2016 Vol. 45, No. 8
column
- Invited paper
- Infrared technology and application
- Laser technology and application
- Optical communication and optical sensing
- Advanced optical imaging technology
- Photoelectric devices and microsystem
- Advanced optical material
- Optoelectronic measurement
- Photoelectric measurement
- Optical design and simulation
- Terahertz technology and application
- Micro-nano optics
- Optical precision manufacturing technology
- Laser radar technology
With a homemade 1 018 nm fiber laser, an all-fiberized tandem pump broadband superfluorescent fiber source (SFS) based on single stage Yb-doped fiber was set up experimentally. It is the first time to experimently investigate the generation of forward superfluorescence by utilizing tandem pump in detail. Experimental results demonstrate the highest slope efficiency of 88% and the widest full width at half maximum (FWHM) of 14.81 nm for this all-fiberized tandem pump broadband SFS. The length of Ybdoped fiber would affect the maximum of output power, slope effiency and the central wavelength. With an increase in the length of Yb-doped fiber, the maximum of output power and slope effiency of the SFS are reduced. The central wavelength shifts towards the longer wavelength. With an increase of the pump power at a certain fiber length, the maximum of output power and slope effiency of the SFS increase. The central wavelength of superfluorescent spectrum has a slight shift. When 5.7 m Yb-doped fiber is employed as the active medium, the widest FWHM is 14.81 nm and the slope efficiency is above 80.3%. The fluctuation of the output power is less than 1% and no self pulsing or relaxation oscillation effect is observed.
The transmission spectrum characteristic of two-segment polarization maintaining fibers Sagnac interferometer was investigated and simulated in detail and the optimal parameters for eliminating the crosstalk between the two polarization maintaining fibers was obtained. A temperature-insensitive pressure sensing technology was proposed. An experimental Sagnac interferometer was built and the solid core polarization maintaining photonic crystal fibers were taken as the sensing probe. The side pressure sensitive coefficients and the temperature crosstalk drift were measured and compared. The experimental results show that the side pressure sensitive coefficient was about 0.287 7 nm/N and the temperature drift was less than 0.1 pm/℃.
2016, 45(8): 802003.
doi: 10.3788/IRLA201645.0802003
A longitudinal microstructured fiber based sensing scheme was proposed, the sensing capacity of which was greatly expanded by using frequency and wavelength encode simultaneously. Quasi-distributed pressure measurement along a single fiber was achieved, showing potential of high capacity multiplexing, high spatial resolution and high accurate detection. The silicone rubber package of sensing fiber made the pressure sensitivity increased to 1.03210-3 relative wavelength shift/MPa, which is 500 times higher than bare FBG. Experimental results of the prototype system including 6 fiber microstructures exhibited good linearity and relatively high measurement accuracy. High Resolution Manometry(HRM) in long distance based on this scheme is promising, which can be widely used in civil structural health monitoring, pipeline leakage detecting and distributed pressure sensing for in-vivo.
2016, 45(8): 804001.
doi: 10.3788/IRLA201645.0804001
Focusing on the problem of heat-flux measuring in complex and extreme circumstances, a new measuring method based on infrared thermography was proposed. Be superior to traditional radiation heat flow meter which can only measure heat flow at one point, the thermal distribution and heat flow distribution could be gotten easily and accurately in one time with help of a made-to-measure beacon, combined the advantages of contact and non-contact measurement. This study was divided by three parts, theoretical analysis, system construction and numerical simulation. Less than 2% theoretical error was obtained which verifies the accuracy and feasibility of heat-flux measurement technology based on infrared thermography.
Target characteristics is not obvious for infrared opto-electronic systems due to the complex scene under the conditions of mobile carriers such as aircrafts, as a result in this situation weak moving target detection is a big difficulty in the field of automatic target detection. A new method was proposed for this problem which was independent of image content. Through the combination of aircraft's inertial integrated navigation information, the geographical location of the pixel points in the image was calculated and then the corresponding points between the consecutive frames were obtained. So the movement of the background was acquired and the motion compensation was conducted, and the target was highlighted. Finally, the target was confirmed by backward verification using target motion information. The experiments show that the new algorithm can obtain a better detection results.
2016, 45(8): 806001.
doi: 10.3788/IRLA201645.0806001
Frequency Modulated Continuous Wave (FMCW)laser ranging has many advantages such as no measuring blind area, noncontact measuring and absolute distance measurement. However the measuring precision of FMCW laser ranging is limited by the modulation nonlinearity of tunable laser. Hence, this technology is not widely used in the field of precision measurement. The precision of FMCW laser ranging was affected by the nonlinearity of laser frequency modulation. The method of dual interferometry FMCW laser ranging was proposed. The distance of the target was equal to the ratio of the interference fringe of two interference systems. Using the method, the influence caused by the nonlinearity of laser frequency modulation was eliminated. The resolution and repeatability precision of the system was 65 m and 15 m respectively. The system has the following advantages. There is no need to measure the wavelength of the laser or lock the frequency of laser. And the structure is simple. This system has a wide application prospect in industrial large scale measurement, space technology, and surveying.
