scholarly journals Study of a High Spectral Resolution Hyperspectral LiDAR in Vegetation Red Edge Parameters Extraction

2019 ◽  
Vol 11 (17) ◽  
pp. 2007 ◽  
Author(s):  
Changhui Jiang ◽  
Yuwei Chen ◽  
Haohao Wu ◽  
Wei Li ◽  
Hui Zhou ◽  
...  
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Spatial Information ◽  
Research Direction ◽  
Parameter Extraction ◽  
Tunable Filter ◽  
High Spectral Resolution ◽  
Red Edge ◽  
Parameters Extraction ◽  
Vegetation Parameter

Non-contact and active vegetation or plant parameters extraction using hyperspectral information is a prospective research direction among the remote sensing community. Hyperspectral LiDAR (HSL) is an instrument capable of acquiring spectral and spatial information actively, which could mitigate the environmental illumination influence on the spectral information collection. However, HSL usually has limited spectral resolution and coverage, which is vital for vegetation parameter extraction. In this paper, to broaden the HSL spectral range and increase the spectral resolution, an Acousto-optical Tunable Filter based Hyperspectral LiDAR (AOTF-HSL) with 10 nm spectral resolution, consecutively covering from 500–1000 nm, was designed. The AOTF-HSL was employed and evaluated for vegetation parameters extraction. “Red Edge” parameters of four different plants with green and yellow leaves were extracted in the lab experiments for evaluating the HSL vegetation parameter extraction capacity. The experiments were composed of two parts. Firstly, the first-order derivative of the spectral reflectance was employed to extract the “Red Edge” position (REP), “Red Edge” slope (RES) and “Red Edge” area (REA) of these green and yellow leaves. The results were compared with the referenced value from a standard SVC© HR-1024 spectrometer for validation. Green leaf parameter differences between HSL and SVC results were minor, which supported that notion the HSL was practical for extracting the employed parameter as an active method. Secondly, another two different REP extraction methods, Linear Four-point Interpolation technology (LFPIT) and Linear Extrapolation technology (LET), were utilized for further evaluation of using the AOTF-HSL spectral profile to determine the REP value. The differences between the plant green leaves’ REP results extracted using the three methods were all below 10%, and the some of them were below 1%, which further demonstrated that the spectral data collected from HSL with this spectral range and resolution settings was applicable for “Red Edge” parameters extraction.

scholarly journals A 10-nm Spectral Resolution Hyperspectral LiDAR System Based on an Acousto-Optic Tunable Filter

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1620 ◽  
Author(s):  
Yuwei Chen ◽  
Wei Li ◽  
Juha Hyyppä ◽  
Ning Wang ◽  
Changhui Jiang ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Near Infrared ◽  
Spatial Information ◽  
Tunable Filter ◽  
High Spectral Resolution ◽  
Spectral Information ◽  
Time Dimension ◽  
Lidar System ◽  
Full Spectrum ◽  
Comparison Results

Hyperspectral LiDAR (HSL) technology can obtain spectral and ranging information from targets by processing the recorded waveforms and measuring the time of flight (ToF). With the development of the supercontinuum laser (SCL), it is technically easier to develop an active hyperspectral LiDAR system that can simultaneously collect both spatial information and extensive spectral information from targets. Compared with traditional LiDAR technology, which can only obtain range and intensity information at the selected spectral wavelengths, HSL detection technology has demonstrated its potential and adaptability for various quantitative applications from its spectrally resolved waveforms. However, with most previous HSLs, the collected spectral information is discrete, and such information might be insufficient and restrict the further applicability of the HSLs. In this paper, a tunable HSL technology using an acousto-optic tunable filter (AOTF) as a spectroscopic device was proposed, designed, and tested to address this issue. Both the general range precision and the accuracy of the spectral measurement were evaluated. By tuning the spectroscopic device in the time dimension, the proposed AOTF-HSL could achieve backscattered echo with continuous coverage of the full spectrum of 500–1000 nm, which had the unique characteristics of a continuous spectrum in the visible and near infrared (VNIR) regions with 10 nm spectral resolution. Yellow and green leaves from four plants (aloe, dracaena, balata, and radermachera) were measured using the AOTF-HSL to assess its feasibility in agriculture application. The spectral profiles measured by a standard spectrometer (SVC© HR-1024) were used as a reference for evaluating the measurements of the AOTF-HSL. The difference between the spectral measurements collected from active and passive instruments was minor. The comparison results show that the AOTF-based consecutive and high spectral resolution HSL was effective for this application.

scholarly journals Hyperspectral and Multispectral Remote Sensing Image Fusion Based on Endmember Spatial Information

