scholarly journals Active Hyperspectral Sensor Based on MEMS Fabry-Pérot Interferometer

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2192 ◽  
Author(s):  
Teemu Kääriäinen ◽  
Priit Jaanson ◽  
Aigar Vaigu ◽  
Rami Mannila ◽  
Albert Manninen
Keyword(s):  
Near Infrared ◽  
Spectral Power ◽  
Spectral Response ◽  
Field Measurements ◽  
Spectral Power Density ◽  
Long Term Stability ◽  
Spectral Discrimination ◽  
Fabry Perot ◽  
Cost Efficient ◽  
Hyperspectral Sensor

An active hyperspectral sensor (AHS) was developed for target detection and classification applications. AHS measures light scattered from a target, illuminated by a broadband near-infrared supercontinuum (SC) light source. Spectral discrimination is based on a voltage-tunable MEMS Fabry-Pérot Interferometer (FPI). The broadband light is filtered by the FPI prior to transmitting, allowing for a high spectral-power density within the eye-safety limits. The approach also allows for a cost-efficient correction of the SC instability, employing a non-dispersive reference detector. A precision of 0.1% and long-term stability better than 0.5% were demonstrated in laboratory tests. The prototype was mounted on a car for field measurements. Several road types and objects were distinguished based on the spectral response of the sensor targeted in front of the car.

scholarly journals A Zero-Cross Detection Algorithm for Cavity-Length Interrogation of Fiber-Optic Fabry–Perot Sensors

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3868
Author(s):  
Ma ◽  
Song ◽  
Huang ◽  
Guo ◽  
Yuan ◽  
...  
Keyword(s):  
Power Density ◽  
Cavity Length ◽  
Fiber Optic ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Maximum Error ◽  
Detection Algorithm ◽  
Slow Variation ◽  
Fabry Perot ◽  
And Performance

A zero-cross detection algorithm was proposed for the cavity-length interrogation of fiber-optic Fabry–Perot (FP) sensors. The method can avoid the inaccuracy of peak determination in the conventional peak-to-peak method for the cavity-length interrogation of fiber-optic FP sensors caused by the slow variation of the spectral power density in peak neighboring regions. Both simulations and experiments were carried out to investigate the feasibility and performance of the zero-cross detection algorithm. Fiber-optic FP sensors with cavity lengths in the range of 150–1000 μm were successfully interrogated with a maximum error of 0.083 μm.

scholarly journals SPECTRAL RECONSTRUCTION BASED ON SVM FOR CROSS CALIBRATION

2017 ◽  
Vol XLII-1/W1 ◽  
pp. 17-21
Author(s):  
H. Gao ◽  
Y. Ma ◽  
W. Liu ◽  
H. He
Keyword(s):  
Near Infrared ◽  
Spectral Response ◽  
Optimal Solution ◽  
Spectral Radiance ◽  
Real Spectrum ◽  
High Frequency Signal ◽  
Spectral Reconstruction ◽  
Non Linear ◽  
Radiance Data ◽  
Hyperspectral Sensor

Chinese HY-1C/1D satellites will use a 5nm/10nm-resolutional visible-near infrared(VNIR) hyperspectral sensor with the solar calibrator to cross-calibrate with other sensors. The hyperspectral radiance data are composed of average radiance in the sensor’s passbands and bear a spectral smoothing effect, a transform from the hyperspectral radiance data to the 1-nm-resolution apparent spectral radiance by spectral reconstruction need to be implemented. In order to solve the problem of noise cumulation and deterioration after several times of iteration by the iterative algorithm, a novel regression method based on SVM is proposed, which can approach arbitrary complex non-linear relationship closely and provide with better generalization capability by learning. In the opinion of system, the relationship between the apparent radiance and equivalent radiance is nonlinear mapping introduced by spectral response function(SRF), SVM transform the low-dimensional non-linear question into high-dimensional linear question though kernel function, obtaining global optimal solution by virtue of quadratic form. The experiment is performed using 6S-simulated spectrums considering the SRF and SNR of the hyperspectral sensor, measured reflectance spectrums of water body and different atmosphere conditions. The contrastive result shows: firstly, the proposed method is with more reconstructed accuracy especially to the high-frequency signal; secondly, while the spectral resolution of the hyperspectral sensor reduces, the proposed method performs better than the iterative method; finally, the root mean square relative error(RMSRE) which is used to evaluate the difference of the reconstructed spectrum and the real spectrum over the whole spectral range is calculated, it decreses by one time at least by proposed method.

scholarly journals USING CALIBRATED RGB IMAGERY FROM LOW-COST UAVS FOR GRASSLAND MONITORING: CASE STUDY AT THE RENGEN GRASSLAND EXPERIMENT (RGE), GERMANY

