2009 Vol. 30, No. 4
The reason why the carrier disturbance produces and the effect of carrier angular momentum on the performance of the optoelectronic imaging system are analyzed. Based on the analysis, LOS stabilization accuracy that the optoelectronic imaging system requires is also analyzed from three aspects of spatial resolution, human visual observation performance and tracking accuracy. It is pointed out that different LOS stabilization accuracy needs match different imaging system and applied situation. The conclusion shows that LOS stabilization accuracy must be determined by the system spatial resolution according to the practical function. The conclusion is verified by an example.
The coaxial eccentric-pupil system has the advantages of long focal length, wide field of view and small volume. It overcomes the shortages of the limited field angle of the coaxial system, and the difficult of manufacture and assembly of the off-axis reflective system. It meets the requirement of high-resolution space-to-earth observation. The design process of coaxial eccentric-pupil three-mirror system is introduced. The coaxial eccentricpupil three-mirror system with focal length of 3000mm and F number of 10 was designed. The result indicates that the field of view of the system can attain to 80.8, and MTF is higher than 0.55 at 50lp/mm. The image quality of the optical system approaches the diffraction limit, and can satisfy the requirement of the system.
The minimized design was realized by using the design of fast zooming route cam curve and the method of cam curve flatness optimization according to the requirement of the detection device TV channel for realizing the conventional color mode and fog transparent black/white mode. In the design, the visible light plus near infrared band and a method of image quality evaluation in the range of the whole band was applied to meet the needs of observation in the conventional color mode and fog transmission black/white mode on the premise of avoiding the focal shift of zoom. The system was passed through MTF test, imaging verification, environment stress screening and environment routine experiment, and was equipped to the detection device successfully.
The head mounted display (HMD) with a free-form-surface (FFS) prism owns merits of small volume, good image quality and wide FOV. The initialization structure of optical system with tilted surfaces was designed according to the parixial vector aberration theory. A FFS optical system for a practical HMD was designed by entering the initial structure paramiters to the Zemax software to optimize the designed results. The result verifies the feasibility of this method, and indicates that the method to design the FFS prism in HMD can be applied to the design of other optical system with titled suface.
Axial gradient index (AGRIN) medium is hopeful to be substituted for the aspherical lens since the image quality of the former is better. The status and application of AGRIN lens are introduced. Its merits comparing with the aspherical lens are briefly presented. The manufacture technology of AGRIN medium is discussed. It is found that AGRIN material using in optical systems not only improves the image quality but also lowers the testing difficulties. A lens with 125mm focus, F/4, 25 FOV, which is suitable for full-frame 28 M pixel DALSA FTF6146M CCD, is designed for a digital aerial survey camera. Three spherical lenses were decreased from the original eleven ones because of the two AGRIN lenses on the premise of keeping the same image quality. The result indicates that the image uniformity and structure of the camera are much better than before.
Three-zone amplitude-type superresolution pupil filters (1-0-1) and three-zone phase-type superresolution pupil filters (-0-) are designed with Matlab optimization toolbox and non-linear programming. The optimal model is established and some examples of optimization are given. The optimization results show the both filters have preferable 3-D superresolution characteristics, the axial resolution is better than transverse resolution, and the phase-type resolution is better than amplitude-type resolution at the same Strehl ratio. The structures of the both filters are simple and easy to be implemented.
The root-cause for the synchronous error of multiple axes of the vehicle panoramic sight platform was found after analysis with the geometric method. Since the synchronous error is caused by the windage angle produced in the working process of the optoelectronic platform, the method to correct the angular deviation at any distance is proposed. The experiment for solving the problem was implemented. The experiment indicates that the method is valid.
The vertex coordinate formulas for outer baffle vanes of R-C system are deduced based on geometrography, and the vanes are designed with Clanguage program. The vertex coordinate formulas of inner baffle are also deduced after assuring the central obscuration ratio, and then the common one-grade conical baffle is improved into the two-grade one. The correctness of baffle design is proved by an example and its simulated analysis, meanwhile an effective way of suppressing the stray light is provided. Finally, the same-height vanes in drawtube between primary and secondary mirrors are designed for further suppressing the stray light in R-C system.
