The infrared (IR) detection methods are more threatening than other detection methods, such as radar or sonar detections, because the object detected by the IR sensor cannot recognize the situation being detected. Recently, many studies for actively reducing IR signal contrast by controlling the surface temperature of the object are being conducted. We propose an active IR stealth technique using repulsive particle swarm optimization algorithm for IR low-observability. We present a pixel-wise application method of an active IR stealth algorithm to synchronize those signals from the object and the background in the midwavelength IR region. The proposed pixel-wise application method of a statistical active IR stealth technique, which determines the IR stealth temperature for the object surface, is proved to be an effective method for various known background images by reducing the average contrast radiant intensity between the object and background up to 96%.
Infrared (IR) signal emitted from objects over 0 degree Kelvin has been used to detect and recognize the characteristics of those objects. Recently more delicate IR sensors have been applied for various guided missiles and they affect a crucial influence on object’s survivability. Especially, in marine environment it is more vulnerable to be attacked by IR guided missiles since there are nearly no objects for concealment. To increase the survivability of object, the IR signal of the object needs to be analyzed properly by considering various marine environments. IR signature of a naval ship consists of the emitted energy from ship surface and the reflected energy by external sources. Surface property such as the emissivity and the absorptivity on the naval ship varies with different paints applied on the surface and the reflected IR signal is also affected by the surface radiative property, the sensor’s geometric position and various climatic conditions in marine environment. Since the direct measurement of IR signal using IR camera is costly and time consuming job, computer simulation methods are developing rapidly to replace those experimental tasks. In this study, we are demonstrate a way of analyzing the IR signal characteristics by using the measured background IR signals using an IR camera and the estimated target IR signals from the computer simulation to find the seasonal trends of IR threats of a naval ship. Through this process, measured weather data are used to analyze more accurate IR signal conditions for the naval ship. The seasonal change of IR signal contrast between the naval ship and the marine background shows that the highest contrast radiant intensity (CRI) value is appeared in early summer.
Infrared signals are widely used to discriminate objects against the background. Prediction of infrared signal from an
object surface is essential in evaluating the detectability of the object. Appropriate and easy method of procurement of
the radiative properties such as the surface emissivity, bidirectional reflectivity is important in estimating infrared signals.
Direct measurement can be a good choice but a costly and time consuming way of obtaining the radiative properties for
surfaces coated with many different newly developed paints. Especially measurement of the bidirectional reflectivity
usually expressed by the bidirectional reflectance distribution function (BRDF) is the most costly job. In this paper we
are presenting an inverse estimation method of the radiative properties by using the directional radiances from the
surface of concern. The inverse estimation method used in this study is the statistical repulsive particle swarm
optimization (RPSO) algorithm which uses the randomly picked directional radiance data emitted and reflected from the
surface. In this paper, we test the proposed inverse method by considering the radiation from a steel plate surface coated
with different paints at a clear sunny day condition. For convenience, the directional radiance data from the steel plate
within a spectral band of concern are obtained from the simulation using the commercial software, RadthermIR, instead
of the field measurement. A widely used BRDF model called as the Sandford-Robertson(S-R) model is considered and
the RPSO process is then used to find the best fitted model parameters for the S-R model. The results obtained from this
study show an excellent agreement with the reference property data used for the simulation for directional radiances. The
proposed process can be a useful way of obtaining the radiative properties from field measured directional radiance data
for surfaces coated with or without various kinds of paints of unknown radiative properties.
We developed an IR image generation S/W to be applied for moving objects. To validate the S/W the IR signal and the surface temperature are measured from a test ship operating along a designated route on the sea, and the weather conditions and the ship positions are also measured simultaneously. Calculations of the surface temperature and the IR signal of the test ship are performed by using the measured weather data. Results obtained from the measurement and the numerical analysis show fairly good agreements and we found an applicability of the developed S/W in analyzing IR signals from moving objects
The goal of the present study is to develop a S/W that predicts infrared signals from objects synthetically by
considering the internal and external factors, such as surface properties, internal heat sources, solar irradiations,
atmospheric temperature, etc. As a part of developing a S/W, this paper contains some results of the measured and
simulated IR signals for comparison and validation. The scaled model ship used in this study is made of 3mm-thick steel
and 1.5m long. It has virtual internal heat sources that are made of a brass block with a heater. The experiments are
performed under an indoor environment to exclude the external effects such as solar irradiance, wind effect, etc. The
radiance from the ship is mainly due to the surface temperature because the effects of solar and wind are excluded. Also
the IR signals are collected by the IR cameras which are operated at MWIR(3.7~5.1μm ) and LWIR(7.5~9.1 μm),
respectively. At the same time, the atmospheric temperature and the relative humidity are measured to use for input
conditions for calculation. The surface temperature and the IR signals within the two wavelengths are calculated by using
the S/W developed in this study considering the 3D ship model, the internal heater temperature, and the atmospheric
conditions. The temperature and IR signals from the scaled model ship obtained from measurements and from the S/W
developed in this study are compared each other by showing fairly good agreements with each other.
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