2020 ◽  
Vol 12 (6) ◽  
pp. 1009
Author(s):  
Xiaoxiao Feng ◽  
Luxiao He ◽  
Qimin Cheng ◽  
Xiaoyi Long ◽  
Yuxin Yuan
Keyword(s):  
Image Fusion ◽  
Spatial Resolution ◽  
Spectral Resolution ◽  
Spatial Information ◽  
Spectral Unmixing ◽  
High Spectral Resolution ◽  
Remote Sensing Image Fusion ◽  
Fusion Methods ◽  
Invariant Regions ◽  
The Difference

Hyperspectral (HS) images usually have high spectral resolution and low spatial resolution (LSR). However, multispectral (MS) images have high spatial resolution (HSR) and low spectral resolution. HS–MS image fusion technology can combine both advantages, which is beneficial for accurate feature classification. Nevertheless, heterogeneous sensors always have temporal differences between LSR-HS and HSR-MS images in the real cases, which means that the classical fusion methods cannot get effective results. For this problem, we present a fusion method via spectral unmixing and image mask. Considering the difference between the two images, we firstly extracted the endmembers and their corresponding positions from the invariant regions of LSR-HS images. Then we can get the endmembers of HSR-MS images based on the theory that HSR-MS images and LSR-HS images are the spectral and spatial degradation from HSR-HS images, respectively. The fusion image is obtained by two result matrices. Series experimental results on simulated and real datasets substantiated the effectiveness of our method both quantitatively and visually.

scholarly journals Quantitative spectral classification of Galactic O stars

2018 ◽  
Vol 616 ◽  
pp. A135 ◽  
Author(s):  
F. Martins
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Equivalent Width ◽  
Classification Criteria ◽  
High Spectral Resolution ◽  
Spectral Classification ◽  
Class V ◽  
Luminosity Class ◽  
Spectral Class

Our goal is to provide a quantification of several spectral classification criteria for O stars. We collect high-spectral resolution spectra of 105 Galactic O-type stars from various archives. We measured equivalent widths of classification lines. We defined average values of classification criteria for given spectral types and luminosity classes. We find that the ratio He I 4471 to He II 4542 well matches the published ratios for spectral types. We have quantified equivalent width ratios of helium and silicon lines among O8–O9.7 stars to refine spectral class typing in this spectral range. We present quantitative criteria to separate between luminosity class V, IV–III–II (grouped), and I among O3–O8.5 stars, mainly based on the strength of He II 4686. We find that these criteria also define very well the f, (f), and ((f)) classes for O3–O7.5 stars. Among O9–O9.7 stars we quantify the ratios of He II 4686 to He I 4713 and Si IV 4089 to He I 4026 for all luminosity classes. The tabulated values of the classification criteria should help classify any new O-type stars. The final step of the classification process should rely on a direct comparison to standard stars of the assigned spectral type or luminosity class.

scholarly journals High spectral resolution interferometric planetary observations in the 7–25 μ region

1971 ◽  
Vol 40 ◽  
pp. 44-47
Author(s):  
R. A. Hanel ◽  
V. G. Kunde ◽  
T. Meilleur ◽  
G. Stambach
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Thermal Emission ◽  
Emission Spectra ◽  
Rotational Structure ◽  
High Spectral Resolution ◽  
The Moon ◽  
Broad Absorption ◽  
Ratio Spectrum ◽  
Venusian Atmosphere

The thermal emission spectra of Venus, Mars, Jupiter, and the moon were observed at the coude focus of the McDonald Observatory 107-inch telescope in the 400–1400 cm−1 spectral range with spectral resolutions of 0.3–0.7 cm−1. A preliminary interpretation of the Venus/lunar ratio spectrum allows identification of four upper state CO2 bands in the Venusian atmosphere at 791, 828, 865, and 961 cm−1 and confirms previous observations of the broad absorption-like depression around 890 cm−1. The rotational structure of the 791 and 961 cm−1 bands is well developed at this spectral resolution.

scholarly journals Spatial Sharpening of KOMPSAT-3A MIR Images Using Optimal Scaling Factor

2020 ◽  
Vol 12 (22) ◽  
pp. 3772
Author(s):  
Kwan-Young Oh ◽  
Hyung-Sup Jung ◽  
Sung-Hwan Park ◽  
Kwang-Jae Lee
Keyword(s):  
Spectral Resolution ◽  
Visual Analysis ◽  
Spatial Information ◽  
Optimal Scaling ◽  
Scaling Factor ◽  
High Spectral Resolution ◽  
Qualitative Assessment ◽  
Dimensional Synthesis ◽  
The One ◽  
Comparison Of The Results

