Atmospheric aerosol effects are often overlooked in target acquisition studies. Typically, performance models only consider extinction and turbulence within the prediction processes. The aerosol modulation transfer function (MTF) is included in range acquisition algorithms to determine how scattering and absorption effects change the target identification predictions. We modeled the aerosols as monodisperse water droplets comparable to a tenuous fog or mist. Integrating the aerosol MTF into the system MTF gives the opportunity to utilize the night vision integrated performance model to predict the target identification range with aerosol contributions. The aerosol MTF is a function of range, water droplet composition, wavelength, and aperture size. The analysis focuses on these variables with an emphasis on wavelength dependence to characterize mid-wave and long-wave performance. Results show that the mid-wave systems have a substantial diffraction advantage over long-wave systems. Only in the limit of increasing optical depths do the mid-wave and long-wave performance models begin to converge, verifying that the aerosols can be the limiting factor for target identification.
KEYWORDS: Remote sensing, Image processing, Agriculture, Thermography, Reflectivity, Visualization, Associative arrays, Color imaging, Data analysis, RGB color model
Remote sensing provides the ability for relatively rapid and early detection of the spatial distribution of a plant disease using methods based on thermography and canopy reflectance in visual and near-infrared wavebands. By remote mapping using color imaging and subsequent data analysis routines, it is possible to realize early detection, identification, and quantification of different relevant plant diseases. In the present work, an applicability of remote sensing with digital color imaging for detecting plant disease is demonstrated. The color and morphological features are used for analysis and classification purposes. As a case study, the image processing is applied to the color photos of banana fields obtained by a manned aerial vehicle equipped with a high resolution camera. Major banana diseases (e.g. panama etc.) exhibit symptoms on leaf area in their earlier stage of infection. Change of color and morphology features act as criteria used to identify and classify the disease. The results of plant disease recognition and identification are demonstrated.
KEYWORDS: Nitrogen, RGB color model, Cameras, Digital color imaging, Neurons, Reflectivity, Neural networks, Image segmentation, Data modeling, Sensors
The advancements in remote sensing in combination with sensor technology, both passive and active, enable growers to analyze an entire crop field, its local features and crop conditions. Nutrient deficiency, and in particular nitrogen deficiency, may cause substantial crop losses. This deficiency needs to be identified immediately. A faster the detection and correction, a lesser the damage to the crop yield. In the present work, an applicability of digital color imaging to monitor nitrogen uptake in crops is demonstrated. The measurements were performed in a carrot and wheat fields as well as in a greenhouse. The images of canopy were taken during the entire growing season by use a hand held digital color (RGB) camera together with plants collection for lab analysis. The nitrogen weight in plant leaves, kg/ha, was obtained by image processing and compared with the standard laboratory analysis. Applicability of digital color imaging to monitor N uptake in crops instead of laboratory test is successfully demonstrated. The availability of RGB image-based data for N uptake is faster, timely and less expensive than that of laboratory test and can be obtained by low-cost ground-based imaging devices, unmanned aerial vehicles (UAV) and satellites.
Electro-optical sensors as well as unprotected human eyes are extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. Laser detector/eye hazard depends on the interaction between the laser beam and the media in which it traverses. The environmental conditions including terrain features, atmospheric particulate and water content, and turbulence, may alter the laser’s effect on the detector/eye. It is possible to estimate the performance of an electro-optical system as long as the atmospheric propagation of the laser beam can be adequately modeled.
More recent experiments and modeling of atmospheric optics phenomena such as inner scale effect, aperture averaging, atmospheric attenuation in NIR-SWIR, and Cn2 modeling justify an update of previous eye/detector safety modeling. In the present work, the influence of the atmospheric channel on laser safety for personnel and instrumentation is shown on the basis of theoretical and experimental data of laser irradiance statistics for different atmospheric conditions. A method for evaluating the probability of damage and hazard distances associated with the use of laser systems in a turbulent atmosphere operating in the visible and NIR-SWIR portions of the electromagnetic spectrum is presented. It can be used as a performance prediction model for directed energy engagement of ground-based or air-based systems.
The advancements in remote sensing in combination with sensor technology (both passive and active) enable growers to analyze an entire crop field as well as its local features.
In particular, changes of actual evapo-transpiration (ET) as a function of water availability can be measured remotely with infrared radiometers. Detection of crop water stress and ET and combining it with the soil water flow model enable rational irrigation timing and application amounts.
