The paper combines with three fields push-broom-type sensor, which is independently developed by Shanghai Institute of Technical Physics, Chinese Academy of Sciences, and with the use of full color light source, reflected mirror, rotating table, parallel light tube, image acquisition software, computers and other laboratory equipment to create a geometric calibration method. The method aimed at three fields’ push-broom- type sensor imaging system, and we can get the geometric calibration raw data. The geometric calibration method can provide a method to establish an image mosaic model, and provide basic data for the geometric correction about image distortion.
Multi-Element scanning imaging is an imaging method that is conventionally used in space-born spectrometer. By multipixel scanning at the same time, increased exposure time can be achieved and the picture quality can be enhanced. But when this imaging method is applied in airborne remote sensing image systems, corresponding imaging model and correction algorithms must be built, because of the poor posture stability of airborne platform and different characteristics and requirements. This paper builds a geometric correction model of airborne long linear multi-element scanning imaging system by decomposing the process of imaging and also deduced related correction algorithms. The sampling moment of linear CCD can be treated as push broom imaging and a single pixel imaging during the whole whisk broom period can be treated as whisk broom imaging. Based on this kind of decomposition, col-linearity equation correction algorithm and a kind of new tangent correction algorithm are deduced. As shown in the simulation experiment result, combining with position and attitude date collected by the posture position measurement system, these algorithms can map pixel position from image coordinate to WGS84 coordinate with high precision. In addition, some error factors and correction accuracy are roughly analyzed.
With the development of spectral imaging technology and polarization imaging technology, capturing
the spectral profile and polarization signatures simultaneously will provide a wealth of evidence which
helps to recognize the objects. Thus it has become a new trend in the area of remote sensing technology.
In this paper, the existing polarization spectral imaging technologies are introduced and compared a
new designing scheme to realize the miniaturized hyper-spectral and full-polarization imager are
proposed, which is based on the combination of Acousto-Optic Tunable Filter (AOTF) and Liquid
Crystal Variable Retarder (LCVR). The designing scheme is mainly composed of three modules: the
spectral splitting module based on AOTF, the polarization control module based on LCVR and the
image acquisition module based on Charge Coupled Device (CCD). The use of AOTF assists in
achieving a hyper-spectral resolution higher than 5nm, as well as the abundant spectral information.
While the LCVR enables us to gain multiple sets of polarization images of the target, after that, the
polarization state of the target can be extracted according to Stokes vector and Mueller matrix. This
designing scheme ensures a wide spectral range from 400nm to 2400nm by means of electronic tuning,
and also achieves the hyper-spectral and full-polarization images of the target in rapid succession
without mechanical moving parts. Besides, the development, testing, calibration and test scheme of the
system are also introduced in the rest of the paper.
Visible and Near-infrared Imaging Spectrometer (VNIS) is one of the scientific payloads mounted on “Yutu” rover in
Chang’e 3 lunar exploration project. The VNIS is composed with a visible and near-infrared (0.45-0.95 μm) spectral
imager and a short waveband (0.9-2.4 μm) spectrometer on basis of Acousto-Optic Tunable Filter. According to the
in-situ analysis, a calibration unit was also equipped for high precisely spectral radiance and reflectance inversion by
using solar as standard calibration source. The calibration unit was driven by lightweight ultrasonic motor, and it could
be located on three fixed position including detection (full-opened), calibration (horizontal) and dust-proof (closed). In
this paper, the principle of VNIS, especially calibration unit was described firstly. Then, radiometric correction
algorithms on lunar surface based on standard solar spectral irradiance were expounded. Through the analysis of VNIS
scientific data, the spectral radiance and reflectance curves of detection area were shown in the end.
In the field of lunar surface content analysis, spectral characteristics of the 2.2~3.2 μm waveband can provide a strong basis for analyzing and identifying specific compositions. For lunar soil, an object’s spectrum in this band includes not only reflective solar radiance, but also emissive radiance from the temperature characteristics of the object itself. These form a mixed spectrum, which complicates the spectral analysis for this band. Based on a mixed spectral model, considering both reflective and emissive radiance on the lunar surface, spectral characteristics for a 2.2~3.2 μm waveband are simulated and relationships are analyzed between reflective/emissive spectra and factors such as temperature, light, an object’s physical composition, etc. Moreover, a simulative platform (incorporating a spectrometer, light source, temperature controller, and simulative object) is developed according to lunar surface conditions, so as to further validate the mixed spectral model, which may provide a reference for lunar surface spectral analysis and the development of spectrometers.
In this paper we study the acquisition technology with the antenna scanning in satellite-ground laser links by theoretical
analysis and practical experiment. Based on the satellite-ground laser communication system, we first set up the
theoretical model and deduce the mathematic expressions of acquisition probability and acquisition time according to the
raster-spiral scanning scheme. Then, we analyze factors which might influence the acquisition probability. Different with
other research, our study explores the impact of fixed offset errors as well as the impact of the scanning step and
scanning speed on the acquisition system in detail. Further, we optimize the average acquisition time by numerical
analysis. Finally, we examine the theoretical model in a real acquisition, tracking and pointing (ATP) system. The
experimental results showed that the proposed analysis can improve the acquisition performance.
The Acousto-Optic Tunable Filter (AOTF) is an electronically tunable optical filter based on Acousto-optic effect and
has its own special compared with other dispersive parts. Imaging spectrometer based on acousto-optic tunable filter
(AOTF) is a useful high-spectral technology, especially in deep space exploration applications because its characteristics of staring imaging, electronic tunable spectral selection and simple structure. Because the diffraction of light in AOTF filters is dependent on both wavelength and angle of incidence, the Spectral and geometrical calibration must therefore
be performed over the entire spectral range of AOTF hyper-spectral imaging systems. In this paper, the dispersive principle of AOTF is introduced firstly and its application predominance in space-based spectral detection is analyzed.
Then, a method for calibration of acousto-optic tunable filter (AOTF) hyper-spectral imaging systems is proposed and
evaluated. This paper introduces the calibration of a VIS-NIR Imaging Spectrometer (VNIS) by the method. The VNIS is
a payload instrument for lunar detection and provides programmable spectral selection from 0.45 to 0.95μm. The
results indicate that the method is accurate and efficient. Therefore, the proposed method is suitable for spectral and geometrical calibration of imaging spectrometers based on AOTF.
One of the advantages of acousto-optic tunable filter (AOTF) is its spectral selectivity, not only central
wavelength, but also bandwidth and passband form, can be controlled by RF signals, which provides us the
opportunity to develop a more flexible hyper-spectral imager. Traditional hyper-spectral imagers collect
hyper-spectral images with certain spectral resolutions and spectral sampling intervals, which means a huge
amount of data and low data efficiency. So, a more flexible device to meet different applications with less but
more effective data is an attractive idea. The idea is brought out this year in SITP, CAS. A custom-made AOTF
which can endure higher power is adopted to realize such a hyper-spectral imager. A RF generating system is
designed to produce and control 12 channels of RF signals independently, and a PC is used to control the system
and record the digital images obtained by a CCD camera. If the controlling RF frequencies are close enough to
each other, the consecutive output passbands will combine into one wider band, and the programmable spectral
resolution and passband form are available. If the RF signals are discrete, the image of several discrete spectral
bands combination which can simply be treated as a fused image is available. In this paper, the theory and
structure of the system is set out, some important details of design principle are introduced, some of the original
test results and a few of experimental images are showed.