2018 Vol. 47, No. 10
column
- Invited column-“Infrared semiconductor lasers”
- Invited paper
- Laser radar technology
- Laser technology
- Infrared technology and application
- Computational imaging technology
- Laser technology and application
- Optical communication and optical sensing
- Photoelectric device and microsystem
- Photoelectric navigation and control
- Terahertz technology and application
- Optical design and simulation
- Photoelectric measurement
- Information acquisition and identification
2018, 47(10): 1003001.
doi: 10.3788/IRLA201847.1003001
Quantum cascade laser (QCL) has been widely applied in directed infrared countermeasures (DIRCM) system, free space optical communication (FSOC) and gas sensing since it has advantages of high efficiency, compact volume, low electrical consumption and wide wavelength tunability. In this paper, the progress in QCLs made over the last 20 years was reviewed. The principle of emission and overview of QCL was demonstrated in the introduction. The design of active region for high output power QCL aiming at DIRCM was described in the first part. In the second part, the progress in distributed-feedback QCLs for gas sensing was introduced. In the third part, the research of high brightness QCL phase locked arrays was demonstrated. In the fourth part, the high speed QCL for FSOC was discussed. Finally, a new device, QCL frequency comb was introduced for its crucial influence on mid-infrared frequency comb.
2018, 47(10): 1003002.
doi: 10.3788/IRLA201847.1003002
Mid-infrared semiconductor lasers possess the advantages of small volume and high efficiency and have important application prospects in the field of environmental detection, space communication and military defense. However, the output power of mid-infrared semiconductor laser device is low, which limits its application in the above fields. Laser beam combining technology is an important approach to enhance the power of mid-infrared semiconductor lasers. In this paper, several beam combining methods and the latest progress of mid-infrared semiconductor lasers were introduced in detail.
2018, 47(10): 1003003.
doi: 10.3788/IRLA201847.1003003
The mid-infrared lasers of 3-4 m can be widely used in industrial gas detection, medical treatment and free space optical communication. At present, the antimonide semiconductor interband cascade laser is an ideal scheme for realizing 3-4 m in the middle infrared band. The interband cascade laser (ICL) may be considered the hybrid of a conventional diode laser that generates photons via electron-hole recombination, and an intersubband-based quantum cascade laser (QCL) that stacks multiple stages for enhanced current efficiency. This paper gives an overview of the basic working principle of inter-band cascade lasers, and describes the development history of major inter-band cascade lasers, including the University of Oklahoma, the US Naval Laboratory, and the University of Woodsburg. The performance of the interband cascade laser developed by the Institute of Semiconductors of the Chinese Academy of Sciences is also included. By analyzing the difficulties in designing and preparing the laser, the technical solution to further improve the performance of this kind of lasers is expounded.
2018, 47(10): 1003004.
doi: 10.3788/IRLA201847.1003004
GaSb based optically pumped semiconductor disk lasers (OP-SDLs) attracts considerable attention in novel mid-infrared laser device research field for their potential excellent beam quality and high output power. The epitaxy structure and basic principle of GaSb based OP-SDLs wafers were summarized. The development of GaSb based OP-SDLs at 2 m wavelength was reviewed respectively by analyzing the aspects of wavelength extending, power scaling, line-width narrowing, short-pulse generation and effective thermal management. The technical development direction and application prospects of this type of laser were discussed.
2018, 47(10): 1002001.
doi: 10.3788/IRLA201847.1002001
With the development of 5G, internet of things and big data, optical communication networks, as the backbone of data transmission, are imperative to expand their capacity, improve transmission stability and network intelligence. Space-division multiplexing technology, which is mainly based on multi-core fiber, few-mode fiber and few-mode-multi-core fiber, is considered to be the key to improve the capacity of optical communication network system and build next-generation optical communication networks. Based on the reported experimental results, the application of space-division multiplexed fiber was mainly studied in optical transmission, high-performance laser and fiber sensing. It is fully demonstrated that the space-division multiplexed fibers are important to the modern optical fiber communication system. It will be a hot spot and should be drawn much attention for the evolving optical communication.
2018, 47(10): 1002002.
doi: 10.3788/IRLA201847.1002002
Iterative phase retrieval, as a computational imaging technique, provides a powerful tool that combines the superiority of post-processing algorithm with an optical system, which will facilitate a low-cost and portable implementation for microscope. Lensfree imaging based on multi-distance phase retrieval becomes a focused topic in the domain of computational imaging, due to its high-resolution, wide field and aberration-less propertyies. Multi-distance phase retrieval reconstructs a full wavefront merely with a dataset of defocused intensity patterns related to different diffraction distances. At present, this technique suffers from tilt illumination artifact, convergence stagnation, measurement uncertainty of the sample-to-sensor distance, color imaging artifact and resolution loss with pixelated problem. Different correction methods to solve these problems were proposed in this paper. Experiment was also given to validate the performance of these methods.
2018, 47(10): 1030001.
doi: 10.3788/IRLA201847.1030001
A high-speed phase modulation of down-looking synthetic aperture ladar was proposed. The spatially polarized beam was divided into two coaxial and polarization-orthogonal beams. In the orthogonal direction of travel, the two beams were modulated to sinusoidal phases, whose changing directions were contrary; in the travel direction, these two beams were modulated with different curvatures to a quadratic phase history,which was associated with position of the targets in slow-time axis. This modulation method has the function of automatic jitter compensation in the azimuthal direction, and can effectively prevent the platform jitter effects on imaging.
