prove up to the hilt that the instrument meets the demand of fluorescence detection.
In the study of X ray coded aperture imaging system, it's known that the point spread function(PSF) decides the performance of a imaging system. MTF can be deduced by PSF and the filter used in image reconstruction can be made thereby, so the accuracy of PSF directly affects the performance of reconstructed image. In this paper, based on the scalar theory， PSF is obtained theoretically under the condition of considering diffraction effects. The filter of the optical system is fabricated based on PSF. The filtering processing for the frequency distribution of coded overlapping image was done with Wiener filtering function and then the reconstructed image was obtained through the inverse Fourier transformation.
The Fraunhofer diffraction phenomenon on the complementary structure of Sierpinski carpet grating is discussed on the basis of FresnelKirchhoff theory and Fourier analytical method. The frequency spectrum,amplitude and lightintensity functions are derived. The diffraction phenomenon of grating is simulated by use of the MATLAB software, and the curves of its frequency response characteristic are plotted. The result shows that in diffraction patterns of allorder gratings, the higher amplitude part is concentrated in the center area of the receiving screen and the lower amplitude in the area around the center, but in the further area far away from center it tends to 0. In the whole, the diffraction patterns manifest the obvious fractal characteristics as well as the basic features of the diffraction.
The signal transfer function(SiTF) is considered as the most basic and important parameter to evaluate the characteristics of the infrared thermal imaging system,and is the linear portion of the responsivity function. The information on gain, Linearity, dynamic range and saturability of UUT can be obtained from the test curves of the responsivity function. The Optic Metrology Station is currently engaged in a research on the evaluation of the synthetic characteristic of the infrared thermal imaging system．In this paper,the CEDIT IIA thermal imaging system is measured with the diblackbody and reflected target system. The equipment can ensure the uniformity and stability for the backgraound radiation，and also ensure it against the effect of the ambient temperature，so the accuracy and reliability of measurement are improved. Finally, according to the practical experience many years，the author lists the causes for variations in the measurement of SiTF.
Experiments indicate that the traditional methods of infrared image detection are not ideal because of the bigger noise of infrared image. The algorithm based on multidegree andorientation gradient fusion is presented to recognize the dotobiects in the lowcontrast infrared image polluted by heavy noise and stray waves. Experiments for detecting dim dottargets with the above method are carried out. The result indicates that the detection performance of the multidegree andorientation gradient fusion is better than that of the adaptive filter and medium filter. The algorithm is especially suited to the surveillance systems of low frame rate and can detect the dottargets with signal to clutter ratio equal to 1.
The temperature differential characteristics of inner and outer faces of absorbing cavity used in absolute calorimeter laser energy meter is studied theoretically and verified experimentally. Firstly, with the thermal conduction equations of second homogeneous boundary and nonhomogeneous boundary condition,we gained the temperature distribution in and after the heating process of the absorbing cavity. Secondly, through the simulation for the process of laser heating of the absorbing face, we obtained the expermental data of the temperature difference.In the end, with numerical simulation method, the theoretic results are analyzed numerically. The experimental data is very close to the theoretic analysis result, which proved that though fixed temperature difference is existed during laser heating, it will be soon reduced and the absorbing cavity will reach the heat balance after laser heating is finished.
This paper introduces a medium and long-range optical-fiber(cable) communication system which can be used in data tranmission of point-to-point or between two local-area-networks. Using optical-fiber as a transmission media, the system is immune from electromagnetic and nuclear radiation interference,and can be applied to some special environments or places unaccessible by human. While the microcontroller is used in the transmitter and receiver in this system,it makes a feature of simple structure, high reliability, the powerful data processing function and flexible design for baud rate of serial port, and fits in with the need of different transmission rate of serial port. It meets the requirement of the remote-control-and-monitor for medium,longrange signal transmission in civil and military fields. Therefore,it has a great potential in the fature.