2016, 45(8): 806002.
doi: 10.3788/IRLA201645.0806002
Laser ultrasonically combined cutting was proposed based on ultrasonic vibration cutting with laser heating assisted cutting. A series of experiments were conducted in conventional cutting, ultrasonic vibration cutting, laser heating assisted cutting and laser ultrasonically combined cutting YG10 cemented carbide with PCBN tools. The tool wear characteristics and tool wear mechanism were observed by using digital microscope with super depth, the energy spectrum analysis was carried out in worn areas of tools by scanning electron microscopy (SEM). The experimental results indicate that the average flank wear of PCBN tool obtained by laser ultrasonically combined cutting is reduced by almost 57.5%, 46% and 41.3% respectively when compared with that by conventional cutting, ultrasonic vibration cutting and laser heating assisted cutting, therefore the tool life is obviously lengthened. The main wear types are crater wear, flank wear and tipping for PCBN tools in cutting YG10 cemented carbide. And the adhesion, oxidation, phase transformation and micro dissociation are the main reasons for the wear of PCBN tool in laser ultrasonically combined cutting YG10 cemented carbide.
2016, 45(8): 806003.
doi: 10.3788/IRLA201645.0806003
According to the phase distortion of laser beam in inner propagation process, a simulation model for the laser beam interacting with the fluid of the inner channel was established, in which the phase distortion caused by the thermal effects was taken into account and the influence of turbulence disturbance of the inner channel on the wavefront phase was simulated by introducing the method of phase screen. The phase characteristics of laser beams propagating through the inner channel on the conditions of different axial wind speeds was discussed in detail in terms of wavefront power spectral density, and the correction effect of laser beam propagation through the inner channel was further analyzed using the adaptive wavefront correction model. The results show that, with the increase of axial wind speed, the high frequency component of the wavefront phase increases at first and then decreases, and the beam quality gets worse at first and then becomes better. Particularly, the high frequency component of the wavefront phase increases most quickly and the beam quality degrades most significantly when the axial wind speed is about 0.65 m/s. This model provides a qualitative reference for the laser beam control system design and performance evaluation.
2016, 45(8): 806004.
doi: 10.3788/IRLA201645.0806004
A scheme of dynamic range optimization for Microwave Photonic Link with Distributed Feedback laser (DFB) was proposed. The nonlinearity of the laser was experimentally studied. The relationship between the bias current and the linear performance of the DFB laser was analyzed experimentally. Based on the experimental results, the linear system of Mach-Zehnder modulator (MZM) system was established. The experimental results show that the third order intermodulation of the system is suppressed, when the center frequency of the input frequency signal is 4 GHz and two tone separation is 10 kHz, the three order distortion is suppressed 23.1 dB and the spurious-free dynamic range can be improved by 8.68 dB.
2016, 45(8): 822001.
doi: 10.3788/IRLA201645.0822001
A new type of dual-wavelength photonic crystal fiber laser was proposed and demonstrated, based on superimposed fiber gratings. Linear cavity structure was used to induce the laser, Er3+-doped Photonic Crystal Fiber was used as the gain medium, and two superimposed fiber gratings whose reflectivity were higher than 99% were used for wavelength selection. Based on gain equalization technologies, modal competition in the cavity was suppressed to realize dual-wavelength laser at room temperature. The 3 dB line-wide is less than 0.02 nm, 30 dB line-wide is less than 0.25 nm, and SMSR is 54.34 dB. The wavelength interval of dual-wavelength laser is 0.932 nm. The experimental result show that the wavelength and the laser energy of the dual-wavelength laser are stable.
2016, 45(8): 822002.
doi: 10.3788/IRLA201645.0822002
For the shock reliability of high-sensitive fiber Bragg grating (FBG) vibration sensor, a dual cantilever FBG vibration sensor with a vibration restricting structures was designed. The relationship between the structural parameters, sensitivity and vibration displacement were analyzed, the structure was optimized and the limit of the vibration amplitude was determined. Sensor sample with a vibration restricting amplitude of about 90 m was fabricated, and the acceleration sensitivity, frequency response, impact properties of the sensors were tested. The results show that the acceleration sensitivity of the sensor is about 525 pm/g, the resonance frequency is about 66 Hz, and after repeated shocks of about 50g, the frequency response shows good reproducibility, which indicates that the sensor has a high reliability.
2016, 45(8): 822003.
doi: 10.3788/IRLA201645.0822003
In demand for the application of China's space information, a simple-managing and controllable-cost space optical network was designed. The established circle backbone network based on MEO satellites was equipped with microwave access ability to realize the backbone-access integrated and optical-microwave hybrid space network system. Coverage capacity was also simulated. The implementation scheme by step which was proposed based on the combination of the characteristics of the GEO relay system and the LEO satellite as well will contribute to the space network system for global information transmission and application.