2018, 47(10): 1030002.
doi: 10.3788/IRLA201847.1030002
Differential absorption lidar (DIAL) is an effective way to measure the concentration of nitrogen dioxide in extensive air with high precision. Based on the tunable solid-state laser absorption technique, the principle and systematic structure of differential absorption lidar were introduced. The absorption spectra of nitrogen dioxide in the range from 3.410 m to 3.435 m were measured with a step of 0.01 nm. The experimental results show that the correlation coefficient between the measured and the simulated absorption spectrum reaches to 92.01% at the standard condition (i.e., 1.0 atm, 25℃). Based on the analysis of measured absorption spectrum,the laser wavelength pair which includes the on-line 3.424 m and the off-line 3.414 m is determined. In addition, the signal pre-processing and denoising methods were studied. The simulation results show that the concentration errors of nitrogen dioxide can be less than 0.1 mg/m3 within 1 km by combining the signal pre-processing and the multiple autocorrelation.
2018, 47(10): 1030003.
doi: 10.3788/IRLA201847.1030003
The mobile lidar of USTC implements the continuous wind measurement in 15-60 km neutral atmosphere at night. Since the signal to noise radio was limited by background light during daytime operation, an ultra-narrow filter which combined an interference filter with a solid FP etalon was designed to reduce the background noise. An approach to solve the optimum parameters for the F-P etalon was proposed, based on the Frequency Discriminator, an etalon filter with bandwidth of 8.4 pm, center wavelength of 354.73 nm, free spectral range of 150 pm and peak transmission of 0.67 was achieved to decrease the background noise to one in eighteen. The improvement of SNR and velocity errors were simulated. The effect of temperature and tilting angle on bandwidth, center wavelength and transmissivity was calculated. A method of tuning by tilting angle was designed. The experiment result is highly uniform with the theoretical value.
2018, 47(10): 1005001.
doi: 10.3788/IRLA201847.1005001
Lasers in the 3-5 m waveband have many important scientific and military applications such as remote sensing, environmental protection, medical treatment, communication and infrared countermeasures. Fe2+:ZnSe crystal has become one of the most promising materials to generate laser in this region due to its advantages in material and optical properties. The characteristics of a polycrystalline ZnSe sample, which diffusion-doped with Fe2+ ions at a concentration of 31019/cm3, were investigated. The diameter and the thickness of the sample were 10 mm and 1 mm, respectively. The output characteristics of the Fe2+:ZnSe laser, which was excited by a non-chain electric-discharge pulsed HF laser, were studied at room temperature. A mid-infrared laser with the maximum output energy of 78.8 mJ at a center wavelength of 4 295 nm was obtained. The efficiency respecting to the absorbed pump energy was 27.7% and the slope efficiency was as high as 28.8%. The Fe2+:ZnSe laser was pumped at a small angle (3) with respect to the optical axis of the laser cavity instead of orthogonal-pump. It solved the problems that a HF laser and a Fe2+:ZnSe laser are both in the mid-infrared band.
2018, 47(10): 1005002.
doi: 10.3788/IRLA201847.1005002
At present, 1.5 m LD pumped Er-glass passively Q-switched micro-laser is a popular research direction in military laser ranging. Achieving high repetition rate and single pulse energy are very important indicators. In this paper, a kHz erbium-ytterbium co-doped phosphate glass passively Q-switched microchip laser for laser ranging was reported. The laser was pumped by a single diode with a center wavelength of 940 nm and erbium-ytterbium co-doped phosphate glass (Er3+,Yb3+:glass) as the gain medium, CO2+:MgAl2O4 (CO:MALO) as the saturable absorber. By analyzing the influence of the pump spot radius on the mode-matching, the pump spot radius was optimized. The effects of the initial transmittance (T0) of saturable absorber and the reflectance R of output mirror on the output laser parameters were experimentally analyzed. In the final pre-pumping experiment, a Q-switched pulse was achieved, with repetition frequency of 1 kHz, wavelength of 1 535 nm, single pulse energy of 40 J, pulse width of 5.09 ns, peak power of 7.89 kW and beam quality of 1.4.
2018, 47(10): 1005003.
doi: 10.3788/IRLA201847.1005003
In order to solve the output wavelength and power stability of high power semiconductor laser, high power semiconductor laser constant current driver and temperature control system were designed. Deep negative feedback circuit was used to control the laser drive current, the analog Proportional-Integral (PI) circuit and constant current driver were adopted to control the working current of Thermoelectric Cooler (TEC), the laser working temperature can be kept accurately. The design can realize the linear adjustment of output current from 0-12.5 A, and has the function of current detection, over-current protection and Transistor-Transistor Logic (TTL) modulation. The control precision of the temperature control system can achieve 0.05℃. Temperature can be adjusted continuously and can be monitored in real time. Experiment results show that the design can guarantee the output current and temperature control stably, which satisfies the requirement of high power semiconductor laser.
2018, 47(10): 1005004.
doi: 10.3788/IRLA201847.1005004
Based on the 1 550 nm single-frequency Erbium-Ytterbium co-doped fiber amplifier (EYDFA), the linewidth broadening with different seed powers and gain fiber temperatures was experimentally investigated. The results demonstrate that, to obtain the same output power, the increase of the seed power was beneficial to improve the output signal to noise ratio (SNR), and to reduce the linewidth broadening. The increase of gain fiber temperature can improve slope efficiency and enhance the amplified spontaneous emission (ASE) intensity but broaden linewidth. Meanwhile, the reason of linewidth broadening was discussed and the ASE was considered as one of the reason of linewidth variation.
2018, 47(10): 1005005.
doi: 10.3788/IRLA201847.1005005
A dual-frequency Yb3+-doped distributed Bragg reflection (DBR) fiber laser was demonstrated, which used a home-made dual-wavelength low reflectivity FBG as the output port of the DBR fiber laser. The wavelength spacing of the FBG was about 0.12 nm, corresponding to 32 GHz frequency difference. The dual-wavelength of the laser output was 1 063.09 nm and 1 063.21 nm, respectively. The spectral signal noise ratio was more than 60 dB. Each of the wavelengths included only one longitudinal mode. The beat frequency of the dual-frequency was 32.014 GHz. The signal-noise ratio of the frequency spectrum was more than 35 dB. Benefitted from the compact structure and the strong anti-interference capability of the fiber laser, the dual-frequency fiber laser is promising as the candidate of high-quality microwave signal generator for the applications such as microwave sensing and communications.
