2014 Vol. 35, No. 1
In this paper, we gave an optic design of stellar oscillations network group (SONG) Shack-Hartmann (S-H). The optical system and main parameters of S-H were determined, mainly according to the demands of diffraction limited imaging quality and magnitude of the telescope; According to the optical parameters of SONG and the micro lens array, an eliminating aberration design was carried out based on two doublets; The performance of the S-H was within diffraction limit. Designing results showed that the 6th magnitude and accuracy of 0.05 could be achieved. Based on the design results, an experimental system was built. A comparative study on measuring accuracy between S-H and 4-D interferometer was carried out. The experimental results showed that the measuring accuracy of S-H is 0.008 m which could meet the requirements of Chinese SONG telescope.
Against the current situation of centering instrument with low precision and dependent on the human eyes, a research method of high-precision centering instrument based on position-sensitive detector (PSD) was put forward. Through the use of self-collimated optical path and PSD, the return light spot from the target was located, and the coordinate value on the computer was read to judge whether the accurately centering was achieved. The design of the centering instrument optical system and the nonlinear correction of PSD by neural network training were carried out. Results show that t can achieve the design requirement of centering accuracy with measuring range of 2 mm~500 mm, which is much better than traditional centering instruments.
To meet the requirements of visible-near infrared(VNIR) high-precision observation of solar spectrum, a calibration method for a novel solar irradiance spectroradiometer based on spectrally-resolving technology was developed. The relative calibration based on standard lamp was carried out in 400 nm ~1 050 nm, and the Langley method was carried out in the band satisfying Beer-Lambert theorem, where after the solar irradiance spectroradiometer was traced to the solar spectral irradiance on the top of atmosphere (TOA) in the whole bands. The experiments carried out in Dunhuang and Hefei showed, the observation results were consistent with the MODTRAN4.0 theoretical model, and the deviations with CE318 were less than 5% in the four aerosol observation bands, which validated the rationality of the calibration method.
In order to analysis the stabilized and isolated ability of control system, the model of two-level stabilization system was established and the controller was designed.The result of simulation showed that the bandwidth of rate stabilized loop was improved to 200 Hz, the isolation at 1 Hz reached -90.1 dB. The error of line of sight(LOS) was measured by position-sensitive detector (PSD),the result of isolation testing experiment showed that the position isolation at 1 Hz reached -73.1 dB,increased by 20 dB approximately,which implied that the stabilized precision could be improved significantly by two-level stabilization system.
Target positioning by airborne reconnaissance equipment is affected by many factors. The systematic errors and random errors in location data can affect the positioning results. We proposed that by using circular error probable(CEP) to process target location data, the different application conditions for CEP should be analyzed and judged. According to the definition of CEP and the general form of the CEP equation, we deduced the CEP simplified formulas under 6 different conditions and used two CEP simplified formulas to compare, calculate and analyze the location data of a target. Results show that the higher data processing accuracy 0.95 can be obtained using the formula under applicable condition, which meets the CEP-defined 50% probability data requirements and means the target location results from reconnaissance equipment can be analyzed accurately.
A design of a 3rd generation image intensifying charged-coupled device camera ( ICCD) was proposed that could operate under high-speed gating. A gated control circuit was designed which was used for the photocathode of a 3rd generation image tube, so that the ICCD could image effectively under a highspeed gated state. After analysis and comparison, a relay lens was designed which had a Bi-Gauss complication optic configuration. The high transmissivity and high modulated transfer function ( MTF ) were achieved on image coupling. A digital CCD and a digital frame capture circuit with an embedded image process module were used. The correlative software about the image process was accomplished , so that the image of ICCD was presented fast. As a result of the design, the 3rd gated ICCD can operate with a 3.3 ns gated width and its spatial resolution is 600 TVL.
Considering the difficulties in the wake bubbles imaging, a wake bubbles measurement system was presented based on the combination of high speed photography and laser sheet scanning technology. In this system, laser sheet was used to illuminate the wake zone to avoid the image stacking of bubbles. Because the particle size of bubbles was in a wide range(10 m～500 m), three switchable magnification lenses were designed for the bubbles imaging. Lenses were split into front and rear groups, with parallel rays transmitting between them. With the sweeping of laser sheet, the image information of bubbles in a volume could be sampled. Moreover, by keeping the front group moving synchronously with the laser sheet, bubbles could always image clearly when the laser sheet swept. The influence on image quality, the determination of laser sheet thickness and the system distortion correction, when laser sheet swept, were also discussed. The systems conducted a sea test at No. 760 institute of China ship building industry corporation(CSIC), the depth of the sea was 5 m,10 m～2 000 m bubbles step from objective test ship, the test results show that the image quality is good and this system satisfies technical requirements.
