2012 Vol. 33, No. 6
A 6-piece lens used for infrared warning or searching system was designed, based on the 4806 long wavelength infrared(LWIR) detector with the F number of 1.27. The designed lens has 325mm focal length, 1.35 F number and 1.05FOV .The transmittance is 76% and the cold shield efficiency is 100%.
High junction temperature of LED has been the technical bottleneck of the development of high power LED. With the rising of heat flux density, the simple straight fin heat sink can not meet the requirement of heat dissipation in natural cooling conditions. We set up a heat dissipation system based on the heatpipe technology, analyzed the heat transfer mechanism and the route of heat dissipation ,then established the model of thermal network according to the physical model and calculated the thermal resistance of each part, finally got the total theoretical thermal resistance and the LED junction temperature. At the same time, we made a simulation analysis of this heat dissipation system by using the finite element method. Simulation results of the LED module(0.025 m0.025 m0.005 m) with 30 W input power show that the junction temperature of LED stable is at 58.19℃, less than 65℃ which is the deadline of requirement. The cooling system applying the heat pipe meets the requirement of design well. The theoretical junction temperature calculated by thermal model is 57.43℃,only 0.76℃ less than the simulation result, implying the error is only 1.31%,this validates the theoretical analysis calculation ,which has guiding significance for practical engineering design.
In modern information warfare, the testing technology is very important to the development, use and maintenance of the optoelectronic reconnaissance and tracking pointing equipment. The development status of optoelectronic reconnaissance and tracking pointing equipment testing technology at home and broad was discussed from four aspects. At present, the comprehensive digital measurement of visible light and low light level imaging performance parameters has been achieved. The measurement uncertainty of image surface uniformity and distortion calibration performance parameters achieves 1% and 0.2% respectively, the infrared thermal imaging system performance parameters such as minimum resolvable temperature difference (MRTD) have began to be measured by the means of objective evaluation, the maximum range allowable measuring error limit of laser ranging system performance parameters such as maximum range is less than 1%. In addition, the measurement uncertainty of the multi-axis consistency can achieve 2. Our future research in this field will be focused on the development of a variety of calibration means which run fast and accurately and the promotion of the shimmering, white, infrared and ultraviolet optoelectronic imaging testing technology, as well as establishing and improving appropriate testing standards and securing systems.
Aiming at the disturbance characteristics of vehicle photoelectric stabilization platform and the separation characteristics of active disturbance rejection control(ADRC) algorithm, an active disturbance rejection control system was provided with integral compensation for improving the servo performance of vehicle photoelectricity stabilization tracking system. Practice swing testing shows that the ADRC method ensures the stabilization precision of platform is 0.129 mil（1）, and improves the automatic tracking performance. It is an excellent controller for stabilization platform tracking circuits.
In order to solve the problem that the alignment calibration method of aiming at stars in naval gun weapon system is easily influenced by the weather, an optical alignment calibration method with need of reference object for the integrated weapon system of radar (photoelectricity) and naval gun is proposed. The gun barrel axis is led out by the laser beam and translated parallel to the radar (photoelectricity) receiving window through the alignment optical module, then the angle difference between the radar axis and barrel gun axis is obtained to be calibrated. Test and experiment results show that the method is characterized by simple operation, high efficiency and real time, it has the alignment calibration error no more than 0.5mrad. This method is impacted less by the weather and environment conditions compared with the method of aiming at stars, and has a significant role to give full play to the operational effectiveness of gun weapon system.
To attaina ground resolution of 0.2 m when flying at an altitude of 10 000 m, we designed a high-resolution CCD aerial photography lens with long focal length and catadioptric optical path. In this design, we used ordinary glass to correct the secondary spectrum from large diameter and long focal length. In the condition of the large area array, high resolution CCD as the receiver with a single pixel size of 8 m and an effective size of 36 mm48 mm, the modulation transfer function of every FOV approached to the diffraction limit at 60 lp/mm, which met the image quality requirements. Finally, it achieved the alltime observation and measurement with wide band range of 470 nm~950 nm.
We made a brief summary of the development and application of free-form surface, introduced the research status of free-form surface in space optical system abroad, described the characteristics of three kinds of free surface mathematical models and the aberration balancing ability, focused on the aberration characteristics of free-form surface optical system compared with the axisymmetric system and plane-symmetric system. In addition, we presented the aberration controlling and evaluation method of the free-form space optical system. Finally, we gave the design results of the freeform surface multi-spectral camera adopting Zernike polynomial representations. The results show that the imaging field of view is 76, it adopts telecentric optical path design ; the wide field of view MTF is superior to 0.56, and it is applicable for space multispectral imaging.