The gas sources such as real leaks, virtual leaks, outgassing and permeation cause the cavity pressure of the sealed vacuum Dewar to increase and the proportion of active gases H2, H2O, and CO accounts for a large part, and H2 can reach more than 80% in gas sources. NEG extracts active gases to obtain and maintain the vacuum degree of the Dewar component of the infrared focal plane detector. The amount of generated gas during the life cycle of sealed vacuum Dewar is related to the design and manufacturing technology and the process capability of vacuum acquisition. The maximum efficiency of NEG will not be achieved without the use of St 172 correctly. Based on the literatures and engineering practice experiences, the effects of the pumping performance parameters and the activation and reactivation conditions on the vacuum maintenance performance of NEG under specific operating conditions were analyzed and discussed. It is pointed out that most of users do not allow the electric reactivation of NEG repair, the correct application of the NP (no particle) St 172/NP and the issues must be noticed.
2018, 47(10): 1004002.
doi: 10.3788/IRLA201847.1004002
The infrared imaging grayscale variation caused by the influence of atmosphere on infrared radiation transmission is a problem that infrared target tracking application needs to cope with. The law of infrared imaging grayscale variation in Lie group was modeled, which was important to design an efficient and robust target tracking algorithm. Firstly the infrared radiation transmission model was analyzed, and then the brightness model of infrared imaging was derived by considering the mechanism of infrared imaging. Furthermore, it was theoretically proved that the infrared imaging grayscale variation caused by the atmosphere obeyed the Lie group structure, and a non-Euclidean mathematical representation of the infrared imaging grayscale variation was proposed. Finally, according to the infrared imaging grayscale variation model, the field experimental data collected under different environments were fitted. The regression analysis results demonstrate the correctness of the model, which validates the rationality of the Lie group representation of the infrared imaging grayscale variation.
2018, 47(10): 1004003.
doi: 10.3788/IRLA201847.1004003
With the increasing demands for new biological extinction materials in military and civilian fields, the artificially prepared flocculent particles were equivalent to bullet rosette particles, which were further used to build the biological particles with different structures as a unit particle. And the structures of biological particles were characterized by parameterization. Then the discrete dipole approximation (DDA) method was used to calculate the average extinction efficiency factor for biological particles in the far infrared band. The results indicate that the average extinction efficiency factor of biological particles is positively correlated to the size factor and porosity in the far infrared band. Based on studying the relationship of average extinction efficiency factor with size factor and porosity, the biological particles average extinction efficiency factor model in the far infrared band was constructed. Using that model, the computation time was shorter than that of the DDA method, and the calculation error is less than 10%. The model provides a theoretical basis for the further development and morphology control of biological extinction materials.
2018, 47(10): 1041001.
doi: 10.3788/IRLA201847.1041001
Correlated imaging was a new type of imaging technology, with great application value and promising prospect, which has recently become a hotspot and one of the frontiers of optical imaging researches. Polarization detecting method can improve system's ability of object detection and recognition, and categorize detected objects based on its materials. By combining correlated imaging with polarization detection, a correlated imaging system was built based on forward modulated polarization, which utilized fixed probe side polarization configuration and used Hadamard mode speckles modulated by time-shared polarization method to illuminate scenes. The system was used to carry out the polarization detection imaging experiments for the scenes with multi-material objects. The intensity and polarized images of scenes were retrieved using the correlation between the detected intensities and illumination speckles. Using evolutionary compressed sampling restoration techniques, the information of scenes was reconstructed under different sampling ratios. The clear images of the intensity and polarization are obtained under the sampling ratio of 12.5%.
2018, 47(10): 1041002.
doi: 10.3788/IRLA201847.1041002
Correlation imaging is an innovative imaging scheme, which transforms the imaging time to a spatial resolution by a single pixel detector. However, there are problems of low reconstruction quality and long data acquisition time. Hadamard coded modulation computation correlation imaging can achieve efficient imaging and significantly improve the applicability, but the noise in imaging reconstruction, which restricted the practicability, is a challenge needs to be tackled urgently. A correlation imaging related noise suppression scheme was proposed by thresholding method and morphological image enhancement, by analyzing the noise characteristics of the reconstructed results of the correlation imaging, which the Hadamard matrix as a measurement matrix and the feasibility of this scheme was verified by experiments, and nearly 8 dB enhancement of optical image was achieved. This imaging scheme is efficient for two valued images and grayscale images, and its work promotes the practicability of correlation imaging technology.
2018, 47(10): 1041003.
doi: 10.3788/IRLA201847.1041003
Reflectance Confocal Microscopy for skin (RCM) is an important skin imaging diagnostic tool, which uses resonant galvanometer that will result in nonlinear distortion at image. In order to correct the distortion, a method of anti-sine signal oversampling based pixel using isochronous sampling system to correct the distorted RCM image caused by resonant galvanometer was presented. The results of experiments on the rectangular grating with a pitch of 20 m indicate that, the standard deviation of the grating spacing is 7.78 m. The distortion rate of image before being corrected is 38.9%. The standard deviation of the image corrected by the anti-sine signal over-sampling based pixel method is 0.85 m, so the distortion rate is reduced to 4.2%. According to the results of a resolution plate and the actual human skin imaging, the distortion correction method proposed in this paper can correct the image distortion caused by resonant galvanometer and meet the human skin real-time non-invasive imaging diagnostic requirements.