In order to achieve multi-color temperature and multi-magnitude output, as well as real-time adjusting of magnitude and color temperature, we designed a new type of calibration single star simulator with adjustable magnitude and optical spectrum output. We used xenon lamp and halogen tungsten lamp as the light source; with different multi-beam narrow band spectra with light of varying intensity, we realized the control of spectral band and temperature of star. When the light source with different spectral characteristics and color temperatures went into the magnitude regulator, we only controlled and adjusted the light luminosity of the light energy attenuation. The entire system was assembled in laboratory，and the controlling and testing platform was set up. Besides,the experiments were carried out and the comparison results between the standard magnitude and measured magnitude under different color temperatures were given.
The ellipsoid condenser is an important part of solar simulator. Light energy emitted from the light source can be collected and aggregated on the second focal plane, and the energy transmission efficiency is directly affected by this procedure. The efficiency of the energy collection procedure is determined by the ellipsoid condenser parameters. In order to increase the efficiency, the luminescence properties of xenon lamp were studied and the characters of the ellipsoid condenser condensation were analyzed by a model built in MATLAB. The ellipsoid condenser parameters such as the first focal length, the max imaging amplified ratio and the containing angle ranges could be determined after the study. The theory correctness was verified by 4 models built in Lighttools. The height of the light center determines the first focal length, the optical integrator F as well as the ellipsoid containing angles determine the max amplified ratio,and the containing angles should be 30～120, moreover the max angle determines the front hole diameter, the min angle and the radial adjustment of the light jointly determinate the back hole diameter. The ellipsoid condenser design can get theory support from the conclusions obtained in this paper, and the conclusions are helpful to accomplish a higher efficiency ellipsoid condenser.
In order to solve the irradiance uniformity problem of the solar simulator, a kind of square optical integrator was designed that could obviously improve the solar simulator irradiance uniformity. According to the composition and working principle of the solar simulator and optical integrator, the square optical integrator parameters were computed and the effect of integrator aberration on the uniformity of woring face was analyzed. Simulation of the solar simulator system was done using Lighttools software, and the optimization methods were proposed for improving irradiation uniformity by projection lens defocus.The irradiation nonuniformity can reach 1.72% in 200 mm200 mm square irradiation surface by using the designed integrator.
The research of light scattering properties of space target has very important application value on the space penetration technology such as target detection, tracking and recognition. We associated the light irradiation with the target scattering intensity by utilizing the bidirectional reflectance distribution function (BRDF) based on the theory of target geometric modeling and track, and calculated the visible light scattering intensity variation of satellite observing at the northeast three stations at a certain time, the three peak values of which reached or approached to 7.510-3W/cm2sr with time, however, the scattering intensity in Aletai of Xinjiang was only 3.7510-3W/cm2sr when the other northeast three stations peaked. The results imply that the satellite optical scattering radiance tendencies at the northeast three sites are similar merely with the time delay induced by the latitude difference, but the radiance variation trend of Aletai, Xinjiang is quite different which has a very big longitude difference. The method proposed has been applied in the acquisition of space target more information selection in multistation observations.
To compare the properties of random mask in the optical image encryption, optical image encryption was stimulated and image encryption effects were analyzed using random phase mask and random amplitude mask in the several typical optical image encryption systems. The stimulation result shows that the correlation coefficient between original image and encryption image is bigger than 0.5 when random amplitude mask is used in double random mask optical encryption system based on optical Fourier transform and the original image can not be encrypted effectively. But the correlation coefficient between original image and encryption image approaches 0 when random amplitude mask is used in optical encryption system based on optical Fourier transform holography and the encryption effect is similar to one when random phase mask is used.
To solve the problem of the traditional log-polar tracking method which could only catch up with circular and quasi-circular objects with scale changing, we introduced ellipse log-polar transform(LPT) to estimate the target-s scale parameters within the framework of Mean Shift tracking. Experimental results demonstrate that the composite algorithm has lower tracking error and better tracking accuracy rate on the condition of small deformation and light intensity changes. Comspoured with the traditional, it has a better robustness.
Band selection is a common approach to reduce data dimensionality of hyperspectral imagery. A new band selection algorithm for hyperspectral imagery based on Kullback-Liebler (K-L) divergence and spectral divisibility was proposed. Firstly by considering every waveband spectral component as the onedimensional vector, the K-L divergence was used to quantify the information amount among them to select the bands combination with maximum information amount and minimum similarity. Then the spectral divisibility distance between two ground objects was calculated to remove redundant bands from the selected bands combination and make the final selected bands combination contain optimal divisibility. Hyperspectral imagery was tested for classification to testify the effectiveness of this band selection algorithm. As shown in the experimental results, the classification accuracy percentage is 92.2% and Kappa coefficient is 0.88, when using spectral angle mapping on the pesudo color synthesis image of 3 selected bands.
