Hyperspectral unmixing has become a key technology in hyperspectral image processing. The hyperspectral images contain rich spectral and spatial information. Most algorithms add various constraints and weight factors to make full use of this information and improve the unmixing accuracy. However, the improvement of unmixing accuracy often comes at the cost of large calculations. To solve this problem, we propose the superpixel and low-rank double-sparse regression unmixing algorithm, which can improve unmixing accuracy with lower computational complexity. This algorithm completes the unmixing process by performing two sparse regressions. The result of the first regression is added as a constraint to the second. For the first regression, we perform superpixel segmentation on hyperspectral image to exploit spatial information. To reduce computational complexity, we utilize the mean of each superpixel to represent all pixels in the superpixel for unmixing. In addition, we impose low rankness and sparsity constraints on the mean vector. For the second regression, we impose joint sparsity on the original hyperspectral image. In addition, we employ the reweighting strategy to further enhance the sparsity constraint on every sparse regression. Simulated and real data experiments have proven that the algorithm has improved the unmixing accuracy and unmixing time.
When the laser terminal guidance system is working, the irradiator emits re-frequency laser pulses that precisely control the light time, so as to provide the seeker with an accurately identified signal source, while avoiding enemy laser interference. The laser irradiator uses electro-optic Q-switched technology to obtain pulses with high pulse energy and precise time control. An experimental device for testing the output pulse time of the electro-optic Q-switched laser was designed. The experimental analysis the action process of the electro-optic effect of the KD*P crystal. The effect of the delay time of Q-switched on the output energy and pulse width of the laser was tested and discussed. The results show that the setting of the optimal delay time can increase the output energy of the laser, which has a positive significance for controlling the light time of the irradiator of laser terminal guidance system.
Repetition frequency laser used in precision strike system can transmit a series of laser pulse trains. The repetition frequency pulse transmitted by common repetition frequency laser device does not meet the high precision measurement and target indication requirements due to the existing of “relaxation oscillation” effect. Thus, a Laser Q modulation technology must be used for the laser pulse shaping. Q switch is formed by applying high voltage to the electro-optical crystal cut at a certain angle through electro-optical Q modulation technology. At present, the Q switch of the high repetition frequency laser system is easy to be damaged under the state of high repetition frequency. “Piezoelectric bell response” exists with the over-high voltage and that will affect the repetition frequency accuracy. Aiming at LGS crystal applied in the repetition frequency laser equipment, we carry out an experimental research in order to solve the technical problems, such as optical rotation effect, frequency stabilization driver, and develop LGS Q switch, driver module and repetition frequency laser system. The experiment results show that the Q switch applied in the high repetition frequency laser system is capable to produce the anti-damage and high repetition frequency effect.
Laser command guidance system transmits commands via pulsed laser, which has the advantages of long transmission distance and high reliability. In this paper, the error correction encoding method during the transmission of pulse command is analyzed and verified through experiments on the laser command guidance system. The experimental system consists of a controller, an encoded laser transmitter, a laser receiver and decoder, a solution drive and a data collector. The basic principle of Hamming code which can realize the detection of 2 error codes on the basis of 1 error code corrected is also analyzed. Experiments of laser command transmission, reception and decoding carried out on the experimental system validated the feasibility and error correction accuracy of the experimental system.
The laser-beam riding guidance system controls the way a missile flies and hits a target by encoded laser information field. This paper discusses the spatial encoding method of the modulating disk in the laser beam riding guidance system and designs a light field modulation optical system for the transmitter of the laser beam riding guidance system. The reshaped laser beam can be projected into the internal and external code channels of the modulating disk, thus generating an encoded information field which will be used to control the flight of a missile. Besides, this paper designs a distributed photo detector light field collection system to simultaneously test the light field modulation status of the information field. This system is composed of modules including a pinhole aperture array, a PIN array, a signal processing electric circuit and a data collecting and processing module. The result demonstrates the accuracy and feasibility of the modulated light field test carried out with this system.
For space target photoelectric detection, the false-alarm problem is analyzed using the radiation theory. Firstly, the mathematic equations are deduced about the radiation of space target and its background; Secondly, the numerical calculation is carried out by taking U.S. KH-12 as research object, and the false-alarm problem is analyzed. The results show that: the main false-alarm sources are sun, earth-atmosphere system, moon and Venus. This work can provide theoretical reference for the design of space-based all-weather imaging system.
A refrigeration system with fluid cycle, semiconductor cooler and air cooler is designed to solve the problems of thermal lensing effect and unstable output of high-repetition-frequency solid-state lasers. Utilizing a circulating water pump, water recycling system carries the water into laser cavity to absorb the heat then get to water cooling head. The water cooling head compacts cold spot of semiconductor cooling chips, so the heat is carried to hot spot which contacts the radiating fins, then is expelled through cooling fan. Finally, the cooled water return to tank. The above processes circulate to achieve the purposes of highly effective refrigeration in miniative solid-state lasers.The refrigeration and temperature control components are designed strictly to ensure refrigeration effect and practicability. we also set up a experiment to test the performances of this refrigeration system, the results show that the relationship between water temperature and cooling power of semiconductor cooling chip is linear at 20°C-30°C (operating temperature range of Nd:YAG), the higher of the water temperature, the higher of cooling power. According to the results, cooling power of single semiconductor cooling chip is above 60W, and the total cooling power of three semiconductor cooling chips achieves 200W that will satisfy the refrigeration require of the miniative solid-state lasers.The performance parameters of laser pulse are also tested, include pulse waveform, spectrogram and laser spot. All of that indicate that this refrigeration system can ensure the output of high-repetition-frequency pulse whit high power and stability.