Nutrient deficiency, and in particular nitrogen deficiency, causes substantial crop losses. This deficiency needs to be identified immediately. A faster the detection and correction, a lesser the damage to the crop yield.
In the present work, to retrieve ET a novel deterministic approach was used which is based on the remote sensing data. The algorithm can automatically provide timely valuable information on plant and soil water status, which can improve the management of irrigated crops. The solution is capable of bridging between Penman-Monteith ET model and Richards soil water flow model. This bridging can serve as a preliminary tool for expert irrigation system.
To support decisions regarding fertilizers the greenness of plant canopies is assessed and quantified by using the spectral reflectance sensors and digital color imaging.
Fertilization management can be provided on the basis of sampling and monitoring of crop nitrogen conditions using RS technique and translating measured N concentration in crop to kg/ha N application in the field.
Different views of the significance of aerosol MTF have been reported. For example, one recent paper [OE, 52(4)/2013, pp. 046201] claims that the aerosol MTF "contrast reduction is approximately independent of spatial frequency, and image blur is practically negligible". On the other hand, another recent paper [JOSA A, 11/2013, pp. 2244-2252] claims that aerosols "can have a non-negligible effect on the atmospheric point spread function". We present clear experimental evidence of common significant aerosol blur and evidence that aerosol contrast reduction can be extremely significant. In the IR, it is more appropriate to refer to such phenomena as aerosol-absorption MTF. The role of imaging system instrumentation on such MTF is addressed too.
Imaging systems have advanced significantly in the last decades in terms of low noise and better resolution. While
imaging hardware resolution can be limited by collection aperture size or by the camera modulation transfer function
(MTF), it is the atmosphere that usually limits image quality for long range imaging. The main atmospheric distortions
are caused by optical turbulence, absorption, and scattering by particulates in the atmosphere. The effects of the turbulent
medium over long/short exposures are image blur and wavefront tilts that cause spatio-temporal image shifts. This blur
limits the frequency of line pairs that can be resolved in the target's image and thus affects the ability to acquire targets.
The observer appears to be able to ignore large-scale distortions while small-scale distortions blur the image and degrade
resolution. Resolution degradations due to turbulence are included in current performance models by the use of an
atmospheric MTF. Turbulence distortion effects are characterized by both short and long exposure MTFs. In addition to
turbulence, scattering and absorption produced by molecules and aerosols in the atmosphere cause both attenuation and
additional image blur according to the atmospheric aerosol MTF. The absorption can have significant effect on target
acquisition in infrared (IR) imaging. In the present work, a brief overview and discussion of atmospheric effects on target
acquisition in the IR is given.
Laser devices are currently in widespread use in particular by armed forces for different tasks. Electro-optical sensors as
well as unprotected human eyes are extremely sensitive to laser radiation and can be permanently damaged from direct
or reflected beams. Laser damage depends on the interaction between the laser beam and the atmosphere in which it
traverses. The atmospheric conditions, including the range, terrain features, turbulence, and atmospheric particulates,
may alter the laser's effect on different electro-optical devices and systems.
When a laser beam passes through the atmosphere the optical turbulence affects the beam. As a result, temporal
intensity fluctuations (scintillations) or spatial variations in intensity within a beam cross-section occur. Atmospheric
scintillations pose a safety problem because an observer or sensor can be subjected to the risk of a localized irradiance
(local focusing effect) much greater than that which would occur in a non-turbulent medium.
In the present work, the influence of the atmospheric channel on laser safety is investigated by use of experimental data
of laser beam propagation statistics for different atmospheric conditions.
The results can be important in the area of laser remote sensing, wireless optical communications, and active imaging.
At present, system design usually assumes the Kolmogorov model of refractive index fluctuation spectra in the
atmosphere. However, experimental data indicates that in the atmospheric boundary layer and at higher altitudes the
turbulence can be different from Kolmogorov's type.
In optical communications, analytical models of mean irradiance and scintillation index have been developed for a
traditional Kolmogorov spectrum and must be revised for non-Kolmogorov turbulence.
The image quality (resolution, MTF, etc.) is essentially dependent on the properties of turbulent media. Turbulence MTF
must be generalized to include non-Kolmogorov statistics. The change in fluctuation correlations of the refractive index
can lead to a considerable change in both the MTF form and the resolution value.