The role and status of star sensor and simulator in the determination of spacecraft spatial attitude were researched, as well as the basic working principle. According to the colorimetry theory and formula, how to form various synthesis light source color with red-green-blue(RGB) color was analyzed, and the mathematical equation was deduced between the RGB color coordinates and brightness coordinates with a synthesized source chromaticity. On the basis of theoretical research, a kind of static multi-star simulator circle controlled light source which used full-color RGB lamp as the light emitting device was put forward. Under the condition of laboratory, the output light power and wavelength stability of the circle controlled light source system were tested in experiments, and the experimental results were given. The experimental results showed that the short-term stability of the light sources was always better than 1/1 000.
With the aim to measure the radius of curvature deviation of spherical lens online in workshop, based on the laser testing technique, a solution of miniaturization sphericity interferometer system without precision guide was proposed, and the principle of the system was analyzed. After the analysis by Zemax simulation, the system could get the astigmatic and local deviation of lens, and measure the radius of curvature deviation fast. The results show that the precision of radius of curvature deviation is better than 0.01%. Compared with the existing sphericity interferometers, the new system is particularly fit for noncontact online testing in workshop, and has advantages of compact structure, no precision guide, high efficiency and low costs.
A design algorithm that can realize the collimating beam of light was proposed based on free-form surface lens,and an illumination optical system for a single LED source was designed based on the algorithm. The equations of the points on the profile curve about the back surface of the lens were established .By using the iterative method and Matlab programming, a number of discrete points of the free-form profile curve were calculated and fitted to optical entity with the SolidWorks software.Then the optical entity was imported into TracePro software for non-sequential ray tracing.The simulation results show that the optical system can achieve uniform illumination and collimate beam.
The current information monitoring and warning system usually works by adopting one of the detectors such as the TV camera, low-light-level (LLL) TV and infrared thermal imager or switching among them. Every detector has its own advantages and disadvantages, which cannot fully reflect the needs of monitoring information when just using general models. In order to solve this problem, a video monitoring system with image fusion technology was designed. Through the analysis of the imaging mechanism and features of the three complementary detectors, the components of this video monitoring system were introduced. Based on the working principle of the system, the main structure of the front detection system was designed. The turntable achieves the field of view of +90~-30in vertical direction and 175in horizontal. The optical-axis parallelism error of the system is less than 0.5 mrad. After the discussion of the fusion algorithm and registration of images from different fields of view, the experiment of image fusion was done to test the performance of this system. Finally, image quality and system real-time testing show that the video image fusion monitoring system can realize all-day information monitoring.
The experiment on micro-displacement measurement based on the comparison of Michelson interferometer fringe was introduced. The beam path of optical interference was composed with He-Ne laser, mirrors and beam splitter. The reflector was fixed on the surface of measured object, it was moving with the object to make the interference fringes changing. The changing interference fringes were captured by using the linear charged coupled device (CCD). After image calculation by using the comparison of sequence image, the micro-displacement of measured object was obtained. Experiment shows that the method of image sequence comparison to measure micro-displacement is feasible. The measurement accuracy can reach micrometer.
We derived a new nonlinear governing partial differential equation (PDE) for calculating the gradient vector fields (GVFs) based on the variational method. By using the topological analysis of GVFs, the skeleton curves of an image were obtained. The main advantage of this method is simplicity. It works directly on the gray-scale images without the segmentation processing. We tested the proposed method on the Newton-ring interference fringe pattern, and compared it with the well-studied and widely-used block thresholding method and fringe extreme tracking method. The experimental results demonstrated the good performance of the proposed method.
A new image edge-detection algorithm is studied in order to inspect the disease of road surface. The edge-detection of road situation image based on fuzzy and genetic algorithm is presented, in order to solve some problems in the fuzzy edge-detection algorithms, such as the lost low gray signal, the low measuring speed on the edge and so on. This new algorithm retains the low gray information lost after fuzzy processing. It improves the efficiency and strengthens the adaptability of the algorithm. Compared with the traditional fuzzy edge-detection algorithm, the proposed algorithm can detect the low gray signal of the image effectively while inspecting the road crack accurately and run fast.