Free space optical communication (FSO) has the advantages of high bandwidth, no need to lay fiber, low power loss, so it has attracted attention. In Gamma-Gamma atmospheric turbulence channel model, weak, medium and strong three atmospheric turbulence intensity were respectively considered, and combined with the phase noise, the performance of circular polarization modulation system with coherent detection was studied, and the closed form expression of the bit error rate(BER) and outage probability were derived. In the different atmospheric turbulence intensity and phase noise, the performance of the circular polarization modulation system with the coherent detection was simulated and analyzed. Compared with the error performance of the direct detection system, the results show that the error performance of the coherent detection system is better than that of the direct detection system. Therefore, in the circular polarization modulation system, employing the coherent detection method can reduce the effect of the atmospheric turbulence and greatly reduce the BER, and improve the performance of the communication system.
2016, 45(8): 822005.
doi: 10.3788/IRLA201645.0822005
The concept of pulsed pre-pump was introduced into Rayleigh Brillouin optical time domain analysis system. A step pulse composed of a sensing pulse and a pre-pump pulse modulated by microwave was used as the modulation signal in the system. The reshaping of Brillouin scattering signal in time domain was achieved through the stimulated Brillouin scattering interaction between Rayleigh scattering generated by the first-order sidebands of time-limited microwave-modulated pre-pump pulse used as the probe wave and the sensing pulse, by which the nonlocal effect was also reduced. The reshaping of Brillouin scattering signal in spectrum domain was achieved through the stimulated Brillouin scattering interaction between the zero-order baseband of microwave modulated pre-pump pulse and the sensing pulse, by which the contradiction between spatial resolution and measurement accuracy was effectively resolved. The transient coupled wave equations were calculated by applying frequency domain analysis method, through which the analytical model of stimulated Brillouin interaction occurred in the fiber during the propagation of the step pulse light was set up. When the sensing pulse is with a width of 5 ns and a power of 100 mW, and the pre-pump pulse is with a width of 50 ns and a power of 16 mW, the simulation results show that, in the fiber length of spatial resolution of 0.5 m, stimulated Brillouin scattering gain with fiber position takes the maximum value at 0.14 m, then decreases linearly to the fiber position of 0.37 m, but in the rest of fiber positions it is approximately zero. The Brillouin spectrum width in pre-pump pulse Rayleigh Brillouin optical time domain analysis system is about 35 MHz, which is only about 1/6 times of 212 MHz that is in the traditional Rayleigh Brillouin optical time domain analysis system, so the measurement accuracy can be improved under the same spatial resolution.
2016, 45(8): 822006.
doi: 10.3788/IRLA201645.0822006
As the investigation deepened, it is necessary to detect the hydrogen concentration with large quantities of points in the field of nuclear power station, aerocraft engine, gaseous fuel et al, but the existing optical fiber hydrogen sensing systems are able to measure only one point at a time. A Wavelength Division Multiplexed (WDM) optical fiber hydrogen sensing system was proposed for the detection of multi-point hydrogen. The topology principle and advantage of WDM optical fiber hydrogen sensing system were expatiated, and the technical feasibility of the novel system was introduced in detail. According to the analysis, a WDM optical fiber hydrogen sensing system was assembled, with four measuring channels. Using the components well developed in the telecommunication industry, an additional scheme was also developed for the hydrogen experiment. The results show that the novel optical fiber hydrogen sensing system is able to measure multi-point hydrogen simultaneously, and different measuring channels do not interfere with one another by measuring spectral evolvement and power of the optical signal. The performance testing shows that good stability (less than 1% in an hour) and small error (less than 2%) are achieved within the measuring range from 0 to 4%. The research results will provide a valuable reference for the optical fiber hydrogen sensing system to measure the hydrogen concentration with large quantities of points.
2016, 45(8): 822007.
doi: 10.3788/IRLA201645.0822007
In order to realize the wavelength demodulation of the optical fiber sensor, a 8 channel 50 GHz dense wavelength division multiplexer was used as the demodulation tool of the fiber Bragg grating pressure sensor. Taking the center wavelength of each channel as the calibration standard, the optical power output obtained from each channel was utilized to acquire the envelope of the distribution curve of the fiber grating reflection spectrum. By using the Gauss polynomial fitting method as peak-seek algorithm of fiber grating wavelength, the accurate position of the center wavelength of the fiber grating reflection spectrum was obtained and a simple structure, low cost, all-fiber wavelength demodulation system was achieved. The experimental results show that the linear fitting degree of the system pressure and wavelength is 0.996 5, the measured wavelength resolution is 0.3 pm, the maximum reference error is 2.6%, and the measurement accuracy is 0.16 MPa.