The autoalignment technique is studied for the PM fiber (PMF) of matching refractiveindex(MRI). The polarization observation by lenseffecttracing technique(POL) is introduced. Based on the POL,an autoalignment system is designed and its performance is then tested. Different lightintensity distribution characteristic is found on the different observation surfaces in a series of experients. The widest range of adjustment is achieved when the observation surface corresponds to a lightintensity distribution with five characteristic points. This means it is easier to focus.The fivepoint method is presented after analysis of the curves of the five characteristic points with respect to the azimuth angle of the optical fiber.By comparison with the POL,this method is easier to be realized and has higher measurement accuracy,so it is suitable for autoalignment system.
Through analyzing some measurement procedures of refractiveindex profile of singlemode and multimode fibers; their essential differences are obtained. Since the core of singlemode fiber is very small, its propagation mechanism can be analyzed only by the wave theory,and the measurements with the farfield and nearfield methods are all based on the scalar Helmholtz wave equation, that is the refractiveindex profile measurements for singlemode fiber are according to its basic transmission theory. Whereas the core of multimode fiber is larger, the ray theory is appropriate to analysis of its propagation principle. The reason is that the multimode fiber refractedray method and nearfield scanning method are all based on the numerical apertures of various radii and the corresponding refractive patterns and propagation patterns.
Ba1-xSrxNbyTi1-yO3 thin film (45nm) deposited on a SiO2/Si substrate by the argon ionbeam sputtering technique is employed to fabricate planar thinfilms resistors used in the IC standard technology.The absorption spectra of the Ba1-xSrxNbyTi1-yO3 thin films, the photocurrent under different illumination and voltage, and the photocurrentfrequency characteristics of the filmresistors are studied.The experimental results show that Sr and Nb doped in BaTiO3 produce the impurity energy level in forbidden gap. Therefore,the energy gap drops down to 2.7eV and there are some consecutive absorption peaks in the visible region. The film has good photobehavior in the range from near ultraviolet to visible light, and it has high photosensitivity, high photoconductive gain and high linear illumination performance. While the illumination intensity is weak, the variaion of the current will be large, which is called onecenter recombination process; while the illuminaion is strong, the variation will be smooth and more linear, which is called twocenter recombination process.In this paper, the frequency response of the Ba1-xSrxNbyTi1-yO3 thinfilm resistor is investigated. The lifetime of optically excited carriers is 27ms at 200Lux.
Since the global optimization seeking method used in the traditional multilayer design is very slow and difficult to get an ideal film system, an optimizing method based on the wellknown Frensnel equations and simplex optimization is used in the design of optical element of multilayer for soft Xray and Xray. The highest theoretical reflectivity of a soft Xray periodical multilayer at different wavelengthes is calculated, and the results are same as those calculated by the random search method, but the computing velocity of the simplex optimization is much faster than the random search method. The simplex method is also used in the optimizing design of the Xray supermirror, and the ideal result is obtained.
A software of thermal analysis，Icepak，is used to calculate the heat exchange in enclosing channels of LAMOST.The effect of the thermal radiation and conduction of the enclosed wall surface on the whole temperature field is emphatically analyzed.Based on the cooling scheme of ventilating duct, the models of the thermal radiation and conduction are set up respectively, and the heattransfer structure on the walls in the dome is described with them. The temperature filed distribution of the main optical assembly (focal surface) is calculated with a simulation method when the thermal radiation and conduction on the wall surface are increased, and the calcution results are compared and analyzed.The numerical calculation and simulation results show that the effect of the wall surface heat transfer on its internal temperature field is not serious, the cooling shcheme of ventilating duct can control the maximal temperature gradient on the focal surface within 0.4℃/m successfully and the characteristic structure of enclosed wall is effective on the heat transfer. The conventional cooling project is still powerful with the new structure of the walls. The thermal analysis and simulation are helpful to the theoretical study on the seeing and the design of the LAMOST dome.
With the development of photonic technique,the novel optical function glasses which could change the polarization, frequency, coherency and monochromaticity of light, produce and detect photon, become a main development subject in optical glass field. In this paper the sgnificant development of optical glasses and their applications in the fields of optics and information technology are introduced. The development trend and the characteristics of the main optical functional glasses such as nonlinear opticl glass, gradient index glass, laser glass and other optical function glass are pointed out. Finally the progress made by chinese optical glass industry has been reviewed.