Multiple prism beam splitter can enlarge the parallel beam width and arrange the intensity distribution, which is used in the experimental simulation of lightening optical emission with different intensity distribution and high parallelism multi-channel beam. In order to obtain multi-channel parallel beam, penta prism scanning method was applied to test the multi-channel beams- parallelism in four-prism beam splitter with four prisms equally separated in the mechanical foundation. After we acquired the intensity distribution diagrams related to multi-channel optical axis by CCD, the software of centroid deviation calculation was programmed to feedback the accurate site-deviation information for prism calibration, which had the advantages of simpleness and convenience. The calibrated four-prism beam splitter had the optical axis matching precision less than 3, 4 and 4.5 in x-direction, y-direction and zdirection respectively, and the ratio of four-beam parallel light-s intensity was about 8∶4∶2∶1. If the resolution of CCD is improved and the focal length of the objective is enlarged, the precision of optical axis matching will achieve the seconds order.
According to the relevant theory of the signals and systems, a test method for frequency response of the PIN photoelectric diode detector was proposed. The test system realized by the method includes the light source of the narrowband pulse laser, the attenuation device of the light intensity and the photoelectric detector, etc. Firstly, the photoelectric detector received the signal of the narrowband pulse laser which went through the attenuation device, meanwhile, the rise time of the corresponding signal waveform was obtained by the digital oscilloscope. Then, according to the relevant calculation formula, the frequency response of the photoelectric detector was got. Finally, the error of test results was analyzed. The experimental result shows that the relative error by this method is about 6% of the detector whose theoretical frequency response bandwidth is 10.6MHz, and the test method is simple,feasible and applied widely.
Based on the spectral phase interferometry of direct electricfield reconstruction (SPIDER), the spectral phase of femtosecond laser pulse was reconstructed with numerical simulations. Several crucial parameters, such as the time delay, frequency shear, width of filter window and dispersion were analyzed on the optimal selection. When the dispersion and pulse width were given, the time delay had an optimum range. When the relative spectral shear was 5% ~15% and the width of filter window was /3 ,the reconstructed phase error was minimum. The noise was reduced by taking mean of the interferograms. The characterization of Ti:sapphire pulse was measured by using SPIDER. The comparison with autocorrelation measurement showed the validity of experiment.
The bandpass colorimetric filter temperature measurement theory was presented, which could accurately measure the object at medium-low temperature, meanwhile, a series of experimental facility were built up based on the theory. The facilities used were calibrated accurately and the discrete data were fitted by using numerical function, a temperature-measurement experiment was done using extended blackbody in the range of 50℃~400℃. Experiment result implies that the facility can precisely obtain the true temperature of a measured objection without the presence of target launch rate. Therefore, it proves the validity of the theory and the feasibility of the temperature-measurement system matching the theory, which plays a key role in the accurate measurement of the medium-low temperature objects.
In order to quantify the terahertz radiation of objects, the terahertz signals in blackbody radiation were measured. All measurements were conducted in vacuum circumstance, with liquid-nitrogen refrigerating to avoid any outside stray light. Meanwhile, those terahertz signals were focused on a detector by Cassegrain telescope. Afterwards, the output signals were further analyzed by a lock-in amplifier, and were compared with each other in different time constants. Results suggested that, with a constant temperature of 323 K, the measurements before and after liquid-nitrogen refrigerating were different with a discrepancy of about 3 v. Moreover, the time constant also had a great influence on the experimental results, with 3 s most appropriate in this study. However, due to the complicated noise sources and high noise levels, the radiation energy of the blackbody was too weak, and made the temperature resolution of the detection systems very low.
Wavelength calibration needs to be done before the spectral measurement of a monochromator. The relationship between the output wavelength and the number of stepping motor pulses of Czerny-Turner double grating monochromator was derived. Experiments of wavelength calibration were carried out. A low pressure mercury lamp was used to provide characteristic calibration lines at ultraviolet and visible wavelength range, spectrum scanning was done by the monochromator to get the data of signal intensity versus indicated wavelength. Finite wavelength correction was computed from the data. Then correction at arbitrary output wavelength ranging from 250nm to 450 nm could be obtained using curve fitting. The wavelength calibration insured the accuracy of the monochromator wavelength.
In order to resolve the pollution effects of ion barrier Al2O3 film on GaAs photocathode sensitivity of third-generation low-light-level(LLL) tube ,we used the quadrupole mass spectrometer to analyze the gas composition released from the ultra-high vacuum chamber ,the microchannel plate(MCP) without film and the MCP with Al2O3 film under electron bombardment. The results show that the MCP with Al2O3 film releases the residual gases of C, CO, CO2, NO, H2O2 and CXHY, which come from the quality pollution during the preparation process of Al2O3 film .After improving the filming technology, we obtained the Al2O3 film with outgasing amount less than 210-9 Pa and without CXHY.