2016, 45(8): 822008.
doi: 10.3788/IRLA201645.0822008
In order to optimize the performance of GEO and LEO laser communication system, the simulation model of satellite communication orbit characteristic was established. The simulation model was designed. Through analysis of satellite data within one year, the range of Doppler frequency shift of satellite communication terminal is 5109 Hz, Doppler frequency shift compensation method can be used to reduce the influence of Doppler frequency shift between GEO and LEO. For coherent communication, frequency shift must be compensated by terminal. The range of point-ahead was larger than laser beam divergence angle, so the lead angle should be compensated by terminal, in order to reduce the influence of relative velocity on laser communication; the laser communication system need amend early according to point-ahead of LOS, the sun interference and earth occlusion have a longer time, satellite network should be carried out to improve the available probability, in the communication process the work flow of the two communication terminals was optimized based on the communication terminal time; LOS changing situation of GEO and LEO terminal was different, so different structures of the satellite should be designed.
2016, 45(8): 822009.
doi: 10.3788/IRLA201645.0822009
The irradiance fluctuation induced by atmospheric turbulence is a major factor to degrade the Signal-to-Noise Ratio (SNR) and bit error rate (BER) of laser communication systems. This paper aims to explore the effect of atmospheric turbulence state on the performance of wireless communication systems. Firstly, the channel was modeled by the logarithmic normal distribution and Gamma-Gamma distribution, respectively. Analysis showed lights on that the former model was not fit for irradiance fluctuation behavior in moderate or strong turbulent conditions, while the latter had wider applications. On this basis, the SNR and BER resulting from the phase noise introduced by irradiance were studied. Simulations were conducted for different channel models, which displayed the change of planisphere and degradation of BER along with irradiance variance. Results illustrates that the phase angle of planisphere and BER increase when the irradiance variance becomes larger. Up to a point, these discussions are valuable for real optical communication applications.
2016, 45(8): 824001.
doi: 10.3788/IRLA201645.0824001
Three dimensional super-resolution gated imaging(3D SRGI) is a novel scannerless 3D imaging technique, and has great potential in underwater imaging, remote surveillance and automatic navigation. The development of 3D SRGI was reviewed, and trapezoidal 3D SRGI and triangular 3D SRGI was compared from intensity states of range intensity profiles, 3D imaging step depth, signal-to-noise ratio, environmental noise sensitivity, range resolution, and range accuracy. For the improvement of 3D SRGI, advanced imaging methods were introduced including range-intensity coding imaging, real time 3D imaging and multi-pulse time delay integration imaging. Furthermore, the specific applications of 3D SRGI were summarized in low contrast target detection, target identification, and underwater 3D imaging. In addition, an overview on some recent 3D SRGI work was given in the Institute of Semiconductors, Chinese Academy of Sciences. The future development trends of three dimensional range-gated imaging are higher depth-to-range-resolution ratio and faster high-resolution 3D imaging.
2016, 45(8): 824002.
doi: 10.3788/IRLA201645.0824002
A 3D small-field imaging system was established by using the fringe projection technique to measure the small objects having large slopes and/or discontinuous surface. A stereo microscope was used to generate a small-field projecting field and to capture the deformed fringe patterns on the measured small objects. Three fringe sets having the optimum fringe numbers were coded into one major color channel to generate color fringe patterns having the maximum fringe contrast of the captured fringe images. Through one channel of the stereo microscope, a Digital Light Processing (DLP) projector projected these generated color fringe pattern images onto the measured objects surface. From another channel, the fringe patterns were deformed with regard to the object surface and captured by a color CCD camera. The absolute phase of each pixel could be calculated from the captured fringe patterns by using the optimum three-fringe numbers selection method. The relationship between the absolute phase and depth was established to move a white plate to several known positions by using an accurate linear translating stage, so the 3D shape data of the measured objects were obtained. Experimental results on measuring 3D shape of small objects show the accuracy and availability of the developed 3D imaging system.
2016, 45(8): 824003.
doi: 10.3788/IRLA201645.0824003
Conventional optical imaging require the image plane at the focal plane of the imaging lens group to get the maximum flux. So the focal length has great impact on imaging quality. In order to investigate the influence of focal length on quality of computational ghost imaging, the experiment of computational ghost imaging was constructed, and the probability density of the measurement of bucket detector was utilized to analyze the results of computational ghost imaging with different focal length and background light. The results show that the variation of focal length and background light have little effect on the quality of computational ghost imaging, which solve the problem that the defocus lead to the deterioration of quality caused by the inequality of two optical path in traditional ghost imaging. Computational ghost imaging can be realized without imaging lens and only using a bucket detector, thus avoiding the allocation of flux on the pixel dimension as well as improving the signal-to-noise ratio.Therefore, computational ghost imaging is very suitable for imaging detection under the extremely weak background.