The incoherent coupling of two mutually incoherent optical beams with the same polarization and wavelength in biased two-photon photovoltaic photorefractive crystals was investigated. The condition which is needed for producing two-photon incoherent coupled bright-dark screeningphotovoltaic soliton pairs is presented in the paper. Taking Cu:KNSBN crystal as a research object, the light intensity spatial distribution of twosoliton components of incoherently coupled bright-dark screening-photovoltaic soliton pairs in two-photon photorefractive crystal is given while =117.3,=83.79,=1.510-4，=104，=0.005，r=10 is selected. The research verified that there are incoherently-coupled bright-dark screeningphotovoltaic soliton pairs in the two-photon photovoltaic photorefractive crystal that has applied electric field. It is pointed out that the soliton pairs are formed by two incoherent beams which have same polarization state and wavelength.
In the case of neglecting the distortion error of the camera lens, the simplified method to calibrate cameras was deduced by establishing the proper coordinate systems, utilizing DLT mode, combining the optimization algorithm calibration method and two-step method, and decreasing the variable number to five. By the aid of a example, the parameters were solved with the tangent line of a circle, the intersection point of tangent and thecoordinates defined by the geometrical relationship of the image based on two propositions proposed in the paper. The numerical example shows that the method has less computation and high accuracy.
The holographic characteristics of water-resisting red-sensitive photopolymer holographic recording material was improved by using compound sensitizer, compound initiator and compound monomer. After improvement, energetic sensitivity of 0.02cm2/mJ and high diffraction efficiency of 83% were obtained. And the refractive index modulation is as high as 410-3, which implies that the photopolymer has the potential ability of high density holographic storage. Therefore, it is a kind of better holographic recording material. The new style holographic grating fabricated with the material has many merits: low loss, narrow channel width, high diffraction efficiency. According to the experiment results and theoretical analysis, this grating is suitable for wavelength division demultiplexer and other optical elements.
The fractional Fourier express of the first-order optical system was derived by decomposing the transfer matrices of first-order optical system into coordinate rotation matrix, scale matrix and chirp matrix in Wigner phase space. The results show that an arbitrary first-order optical system can be expressed as the scaled and chirp modulation fractional Fourier transform. The transfer matrix and diffractive integral formula in frequency domain were acquired by rotating the input and output optical field /2 in the phase space. Accordingly the fractional Fourier transforms of a first-order optical system in frequency domain were also obtained. By comparing the transfer matrices of two first-order optical systems in space and frequency domains respectively, it is found that the two first-order optical systems in different domain can be expressed as two different expressions of one and the same transfer based on different coordinates. At last the condition is derived for an optical system to implement the fractional Fourier transform in space and frequency domains with the same order.
To solve the image obscuration in dynamic images, an image block algorithm based inter-rame predictor is presented to detect missing image region in sequence images and a pixel inserted compensation algorithm based on gray correlation is given. The inter-rame predictor based on image block algorithm can be used to detect the missing image region in sequence images, which is caused by a partially obscured CCD. A method using modified pixels with inter-rame gray correlation is presented to compensate the missing image region. The simulation results show the compensation algorithm is effective.
Since the problem of how to accurately find the corresponding matching characteristics by the heterologenetic sensors when image registration, in combination with the characteristics of the red and visible images，the extraction of the Canny edge of images is proposed by utilizing the similar characteristics of the edge outline when the different two sensors image a same scene. That is, find the corresponding matching point at the edge outline according to the similarity of the location included angle between the pixels on the edge curves. The validity and registration accuracy of the algorithm were verified through the simulation and comparison of the experimental data with the true value.