In this paper we demonstrate that the optical encryption scheme with a reference wave in joint transform correlator (JTC) is vulnerable to the chosenplaintext attack (KPA) from the point of view of cryptanalysis. First of all, we selected a dark image as the plaintext and recorded its joint power spectrum, then we recorded the intensity of the reference wave by keeping the input plane out, thereafter we recorded the intensity of the Fourier transform of the encrypting key by sheltering the reference wave and the plaintext. With the obtained three images, the intruder could retrieve the encryption key with the help of several skillful steps. Consequently, the intruder could further access the plaintext with the retrieved key. The theoretical analysis and a set of numerical simulations were carried out to demonstrate how the secret key of the encryption system could be derived out with our proposed strategy.
A novel system calibration model in fringe projection profilometry (FPP) was proposed, which does not require the connecting line between two optical center parallel to the reference plane, the optical axis of the imaging system is perpendicular to reference plane and the two axes intersect. The coefficients of the phase-to-height relationship can be deduced by using only two different height gauge blocks, which are irrelevant to the coordinate system. The maximum relative error is 0.6% among 4 measured gauge blocks. The experiments demonstrate that this calibration method is flexible and the accuracy is high.
In order to solve stitching testing of precise optical flat mirror, based on least squares fitting, we established reasonable stitching algorithms and mathematical models. In addition, relative program was written and a 120 mm precise flat mirror was tested with stitching method. A marked point was used to accomplish the alignments between subspertures. At the same time, relative stitching accuracy was analyzed based on the full aperture testing result and self-examination subaperture testing result. It is proved from the experiment results that there is no gap in the stitching result. The peak value(PV) and root-mean-square(RMS) errors between stitching results and full aperture testing results are 0.020 and 0.002 respectively. The stitching result is in consistent with the full aperture testing result and self-examination testing result, respectively, which proves the reliability and accuracy of the stitching.
For achieving a correct measurement of the extinction coefficient of visibility, parallelism importance of the probe beam was discussed, the detection method of probe beam divergence angle was proposed and the measuring device was designed. The device includes a fixed focus imaging system and a linear motion system. Divergence angle was derived by using the imaging geometry and spatial relationship. With ultraviolet (UV) LED as the light source, measurement systems and control software were completed. According to the imaging results, the horizontal and vertical divergence angles were calculated. The probe beam was analyzed with divergence angle. Experimental results show that the UV LED light horizontal divergence angle is 7.8 and the vertical-s is 6.9. By comparison, the visibility ratio of non-parallelism to parallelism is 0.51. Visibility by this method is closer to the actual value.
A new method of spectropolarimeter aimed at polychromatic light based on photoelastic-modulator (PEM) was proposed, which included a linear retardance oriented 0(-45) PEM and a polarization analyzer at 45(0). The light was first modulated by PEM, then pass through the analyzer and formed the modulated interference signal after detected by detector. Finally the incident light polarized spectra (S1、S2 and S3 of Stokes parameters) were obtained by Fourier transform of the modulated interference signal. The method reduces the complexity of polarized optical length measurement. The basic principle was introduced, the correctness and feasibility were verified through the corresponding numerical simulation.
Due to the requirement of disassemble for existing sky screen position detection method in flying projectile, a novel position detection method was proposed without dismantling the flying projectile. At first, the theodolite was used to build the datum plane. In the second, by using the specified stroboflash tiny illuminant and setting the output threshold of sky screen, based on the relative displacement distance between the transition table and the datum plane while the output signal of illuminant was showing on the sky screen, the relative position parameters were detected. Finally, when the sky screen tilted 2,-2 and -5,the error of measured tilted angle and actual angle was always less than 1, the experiment results showed that the detection accuracy was more than 1 which agreed with the theoretical analysis. The proposed method does not require the disassemble of the flying projectile, it saves the time and can be further used in the position measurement of fly projectile.
By using the virtual instrument technology, non-uniformity correction system of pyroelectric infrared focal plane array (IRFPA) was designed based on LabVIEW software platform. The system can select correction algrithm by using the control panel, and choose three different normal pixels to make different standard correction curves. Moreover,it can be used to acquire the IRFPA pixels- output, test the non-uniformity parameter and correct the non-uniformity. The system can observe the correction contrast with the three-dimensional waveforms and images as well as compute the value of NU (non-uniformity). The non-uniformity correction experiment was done on the 120160 pyroelectric IRFPA video signals. Meaningwhile, the non-uniformity correction algorithms were compared, and the simulation data results were analysed. The feasibility of this system was validated. And it is indicated that the mean algorithm of the twopoint correction is the least for the pyroelectric IRFPA to correct non-uniformity. By the statistical data, it is proved that the value of NU can be averagely decreased by 30%.