2016, 45(8): 824004.
doi: 10.3788/IRLA201645.0824004
Color cameras are widely used in the printing industry, graphic arts, medical area, environment and many other applications. In order to save cost and maintain high colorimetric accuracy, a method that utilizing a single-channel pre-filter to calibrate color camera's spectral sensitivity curve was put forward. The pre-filter's simulation accuracy depended on the degree of matching Luther conditions, and it was impossible to match perfectly due to the limitation filter material, the film design, and the nonideal filter fabrication. The goal of this work was to design the target curve according to analyzing the influence factor of the simulate accuracy, using the continuously tunable monochromatic light source system to test the color CCD relative spectral response, selecting appropriate evaluation function model to simulate theoretical spectral transmittance, referring the CIE standard test colors and using CIE2000 color formula to evaluate the theoretical color error. This work shows that after increasing the pre-filter, the mean change of the color error is about 73%, and the color effect of the camera has been enhanced significantly.
2016, 45(8): 824005.
doi: 10.3788/IRLA201645.0824005
In order to stitch the sub-aperture data rapidly and precisely in microsphere profile inspection, the model of microsphere surface measurement was given, which was based on point diffraction interference. After analyzing the distribution of interference field lateral resolution in detail, a method of sub-aperture stitching based on mapping image matching was proposed. After equal-scale transformation of profile data, the homogenization of lateral resolution was achieved. The dimension of 3D point clouds data was reduced to a mapped 2D image for transforming the sub-aperture rotation-ship of the profile data to a translation relation on the CCD coordinate system. And the corresponding transformation offset between sub-apertures could be obtained by the feature points matching in ways of image matching algorithm, so the sub-aperture stitching could be realized. Finally, the feasibility and effectiveness of the proposed mapping image matching method for sub-aperture stitching was proved by the simulation experiment.
2016, 45(8): 820001.
doi: 10.3788/IRLA201645.0820001
The transverse mode and transmission properties in frequency region of 1-100 GHz of a microstrip transmission line model based on nematic liquid crystal (LC) were studied. The influences brought by the distribution of dielectric anisotropy of liquid crystal on the solution and S-parameter of microstrip line were researched through the finite element method accurately and comprehensively, as well as the influences of the bias voltage. Simulation results indicate that the distribution property reduce the echo loss of microstrip line, which is obtained in consideration of the distribution of dielectric anisotropy of liquid. Besides, the S-parameter changes continuously since the voltage between the strip and the gound gradually increases while the resonant frequency moves the same way. Moreover, this accurate method can amend the motion of resonant frequency by 2.4 GHz, compared with the results obtained by those methods in the past. This paper provides a theory basis for researches in the field of LC microwave devices.
2016, 45(8): 820002.
doi: 10.3788/IRLA201645.0820002
A new microwave photonic filter based on stimulated Brillouin scattering was proposed. By tuning the center wavelength of the optical filter, the switchability between the microwave photonic bandpass filter and the microwave photonic notch filter can be obtained. The passband or the notch center frequency of the microwave photonic filter can be tuned continuously by tuning the wavelength of the pump laser. Since no electrical component was involved, the microwave photonic filter was all-optical. Therefore it can achieve a very broadband operating frequency range. The maximum measured tuning frequency range in the experiment was limited by the displaying range of the vector network analyzer. Since an optical phase modulator was used, no bias voltage was needed. Therefore, there was no bias voltage drift problem. Experimental results demonstrate a switchable and continuously tunable microwave photonic filter with a broadband operating frequency range from 9-26.5 GHz. The bandpass filter has a narrow 3 dB bandwidth up to 28 MHz, which is limited by the optical fiber Brillouin gain linewidth.
2016, 45(8): 820003.
doi: 10.3788/IRLA201645.0820003
Integration of optical devices onto silicon substrate is attracting increasing attention in the field of optoelectronics. The fluidic self-assembly technology was applied to the integration of thin-film metal-semiconductor-metal (MSM) photodetector, the integration results was related to the geometry of the binding site. The spacing and shape of the binding sites on the thin-film MSM photodetector will affect the integration process of device onto the host substrate. In order to effectively predict the effect, MATLAB was used to simulate the distribution of interfacial free energy for the integration process. Firstly, based on the introduction of thin-film MSM photodetector and its integration, a model of translation and rotation during the integration was established for the simulation. Then, according to the linear relationship between the interfacial free energy and the matching degree, the distribution of the matching degree was investigated for the different binding sites with the different spacing and shape. By analyzing the relationship between the slope of the matching degree and the correct-assembly/false-assembly state, it predicted that the integration results would be better when the spacing between the binding sites is longer and the shape of the binding sites is trapezoid. Finally, considering that the thin-film optical devices may have specific requirment of positive and negative contacts, the binding sites with asymmetric shape was designed to avoid the reverse binding connection during the integration process.