2018, 47(10): 1041004.
doi: 10.3788/IRLA201847.1041004
Time of flight (TOF) three-dimensional imaging technology has the advantages of active parallel detection in the frame, good real-time acquisition of scene information, small influence of ambient light, high accuracy of detection data, strong anti-sport interference and low average power consumption. In three-dimensional intelligent sensing, industrial inspection, SLAM and other fields have a wide range of applications, especially in autonomous navigation, driving control and intelligent systems as a real-time three-dimensional imaging information of the sensor has been rapidly developed. The principle and characteristics of two kinds of TOF imaging were studied. Two types of TOF imaging principle and characteristics, system composition were discussed. TOF imaging system was compared with other mainstream three-dimensional imaging technology. Its main source of error and type was classified and analyzed, its error model was studied. As a new generation of three-dimensional imaging technology, TOF is still in the development stage, which can effectively enhance the imaging perception and measurement level of the intelligent system and promote the technological progress in related fields.
2018, 47(10): 1006001.
doi: 10.3788/IRLA201847.1006001
In order to study the influence of femtosecond laser-produced plasma filaments array on the transmission characteristics of 10 GHz microwave, the numerical simulation model of the interaction between femtosecond laser-produced plasma filaments array and microwave was established by COMSOL. The effects of plasma filaments array parameters, plasma characteristic parameters and array layer number on the reflectance and transmittance of microwave were studied. The numerical results show that the plasma filaments array becomes transparent when the direction of the microwave electric field is perpendicular to the filaments axis, regardless of the incidence angle of the microwave with respect to the filaments. Increasing the filaments diameter or electron number density, or decreasing the filaments spacing or electron temperature will lead to the reflectance increasing and the transmittance decreasing. The maximum reflectance of 10 GHz microwave with plasma filaments array is up to 0.88 while the filaments diameter is 500 m, the filaments spacing is 1 mm, and at this time the electron number density is 11023 m-3 and the electron temperature is 0.3 eV. When the number of filaments array layer number is increased, the transmittance decreases, eventually approaches zero, and the reflectance remains constant. The results of this study are helpful for the femtosecond laser-produced filaments array to interfere with microwave.
2018, 47(10): 1006002.
doi: 10.3788/IRLA201847.1006002
According to the application requirement of ICF system, an analysis model of energy superposing on the target plane of four-ultrashort chirped Gaussian pulses was established. By using the analytical expression of the envelope of complex exponential function, the spatial singularity of one pulse and superposition of multi-pulses were analyzed by numerical simulation. The results show that the pulse width is the main factor to influence the spatial singularity phenomenon of the ultrashort chirped Gaussian pulse. While the pulse width was less than one oscillation period, the parameters should be controlled carefully within reasonable horizontal distance, which was less than 1w0 in order to prevent the spatial singularity.
2018, 47(10): 1006003.
doi: 10.3788/IRLA201847.1006003
The attenuation property of 1.06 m laser radiation in water fog was investigated experimentally. The attenuation of 1.06 m laser radiation in water fog was measured at different meteorological optical range (MOR). Based on experimental data, the equivalent MOR of 1.06 m laser radiation was calculated. The extinction coefficient of 1.06 m laser radiation in water fog at different MOR was calculated based on empirical equation and experiment data, respectively. The comparison of the result shows the empirical extinction coefficient has significant deviation with experiment result, especially at low MOR. A new equation was derived for calculating the extinction coefficient of 1.06 m laser radiation in water fog based on MOR value, which is of great importance in evaluating the attenuation properties of near infrared laser radiation in water fog.
2018, 47(10): 1006004.
doi: 10.3788/IRLA201847.1006004
In order to reduce the ranging error caused by the pulse timing or phase comparison of the complex circuit system in the traditional laser ranging method, the laser ranging based on polarization modulation was demonstrated. Using the characteristic that the crystal refractive index of the electro-optical modulator changed with the linear change of the applied electric field, the laser pulse reflected by the object to be measured was made into a function of time, and the distance was solved by the ratio of the light intensity in the two vertical directions. Based on the principle of distance measurement, distance equation and error analysis, the accuracy expression of theory ranging that was obtained by the ranging method in the paper, the influence of three kinds of modulation functions of sine, sawtooth and exponential on the accuracy of ranging was analyzed by simulation. In the same distance range, the sawtooth function had better applicability, and the combination of sine and exponential had higher accuracy of ranging. By analyzing the influence of different modulation bands of sine function on the accuracy of ranging, the applicability and the accuracy were greatly improved by using -/6-/6 band. The results will be helpful to improve the accuracy of laser ranging based on polarization modulation.
2018, 47(10): 1006005.
doi: 10.3788/IRLA201847.1006005
In laser guided weapon hardware-in-the-loop simulation, laser energy is controlled accurately to simulate the laser energy in battlefield environment. In order to assure simulation reliability, simulating error should be analyzed. The laser signal transmitting process was analyzed, and the energy control uncertainty of every transmitting link was introduced. The laser energy simulating error model was developed and error analysis method was introduced by an example. The error model can be used to evaluate laser energy simulating error and to optimize simulation design, which can assure hardware-in-the-loop simulation result precision.
2018, 47(10): 1006006.
doi: 10.3788/IRLA201847.1006006
Graphene is doped into the photoresist which is made by mixing the 2-benzyl-2- (dimethylamino)-4'-morpholino-butyroph and pentaerythritol triacrylate. A series of 2D image and 3D microstructure were fabricated based on the technology of femtosecond laser two-photon polymerization (TPP). The infiltration of the mixture was characterized by the hydrophilic angle test, and the penetration of the mixture was characterized by laser penetration depth test. The experimental results show that the mixture with graphene still has strong binding force with glass and laser penetration. At last, 2D image and 3D microstructure were characterized by Raman mapping and scanning electron microscope (SEM). It is confirmed that graphene can be relatively evenly mixed in microstructure by using deionized water as dispersion liquid, and the composite microstructure is more stable and the appearance is more uniform than the pure photoresist microstructure.