This paper present efficient methods for merging KOMPSAT-3A (Korea Multi-Purpose Satellite) medium wave Infrared (MIR) and panchromatic (PAN) images. Spatial sharpening techniques have been developed to create an image with both high spatial and high spectral resolution by combining the desired qualities of a PAN image with high spatial and low spectral resolution and an MS/MIR image with low spatial and high spectral resolution. The proposed methods can extract an optimal scaling factor, and uses the tactics of appropriately controlling the balance between the spatial and spectral resolutions. KOMPSAT-3A PAN and MIR images were used to test and evaluate the performance of the proposed methods. A qualitative assessment were performed using the image quality index (Q4), the cross correlation index (CC) and the relative global dimensional synthesis error (Spectral/Spatial ERGAS). These tests indicate that the proposed methods preserve the spectral and spatial characteristics of the original MIR and PAN images. Visual analysis reveals that the spectral and spatial information derived from the proposed methods were well retained in the test images. A comparison of the results of the proposed methods with those obtained from applying existing ones such as the Multi Sensor Fusion (MSF) technique or the Guide Filter Based Fusion (GF) show the efficiency of the new fusion process to be superior to the one of the others. The results showed a significant improvement in fusion capability for KOMPSAT-3A MIR imagery.

scholarly journals A Monolithic Spatial Heterodyne Raman Spectrometer: Initial Tests

2020 ◽  
Vol 75 (1) ◽  
pp. 57-69
Author(s):  
Abigail Waldron ◽  
Ashley Allen ◽  
Arelis Colón ◽  
J. Chance Carter ◽  
S. Michael Angel
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Signal To Noise Ratio ◽  
Focal Length ◽  
High Spectral Resolution ◽  
Signal To Noise ◽  
Free Standing ◽  
Raman Spectrometer ◽  
Construction Techniques ◽  
The Stability

A monolithic spatial heterodyne Raman spectrometer (mSHRS) is described, where the optical components of the spectrometer are bonded to make a small, stable, one-piece structure. This builds on previous work, where we described bench top spatial heterodyne Raman spectrometers (SHRS), developed for planetary spacecraft and rovers. The SHRS is based on a fixed grating spatial heterodyne spectrometer (SHS) that offers high spectral resolution and high light throughput in a small footprint. The resolution of the SHS is not dependent on a slit, and high resolution can be realized without using long focal length dispersing optics since it is not a dispersive device. Thus, the SHS can be used as a component in a compact Raman spectrometer with high spectral resolution and a large spectral range using a standard 1024 element charge-coupled device. Since the resolution of the SHRS is not dependent on a long optical path, it is amenable to the use of monolithic construction techniques to make a compact and robust device. In this paper, we describe the use of two different monolithic SHSs (mSHSs), with Littrow wavelengths of 531.6 nm and 541.05 nm, each about 3.5 × 3.5 × 2.5 cm in size and weighing about 80 g, in a Raman spectrometer that provides ∼3500 cm−1 spectral range with 4–5 cm−1 and 8–9 cm−1 resolution, for 600 grooves/mm and 150 grooves/mm grating-based mSHS devices, respectively. In this proof of concept paper, the stability, spectral resolution, spectral range, and signal-to-noise ratio of the mSHRS spectrometers are compared to our bench top SHRS that uses free-standing optics, and signal to noise comparisons are also made to a Kaiser Holospec f/1.8 Raman spectrometer.

scholarly journals High spectral resolution ozone absorption cross-sections – Part 2: Temperature dependence

2014 ◽  
Vol 7 (2) ◽  
pp. 625-636 ◽  
Author(s):  
A. Serdyuchenko ◽  
V. Gorshelev ◽  
M. Weber ◽  
W. Chehade ◽  
J. P. Burrows
Keyword(s):  
Temperature Dependence ◽  
Spectral Range ◽  
Cross Sections ◽  
Spectral Resolution ◽  
Uncertainty Budget ◽  
Companion Paper ◽  
High Spectral Resolution ◽  
Absorption Cross ◽  
Ozone Absorption ◽  
Section Data

Abstract. We report on the temperature dependence of ozone absorption cross-sections measured in our laboratory in the broad spectral range 213–1100 nm with a spectral resolution of 0.02–0.24 nm (full width at half maximum, FWHM) in the atmospherically relevant temperature range from 193 K to 293 K. The temperature dependence of ozone absorption cross-sections was established using measurements at eleven temperatures. This investigation is superior in terms of spectral range and number of considered temperatures compared to the previous studies. The methodology of the absolute broadband measurements, experimental procedures and spectra processing were described in our companion paper together with the associated uncertainty budget. In this paper, we report in detail on our data below room temperature and compare them with literature data using direct comparisons as well as the standard approach using a quadratic polynomial in temperature fitted to the cross-section data.