In order to study the properties of the ion barrier film of microchannel plate(MCP), the Al2O3 ion barrier film was successfully fabricated on the input-face of MCP by the e-beam evaporating method．The optimal thickness of the ion barrier film was 2 nm. After measurement，the electron transmittance characteristics through the ion barrier film for unfilmed and filmed MCPs were shown. The relationship between the thickness of the ion barrier film and the dead voltage was given, the dead voltage of Al2O3 ion barrier film with the thickness of 2 nm and 4 nm was 150 V and 200 V, respectively. The stopping function on incident ions was analyzed by Monte-Carlo method, the barrier rate for 2 nm and 4 nm Al2O3 ion film was above 40% and 86% , respectively .Besides, the electrical characteristics of unfilmed MCP were tested, and the results showed that with the Al2O3 ion barrier film of 2 nm and 4 nm, the electron gain of MCP reduced by 51% and 81%,respectively.
A method for fast testing aspheric surface with small asphericity (less than 0.01 mm) was proposed, which does not need compensation system or other optical elements. First the practical wavefront aberration was measured by phase-shifting interferometer, and the adjustment errors were eliminated. Then the theoretical wavefront aberration of aspheric surface on-axis or off-axis was calculated based on the equation of aspheric surface. At last the residual wavefront aberration (surface error) was obtained by subtracting the theoretical wavefront from practical wavefront. A hyperboloidal mirror with the diameter of 135 mm was measured by this method, meanwhile this mirror was tested by null compensation; the tested results by these two methods are similar. It concludes that the method of digital wavefront for testing aspheric surface is feasible.
A new processing method of wedge mirror with double-symmetric angle which has two ultra-smooth surfaces was presented. According to the characteristics of the optical elements, the traditional processing method was improved. The elements were processed by using the way of wedge plate combination tooling and bonding. The flaw, figure, roughness and consistency of optical surface were greatly improved. The root mean square (RMS) roughness of ultra-smooth surface was always better than 0.2 nm (AFM measurement), the surface defect reached 0 level, the angle precision was 15, and the qualification ratio under first acceptance check was above 85%. This method can effectively solve the bottleneck problem in production.
In order to theoretically analyze and calculate the optical film-thickness distribution deposited on the surface of large curvature spherical accessory, we firstly determined the processing configuration, then determined the calculation function formula through mathematic model, finally carried out the calculation through numerical integration when the evaporation source was point evaporator (n=0) and plane evaporator (n=1, 2) respectively. Results of the calculation were compared with the experiment results. It is revealed that the calculation results when n=2 accord with the experiment results well under the processing conditions determined in this paper. It is also proved that the film-thickness deposited on the surface of large curvature spherical accessory can be calculated by numerical calculation adopting the designed modeling method and appropriate beam characteristics of evaporation source.
A hybrid refractive/diffractive IR thermal imager with light weight and wide temperature range was designed. The working wavelength was 3.7 m～4.8 m; the relative aperture was 1/2; the efficient focal length (EFL) was 120 mm ; the full field of view was 5.18and the system satisfied 100％ cold shield efficiency. The system was designed with three lenses and two kinds of materials-Si, Ge-and an aspheric surface and a diffraction surface to realize operation with light weight and wide temperature range. The imaging quality of the system approaches to the diffraction limit at -60℃～160℃. It is compatible with the staring midwave infrared detector which has a format of 256256 and the pixel pitch of 30 m. The system can recognize the tank from 2.3 km.
To increase the fidelity of infrared staring focal plane array(FPA) detector-s imaging simulation, we analyzed the mechanism of spatial sampling effects in the IRFPA detector,built the model in spatial region,and carried out the simulation experiment based on pixel processing method. In order to objectively evaluate the spatial sampling effects on the detector imaging quality,it defined a negative index of image smoothness. The experimental results show that the smoothness of the detector output image with spatial sampling effects is reduced by 11.7%, and the local fluctuation of image is larger, which verifies the necessity of considering the sampling effects in IR detector imaging simulation.
According to the simulation testing requirements of shipboard EO tracker, a design of optoelectronic simulator based on the infrared image simulation was presented. By using the Vega simulation platform, the linear relationship between the radiance and the gray value of simulation image was calculated , then the linear map was solved and the infrared simulation scene image was analyzed and calibrated. The type test by a photoelectric tracker verified that the tracking precision reached 1 mrad, which satisfied the system demand. The EO simulator could test the dynamic performance, tactical and technical index of EO tracker under comprehensive background and night environment.