On the basis of existing near infrared(NIR) detection technologies both at home and abroad, a pulverized coal calorific value detection system based on near infrared was designed. 100 pulverized coal samples were selected to create the near infrared model of pulverized coal colorific value, and then 50 samples of the validation set were used for validation analysis on the precision and stability of the model. It was turned out that the correlation coefficient between the forecast value and real value of pulverized coal colorific value was up to 0.995 8, with relative deviation less than 2%. The result indicated that the system had a good forecast precision and stability, could meet the demands for rapid detection to the pulverized coal calorific value and the system was characterized by small volume, simple structure, convenient operation and had a very good transportability.
The high-gradient concave optics polishing is a problem in optical manufacture. The optical belt deterministic polishing method is one of the efficient ways to solve such optics polishing problem. We introduced the theory and method of the optical belt polishing technique, studied the feasibility of figuring the optical surface with the optical belt polishing method. To demonstrate an optical belt polishing process, a 80 mm K9 glass plane mirror was processed on a 5axis precise computer-numerically-controlled (CNC) machine. Its surface figure accuracy root-mean-square (RMS) was improved from initial 0.10 9 (= 632.8 nm) to final 0.02 8 through three ion beam polishing (IBF) processes, and the mean iterative convergence ratio was 1.3. The result shows that the polishing method has rapid convergence rate as well as machining accuracy on surface figuring. This experiment proves that the optical belt polishing can figure this kind of optical glass, which lays the foundation for figuring high-gradient optics.
Based on geometrical optics and irradiance theory, the illumination distributions of the rhombus, circular ring and honeycomb LED arrays under uniform near field lighting were analyzed. Formulae for calculating total irradiance to target surface of different array light sources were deduced. According to Sparrow's criterion, the optimal distance between LED arrays was determined. Moreover,based on the illumination formulae presented in this paper, three LED arrays were simulated and comparatively analyzed, and the different illuminance distribution characteristics of the LED arrays were received. The rhombus array can obtain a wide range of flatness; The flat range of circular ring array is small, and the energy is concentrated in a circular range, which can collect the light effectively; The flat range of honeycomb array is small and the light occupies small panel space, which can reduce the design costs to a certain extent.
Thermal design of air convection for an LED lamp was carried out. The simulations for the lamp with or without air convection were studied. In order to ensure the accuracy of simulation result, the thermal analysis model was modified repeatedly. The simulation and test results show that the junction temperature of the LED lamp reduces by about 8℃ with air diversion cooling, the lifetime of the LED lamp can extend by 2 000 hours. Further study shows that many factors affect the heat radiation apparently, such as the emissivity of base plate subsurface, the thermal contact resistance, and the distance between convection hole and LED. Sensitivity analysis for each factor was carried out, and some advices on how to further reduce the junction temperature of the LED lamp were put forward.
FY-2 radiometer is a multi-field Ritchey-Chretien（R-C） optical system. Stray light outside the field grazes the secondary mirror, then goes across the primary mirror, and finally hits the detector, which produces the straight hit path. To eliminate this straight hit, we used Tracepro software package to trace the path and used Zemax software package to find out the generation mechanisms of it, and then calculated the area of the straight hit. Based on the simulation and calculation, a shutter with some laminas was designed, which could allow signal light to transmit but prevent the stray light entering into the detector. Results of the simulation illuminate that the direct stray light in this area can be eliminated completely by using the designed shutter. Also the integrated sphere experiment indicates the shutter can decrease 95.2% of the visible stray light.
To meet online automatic infrared camera minimum resolvable temperature difference (MRTD) field testing requirements, a novel method for detecting MRTD was presented. In hardware aspect, the use of the single blackbody temperature control technology not only reduced the volume and quality of testing equipment but also guaranteed the accuracy of the temperature difference control between blackbody target and environment background, and by combining serial interface communication technology with CCD technology, the cooperation of the temperature control and image acquisition was achieved; In software aspect, the use of optimized algorithm could precisely extract the target and background region, and calculate the MRTD using gray difference between target and background region. The experiments show that the error is less than 0.02 ℃ compared with the results observed by eye. The testing equipment has simple structure, small volume, convenient operation, it can realize the automatic test of MRTD under field condition.