2017 ◽  
Vol XLII-2/W6 ◽  
pp. 229-233 ◽  
Author(s):  
U. Lussem ◽  
J. Hollberg ◽  
J. Menne ◽  
J. Schellberg ◽  
G. Bareth
Keyword(s):  
Precision Agriculture ◽  
Low Cost ◽  
Spectral Response ◽  
Vegetation Indices ◽  
Field Measurements ◽  
Fertilizer Application ◽  
Real Time Analysis ◽  
Rgb Images ◽  
Intensively Managed ◽  
Cost Efficient

Monitoring the spectral response of intensively managed grassland throughout the growing season allows optimizing fertilizer inputs by monitoring plant growth. For example, site-specific fertilizer application as part of precision agriculture (PA) management requires information within short time. But, this requires field-based measurements with hyper- or multispectral sensors, which may not be feasible on a day to day farming practice. Exploiting the information of RGB images from consumer grade cameras mounted on unmanned aerial vehicles (UAV) can offer cost-efficient as well as near-real time analysis of grasslands with high temporal and spatial resolution. The potential of RGB imagery-based vegetation indices (VI) from consumer grade cameras mounted on UAVs has been explored recently in several. However, for multitemporal analyses it is desirable to calibrate the digital numbers (DN) of RGB-images to physical units. In this study, we explored the comparability of the RGBVI from a consumer grade camera mounted on a low-cost UAV to well established vegetation indices from hyperspectral field measurements for applications in grassland. The study was conducted in 2014 on the Rengen Grassland Experiment (RGE) in Germany. Image DN values were calibrated into reflectance by using the Empirical Line Method (Smith & Milton 1999). Depending on sampling date and VI the correlation between the UAV-based RGBVI and VIs such as the NDVI resulted in varying R2 values from no correlation to up to 0.9. These results indicate, that calibrated RGB-based VIs have the potential to support or substitute hyperspectral field measurements to facilitate management decisions on grasslands.

scholarly journals Theoretical Modeling and Analysis of the Contribution of the Near-Field Absorption to the Dipole Radiation Power in Top-Emitting Organic Light-Emitting Diodes

2021 ◽  
Vol 11 (7) ◽  
pp. 3181
Author(s):  
Jiyong Kim ◽  
Jungho Kim
Keyword(s):  
Plane Wave ◽  
Spectral Power ◽  
Radiation Power ◽  
Spectral Response ◽  
Near Field ◽  
Spectral Power Density ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Dipole Radiation ◽  
Total Spectral Power

We theoretically model the near-field (NF) absorption for a multilayer micro-cavity (MMC) structure and investigate the contribution of the NF absorption to the dipole radiation power in top-emitting organic light-emitting diodes (OLEDs). The NF absorption occurs due to the interaction between an evanescent wave with a large in-plane wave vector and a planar metal layer in the vicinity of the dipole radiation. The analytical expressions of the NF absorption in the MMC structure are derived from the plane wave expansions of the electric field amplitude, which includes the two-beam and multi-beam interference terms. The transverse magnetic polarization light emitted by both horizontally and vertically oriented dipole emitters is considered in the NF absorption while the contribution of the transverse electric polarization light is neglected. Based on the total spectral power density calculated in a top-emitting OLED, the respective spectral response functions of surface plasmon (SP) modes and NF absorption are compared, where the summation of the Lorentzian line shape functions is used to represent spectral responses of SP modes. At large values of in-plane wave vectors, the spectral response caused by the NF absorption becomes significant and approaches the total spectral power density. In addition, the relative optical powers from various dipole dissipation mechanisms are calculated with respect to the dipole emitter position in the emission layer (EML), which shows the optical power coupled to the NF absorption is predominant over other mechanisms when the distance between the dipole emitter and the EML/Ag interface is less than 10 nm in the top-emitting OLED.

scholarly journals A Fiber-Optic Gas Sensor and Method for the Measurement of Refractive Index Dispersion in NIR

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3717 ◽  
Author(s):  
Matej Njegovec ◽  
Denis Donlagic
Keyword(s):  
Refractive Index ◽  
Optical Fibers ◽  
Near Infrared ◽  
Optical Design ◽  
Infrared Region ◽  
Refractive Index Dispersion ◽  
Measurement Resolution ◽  
Fabry Perot ◽  
Good Potential ◽  
Cost Efficient

This paper presents a method for gas concentration determination based on the measurement of the refractive index dispersion of a gas near the gas resonance in the near-infrared region (NIR). The gas refractive index dispersion line shape is reconstructed from the variation in the spectral interference fringes’ periods, which are generated by a low-finesse Fabry-Perot interferometer during the DFB diode’s linear-over-time optical frequency sweep around the gas resonance frequency. The entire sensing system was modeled and then verified experimentally, for an example of a low concentration methane-air mixture. We demonstrate experimentally a refractive index dispersion measurement resolution of 2 × 10−9 refractive index units (RIU), which corresponds to a change in methane concentration in air of 0.04 vol% at the resonant frequency of 181.285 THz (1653.7 nm). The experimental and modeling results show an excellent agreement. The presented system utilizes a very simple optical design and has good potential for the realization of cost-efficient gas sensors that can be operated remotely through standard telecom optical fibers.