The major method to improve the wide-field optical coherence tomography (WFOCT) is to meliorate the light source and beam path of optical systems. The effect of the imaging state and environment of a wide-field optical coherence tomograph on its transverse resolution was investigated. The interference effects of the system were simulated by the aid of ZEMAX software. The 2-D image information of the sample was analyzed with the eight-step phase-shifting technique in the experiment. The simulation results show that the interference fringe with better contrast and high parallelism can be acquired by simulation, and verify the feasibility of simulating the interference system by ZEMAX software.
In order to get the perfect reconstruction result, the reconstruction parameters of the common iterative algorithms as ART and SIRT used in the optical chromatographic technique are analyzed. The reconstruction requirement was satisfied by selecting the appropriate reconstruction parameters, comparing the reconstruction errors (average error, max error, root-mean-square error), and implementing the computer numeric simulation. This simulation proves that the selection of relaxation factors has a very important influence on the iterative reconstruction algorithms. In ART, while the other conditions are unchanged, the relaxation factor range from 0.4 to 1.5 can meet the requirement of reconstruction accuracy basically and the best selection is 0.8. In SIRT, the relaxation factor range from 4 to 12 is appropriate and 12 is the best selection. The influence of the relaxation factor on the iterative reconstruction algorithms was studied, and the selection law of the relaxation factor under different conditionswas summarized in the algebraic reconstruction technique and simultaneous iterative reconstruction technique. In ART, the relaxation factor will decrease if the number of projection direction increases but the number of each direction projection and reconstruction resolution have no influence on it, and the error will increase if the number is too big or too small while the relaxation factor is unchanged. In SIRT, the relaxation factor will decrease if the number of projection direction increases, and the optimal relaxation factor will decrease 50% if it increases 2 times; the optimal relaxation factor will decrease if the number of every direction projection increases, and the optimal relaxation factor will decrease 50% if it increases 2 times; the relaxation factor will increase if the reconstruction resolution increases.
Measurement of 3 dimension structural displacement with wide range and high precision is needed in the manufacturing process of large airplanes. For the displacement measurement requirement of airplanes and other great engineering structures, a videometric system of structural displacement was designed and implemented. The system adopted several digital cameras to take photos of the cooperative mark-points located on the frame and wing of the tested airplane from different directions, the parameters of the cameras were calibrated before the test, the image sequences acquired by the cameras were analyzed in real time during the test, the 2-dimension coordinates in the images of the mark-points were detected and tracked. Based on the cameras parameters and markpoints 2-dimension coordinates, the 3-dimension coordinates of the mark-points were calculated, then the displacement and deformation of the structure were obtained, the 3-dimension results were visually provided, and the displacement curve was examined. The test results showed the standard deviation of systems displacement measurement error is less than 1mm, and the relative error is less than 1%. The system was used in the wing displacement measurement of a specific airplane, and the efficiency and precision of the measurement were improved.
The measurement of polarization rotary angle for faraday mirror based on polarization-beam-splitter was proposed. The orientation of the light from the faraday mirror was changed through a non-polarized beam splitter (NPBS). With a polarized beam splitter (PBS), the light reflected from NPBS was split into S light and P light. Their intensities were measured, and the theoretical expression of rotary angle was deduced after the impact of optical fluctuation is eliminated by signal processing. The influence of non-zero extinction ratio and polarized-angle error on output results was analyzed. Finally the intensities were repeatedly measured, and the average rotary angle was 89.68, the mean square deviation of all the experimental data was 0.01493.
During the micro-scale combustion experiment, it is necessary to measure the temperature of the whole combustion area to get the flame height data using thermocouple temperature measurement method. Due to the small micro-flame combustion area, the thermocouple may disturb the combustion stability. To solve the problem, digital image processing method is used to analyze flame image based on the linear relationship between image grey values and flame temperature to get the flame height data indirectly. Results show that the flame height data is accurate and agrees with the experiment result. This indirect measurement method for microflame is simple and feasible.