The thermal lensing effect of crystal is the biggest problem for the output of laser pulse with high power and high beam quality. Through the design of laser cavity, this effect can be removed a certain extent. In this paper, a high-repetition-frequency laser based on electro-optic Q-switch made of LGS is designed. Using flat-flat cavity, the purposes of simple structure and steady output are achieved. Firstly, using a LGS as Q-switched crystal, a Brewster plate as a polarizer, a xenon flash-lamp pumped 1064 nm high-repetition-frequency pulsed Nd:YAG laser with flat-flat cavity is demonstrated. Then, the stability of the laser cavity is analysed. Considering the thermal lensing effect of Nd:YAG crystal, the focal length of thermal lens is calculated. Utilizing MathCAD, the ABCD matrix of laser cavity is calculated, and the G value is obtained, that is G=0.792<1, so the laser cavity is steady. Furthermore, the distribution of light beam in the laser cavity is also simulated by using LAS-CAD, the results indicate that the laser works at stead state. Thirdly, the thermal lensing effect of Nd:YAG crystal is analysed by using LAS-CAD. The temperature and refractive index distributions of Nd:YAG crystal are simulated, the results show that the crystal can be equivalented as a lens with certain focal length. Furthermore, utilizing finite element analysis (FEA) method, the three-dimensional view of temperature field is obtained.
With the advantages of stealthiness, all weather effectiveness, visible target recognition and long affect distance, infrared thermal imaging system play important role in scouting, aiming and tracking. In order to eliminate influences of thermal camouflage to traditional intensity infrared thermal imaging system, we proposed design method of ARM based infrared camouflage target recognition system. Considering the measurement of Stokes parameters, we analyzed design method of polarized image acquisition module, designed ARM core board and its data connection with other devices, adopted LCD to display polarization image computed out by ARM. We also studied embedded Linux platform and polarized image processing program based on this platform, finally actualized the design method of ARM based infrared camouflage target recognition system. Results of our experiment show that data stream can be successfully transmitted between modules of the system and the platform we used is fast enough to run polarized image processing program. It’s an effective method of using ARM to actualize infrared camouflage target recognition system.
Large field of view IR fish-eye system can survey real-time the target in hemisphere airspace. For the single target, it can
find the cooperative target and experimentalism easily. But multitasking for the multiple detecting, tracking and judging
the level of threat it could find the cooperative target and prove the studied algorithms and hardware system very difficultly. The paper brings forward an experiment system which is used for identifying multiple target. Through the system the simulation of the parameters in fairway, distance, direction and velocity are achieved. The system is composed of many controlled fountain of heat, which are made up of symmetrically heated flat and temperature
controlled equipment. Each fountain of heat is fixed on the carrier moving free in three dimension space, in front of which diaphragms are fixed for changing the size of diaphragms and distributing of temperature. The fountain of heat moves on the different track at different speed and direction when it's working. The experiment system is proved to be feasible and precise through simulating single target and tracking the plane and other targets. Based on this system, the algorithms of multi-target tracking are validated.
The paper presents the algorithms of data process on multi-target tracking and threat level sequence in large visual area
IR (infrared ray) fish-eye system. The targeting information is associated and filtered with the polar coordinates. Firstly,The characteristic point of every target is picked up and tracked with special restriction for each of them. Secondly,the parameters of fairway, which are gained by aberration revising and researching the characters of temperature area, are picked up from serial images. The threat level of attacking objects is sorted by the speed, acceleration and direction of all targets. Finding out the most prior target which is in the certain distance in order to make
sure that effective warning information is emitted in time. The algorithms are proved to be quick and effective through
simulation and the muiti-target experiment system developed by the writers.
A tracking device of multiple target is proposed, whose field range reaches hemisphere airspace(sr) because of the using
of IR Fish-eye system. The infrared ray is collected by Fish-eye lens, by this way can get the thermal image about the
whole space, whose range depends on the lens used. Thanks to the Fish-eye system and Ptsi staring focal plane array, the
tracking device can get a big range, that means can get multiple target at one time. Depends on the algorithm adopted to
process the image has been gotten, the tracking device specify some points with intensive ray which means elevated
temperature, and that will be the targets. At the next step after targets detection, the algorithm will compute out the speed
and orientation of every target, then figure out a quotient-for-danger about every target. With this quotient, the algorithm
can judge which one is the most dangerous from those flying to us, and it should be treated firstly, then the less
dangerous ones, etc. To ensure the whole system run at real-time, all of the processing has to be finished at a moment. A
TM320 DSP is adopted to run the algorithm. The result will be displayed at a LCD with every target labeled by their
quotient-for-danger. The reaction speed and precision of this tracking device has been proved on our multiple target