scholarly journals Broadband Absorption in Patterned Metal/Weakly-Absorbing-Spacer/Metal with Graded Photonic Super-Crystal

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 114
Author(s):  
Steve Kamau ◽  
Safaa Hassan ◽  
Khadijah Alnasser ◽  
Hualiang Zhang ◽  
Jingbiao Cui ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polariton ◽  
Near Infrared ◽  
Broadband Absorption ◽  
Au Film ◽  
Fabry Perot ◽  
Absorbing Material ◽  
Multiple Band ◽  
Band Absorption ◽  
Plasmon Polaritons

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light absorption in two devices: a stack of Au-pattern/insulator/Au-film and a stack of Au-pattern/weakly-absorbing-material/Au-film where the Au-pattern was structured in graded photonic super-crystal. We observed multiple-band absorption, including one near 1500 nm, in a stack of Au-pattern/spacer/Au-film. The multiple-band absorption is due to the gap surface plasmon polariton when the spacer thickness is less than 30 nm. Broadband absorption appears in the near-infrared when the insulator spacer is replaced by a weakly absorbing material. E-field intensity was simulated and confirmed the formation of gap surface plasmon polaritons and their coupling with Fabry–Pérot resonance.

scholarly journals Rapid Quantification of Microalgae Growth with Hyperspectral Camera and Vegetation Indices

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 341
Author(s):  
Pauliina Salmi ◽  
Matti A. Eskelinen ◽  
Matti T. Leppänen ◽  
Ilkka Pölönen
Keyword(s):  
Chlorophyll Fluorescence ◽  
Chlorophyll A ◽  
Near Infrared ◽  
Vegetation Indices ◽  
Hyperspectral Data ◽  
Strong Correlations ◽  
Algae Biomass ◽  
Chlorophyll A Concentration ◽  
Cost Efficient ◽  
Hyperspectral Camera

Spectral cameras are traditionally used in remote sensing of microalgae, but increasingly also in laboratory-scale applications, to study and monitor algae biomass in cultures. Practical and cost-efficient protocols for collecting and analyzing hyperspectral data are currently needed. The purpose of this study was to test a commercial, easy-to-use hyperspectral camera to monitor the growth of different algae strains in liquid samples. Indices calculated from wavebands from transmission imaging were compared against algae abundance and wet biomass obtained from an electronic cell counter, chlorophyll a concentration, and chlorophyll fluorescence. A ratio of selected wavebands containing near-infrared and red turned out to be a powerful index because it was simple to calculate and interpret, yet it yielded strong correlations to abundances strain-specifically (0.85 < r < 0.96, p < 0.001). When all the indices formulated as A/B, A/(A + B) or (A − B)/(A + B), where A and B were wavebands of the spectral camera, were scrutinized, good correlations were found amongst them for biomass of each strain (0.66 < r < 0.98, p < 0.001). Comparison of near-infrared/red index to chlorophyll a concentration demonstrated that small-celled strains had higher chlorophyll absorbance compared to strains with larger cells. The comparison of spectral imaging to chlorophyll fluorescence was done for one strain of green algae and yielded strong correlations (near-infrared/red, r = 0.97, p < 0.001). Consequently, we described a simple imaging setup and information extraction based on vegetation indices that could be used to monitor algae cultures.

scholarly journals The Changes of Ergonomic Engine Vibroacoustic Response Regarding Their Development

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4215
Author(s):  
Radosław Wróbel ◽  
Lech Sitnik ◽  
Monika Andrych-Zalewska ◽  
Łukasz Łoza ◽  
Radostin Dimitrov ◽  
...  
Keyword(s):  
Human Health ◽  
Power Density ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Steering Wheel ◽  
Combustion Engines ◽  
Head Restraint ◽  
Vibroacoustic Response

The article presents the results of research on the vibroacoustic response of internal combustion engines mounted in a vehicle. The vehicles studied belong to popular models, which became available in successive versions. Each group included vehicles of the same model of an older generation (equipped with a naturally aspirated engine) and of a newer generation, including downsized (and turbocharged) engines. Tests in each group were carried out under repeatable conditions on a chassis-load dynamometer. The vibrations were measured using single-axis accelerometers mounted on the steering wheel, engine, and driver’s head restraint mounting. The primary purpose of the study was to verify whether the new generations of vehicles equipped with additional high-speed elements (compressors) generate additional harmonics (especially those within the range potentially affecting travel comfort and human health) and whether there are significant changes in the distribution of spectral power density in the new generations. As the study showed, new generations of vehicles are characterized by a different vibroacoustic response, and the trend of change is the same in each of the families studied.

Boston University's high-resolution near-infrared Fabry-Perot spectrometer

1994 ◽  
Vol 33 (2) ◽  
pp. 451 ◽  
Author(s):  
John Noto
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Fabry Perot
Sign in / Sign up

Export Citation Format

Share Document