Compressive imaging（CI）can offer a versatile improvements for imaging systems, such as smaller compressed data volume and super-resolution. Among various methods to realize Compressive imaging, pushing encoding mask has attracted the most attention with its compatibility to the space remote sensing. However, complex pre- calibrations are usually needed for calibrating the encoding mask to achieve the measurement matrix for the image reconstruction. Herein, we design a pushing compressive imaging system which fixed with the function of situ calibration of the encoding mask. The pushing compressive imaging system was constructed, and the experimental results confirmed that the system had the ability for data compression and super-resolution. And above all, the system can avoid the complex pre-calibration, which makes the on-orbit calibration feasible. In the simulations, twice, three times and four times resolutions higher than the captured image’s resolution are performed respectively, which confirm that the method can improve the target image resolution based on the relative low resolution raw captured target images. Furthermore, by pushing the mask precisely which can be considered equivalent to the real pushing imaging, we have reconstructed the true super-resolution target image accurately based on the mask calibration and 6 captured pushing imaging frames.
Retroreflective free-space optical communication is a new method of optical communication, it is achieved by using a multiple-quantum-well (MQW) modulator as a passive data transmitter. This work analyzes the polarization propagation of light in the MQW modulator, and the corresponding influence to a retroreflective link. Results show that, on the condition that the intensity and incident angle of the incident light remains to be constant, the polarization and intensity of the transmitted light varies markedly; if the polarization of the incident light is carefully considered for a specific MQW modulator, the retroreflective signals can be improved for a retroreflective free-space optical communication link.
Both radially polarized (RP) and radially polarized vortex (RPV) beams are generated by an experimental setup with one phase-only liquid crystal spatial light modulator which efficiently modulates the phase retardation distributions of input beam by twice reflections. The polarizing properties and double-slit interference of both RP and RPV beams are investigated in detail. Misplacement and tilt appear in double-slit interference fringes of both RP beams and RPV beams in simulations and experiments. The fringe tilt number F in the intermediate region is proportional to the topological charge l of RPV beams with the approximate relation Fs(l)=0.8125l in simulations and Fe(l)=0.8182l in experiments. The double-slit interference method can be utilized to determine and analyze the topological charge of the beams.
The generation of femtosecond optical vortex beam based on direct wave-front modulation with phase-only liquid crystal spatial light modulator is demonstrated. The spatial and temporal properties of the generated femtosecond vortices are investigated in detail. The experimental results show remarkable agreement with the results of the theoretical analysis and simulations, and indicate that the method we utilized can efficiently generate femtosecond optical vortex beam of arbitrary topological charge. The temporal and spectral properties of the femtosecond pulsed beam are hardly affected by the phase dislocation imposed on the wave-front.
Both in-phase and out-phase radially polarized femtosecond-pulse (RPFP) beams have been generated with one phase-only liquid crystal spatial light modulator, which effectively modulates the phase retardation distributions of a pulse beam wavefront by two reflections. The intensity distributions and polarizing properties of both in-phase and out-phase RPFP beams are detected, and the temporal properties of in-phase RPFP beams are investigated in detail. Experimental results indicate that we effectively produce an RPFP beam. And the temporal duration of the output in-phase RPFP beam is 183 fs about 14 fs shorter than the input Gaussian femtosecond-pulse beam. The temporal durations of arbitrary polarized components of an in-phase RPFP beam vary less than 3.5%.
With low radiation background of solar-blind UV and strong scattering of UV photons by atmospheric particles, UV
communication can be made use of to set up a non-line-of-sight (NLOS) free-space optical communication link. Polarization modulation, besides the traditional intensity modulation, is presented to enhance the data rate of the UV
communication system. The configuration and the working process of the dually modulated UV communication system
with intensity modulation and polarization, the theoretical evaluation of polarization modulation, and a numerical of the scattering matrix are presented, with the conclusion that polarization modulation is achievable. By adding the polarizing devices and changing the coding procedures, the existing singly-modulated UV communication systems with intensity modulation are easily modified to be dually-modulated ones with polarization modulation and intensity modulation. Ideally speaking, the data rate of the dually-modulated UV communication system is the product of the data rate of the singly modulated system and the number of polarization modulation.