2018, 47(10): 1006007.
doi: 10.3788/IRLA201847.1006007
Based on light transfer matrix and generalized Huygens-Fresnel optical diffraction formula, the propagation evolution of Airy Gaussian vortex beam's normalized intensity distribution on emergent surface, side transmission view in periodic slab system contained right-handed and double negative material (DNM) were explored. Research shows that the original Airy Gaussian vortex beam intensity can be restored immaculately by using periodic slab system contained negative index material as long as the negative refractive index abs (nl)=nr and each unit length R:L=1:1; while abs (nl)nr but R=L, both types of emerging beams had poor quality, and in order to achieve beam reconstruction, the larger abs (nl) was, the longer DNM unit length was needed, and vice versa. Relation between DNM unit length and nl was thoroughly studied as well. It is expected that the relevant conclusions could provide important reference value for extension applications of optical control and communication transmission technique of the Airy Gaussian vortex beam propagating in the periodic and quasi-periodic metamaterials structure.
2018, 47(10): 1006008.
doi: 10.3788/IRLA201847.1006008
Precise ranging system is of key importance in fields like multiple satellites flying formation, planets spatial positioning, shape measurements of large-scale structure, measurement of tiny displacement and measurement in commercial manufacture. For the advantages of fast measuring speed and high precision, the distance measurement technique with femtosecond optical frequency comb has become the focus of study in recent years. Based on a brief introduction of basic theory and main applications of femtosecond optical frequency comb, several distance measurements and results were given, including time-of-flight method, multi-wavelength method, dual combs method, spatial dispersive interferometry method, method based on real-time dispersive Fourier transformation and multi-technique method. The approaches of atmospheric refractive index correction and dispersion compensation were briefly introduced. A comparison and a summary of these methods were given and the latest progresses were introduced.
2018, 47(10): 1022001.
doi: 10.3788/IRLA201847.1022001
Considering the slow modulation rate and large volume of the gas lamp and the laser, and the high working voltage of the photomultiplier tube (PMT) in UV communication, a solar blind ultraviolet LED real-time video transmission system based on Field Programmable Gate Array (FPGA) was proposed, which utilized single UV LED with wavelength of 265 nm at the transmitter and an UV PIN at the receiver. The video transmission system was established by designing the circuit and logic module. The relationship between the optical power density and the communication distance of the communication system was investigated. The experimental results show that the maximum transmission rate is 2.88 Mbit/s, when the communication distance is 4 m, the transmission rate can be up to 1.92 Mbit/s based on the mode of On-Off Keying (OOK) modulation for the system.
2018, 47(10): 1022002.
doi: 10.3788/IRLA201847.1022002
Wireless ultraviolet (UV) communication has the characteristics of high speed and high reliability, which can meet the needs of complex environment. The approximate line of sight (ALOS) communication mode was proposed through the process of helicopter assisted landing, and the ALOS link of wireless UV MIMO system was studied. Meanwhile, the error performance of MIMO system in ALOS link under weak turbulence was calculated, the influence of SNR, transmitting power, transmitting (receiving) elevation angle and communication distance on the BER were calculated and analyzed. When the elevation angle of transmitting (receiving) was less than 35, the BER increased rapidly with the increase of elevation angle, the trend growth of BER was slowing down with the increase of elevation angle when elevation was greater than 35. The result indicates that adopting the MIMO technology with antenna array and multi-detector can reduce BER, suppress the atmospheric turbulence and improve the ability of anti-fading in the wireless ultraviolet ALOS link.
2018, 47(10): 1022003.
doi: 10.3788/IRLA201847.1022003
In the free space optical orthogonal frequency division multiplexing (FSO-OFDM) system, nearly 20% of the bandwidth is consumed due to add a cyclic prefix, the data transmission efficiency is reduced. In order to further reduce the bandwidth loss and improve the system performance, a wavelet packet transform was used instead of the Fourier transform in FSO-OFDM, free space optical orthogonal frequency division multiplexing system based on wavelet transform (FSO-WOFDM) was designed. The system didn't need to add a cyclic prefix, and the orthogonality of the wavelet basis functions was used to suppress inter-carrier interference. According to the principle of FSO-WOFDM system, the effects of channel estimation method, turbulence intensity and wavelet based on the bit error rate of FSO-WOFDM system were studied. The system performance of FSO-WOFDM and FSO-OFDM was compared and analyzed. The experiment verifies the feasibility of FSO-WOFDM system and its excellent ability to resist mixed noise.
2018, 47(10): 1022004.
doi: 10.3788/IRLA201847.1022004
Based on the principle of multi-mode interference of multimode fiber and the algorithm of image processing, the characteristics of gray level co-occurrence matrix of phase spectrum of multi-mode fiber output speckle pattern were extracted, a new speckle pattern processing algorithm was proposed and applied to micro-displacement sensing. The relationship between the displacement and the characteristics of the phase spectrum of the output speckle pattern was analyzed in detail, when the single-mode-multimode fiber structure based on step-index multimode fiber generated micro-displacement in the radial direction of the two optical fibers. The analysis of speckle patterns of various structural parameters shows that, the approximation linear relationship between radial micro-displacement of the two optical fibers and the two characteristics including correlation and homogeneity can be obtained. Therefore, in order to achieve micro-displacement measurement, the method of image processing algorithm over speckle pattern can be used, making further efforts to realize optical fiber sensing. The experimental results show that compared with the commonly used algorithm of calculating normalized intensity inner product of the speckle pattern, when the core diameter of multi-mode fiber is small, the linearity and dynamic range are relatively close, when the core diameter is larger, the dynamic range is doubled while the linearity is improved. Therefore, the proposed algorithm has better stability and wider application range.