2016, 45(8): 820004.
doi: 10.3788/IRLA201645.0820004
To start from microchannel-plate photoelectric multiple model, constraint conditions for vacuum multiplier system caused by anodized transmission of composite waveguide and position-sensitive anodes were studied deeply, and Mott interpolation method was employed to research the electro-optical properties of new optoelectronic device. Firstly, structure and working principle of composite waveguide anode were introduced, and the correspondence between the transmission anode and position-sensitive anode was given. On this basis, constrained relationship between high-speed signal detection and precise positioning of incident light axis was analyzed, and the corresponding devices design and experimental methods were given. Finally, the verification testing of the new device was conducted in vacuum furnace. Test results show that the new device is feasible both in theory and practice,to search for the adaptive adjustment mechanism of interelectrode tunneling voltage is a trend as inevitable for extending its application field.
2016, 45(8): 821001.
doi: 10.3788/IRLA201645.0821001
Generalized gradient approximation projector augmented wave method based on first-principle in the frame of density functional theory (DFT) were put forward. The slab model of GaAs (110) crystal plane was adapted for calculating adsorption system on basis of the optimization of bulk GaAs structure. Three types of adsorption system including specific adsorption sites, total binding energy, and adsorption electronic structure were taken fully into account with adsorbate quantity of =0.5 monolayer (ML) sole Cs,=0.5 ML sole O, and =1.0 ML Cs, O, respectively. The comparison results of calculated total binding energy and projected maps of electron density show that when adsorbates of Cs, O reach to=1.0 ML, they don't form local domain of competitive chemical adsorption, while they form a compound uniformity phase of cooperative chemical adsorption. Considering electronic dipole correction in the calculation, the work function of the three adsorption systems were 4.423 eV, 5.749 eV, 4.377 eV, the method and mechanism for improving and maintaining photoemission characteristics in GaAs photocathode preparing technology were further obtained.
2016, 45(8): 817001.
doi: 10.3788/IRLA201645.0817001
Large photo-electricity telescope plays a more and more important role in exploring objects in the space and astronomy observation, its detectivity and pointing precision are the main factors that affecting its development. Firstly, detailed analysis on different errors affecting the pointing precision of the telescope was conducted in the paper; then topology of the telescope was constructed and the spatial error pointing model was established based on multi-system theory; finally the relation between three axis differences and angle measurement errors was researched. Compared with traditional spherical function, a comprehensive item of errors were contained in the model which provided reference for error distribution and error correction.
2016, 45(8): 817003.
doi: 10.3788/IRLA201645.0817003
The technology of the measurement of relative position and pose between two spacecrafts based on laser lidar is one of the key technologies in many space applications, such as on-orbit servicing to satellites of losing control, debris removal, etc. Firstly, the current research at home and abroad was described. Secondly, the measurement technology principle of relative position and pose was introduced and the point cloud registration method was highlighted. Finally, the simulation experiment of the spacecraft simulator was given. The result shows that measurement of relative position and pose between two spacecrafts based on laser lidar method is reasonable and feasible and it has high accuracy. It meets the relative navigation mission requirements and provides a greater reference for the implementation of engineering applications.
2016, 45(8): 817002.
doi: 10.3788/IRLA201645.0817002
A simple system of measuring solid-state laser instantaneous facula intensity space-time distribution was established, based on the principle of CCD diffused transmission imaging. Experiments of verifying the feasibility of this system were carried out, and the pulse laser spot images were obtained with precision, and the laser intensity space-time distribution parameters such as beam radius, facula dithering, beam quality, light distributions and average power were obtained through CCD measuring data which were processed by Matlab soft ware. At last, the experiment result show that the method of CCD diffused transmission imaging for measuring laser instantaneous distribution is feasible, and the system acquisition frequency could reach 120 Hz. This system had advantage of high resolution, high frame frequency, low-cost and easy to use, which could realize the synchronous measurement between large laser spot intensity distribution and power, with less than 2 percent power measured error.
2016, 45(8): 818001.
doi: 10.3788/IRLA201645.0818001
In order to improve the imaging performance of aviation camera optical system in high-altitude and high-speed environment, an analysis of the influence on the optical window surface deformation caused by the aerodynamic pressure and aerodynamic heat loading in different flying altitudes environment was conducted, and the thickness of optical window was well designed. Based on fluid-solid interaction model and fluid-heat interaction model with finite element, how aerodynamic pressure and aerodynamic heat loadings affected optical window was simulated and how different flying environment altitude impacted on the surface deformation of different thickness of optical window was analyzed. A proper optical window thickness was chosen in the consideration of not only strength requirement but also various flying altitude circumstances to meet unique flying environment demands; and then, to judge the influence on the imaging performance of optical system caused by the surface deformation of optical window with that thickness can be accepted or not, Zernike polynomial was used to fit the surface deformation of optical window in that working condition. Putting the Zernike polynomial coefficients into optical software, taking MTF and wavefront error as assessment indexes, the influence of deformation of optical window on the imaging performance of optical system was analyzed. Finally, the appropriate thickness of optical window was gotten. The result shows when an aviate flies at a speed of 3 Ma, in the 5 -30 km altitude ranges and with the 5 angle, designing its optical window thickness to be 15 mm is fitted with the 200 mm diameter. A foundation is also built in the aspect of selecting and optimizing for the thickness of optical window in different flying altitude scopes.