Studies on cavity tuning characteristics of dual-frequency lasers can be helpful for expanding laser physics theory and sensing applications. Based on microchip Nd:YAG orthogonally polarized dual-frequency laser, several important cavity tuning characteristics of dual-frequency laser are studied, including intensity tuning, frequency difference tuning, sub resonant cavity effect and frequency difference lock-in. Experimental results and data are presented. With cavity tuning, the variation of frequency difference between two orthogonally polarized frequencies can be up to 350 kHz; when sub resonant cavities exist, the maximum variation can be up to 2 MHz; frequency difference lock-in has not been found and the minimum frequency difference is about 14 MHz.
In order to reduce the production cost of laser displacement sensor, we put forward a design method of a new type of laser displacement sensor system. Based on the triangle measurement principle, the design uses the CCD single board computer as the photoelectric detector, utilizes the pinhole optical system to replace lens. We discussed the method to determine the important parameters of the senor system according to the characteristics of the pinhole optical system, and wrote the image processing algorithm for extracting displacement information of the target image, so as to achieve non-contact displacement measurement. Finally, we set up a set of this new type of experimental system of laser displacement sensor to carry on displacement measurement experiment, and the results show that this system can meet the measurement requirements of 50 mm range and 1 m precision.
Laser beam expander is used to compress the laser divergence angle, in order to reduce the energy losing in long distance scanning acquisition system. To meet the requirements of the laser communication experiment, a laser beam expander system was designed. The system has 10 times magnification and 48 40 working field, which is used in 1 550 nm, 1 064 nm, 800 nm and 632.8 nm laser wavebands(632.8 nm waveband is mainly used for system test). After the calculation of primary structrue parameters and the optimization by Zemax, four conic mirrors were used to compose the system. Considering the tolerence, the system-s maxium wavefront aberration(WFE) is 0.095(=632.8 nm) that satisfies the requirement of the RMS of WFE ＜0.1. It has a total size of 9010060 mm3 and transmission of about 92%，which also meets the 85% transmission demand.
In order to coordinate with the ground detection tracking system for detecting the flight target, we designed an air-based monochromatic beacon system. A 40W high-power semiconductor laser is used as the light source of the system, which has a certain beam divergence. As the beacon system should meet the requirements of smaller in size, lighter in weight and faster in heat dissipating to fit the air-platform, we designed the aluminum shell as fin chip in onepiece for laser, which helped solve the heat dissipation problem and reduce the system weight. To achieve the 60A high constant current, we need to drive the 40W semiconductor laser module in the limited room, the principle of diphase overlay synchronous and buck transformation circuit structure is adopted. To make the laser output power and central wavelength stable in high altitude, we designed the temperature control system with digital and analog hybrid for heating or cooling. The ZEMAX is used to design the structure of the beam expander device with double-concave lens group, which can regulate the angle of divergence of the light beam. By conducting the environmental assessment and test, we proved that in the 0℃～15 ℃ environment, the stability of the output power and the control precision of the central wavelength could meet the requirements.
The theoretical formula between the reflection phase retardation difference of S polarized beam and P polarized in square ring resonator and the beat frequency driving voltage difference in the piezoelectric ceramic (PZT) was derived. The frequency response characteristic of S polarized beam and P polarized beam in the square ring resonator was analyzed, and a new method for measuring the phase retardation difference by measuring the voltage difference was proposed. The passive ring resonator frequency response measuring system was set up, and the validity of the theoretical analysis was verified by experiment. The results indicate that the measuring error is less than 1.5%, which satisfies the requirement for the reflection phase retardation measurement.
Adopting the ceramic packaging technology, we designed and produced several fiber Bragg grating (FBG) temperature sensor probes to test the sensitivity, stability, repeatability, speed of response of the probe and other parameters affected by the packaging processed form. The parameters of FBG were analyzed by a water bath apparatus with constant temperature to calibrate the thermal response of FBG with the central wavelength around 1 540 nm and 1 550 nm, and the temperature increased from 36℃ to 45℃. The experiment results showed that the scalar efficiency of the FBG probe with ceramics package was 9.815 pm/℃ with standard deviation of 0.08 ℃.
The manual-align system for packaging planar optical waveguide was improved with 3 monochrome cameras added, as well as 3 AV to USB capture cards, through which the align images could be gathered. In order to achieve the parallelism detection of the waveguide splitter with the input and the output of optical fiber array, by using the LabVIEW8.2 and IMAQ vision software programming, a series of processing and identification including image brightnesscontrast-gamma(BCG) adjustments, reverse, closing, edge detection, manual thresholding, morphological changes and linear fitting were carried out. It was proved that this system could save 10 min of the packaging time on average taking the 132-channel planar optical waveguide by one journeyman for example, reduce the amount of labor of the operator and the alignment loss, as well as the human error.