In order to measure the size and volume concentration of particles of several microns accurately and rapidly, an experimental device was designed with a linear array CCD as detector, based on the Fraunhofer diffraction. The Shifrin-transform method was adopted to analyze the particle size distribution, peak value, and mean size and volume concentration. Compared to the conventional Swithenbank conversion method which adopted the self-scanned photodiode array to achieve particle size distribution, the method doesnt need to have precognition information such as upper and low limit as well as interval separation of the particle, and etc. The agreement has been obtained between theory and experiment. The experimental results show that higher accuracy in the measurement of particle size and volume concentration is achieved.
Current research status on application of hyper-spectral image technology in the quality of agricultural product and food safety as well as its application in non-destructive detection is reviewed. A method to detect the pesticide residue is provided using hyper-spectral image technology. Its potential application in biomedical information detection and pesticide residue detection is predicted. Hyper-spectral image technology is a new method to biological tissue function information analysis and a potential technology to detect the pesticide residue in agricultural product, which is a serious food safety problem in China.
A bulk absorption laser energy calorimeter operating in non-standard environment was designed. The thermal radiation, conduction and air convection of the calorimeter were analyzed, and its heat exchange equations were derived. The mathematical model of thermal loss of the calorimeter was established. The thermal loss in the process of temperature rising was compensated based on the model. The measurement repeatability error of the calorimeter for different input laser pulses was decreased from 4.7% to 0.6%, and the negative influence of thermal loss was removed. When the copper-constantan thermal couple was used to measure the same temperature difference in different environments, the calorimeters output changed greatly, it increased by 30% when the environment temperature increased from -40℃ to 70℃. Laser energy measurements were carried out at different temperatures in an environment controlled chamber, and the correction coefficients of the calorimeter at different temperatures were obtained. The dependence of the coefficients on environmental temperatures was determined by using the least square method. The impact of the environment temperature variation on measurement result was corrected.
In order to reveal the influence of the voltage variation of microchannel plate on the signal-to-noise ratio of LLL image intensifier and optimize the performance of the image intensifier, the curves that the signal-to-noise ratio of super Gen II and Gen III image intensifiers variates with the voltage of a microchannel plate were obtained by the aid of a signal-to-noise ratio tester. As for the super Gen II image intensifier, when the microchannel plates voltage is in the range of 600～800V, the signal-to-noise ratio is monotonically increased to 25.9, when it is in the range of 800～900V, the ratio is 25 or so and has downtrend, and when 900～1000V, the ratio is rapidly decreased to 21.8. As for the Gen III image intensifier, when the microchannel plates voltage is in the range of 800～1000V, the signal-to-noise ratio is monotonically increased to 27.87, and when the voltage is in 1000～11800V, the ratio fluctuates from 26.61 to 28.66.In combination with the theoretical analysis of microchannel plates noise factor, a method to reduce the noise factor of microchannel plates and improve the signal-to-noise ratio of LLL image intensifiers is proposed.
Since the different cesium and oxygen currents during the activating process may cause the undefined influence on the sensitivity and stability of GaAs photocathodes, the long-term research was implemented. For the purpose of increasing sensitivity and stability of GaAs photocathodes, three different cesium-to-oxygen current ratios (fixed cesium current and alterable oxygen current) were used to activate the similar GaAs photocathodes, and three sets of experimental results were obtained. The analysis results of experimental data show that the appearance times of photocurrent are almost identical and the peak values of the first photocurrent are very close; ICs/IO=1.07 is the optimum current ratio for high sensitivity and high stability, ICs/IO=1.10 is for low sensitivity but high stability, and ICs/IO=1.03 is for high sensitivity but low stability. Based on the double-dipole model, the stable and uniform double-dipole layers of GaAs-O-Cs:Cs-O-Cs are formed and negative electron affinity is achieved on GaAs surface activated by cesium and oxygen, which cnsists with the analysis results for theexperimental data. The effective technical method can be used to improve the sensitivity and stability of GaAs photocathodes.
