The modeling of a novel filter for the visible spectrum, constructed of an array of micron sized Fabry-Perot band-pass filters, is presented. An example filter array consists of a hyperspectral 5x5 sub-array, where each squared cavity pixel, 9 μm wide, is resonating at a different wavelength than the neighboring pixels. For such small cavities, traditional 1D modeling of Fabry-Perot cavities of infinite extent is insufficient. To study pixel edge effects and pixel cross-talk, 2D FDTD simulations were carried out. Extensive modeling was done for a cavity array with several pixels, and sloped cavity edges were compared to vertical ones. Both the optical field inside each cavity, and the corresponding integrated power over the whole cavity were calculated. Comparisons of the peak power and spectral bandwidth were made between a finite pixel cavity and a cavity of infinite extent. Both normal and oblique incident light was included in the simulations.

The construction and validation of soldier combat models requires data on the conspicuity of camouflaged targets in the field, and human targets in particular. So far, this data is lacking. Also, it si currently unknown to what degree luminance contrast and motion contribute to target conspicuity. These data are needed to enable the validation and further development of human visual search performance modules in soldier combat models like SCOPE or IWARS. In this study we measured the conspicuity of a person wearing a Dutch army camouflage uniform, while he was either standing still, walking or running along a forest in the background, both for viewing with the naked eye (NE) and for viewing dynamic thermal scene recordings (IR). We varied the viewing distance (80m and 230 m), the camouflage pattern (woodland and desert), the type of background (pine-tree and deciduous forest), and season (summer and winter), The IR (thermal) conspicuity of the person was much larger than his NE (visual) conspicuity. In both cases the effects of movement were large and saturated as a function of retinal target speed. For NE, we find large effects of shading that can not explained by local luminance contrast variations. Also for NE, conspicuity was reduced in winter, probably as a result of an increase in scene clutter. The results suggest that conspicuity is not only a function of retinal target motion and global luminance contrast, but also depends on the amount of clutter in the scene.

Reflective band sensors are often signal to noise limited in low light conditions. Any additional filtering to obtain spectral information further reduces the signal to noise, greatly affecting range performance. Modern sensors, such as the sparse color filter CCD, circumvent this additional degradation through reducing the number of pixels affected by filters and distributing the color information. As color sensors become more prevalent in the warfighter arsenal, the performance of the sensor-soldier system must be quantified. While field performance testing ultimately validates the success of a sensor, accurately modeling sensor performance greatly reduces the development time and cost, allowing the best technology to reach the soldier the fastest. Modeling of sensors requires accounting for how the signal is affected through the modulation transfer function (MTF) and noise of the system. For the modeling of these new sensors, the MTF and noise for each color band must be characterized, and the appropriate sampling and blur must be applied. We show how sparse array color filter sensors may be modeled and how a soldier's performance with such a sensor may be predicted. This general approach to modeling color sensors can be extended to incorporate all types of low light color sensors.

Image noise, originating from a sensor system, is often the limiting factor in target acquisition performance. This is especially true of reflective-band sensors operating in low-light conditions. To accurately predict target acquisition range performance, image degradation introduced by the sensor must be properly combined with the limitations of the human visual system. This is modeled by adding system noise and blur to the contrast threshold function (CTF) of the human visual system, creating a combined system CTF. Current U.S. Army sensor performance models (NVThermIP, SSCAMIP, IICAM, and IINVD) do not properly address how external noise is added to the CTF as a function of display luminance. Historically, the noise calibration constant was fit from data using image intensifiers operating at low display luminance, typically much less than one foot-Lambert. However, noise calibration experiments with thermal imagery used a higher display luminance, on the order of ten foot-Lamberts, resulting in a larger noise calibration constant. To address this discrepancy, hundreds of CTF measurements were taken as a function of display luminance, apparent target angle, frame rate, noise intensity and filter shape. The experimental results show that the noise calibration constant varies as a function of display luminance. To account for this luminance dependence, a photon shot noise term representing an additional limitation in the performance of the human visual system is added to the observer model. The new noise model will be incorporated in the new U.S. Army Integrated Performance Model (NV-IPM), allowing accurate comparisons over a wide variety of sensor modalities and display luminance levels.