In this work, on the basis of experimental observations and modeling, generalized atmospheric turbulence statistics
including both Kolmogorov and non-Kolmogorov path components are discussed, and their influence on imaging and
communications through the atmosphere estimated for different scenarios of vertical and slant-path propagation. The
atmospheric model of an arbitrary (non-Kolmogorov) spectrum is applied to estimate the statistical quantities associated
with optical communication links (e.g., scintillation and fading statistics) and imaging systems.
Implications can be significant for optical communication, imaging through the atmosphere, and remote sensing.
At present, system design usually assumes the Kolmogorov model of refractive index fluctuation spectra in the
atmosphere. However, experimental data indicates that in the atmospheric boundary layer and at higher altitudes the
turbulence can be different from Kolmogorov's type.
In optical communications, analytical models of mean irradiance and scintillation index have been developed for a
traditional Kolmogorov spectrum and must be revised for non-Kolmogorov turbulence.
The image quality (resolution, MTF, etc.) is essentially dependent on the properties of turbulent media. Turbulence MTF
must be generalized to include non-Kolmogorov statistics. The change in fluctuation correlations of the refractive index
can lead to a considerable change in both the MTF form and the resolution value.
In this work, on the basis of measurements and model calculations, the influence of non-Kolmogorov turbulence on
imaging and communications through the atmosphere is estimated for different scenarios of vertical and slant-path
propagation. The atmospheric model of an arbitrary (non-Kolmogorov) spectrum is applied to estimate the statistical
quantities associated with optical communication links (e.g., scintillation and fading statistics) and imaging system.
Implications can be significant for optical communication, imaging through the atmosphere, and remote sensing.
A summary of different approaches for laser beam wander statistics estimation is presented. The principles of an imaging LIDAR technique for remote measurements of refractive turbulence vertical profile based on image motion analysis of a secondary source created by a laser beam at a given altitude are described. The turbulence-induced beam displacement statistics and angle-of-arrival variance of backscattered wave-front are analyzed for different sensing configurations. This study has implications for airborne reconnaissance image restoration, optical satellite communication, adaptive optics, and atmospheric effects on laser weaponry.
Influence of Kolmogorov and non-Kolmogorov turbulence statistics on imaging system performance in terms of
modulation transfer function (MTF) is analyzed for different propagation scenarios.
In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase
of the received light signal, affecting link performance.
Influence of Kolmogorov and non-Kolmogorov turbulence statistics on laser communication links are analyzed for
different propagation scenarios.
The estimation of the performance of electro-optical systems depends on the accuracy of the atmospheric models being used in the propagation prediction codes. In the present work we demonstrate that in a real atmosphere (above the surface layer) the turbulent field of passive scalar fluctuations can differ from Kolmogorov's model. From the spectrum of the intensity fluctuations of LIDAR signals scattered by aerosol concentration inhomogeneities, the behavior of atmospheric turbulence spectrum (power law exponent γ) is estimated. As follows from the experimental data the power law exponent of the turbulent spectra can be different from the case of purely Kolmogorov (γ=5/3). Also, results of lidar measurements of aerosol size distribution, volume, and number concentration at different heights in the Mediterranean region (Be'er-Sheva, Israel) and comparison with models (AFGL, MODTRAN) are presented. Implications can be important for optical communication, imaging through the atmosphere, and adaptive optics.
The estimation of the performance of electro-optical systems depends on the accuracy of the atmospheric models being used in the propagation prediction codes. On the basis of a large set of imaging LIDAR measurements a Middle East model of refractive turbulence strength (Cn2) vertical profile has been developed. The model is presented in this work. Also, the results of lidar measurements of aerosol size distribution, volume, and number concentration at different heights in the Mediterranean region (Be'er-Sheva, Israel) and comparison with models (AFGL, MODTRAN) are
presented. Implications can be important for optical communication, imaging through the atmosphere, and adaptive optics.
The results of lidar measurements of aerosol size distribution, volume, and number concentration at different heights in the Mediterranean region (Be'er-Sheva, Israel) and comparison with models (AFGL, MODTRAN) are presented.
The estimation of the performance of electro-optical systems depends on the accuracy of the atmospheric models being used in the propagation prediction codes. On the basis of a large set of imaging LIDAR measurements a Middle East model of refractive turbulence strength (Cn2) vertical profile has been developed. The model is presented in this work. Implications can be important for optical communication, laser weaponry, imaging through the atmosphere, and adaptive optics.