2016, 45(8): 818002.
doi: 10.3788/IRLA201645.0818002
The adaptive optics system with Rayleigh guide star could compensate the image in observational astronomy, and could improve sky coverage. Projecting a suitable Rayleigh guide star is the precondition of adaptive optics with laser guide star. To realize the image compensation in observational astronomy, a laser launched system was designed. All kinds of parameter were analyzed and a suitable method of launching a laser guide star was completed. First, based on the demand of adaptive optics system with Rayleigh guide star, all kinds of parameter of laser box were probed. Next, the laser launched telescope aperture and the guide star spot size were analyzed according to the turbulence theory. Then, the laser launched system was designed by Zemax. The aperture of launching telescope is 260 mm. The optimal altitude of laser beam waist is 9.8 km, with Rayleigh guide star at 10-11 km. The laser spot size is 0.45 without turbulence and less than 1义with turbulence. Finally, the system was analyzed with tolerance by Zemax, and the results demonstrated that the system was easily to process. The laser projected system could suffice the demand of laser guide star adaptive optics and the method to design the system could be widely used.
2016, 45(8): 818003.
doi: 10.3788/IRLA201645.0818003
Deformable mirror as the key part of the adaptive optics systems, plays a role of correcting the wavefront error. The transversal piezoelectric deformable mirror is widely used, and its design parameters have important influence on the system performance, so the optimization is needed. The simulation results show that minishing the thickness of Si mirror and PZT player can increase the maximal displacement, but decrease the first natural frequency of the system. The system working requirements can be satisfied by the orthogonal matching of thicknesses. The material and structure parameters of the fixture affect the system thermal deformation performance. Using the same material as the mirror for the fixture, the system thermal deformation is minimum, the height and wall thickness of the fixture can be optimized to reduce or even eliminate the system thermal deformation. Finally, the influence function of the discrete electrode is obtained by the simulation of voltage performance.
2016, 45(8): 818004.
doi: 10.3788/IRLA201645.0818004
A new hyper-field zoom bionic eye optical system based on the model of bionic fisheye was presented. The variable focal power lens was employed to design the bionic eye with zoom system more compact and no move lens. The fisheye lens is a kind of retro-focus lens system. Fisheye zoom first-order geometric optics theory based on matrix theory and zoom principle were established. The former group and the latter group focusing optical power equation were deduced. Furthermore, the boundary equation of optical power in the zoom system was discussed. Finally, the bionic fisheye field can be acquire to 164. The focal lengths was from 5 mm to 15 mm. The design example can be applied in intelligent control, aerospace industry, robotics systems which provide a useful exploration.
2016, 45(8): 818005.
doi: 10.3788/IRLA201645.0818005
To meet the commands of Spatial Heterodyne Spectrometer (SHS) based on Fourier Transform that are high spectral resolution, minimum distortion, homogeneous illumination, high signal to noise ratio and the limited resources of volume and weight, an imaging optical system of SHS was designed. According to the characteristic of spatial interference in SHS, the interferogram on the location plane of the fringes near the gratings was imaged onto the detector with a specific magnification, which determined the spectral resolution and the band width of SHS. For the case of SHS in which magnification was the limit factor, the constant magnification could be obtained by use of the match of fore lens and rear lens to achieve a telecentric optical system. The imaging optical system actually contained a spread of optical elements from grating to detector, and hence, the diffracted wavefront error of gratings and RMS change in wavefront error of beam splitter and field widened wedges in interferometer would decrease the modulation efficiency. The imaging optical system offered the constant magnification, and it is apparent that even minor change in the position of FPA have a slight effect on the spectral resolution and band width, furthermore, the maximum distortion decreases to less than 0.1% over the field of view. The theoretical Modulation Transfer Function (MTF) is high than 0.60 at the spatial frequency in cycles per mm of 38.5 over the entire defined format. Based on the analysis of stray light, uniformly illumination and the ability of field widened of interferometer contained in the imaging optical system, a tolerance sensitivity analysis to determine the worst tilted error of the filter is performed. The optical system has well suited to SHS applications that require high spectral resolution and high modulation efficiency over a relative narrow spectral band.
2016, 45(8): 825001.
doi: 10.3788/IRLA201645.0825001
Ceramic Matrix Composite (CMC) has been widely applied for its excellent protection performance. It was hard for raditional testing means as ultrasonic to complete internal spection due to the porous structure of CMC. Terahertz Time-Domain Spectroscopy (THz-TDS) was applied to establish the THz Nondestructive Testing(NDT) model of thickness at single point and to extract optical parameters of material samples. In further verifying experiments, exploratory detection and evaluation were developed on porosity distribution and defect sizes. Scanning imaging performance and conclusion of time-frequency spectrum analysis are relatively plausible on CMC internal testing through the experiments. The study in this paper proves the revealing ability of THz-TDS on quantitative NDT and properties exploring of specific materials.
