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Electro Optic Infrared (EOIR) Research at UCF
Electro Optic Infrared (EOIR) Research at UCF
Infrared (IR) radiation is emitted by all objects at temperatures above absolute zero.electro optic infrared These IR emissions are the result of molecular motion, and their spectral distribution is determined by the temperature of the emitting object. Four basic laws govern the emission and absorption of IR radiation: Kirchhoff’s law, Planck’s law, and the Stefan-Boltzmann law.
The absorption of IR radiation at wavelengths shorter than the transmission region is dominated by water and carbon dioxide.electro optic infrared This is why IR systems tend to focus on the SWIR (1-2.5 um), MWIR (3-7 um), and LWIR (8-14 um) spectral regions. In addition to atmospheric attenuation, IR transmission is also reduced by a variety of other factors including surface roughness, scattering and refraction, coatings, and degradation due to changes in temperature.
EOIR research at UCF spans the spectrum from targets, backgrounds, atmospherics, and sensors, to optics, imaging systems, signal and image processing, and displays.electro optic infrared Our EOIR groups develop new military and aerospace materials, devices, cameras, systems, concepts, and design approaches.
Electro-optic sampling is a powerful field characterization technique for ultrafast phenomena that can be used to achieve sensitivity and dynamic range far beyond the limit set by traditional detector technologies.electro optic infrared In the IR-visible range, this can be accomplished using tailored electric field waveforms generated with a two-channel field synthesizer. In this experiment, a tailored waveform with a full-width-at-half-maximum duration of just 3.8 fs was synthesized and measured for CH1 and CH2 with a wavelength interval of 1400 THz. The resulting spectra, shown in the figure below, were resolved into their component frequencies with a Fourier transform to obtain the spectrum of each channel.
The spectral radiance of the object increases with the temperature, which can be used to compute its emissivity and reflectivity. The emissivity is the ratio of radiated power to the incident power and it depends on the color, material, and temperature properties of the object. The reflectivity is the ratio of reflected power to the incident power and is proportional to the surface area of the object.
Detectors are the critical element in any IR system, and their performance is often assessed by a figure of merit called the net electrical performance (NEP), which is dependent on the detector’s responsive area. A more desirable measure of detector performance is its detectivity, which is independent of the detector’s responsive area and is defined as the detectivity divided by the NEP.
Another factor that influences optical detector performance is the coefficient of thermal expansion (CTE), which is a measure of how much a material expands or contracts when its temperature changes. A lower CTE value is desired for IR and visual applications because it will reduce the impact of thermal noise on optical performance. To further reduce the effects of thermal noise, some IR sensors use band-pass filters to remove spectral components outside the desired spectral region. This is done in order to increase the signal-to-noise ratio of the sensor, and it also improves the system’s tolerance to atmospheric turbulence.
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