Beam splitters for infrared spectrum are used to split the band of 3m to 5m and 8m to 12m in infrared detection devices. A new method of designing and fabricating infrared beam splitters with a conventional coater is introduced. In the course of design, we estimated the highest value of average transmission with the formula of Willey, which was used in the design of the beam splitters. Considering the low precision of the available coater, we attempted to design coating with quarterfilms. For improving transmission from 8m to 12m, a self-prepared low refractive index material was deposited on the coating. The beam splitters for infrared spectrum fabricated met the required technical specifications.
Optical thin-film technology and laser holographic technology were combined to fabricate 1-D coated laser hologram photonic crystals. The interleave filter characteristics of 1-D coated laser hologram photonic crystal were studied with the eigen matrix. The central wavelengths of transmittance peaks move to centre and the intervals between transmittance peaks decrease with the increase of both sides thin films periodicity. The number of transmittance peak increases and the intervals between transmittance peaks decrease with the increase of laser hologram photonic crystals periodicity. The central wavelengths of the transmittance peaks shift to long-wave direction and the interval between transmittance peaks decrease with the increase of lasers intensity.
Spectrum splitting filter is a key element for imaging spectrum technique. Based on the high reflection feature of the metal film and induced transmission theory, a novel element transmitting in 0.45m～1.6m and reflecting in 8m～12m was introduced. The deposition materials and the film design were presented. By using JGP560A2 magnetron-sputter deposited device, the element was produced and its optical characteristics were tested. Its average transmission ratio is more than 80% in 0.45m～1.6m, and average reflection ratio is more than 91% in 8m～12m.
A flexible and efficient solution for fabricating the ultra-thin light guided plates (LGP) is presented. The approach is based on maskless lithography which is realized by the aid of a digital micro-mirror device (DMD). The image of microstructures created by DMD is projected by passing through a projection optical system to the substrate with a photoresist layer. After exposure, development and electroforming, a nickel template with patterned microstructures is obtained and can be used to fabricate LGP by hot embossing. The proposed method has the advantages of arbitrary microstructures created by DMD lithography and cost-effective mass production by embossing replication. A fabricated LGP with thickness down to 0.381mm was demonstrated, in which the microstructures have the resolution of 2m. The process provides a effective scheme for fabricating large format LGP with more complex microstructures.
The technical study of laser cutting for cardiovascular stents was fulfilled. It is a typical application of laser micro-fabrication. The discipline of influence of the technological parameters (including the focal length of lens, focus position, laser power, cutting speed, pulse frequency, pulse width and assist gas pressure) on the quality of the cardiovascular stents were obtained with the most advanced fiber laser in the world. The results show that the kerf width increases with the increase of laser power, pulse frequency, pulse width and assist gas pressure, but decreases with the increase of cutting speed. The optimal technological parameters for cutting cardiovascular stents with laser were acquired on the base of the experiment. Stents whose kerf width is less than 20m were cut after a lot of experiments.
The binary phase-sampled fiber Bragg gratings (FBG) were designed and optimized using Particle Swarm Optimization (PSO). The dispersion and its slope can be compensated by using binary phase-sampled FBG. The binary phase-sampled FBG was obtained，whose reflective spectrum is uniform, time delay is linear, bandwidth, dispersion and its slope could be adjusted according to the type of fiber, and the required index change is small. Its fabrication is simpler than multilevel phase-sampled FBG because there is only phase shift of in it. Compared with other algorithms, the PSO is simpler and faster convergent.
A method to design the hybrid athermal infrared optical system is studied. A design concept of the mutual compensation of the thermal dispersion and chromatic dispersion was introduced in the design, in which the equations that the athermal design should meet are acted as a constraint condition in the optimization. A refractive/diffractive hybrid athermal infrared optical system, whose cold shield efficiency is 100%, F/number is 2, field of view is 5, effectivefocal length is 70mm and working wavelength is 3.7m～4.8m, is designed. The image quality of the system approaches the diffraction limit at the working temperature of -40℃～60℃. The system can be compatible with the high-resolution cooled staring focal plane detector whose pixel size is 15m.