Passive athermalizing technology of low-cost mirror-lens infrared optical system was studied, and the athermalization relationship was deduced and the condition expression for mirror-lens secondary imaging system athermalization was got. Defocusing aberration caused by thermal change could be regarded as a kind of primary aberration, and the Mangin mirror was introduced as secondary mirror to eliminate the thermalization aberration. The same as the normal system, four methods could be used to get an athermalization optical system: appropriate focal power distribution, optical material and housing material matching, lens surface shape changing and asphere surface introducing. A generalized optical model was built, and the results show that the MTF is more than 0.5 at 17 lp/mm in -45℃~+60℃ with less than 0.52℃ Narcissus.
In recent years, the femtosecond laser becomes a promising tool to fabricate 3D microstructures for their applications in micro-optics, microfluidics and biofabrication. Various femtosecond-laser-based processes have been used for machining high-precise microstructures with arbitrary shapes. However, the efficiency problem of the femtosecond laser micro-fabrication has hindered its practical applications. Here we present a simple, high-efficient maskless technique to fabricate 3D microstructures on glasses using a femtosecond laser wet etch (FLWE) process. In the FLWE process, the ultrafast laser delivers intensity and time-controlled, programmable arranged, individual pulses to a glass chip. The sample is then subjected to wet-etch processing. The laser pulses change the physical and chemical properties of the glass in the focal spots, and the wet-etch processing that follows carves out a unique 3D microstructures array pattern. Using this method, we fabricated microlens with the diameter: 80 m, height: 6.7 m and surface roughness: less than 10 nm. We fabricated microstructures on glass surface like microlens arrays with different characteristics like high-fill ratio, high-aspect ratio, controllable shape and arrange, and so on. We also fabricated microstructures like spiral microchannels inside glasses using the FLWE process. The diameter of the spiral microchannel is 20 m, and the length-diameter ratio is more than 100. These 3D microchannels will be served as the alternatives of the 2D microstructures in the conventional microfluidic devices.
Radius of curvature is one of the primary parameters of optical elements, and radius-of -curvature measurement is critical for precision optics manufacturing. A laser differential confocal radius-of-curvature measurement system was constructed and uncertainties of two groups of curvature radius measurement results were evaluated. It is demonstrated that the measurement results of two groups of curvature radius have a difference of 0.001 15% with each other, which are all consistent with the nominal value, moreover the uncertainties of two groups are both superior to 3.211 1110-4 mm.
A 1 064 nm continuous wave (CW) passively mode-locked ultrashort pulse laser based on graphene saturable absorber was reported. The graphene film was deposited on an antireflection lens, the Nd∶YVO4 crystal was pumped by 808 nm laser diode. On the basis of W-folded cavity, the stable pulses of CW mode-locked were obtained with the average output power of 185 mW when the pump power reached 8.0 W. When pump power reached 16.0 W, the 1 064 nm CW mode-locked ultrashort laser with the average output power of 323 mW, the pulse width of 518 fs and the repetition rate of 66.7 MHz was obtained, which spectrum was centered at 1063.4 nm. Experiment results shows that graphene is an excellent saturable absorber for stable and reliable passively mode-locked pulse generation around 1 064 nm wavelength.
To compare the jamming effect of laser on charged-coupled device (CCD) and complementary metal-oxide semiconductor （CMOS） imagers, jamming experiments with the wavelength of the 1.06 m high-repetition-rate laser were conducted. The relationships of the two cameras- laser incident power with the jamming effective area, saturated pixel number and the imaging correlation were analyzed individually. The experiment results show that the laser power threshold of one pixel saturation of CMOS camera is 20 times than CCD camera; in order to reach the same jamming effective area, the laser power of CMOS camera is 10~100 times higher than the CCD camera; and to reach the same saturation pixel, the laser power of CMOS camera is 10~60 times higher than the CCD camera. Therefore, the CMOS camera is better than CCD camera on the antijamming of the 1.06m laser.
In the oil well logging, fluid flow is an extremely important parameter which determines the transmission characteristics of the oil production. A new type of flowmeter based on non-intrusive fiber optic interferometer was proposed.The fiber optic sensors wrapp closely around the outside wall of the pipe, and when fluid flows through the pipe, the vibration of pipe can be induced by turbulent flow,which results in the changes of dynamic pressure ,and then leads to the changes of light phase, so the relevant flow may be obtained from measuring these changes. The frequency characteristic of the pipe-s vibration signals was found in experiment,then the fixed relationship between the standard deviation of the pipe wall-s vibration acceleration impulse value induced by turbulence and the average fluid flow was determined, and the experiment acommplished fluid flow monitoring whose rang was from 5 m3/h to 50 m3/h.