With both ultrafast optical properties of femtosecond pulse and cylindrically symmetric polarization properties of
radially polarized light, the radially polarized femtosecond pulse beam has significant applications in super-high density
optical storage and ultra-intense lasers. A scheme for generating radially polarized femtosecond pulse beam by a
polarization plates array is proposed, in which a phase-only liquid crystal spatial light modulator (LC-SLM) is used to
load different phase retardation distribution in transverse into linearly polarized femtosecond pulse beam. Associated
with a quarter wave plate, the input linearly polarized femtosecond pulse beam will be converted to radially polarized
femtosecond pulse beam at the back of the polarization plates array. The experimental results indicate that the scheme
can be well used to generate radially polarized light, and more effective results can be obtained with the increase of
sectored polarization plates.
As it contains the spectral and image information of targets, the hyperspectral image measured by the airborne CASI
imaging spectrometer can improve the accuracy of target identification effectively. Usually, the spectral matching
methods are used in identification by extracting spectral information from hyperspectral image. Two matching
algorithms, the spectral angle matching method and the binary encoding method, are investigated under the condition of
different spectral resolutions. Firstly the atmospheric correction, the spectral curve smoothing and re-sampling are
carried out in ENVI software. Then the different spectral resolutions are constructed by selecting spectral subsets from
the hyperspectral image. The matching result indicates that the spectral resolution threshold of the spectral angle
matching method is above the threshold of the binary encoding method. The result of this study has important guiding
significance to the use of the matching algorithm and the selection of spectral resolution.
The detection of explosive agents is becoming more important and receiving much greater emphasis for homeland
defense. Raman spectroscopy is a well established tool for vibration spectroscopic analysis and can be applied to the
field of explosives identification and detection. The major bands of the Raman spectroscopy of industrial TNT
(Trinitrotoluene, CH<sub>3</sub>C<sub>6</sub>H<sub>2</sub>(NO<sub>2</sub>)<sub>3</sub>) are analyzed and seven prominent peaks, that is 1616.9cm<sup>-1</sup> (C=C aromatic
stretching vibration), 1533.9cm<sup>-1</sup> (NO<sub>2</sub> asymmetric stretching vibration), 1360.1cm<sup>-1</sup> (NO<sub>2</sub> symmetric stretching
vibration ), 1210.5cm<sup>-1</sup> (C<sub>6</sub>H<sub>2</sub>-C vibration), 822.9cm<sup>-1</sup> (nitro-group scissoring mode), 792.3cm<sup>-1</sup> (C-H out-of-plane bend),
and 326.7cm<sup>-1</sup> (framework distortion mode) are used to identify the TNT. The Raman spectroscopes of TNT solved in
acetone at different mass ratios are studied, and the TNT in the solution can be detected correctly according the relative
distance, intensity, and peak area of the seven peaks. The TNT prominent peaks appear clearly in high level solution (the
mass ration of TNT and acetone is more than 1:10). With the decrease of TNT concentration in solution, the signature of
TNT becomes more and more weak. The low detection limit of TNT is limited by the noise of the instrument (NXR
FT-Raman accessory module with Nicolet 5700 FT-IR spectrometer is used for our experiments. The low detection limit
in our experiments is mass ratio 1:200, which is about 4mg/mL). The prominent peak heights are discussed in
consideration of the TNT concentration. Taking one of the acetone's peaks (1716.9cm<sup>-1</sup>) as the internal standard line, the
relative height of the prominent TNT peaks is almost proportional to the concentration of the TNT in the solution. A
fitting curve for the relations of prominent peak height according to the concentration is proposed with multinomial
fitting method, which can be used to analyze the concentration of TNT more accurately.