scholarly journals Compressive spectral image fusion via a single aperture high throughput imaging system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hoover Rueda-Chacon ◽  
Fernando Rojas ◽  
Henry Arguello
Keyword(s):  
Image Fusion ◽  
Spectral Resolution ◽  
Spatial Information ◽  
Imaging System ◽  
Research Work ◽  
Visible Spectral Range ◽  
Computational Imaging ◽  
High Spectral Resolution ◽  
Spectral Image ◽  
The Rich

AbstractSpectral image fusion techniques combine the detailed spatial information of a multispectral (MS) image and the rich spectral information of a hyperspectral (HS) image into a high-spatial and high-spectral resolution image. Due to the data deluge entailed by such images, new imaging modalities have exploited their intrinsic correlations in such a way that, a computational algorithm can fuse them from few multiplexed linear projections. The latter has been coined compressive spectral image fusion. State-of-the-art research work have focused mainly on the algorithmic part, simulating instrumentation characteristics and assuming independently registered sensors to conduct compressed MS and HS imaging. In this manuscript, we report on the construction of a unified computational imaging framework that includes a proof-of-concept optical testbed to simultaneously acquire MS and HS compressed projections, and an alternating direction method of multipliers algorithm to reconstruct high-spatial and high-spectral resolution images from the fused compressed measurements. The testbed employs a digital micro-mirror device (DMD) to encode and split the input light towards two compressive imaging arms, which collect MS and HS measurements, respectively. This strategy entails full light throughput sensing since no light is thrown away by the coding process. Further, different resolutions can be dynamically tested by binning the DMD and sensors pixels. Real spectral responses and optical characteristics of the employed equipment are obtained through a per-pixel point spread function calibration approach to enable accurate compressed image fusion performance. The proposed framework is demonstrated through real experiments within the visible spectral range using as few as 5% of the data.

Optical properties of Gobi dust and its pure compounds: experimental extinction spectra and complex refractive indices determination.

2021 ◽  
Author(s):  
Lise Deschutter ◽  
Hervé Herbin ◽  
Denis Petitprez
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Spectral Range ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Refractive Indices ◽  
Effective Medium Approximation ◽  
Extinction Spectra ◽  
Pure Compounds ◽  
Particle Sizer

<p>Spectrometers are powerful instruments to detect atmospheric aerosols, especially on satellites since they allow measurements at a global scale and over different spectral ranges with high spectral resolution. However, to fully exploit their capabilities and to link optical properties, chemical composition and mass concentration, it is essential to have reference optical properties of various particles and mainly the complex refractive indices (CRI). The CRI of a natural aerosol source can be determined from a real sample of it or applying the effective medium approximation using the CRI of the pure compounds present in the natural sample. But in that case, it is necessary to know the mass fraction of each individual compound and above all their CRI. Nevertheless, the literature and CRI databases provide only reflectance measurements on bulk materials or pressed pellets and over a limited wavelength range (Querry <em>et al.</em>, 1987).</p><p>In the present work, dust from the Gobi desert is studied as it is the second most active dust source, after the Sahara desert, in terms of mass emissions (Querol <em>et al.</em>, 2019). For that extinction spectra have been recorded for natural Gobi dust sample and for its major compounds (Illite, Calcite and Quartz). Particles as a powder in a vessel are generated thanks to a magnetic stirring and a flow of nitrogen (Hubert <em>et al.</em>, 2017). The continuous flow of aerosols is directed into a 10-meters multipass cell fitted to a Fourier transform infrared spectrometer and a 1-meter singlepass cell within a UV-Visible spectrometer which cover a continuous spectral range from 650 cm<sup>-1</sup> to 40000 cm<sup>-1</sup>. Moreover, at the exit of the spectrometers the size distribution is recorded by an aerodynamic particle sizer and a scanning mobility particle sizer which allow to measure size particles from 14 nm to 20 µm. An inversion algorithm is carried out using experimental extinction spectra and the size distribution as input data (Herbin <em>et al.</em>, 2017). Applying the Mie theory and the single subtractive Kramers-Kröning integral, the real and the imaginary part of the CRI are retrieved at each wavelength with an optimal estimation method.</p><p>For the first time, CRI of Illite has been retrieved with a high spectral resolution (1 cm<sup>-1</sup>) and over a wide spectral range for suspended particles. For calcite and quartz particles, the crystalline phase has to be considered by introducing the ordinary and extraordinary indices. These pure compound sets of CRI will be used for testing effective medium approximation on Gobi dust for which effective CRI have been also retrieved.</p>

Sign in / Sign up

Export Citation Format

Share Document