The estimation of the performance of atmospheric electro-optical systems depends on the accuracy of the atmospheric models being used in the propagation prediction codes.
On the basis of a large set of imaging LIDAR measurements a Middle East model of refractive turbulence strength (Cn2) vertical profile has been developed. The model is presented in this work, and laser beam wander and widening at different elevation heights in target plane is estimated.
Implications can be important for optical communication, laser weaponry, imaging through the atmosphere, and adaptive optics.
Most models of optical radiation propagation through turbulent media are based on the assumption that turbulence is of Kolmogorov's type. It is assumed, also, that this type of turbulence corresponds to fluctuations of passive scalar field (temperature, aerosol, etc.). In the present report we demonstrate that in a real atmosphere (above the surface layer) the turbulent field of passive scalar fluctuations can differ from Kolmogorov’s model. From the spectrum of the intensity fluctuation of LIDAR signals scattered by aerosol concentration inhomogeneities, the behavior of atmospheric turbulence spectrum (power law exponent γ) is estimated. As follows from the experimental data the power law exponent of the turbulent spectra should be different from the case of purely Kolmogorov's (-5/3).
An imaging LIDAR system for measuring vertical profile of the atmospheric refractive index turbulence has been developed and its performance demonstrated. The turbulence profile retrieval technique is based on image motion analysis. In the present work LIDAR measurements of Cn2 vertical profiles are demonstrated. Unlike the existing turbulence models, the experimental results show the various strata and layers in the vertical turbulence profiles.
Atmospheric turbulence and aerosol particles are significant sources of laser-based and imaging system performance degradation. Quantitative estimation and characterization of turbulence and aerosol properties in the atmosphere therefore are very important for system development and applications (optical communications, laser weaponry, image restoration, etc.)
To investigate the influence of aerosols and turbulence on laser-based sensing systems and to profile aerosol extinction, size distribution, and turbulence strength, a LIDAR system was developed. The new setup combines LIDAR and imaging techniques and permits measurement of aerosol and turbulence vertical profiles near simultaneously.
It is usually assumed that the turbulent field is of the Kolmogorov type and calculations of intensity and angle of arrival fluctuations variance and other parameters for prediction of optical systems performance are based on this type of turbulence. However, we find that in the atmospheric boundary layer and at higher altitudes the turbulence can be different from Kolmogorov’s case.
In this work, on the basis of LIDAR measurements, we investigate spectra of aerosol concentration fluctuations at different altitude elevations and at different wavelengths and use the results for turbulence strength profile retrieval.
The turbulence profile retrieval technique is based on LIDAR measurements of angle of arrival fluctuation variance.
Implications can be important for optical communication and imaging through the atmosphere.
A new lidar system for measuring near simultaneously aerosol extinction, size distribution and turbulence profiles up to 20 km altitude has been developed. On the basis of measurements and a Monte Carlo beam propagation model, the atmospheric aerosol contributions to laser beam widening for a horizontal propagation path at various elevations is estimated and compared with beam widening caused by turbulence.
A new lidar system for measuring simultaneously aerosol extinction, size distribution and turbulence profiles up to 20 km altitude has been developed. On the basis of measurements and a Monte Carlo beam propagation model, the atmospheric aerosol contributions to laser beam widening for a horizontal propagation path at various elevations is estimated and compared with beam widening caused by turbulence.
On a basis of a Monte Carlo simulation model, the atmospheric aerosol contributions to laser beam widening for a horizontal propagation path at various elevations is estimated and compared with beam widening caused by turbulence. It is shown that the beam widening caused by atmospheric aerosols is significant, often even more significant than that caused by turbulence.
On a basis of a multiple-forward-scatter propagation model the atmospheric aerosol contributions to laser beam widening for a horizontal propagation path is estimated and compared with beam widening caused by turbulence. It is shown that the beam widening caused by atmospheric aerosols is significant, often even more significant than that caused by turbulence.
On a basis of a multiple-forward-scatter propagation model the atmospheric aerosol contributions to laser beam widening for a horizontal propagation path is estimated and compared with beam widening caused by turbulence. It is shown that the beam widening caused by atmospheric aerosols is significant, often even more significant than that caused by turbulence.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.