The infrared radiative transfer model of pollution clouds is proposed. The infrared spectra of pollution cloud radiative transfer are studied through the proposed simulation model. Aiming at the established three-layer infrared radiative transfer model of pollution cloud, the infrared radiative spectra of the pollution clouds at different concentrations were simulated with the field background spectra (that are measured by Fourier transform infrared spectrometer) and every interferent radiative spectrum as the basic radiative data. The result shows that there are obvious spectrum characteristic peaks at the wave bands of 810cm-1，920cm-1 and 1040cm-1. The simulated spectra are consistent with the field experimental spectra, and the RMS error of the two spectra is only 1.0.
The population pulsation effect in the gain medium was considered to research the fine mode coupling effects in the laser gyro. Proceeding from the laser physics principle, the generation mechanism of population pulsation is analyzed. In association with the characteristics of four-frequency differential laser gyro, it is found that the population pulsation effect is one of the fine mode coupling effects. The level of the population pulsation effect in the coupling effects was calculated numerically. The result shows that the variation of the population pulsation effect with the cavity tuning is basically in accordance with other coupling effects, and it has small value in large cavity tuning ranges, which is less than 4% of other coupling effects; but it has relatively large value in some cavity tuning ranges (0.37＜＜0.46, 0.02＜＜0.06, 0.86＜＜0.88), which is more than 80% of other coupling effects. Therefore, it cant be ignored in the mode coupling analysis of the laser gyro.
Aiming at the problem of pointing error of laser spot in atmosphere environment, in combination with the approximate integration on the refractiveindex fluctuations of the modified Von Karman spectrum model and the Hufngel-Valley turbulence profile model, the pulse broadening and scintillation index of Gaussian pulsed beam in the far-field horizontal and slant path propagation in the turbulent atmosphere are studied. The relation between the light intensity distribution and pulse broadening of 1.06 quasi-monochromatic laser beam propagating in the far-field strong atmospheric turbulence are analyzed. The comparison and validation of the numerical results are presented, which show that the critical parameters affecting the pointing error are the optical wavelength and propagation distance. Theoretical analysis and experiment results show that application of the laser spot whole-field data and analysis result in the available error compensation method can make effective compensation to the pointing error.The laser pointing error is A0.1mrad when the visibility of air in the range of 1km～3km.
The LD side-pumping structure was designed to meet the requirement of miniaturization and spot uniformity of the laser system for weapon systems. The compact laser resonator was designed. In this design, the thermal effect is compensated by the total reflection concave mirror. The laser output, whose average single pulse energy is 96mJ (energy fluctuation ＜6%), pulse width is 10ns and divergence angle is 3mrad was obtained as the current is 60A and the frequency is 20Hz. The laser system can still work stably when the temperature rise to 50℃.
The cooling system based on the water-cooled and air-cooled combination was designed for simplifying the cooling system, reducing the size and lowering the cost. It has the advantages of both water-cooled and air-cooled systems, and can achieve stable green laser output. LD endpumped Nd∶YVO4 and KTP green laser with the simple and compact flat-concave cavity design was obtained. When the crystal absorbs the pumping power of 24.3W, the 532nm laser power is 4.2W and light-optical conversion efficiency is 17.2%. The power change range of about 2.5% and the temperature change range of about 0.1 were observed as the green output power was 3W. The experimental results show that the cooling system can effectively transfer the heat produced by the thermal effect of the crystal, and higher conversion efficiency of green light output can be realized. The technology is favorable to the miniaturization of high-power laser.
According to the special test request of the laser guidance system for the high power narrow pulse semiconductor lasers, a test setup for testing peak optical power output, threshold current, forward voltage, rise time, peak wavelength and spectrum width of the high power narrow pulse semiconductor lasers was developed. The setup consists of the miniaturization power-amplification module of high-power actuator, large-scale adjustable DC-DC module, signal generator, collimating mirror, laser peak power meter, laser spectrum analyzer and CCD pickup camera. The peak power of emission, peak wavelength of emission, wavelength drift characteristic with temperature and luminous core uniformity of high power narrow pulse semiconductor lasers can be tested. The features of the test setup are presented and the test results are elaborated.