This paper provides an overview of the development of different models to determine the range performance of infrared imaging systems. It starts with the grassroots of the motivation of these models to be able to compare the detection, recognition and identification ranges of different infrared imaging systems. With the development of these imaging systems further progress of the performance models were needed and will be described. The rapidly evolving complexity of imaging systems leads to a more divers approach to the comparison of these new systems. I will supply some examples to conquer the new challenges in the development of image enhancement procedures.
Laser speckle patterns typically occur when a laser beam with a narrow spectral linewidth is reflected by small-scale rough surfaces. These intensity patterns are of great interest for active imaging techniques such as gated-viewing, optical coherence tomography, or any other measurement techniques involving laser illumination. In addition to turbulence effects, surface roughness elevation plays an important role in this process. This paper presents the 2D simulation of isotropic small-scale rough surfaces with the corresponding objective speckle patterns, caused only by the reflection of laser light by those surfaces. In addition, laser speckles generated from sea surfaces, whose structures are anisotropic due to the effect of wind, are also shown. The numerical procedure for the simulation of the (material/sea) surface roughness is based on Fast Fourier Transform (FFT). Our method can simulate surfaces with given power spectral density or auto-covariance function (ACF). The most common are the Gaussian and exponential ACF’s. Thereby, the root-mean-square (rms) of surface heights and the correlation length are the main roughness descriptors for surfaces. A surface realization, using a fractal power-law for the spectral density, is also shown. For the simulation of the sea surface roughness, the main input parameters for the wave power spectrum are wind speed, wind direction and fetch. The simulation of the speckle patterns comprises the free-space propagation of a Gaussian-shaped laser beam in forward direction, the subsequent reflection at the rough surface, which introduces fluctuations in the wave phase, and the backward propagation of the reflected laser beam. The method is similar to that of the laser beam propagation in a turbulent atmosphere that uses a 2D spatial field of phase fluctuations (phase screens), whereas here, only a single 2D phase screen is considered that defines the reflective medium.
In this paper we introduce a software tool for image based computer simulation of an underwater gated viewing system. This development is helpful as a tool for the discussion of a possible engagement of a gated viewing camera for underwater imagery. We show the modular structure of implemented input parameter sets for camera, laser and environment description and application examples of the software tool. The whole simulation includes the scene illumination through a laser pulse with its energy pulse form and length as well as the propagation of the light through the open water taking into account complex optical properties of the environment. The scene is modeled as a geometric shape with diverse reflective areas and optical surface properties submerged in the open water. The software is based on a camera model including image degradation due to diffraction, lens transmission, detector efficiency and image enhancement by digital signal processing. We will show simulation results on some example configurations. Finally we will discuss the limits of our method and give an outlook to future development.
The Triangle Orientation Discrimination (TOD) is one of several methods to characterize electro-optical system performance. It is conducted by presenting an equilateral triangle pointing either up, down, right or left, to an observer who is forced to judge the direction. Based from the probability on the correctness of the answers in dependence of the size of the triangle, the quality of the system can be assessed. In order to gain experience with this method it was applied here to test Fraunhofer IOSBs new equipment for perception experiments.
An experiment with four observers, ten contrast levels and six triangle sizes was conducted. Its results were analysed for observer performance versus time, illumination conditions and variations in the TOD-curve. Furthermore, different approaches on analysing the data were compared.
The outcome showed the observers performance variation on different days to be statistically insignificant. In addition, the illumination conditions had no statistically significant influence on the result. Interestingly a larger difference was found between the observers. Although they had normal or corrected to normal eyesight, different visual acuity is the only explanation for the differences. This leads to the necessity to check observers of perception experiments more closely. The different approaches to curve fitting also gave variations, which would result in different ranges when applied in camera assessment. Here a standardization seems necessary when the method is applied in analytical models for imaging systems.
There is a large diversity of phase functions for the computer simulation of light under water. Some papers look at the influence of these phase functions on the results of computer simulations of the remote sensing reflectance. We study the influence of these phase functions on the computer simulation of the resulting image of a target illuminated by a laser. For these simulations we are only interested in those parts of the light that reach the camera position. Therefor we investigate the influence of the phase function on the image. We use a Monte Carlo Simulator with several Fournier-Forand, Henyey-Greenstein phase functions. The resulting signals at the receiver of these simulations are compared to a simulation with a Petzold function that is based on measurements of the phase function.
Conference Committee Involvement (8)
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXVI
13 April 2025 | Orlando, Florida, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXV
23 April 2024 | National Harbor, Maryland, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXIV
3 May 2023 | Orlando, Florida, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXIII
6 April 2022 | Orlando, Florida, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXII
12 April 2021 | Online Only, Florida, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXXI
27 April 2020 | Online Only, California, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXX
16 April 2019 | Baltimore, MD, United States
Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXIX
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.