2016, 45(8): 816001.
doi: 10.3788/IRLA201645.0816001
Si nano-optical waveguide resonant cavity with low loss and high Q value is the key for high sensitivity detectors, biosensors, optical communication devices, and so on. However, the surface roughness of optical waveguide will cause high transmission loss which becomes a serious constrain to the high Q value of Si nano-optical waveguide resonant cavity. Therefore, it has become a key issue to reduce the surface roughness of silicon-based nanometer optical waveguide for the development of photonic devices. Nowadays hydrogen annealing technology is an important method to reduce the surface roughness of waveguide. According to the theory of surface Si-H bond current density, the simulation study was done by Materials Studio software. The reaction between silicon atoms and hydrogen atoms in the smoothing process of hydrogen annealing was simulated. The reaction transition state was searched. The influence of silicon hydrogen bond and temperature on the reaction process was also studied. The results indicate that chemical bond can be formed between silicon atom and hydrogen atom under high temperature with H2 atmosphere. Higher temperature is benefit to accelerate the moving rate of surface silicon atoms which makes the surface transition from upper state to lower state, and realize its smoothing.
2016, 45(8): 819001.
doi: 10.3788/IRLA201645.0819001
To accomplish the processing to aspherical mirror with large aperture, the tri-station processing center was designed which has three work stations. Based on the processing center, an aspherical processing model was established. With two rotating axes, it could be used to accomplish the full aperture processing. To verify the practicability of the model, with actual project, the processing to a 1 450 mm off-axis parabolic mirror was finished. The result shows that after a cycle of processing, the map of the mirror restraint from PV 4.653 m, RMS 0.409 7 m to PV 3.585 m, RMS 0.258 1 m. The converging rate of RMS is 37%, which verifies the accuracy and practicability of the model.
Synthetic aperture ladar (SAL) is an ideal approach for the high resolution region observation with long distance. However, there is a contradiction between the azimuth resolution and the range swath in the single transmitter single receiver SAL system. So the range swath is restricted to a much narrow range. In this paper, the multiple-transmitter-multiple-receiver SAL system was proposed to overcome this limitation. The SAL system worked in the low pulse repetition frequency (PRF) mode to make the range swath unambiguous, and azimuth multiple-channels approach made the azimuth Doppler unambiguous by the way of combination virtue aperture and the real aperture through adaptive digital beam-forming method to realization the high resolution wide swath SAL imaging. The basic principle of increasing the azimuth resolution with the Multiple-Transmitter-Multiple-Receiver SAL system was depicted. Secondly, the concept of the Multiple-Transmitter-Multiple-Receiver SAL system mode was presented, and the signal model for the SAL mode was given as well. According to the Doppler ambiguous in the low PRF system, an adaptive signal processing approach was propoed to de-ambiguous. Finally, the simulation of Three-Transmitter-Three-Receiver SAL system was provided. The performance of the simulation shows the Multiple-Transmitter-Multiple-Receiver SAL system can overcome the Doppler spectrum aliasing and increase the azimuth resolution, and proves the feasibility of the Multiple-Transmitter-Multiple-Receiver SAL system.
2016, 45(8): 830002.
doi: 10.3788/IRLA201645.0830002
The six-dimensional(6-D) motion errors of helicopter loading platform(including three-dimensional (3-D) flight trajectory and 3-D attitude angle motion errors) have significant effects on point density and coverage area of the obtained laser point cloud from helicopter-borne LiDAR. Quantitatively comparing the influence characteristics of each of the 6-D motion errors on quality of the laser point cloud, has practical significance for eliminating the effects of these motion errors and for improving accuracy of the reconstructed 3-D imaging products. The transfer relationships between the 3-D position errors of the laser points and the 6-D motion errors were established. Through numerical simulation experiment, changes of point density and coverage area of the laser point cloud caused by the 6-D motion errors were quantitatively evaluated respectively and transversely compared. Simulation experimental results show that, the effects of the 3-D attitude angle motion errors are more significant, and also increase with increasing flight height; while the impacts of the 3-D flight trajectory motion errors are much smaller.
2016, 45(8): 830003.
doi: 10.3788/IRLA201645.0830003
Progress on key technology of mid-infrared liquid crystal optical phased arrays was summarized. The fundamental principles and schemes were introduced. Meanwhile, graphene and mid-infrared liquid crystal were the key technique to realize the practical mid-infrared liquid crystal optical phased array. The latest development on these two technique were emphasized on the topic of non-mechanical mid-infrared laser radar system. The recent development on mid-infrared liquid crystal included tolane liquid crystals and fluorinated liquid crystal. The transparent spectrum and its composite were both given including their working conditions. The recent development on mid-infrared transparent conductive films included graphene, nano-metal-network, graphene-metal composite film. The fabrication process of each kind of film were given, also their properties such as transparent spectrum and mechanical attach forces were introduced in detail.