2018, 47(10): 1020001.
doi: 10.3788/IRLA201847.1020001
The unimorph deformable mirror (DM) is widely applied in adaptive optics, which utilizes the lateral reverse piezoelectric effect of piezoelectric ceramics to drive the mirror to deform. The hysteresis curve of the deformable mirror is a special butterfly shape in the high electric field strength, which increases the difficulty of control, and the deformable mirror cannot work normally. The theory of piezoelectric ceramic polarization and the hysteresis loop of ferroelectric materials were analyzed so that the cause of the butterfly curve could be confirmed. The experimental results show that the covariate field of the DM is between -500 and -400 V/mm, and the hysteresis curve is normalized willow shape. Then a static PID closed loop correction system was designed for the characteristics of the hysteresis curve, and the correction experiment was carried out. The results show that the linearity is obviously improved, and the hysteresis rate is reduced to 1.8% by the PID closed loop correction.
2018, 47(10): 1020002.
doi: 10.3788/IRLA201847.1020002
Accurate detection of reference beam was one of the key factors to enhance the ranging accuracy in the laser active imaging system with direct ranging. The circuit design of detection of reference beam based on PIN detector was researched in detail. Firstly, the comparative analysis of performance and difficulty of power supply circuit between avalanche photodiode (APD) and PIN photodiode was conducted. Considering the power stability and designing difficulty of the reference beam, the PIN detector was selected to detect the reference beam in ladar. Two modes including normal power and current monitor existed in LT3482, and the difference when used to drive PIN detector was analyzed deeply. The transimpedance amplifier OPA657N with high gain-bandwidth product was used to convert the current of PIN detector to voltage, and the selection method of key external components was introduced. Also, points for attention in usage of MAX9601 were given. At last, the circuit was designed for experimental verification. The results show that voltage converted from the current of PIN detector through transimpedance amplifier is -3.7 V when the pulse width of laser is 10 ns and bias voltage applied to the PIN detector is 89.449 V. The pulse width of voltage is extended to be 15 ns, but the starting signal is ensured to be detected. The timing discrimination signal according to the reference beam could be given effectively by the module. PIN detector based on integrated high-voltage chip combined with constant threshold timing discrimination was feasible in direct ranging laser active imaging system detection of reference beam.
2018, 47(10): 1020003.
doi: 10.3788/IRLA201847.1020003
In order to study the thermal characteristic of fast steering mirror during the working process of high power CW laser, a time-dependent fast steering mirror model coupled with heat transfer and structure mechanic was established to calculate the distribution of temperature, thermal deformation and thermal stress by finite element software, and the material was fused silica, zerodur and sic respectively. The wave front of fast steering mirror was fitted by Zernike polynomial algorithms. The results indicate that under the same laser power irradiation conditions, the minimum temperature rising and thermal distortion of the three material is zerodur. By comparison, zerodur material is optimized as fast steering mirror, and its dominant thermal aberration are piston, spherical aberration and defocus, which can provide wavefront correction to theoretical reference in the field of engineering application.
2018, 47(10): 1020004.
doi: 10.3788/IRLA201847.1020004
Silicon Photomultiplier (SiPM) is a new type of solid state photodetector developed rapidly in recent decades, and has the potential to replace photo multiplier tube (PMT) in the Raman detection. A time-resolved Raman spectroscopy system based on a Silicon Photomultiplier (SiPM) was established in order to limit the influence of intense fluorescence on Raman spectroscopy, and alleviate the high dark count rate (DCR) problem of the SiPM. The variation of the Peak-to-Background Ratio (PBR) of Raman peaks along with counting time was investigated using trinitrotoluene (TNT) as the sample. Results indicate that with counting time increasing, the PBR of Raman peaks is increasing first and then decreasing, finally changing slowly. When counting time is 400 ps, a best PBR is achieved for the Raman peaks. The results are superior to that achieved by the commercial Raman spectrometers and the methods used in the literature. Also, the dark counts system collected are comparable to PMT. The method proposed in the paper is capable of reducing the high fluorescence background and the effects of SiPM's high DCR to a great extent, facilitating a marked improvement in the Raman PBR.
2018, 47(10): 1031001.
doi: 10.3788/IRLA201847.1031001
An integrated aircraft/scramjet reference trajectory design method for ABHV was proposed. The influence on starlight navigation was analyzed. First, based on the characteristics of intricate coupling for hypersonic airbreathing vehicle and combined with the characters of starlight navigation system, minimizing the coupling degree between aircraft and scramjet was referred to as the optimization index. Second, considering multiple constraints of angle of attack, fuel equivalent ratio, angle of attack rate, shock train axial relative length, a smooth solution for multiple constrained optimal problems was adopted. Then, a reference trajectory which is good for starlight system was designed, and the degradation of navigation performance under this trajectory was analyzed. The trajectory design method can further tap the potential of the overall performance indicators with core competitiveness, such as scramjet stability and aircraft high-precision strike. Taking an ABHV as example, the simulation analysis was carried out on the basis of accurate simulation model. The simulation results show that the method is effective and reliable.
2018, 47(10): 1025001.
doi: 10.3788/IRLA201847.1025001
In the process of generating terahertz (THz) waves using femtosecond lasers, the plasma absorbs the THz wave energy, and the absorption characteristics have a great application prospects in the THz wave radar detection, plasma stealth, electromagnetic interference research. A measurement system of THz absorption via plasma was designed combining the theoretical analysis, and it was proposed that the interaction between plasma particles was the main reason for the plasma absorption of terahertz waves. The results show that the plasma density, the focal length of the optical lens and the angle of the incident femtosecond laser and the multiplier crystal are the main factors that affect the absorption degree, which provides a more comprehensive theoretical support for the plasma absorption application, it will be helpful to promote the THz wave technology in the military and civilian areas with rapid development.
2018, 47(10): 1025002.
doi: 10.3788/IRLA201847.1025002
The aging of natural rubber products is a common phenomenon in its use, and the essence of aging is that the material itself is flawed and easily affected by external factors. Dielectric spectrum is a macroscopic manifestation of micro-polarization which is the dependence of dielectric constant on electromagnetic frequency or temperature. According to the plastic/rubber hot air aging standard GB/T3512-2014, the thermal oxygen experiment of natural vulcanized rubber was carried out in the experimental chamber of 100℃ for more than 1 000 hours, and the relationship between the dielectric spectrum of samples and aging time was studied. By tracking test, the effective data of complex permittivity and loss tangent value of 0.2-1.2 THz rubber were obtained every 24 hours. Based on the complex permittivity values, the polarization characteristics of the deduced rubber and the statistical microcosmic movement types can be calculated, and the molecular structure changes of the natural vulcanizates characterized by terahertz dielectric spectrum were analyzed. Due to the similarity of the aging of the material, the results can also play a positive role in studying other polymer materials aging.
2018, 47(10): 1018001.
doi: 10.3788/IRLA201847.1018001
An optimization design method combining surface optimization strategy and field-of-view optimization strategy was presented for expanding the field-of-views, which is used for the design of off-axis reflective optical system with freeform surface. Based on the coefficients of Zernike standard polynomials representing the wavefront error of the optical system, sequence of the aberration was determined. The optimization procedure was implemented in small field-of-views to achieve satisfied results, and then the field-of-view was expanded gradually, and the optimization steps were repeated. At last, the optical system structure parameters were got for the full field-of-views. With proper XY polynomial terms as well as optimization weight of different field-of-views selected and optimized, an F-12 off-axis three-mirror system was designed with 1 200 mm focal length and 303 field-of-view, in which, only 15 XY polynomials terms were adopted for the freeform surface. The imaging quality of the system is close to the diffraction limit that meets application requirements. This method can also guide the design of optical systems with freeform surface and larger field-of-view.
2018, 47(10): 1018002.
doi: 10.3788/IRLA201847.1018002
An improved laser triangulation probe was designed based on the traditional direct laser triangulation method. A new single lens design was proposed based on general direct laser triangulation ranging method. The optical path was improved. In optical systems, a beam splitter was used to replace the focusing lens and imaging lens of traditional laser triangular probe, making it coaxial with concentrator lens and photo detector, which made the system structure more compact, and the Scheimpflug condition was deduced to meet the structure. While taking advantage of Zemax optical design software to simulate the optical system, pupil diameter of 4 mm, focal length of 20 mm, total length of 20.5 mm, can achieve miniaturization of measuring system. Together with the appropriate light source and detector, a larger scope of work can be obtained in ensuring high measurement accuracy of the premise, and improving the environmental adaptability of measurement system. It can be widely used in industrial real time online testing and military fields.
2018, 47(10): 1017001.
doi: 10.3788/IRLA201847.1017001
A method of laser cubic prism collimation and attitude measurement was proposed in this paper, and the accuracy was analyzed. A single cubic prism and double cubic prisms were collimated and measured respectively by using high precision electronic theodolites and laser tracker system. The angle of adjacent surface and coordinate transformation parameters were calculated, and the measuring accuracy of new method was compared. The measurement efficiency and environmental requirements was also compared. The experiments results show that the new method achieved an accuracy of 10, which is significantly inproved compared to other traditional methods with an accuracy of 0.5', indicating that this new method had the equivalent accuracy to other mainstream theodolite method. At the same time the efficiency of new method was improved by more than double, and the requirements for the measurement environment were also more relaxed. It could replace the method of theodolite in the actual production.
2018, 47(10): 1017002.
doi: 10.3788/IRLA201847.1017002
To study the effect of total dose effect and biasing effect on image sensor performance, Cobalt-60 gamma ray irradiation and annealing experiments were carried out on 0.18 m process buried 4T-CMOS active pixel image sensor under different bias conditions. Emphasis was placed on the variation of parameters such as dark current and full well capacity with cumulative dose. The experimental results show that with the accumulation of total dose of irradiation, the dark current increases slowly in the early stage, and then the degradation is obviously aggravated. The main source of dark current in 4T -CMOS image sensor currents from STI interface and depletion width increase touching to STI, which aggravates degradation of dark current. Full well capacities have a drop after irradiation, which was due to the the photodiode capacitance decreases when the depletion width increases induced by radiation. And there is no remarkable biasing effect at 4T-CMOS image sensor. degradation of dark current.
2018, 47(10): 1017003.
doi: 10.3788/IRLA201847.1017003
A new transmission visibility measurement system was introduced. Integrating sphere played an important role in monitoring and receiving light. The white LED light source in this system was modulated by external high frequency pulse signal and demodulated in receiver, which would effectively detach the interference by stray light. Integrating sphere was applied to monitor variation of the light source, which can eliminate the error caused by the instability of light source. The collimation lens and beam expanding lens group makes divergence angle in 1 mrad. The high reflection mirrors increase the optical path in the limited space, which also increases the volume of sample and shorten the baseline of transmission system. Adjusting optical path becomes easy by telescope and integrating sphere. After completion of the system, comparison experiment was made with nephelometer. The result shows that the relative deviation between two systems is less than 4% from 1.7 km to 20 km.
2018, 47(10): 1017004.
doi: 10.3788/IRLA201847.1017004
Angular weight estimation is an important part of multi-angle dynamic light scattering technique. Its methods include autocorrelation function baseline method and light intensity average method. The effect of angular error on the measurement accuracy of particle size distribution, in the multi-angle dynamic light scattering, largely depends on the estimation of the angular weight coefficient. Based on the inversion of simulated and measured dynamic light scattering data, the effect of angle error on the inversion of particle size distribution by the weight estimation of autocorrelation function baseline method and light intensity average method was studied. The results show that there is no significant difference between the two methods without angle error. However, when the angle error exists, the influence of error on the inversion result of light intensity average method is greater than that of autocorrelation function baseline method, and the influence on large particles is greater than that on small particles. The reason for this result is that the weight coefficient obtained by light intensity average method based on Mie theory is the theoretical value, and there is a deviation between the theoretical value and the weight coefficient corresponding to the measured light intensity autocorrelation data. Moreover, with the increase of particle size, Mie scattering intensity exhibits a more drastic fluctuation with the scattering angle change, which causes the deviation to increase. Therefore, the angle weighted method based on Mie scattering intensity value was applied, and the precision of the multi-angle light scattering measurement device should be higher.
2018, 47(10): 1017005.
doi: 10.3788/IRLA201847.1017005
A one-dimensional nano-positioning control system based on a controller using DSP (Digital signal processor) chip was developed. The system was mainly composed of a driving stage, a miniature Michelson interferometer and a DSP controller. The driving stage module included a linear stage, an ultrasonic motor HR4 and a motor driver AB2. The HR4 and AB2 were used to drive the ceramic strip adhered to the side of the linear stage by friction. The miniature Michelson interferometer was used to detect the displacement of the stage. Both the PID control algorithm based on BP neural network and the signal processing of the Michelson interferometer were finished by the DSP controller. The experimental results show that the positioning accuracy of the nano-positioning system is better than 10 nm within 20 mm range, and the standard deviation of repeated positioning is 7 nm. The positioning system has the advantages of simple structure, high positioning accuracy, and can be used on the occasion of high-precision positioning.
2018, 47(10): 1026001.
doi: 10.3788/IRLA201847.1026001
The analysis of the missile plume shows that the main factors influencing its spectral change include the engine, fuel, etc., so the purpose of missile model recognition can be achieved according to the tail flame spectrum. In order to ensure the efficiency of recognition, the characteristic spectrum was used to represent the plume characteristics, which can greatly reduce the data volume. Firstly, the radiation difference of each wavelength was calculated according to the spectral difference model. By setting the threshold value, the radiation difference segment was obtained, and the band of higher than the threshold was the selected characteristic band. Changing the number of steps and thresholds can obtain several sets of different data. The Spectral Angle Matching algorithm (SAM) and fuzzy algorithm were used to deal with the data of different precision and different feature bands. The accuracy of the recognition results and the similarity distance between the samples and the different spectra were measured, and the fuzzy algorithm can identify with SAM, but it was better than SAM in algorithm complexity.
2018, 47(10): 1026002.
doi: 10.3788/IRLA201847.1026002
Conventtrial denoising and antialiasing algorithms are usually for single band images. Previously, numerous studies have only designed for single band images. Aiming at the data characteristics of hyperspectral image and the influence of noise and aliasing on the image, a multidimensional filtering algorithm combining tensor and reciprocating cells was proposed and applied to denoising and antialiasing of hyperspectral images. The method introduced the tensor, and the hyperspectral image data was regarded as the third-order tensor expression. The reciprocal cell was used to obtain the spectrum extrapolation which containd less image aliasing and noise. From the point of view of the minimum mean square error, the algorithm alternately iterated to solve the three directions of the filter, and finally completed the image filtering. The algorithm could effectively reduce the image aliasing and noise under the premise of ensuring the consistency of image space and spectral information. The effectiveness of the proposed algorithm was proved by comparing with multiple sets of hyperspectral data of the two-dimensional Wiener filter algorithm and tensor multidimensional denoising algorithm.
2018, 47(10): 1026003.
doi: 10.3788/IRLA201847.1026003
Phase, as an important property of light field, is difficult to be obtained by the existing detection equipment, which can only detect the intensity information of the light field, however, losing the phase information, hence the phase problem can be summarized as the demand of retrieving a sample's complex-field from measurements of intensity. Transport of intensity equation (TIE) based method is one of the typical phase retrieval approaches. When the intensity distribution of the test plane and the axial intensity derivative are known, the phase distribution of the test plane can be calculated directly by solving the equation. Conventionally, intensity derivative is approximated by a finite difference between one in-focus image and one defocused image or two defocused images recorded symmetrically about the focal plane, therefore the proper selection of the distance parameter between defocused image and in-focus image becomes particularly important. A novel approach combining the image interpolation and lens-based TIE was proposed. Firstly, the relationship among two defocused images and one focused image captured was described in geometrical optics model. Secondly, new defocused images with different blur parameters were calculated by image interpolation. Lastly, these new images interpolated and the focused images captured were applied to calculate the phase information. The method could obtain the desired intensity distribution at any positions rapidly with only three captured intensity images, without the mechanical movement of CCD or sample, providing an available way for some special occasions that the intensity acquisitions at appropriate location existed a certain restriction. A practical image acquisition platform was also constructed, the interpolated intensity image was compared with the intensity image obtained by CCD to verify the correctness of the interpolation result, the phase retrieval results under two different computational intensity derivative conditions were given relatively. The experimental results presented verified the feasibility and effectiveness of the method.
2018, 47(10): 1026004.
doi: 10.3788/IRLA201847.1026004
Aiming at the moving target detection in image sequence for dynamic scene, block projection and matching were utilized for global motion estimation. Then, the background image was compensated by applying the estimated motion parameters so as to stabilize the image sequence. Finally, background subtraction was employed in the stabilized image sequence to extract moving targets. Experiment tests denote that the proposed moving target detection algorithm based on block projection and matching can efficiently extract moving targets in dynamic scene.