It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band with wavelength between 0.9 and 1.7 μm. By examining images in an urban and a rural setting, we investigate the correlation between the appearances of passive dark of night images in the SWIR with NIR- visible. The experimental setup consists of two sensors, a NIR-visible CCD and an InGaAs array sensitive in the SWIR, both colocated on an AZ-EL mount, and both co-boresighted so that different viewing angles of the sky and terrestrial scenes are possible. By making corrections for focal length and pixel size, the visible and SWIR data can be compared. After taking several nights of data in the urban environment of Albuquerque, NM, the entire system was then re-located to a rural location on the island of Kauai in a rural setting with very low ambient light. It is shown that under most conditions the SWIR sensor produces significantly better imagery using the airglow illumination source.

Predicting an accurate Minimum Resolvable Temperature Difference (MRTD) for a thermal imaging system is often hindered by inaccurate measurements of system gain and display characteristics. Variations in these terms are often blamed for poor agreement between model predictions and measured MRTD. By averaging over repeated human measurements, and carefully recording all system parameters affecting image quality, it should be possible to make an accurate prediction of MRTD performance for any resolvable frequency. Utilizing the latest NVESD performance models with updates for noise, apparent target angle, and human vision, predicted MRT are compared with measured curves. We present results for one well characterized mid-wave thermal staring system.

The triangle orientation discrimination (TOD) method is an emerging technique for the evaluation of electro-optical (EO) systems. In this method, the test pattern is a non-periodic equilateral triangle in one of four different orientations (apex up, down, left, or right), and the measurement procedure is a robust four-alternative forced-choice psychophysical process. This leads to a time-consuming task. Consequently, software models have been developed to replace the required human observers. These models base their decision on the orientation of the target using correlation between observed data and the set of four differently oriented targets. This study investigates for the first time how this method can be applied to highly distorted OE systems like hemispheric imagers. These types of systems have inherent large distortion, but the distortion should not be considered as an aberration but rather the result of the projection of a hemispheric field (3D) on a 2D sensor. The distortion deforms the image of the targets and image processing is usually performed to remove distortion and straighten the field of view. We present a comparison in accuracy and computational burden for the evaluation of EO system performance between cases where tested images are pre-processed and correlated to unchanged triangle targets and where untouched (distorted) images are correlated with position-wise distorted targets. This is a first evaluation of the application of the TOD with the goal of obtaining an image quality criterion for panoramic imagers.

The raw output of a generic infrared vision system, based on staring arrays, is spatially not uniform. This spatial noise can be much greater than the system NETD, and determines a strong drop in system performance. Therefore we need to model all system non-uniformity (NU) sources to highlight the parameters that should be controlled by optical and mechanical design, the ones depending on the focal plane array and those that can be corrected in post-processing. In this paper, we identify the main NU sources (optical relative irradiance, housing straylight, detector pixel-pixel differences and non linearity), we show how to model these sources and how they are related to the design and physical parameters of the system. We then describe the total signal due to these sources at the detector output. Applying different NUC algorithms to this signal, the final results on the image can be simulated finding a proper correction algorithm. At the end we show the agreement between the model with the experimental data taken on a real system. Changing a limited set of parameters, this model can be applied to many third generation thermal imager configurations.

The structural image similarity index (SSIM), introduced by Wang and Bovik (IEEE Signal Processing Letters 9-3, pp. 81-84, 2002) measures the similarity between images in terms of luminance, contrast en structure. It has successfully been deployed to model human visual perception of image distortions and modifications in a wide range of different imaging applications. Chang and Zhang (Infrared Physics & Technology 51-2, pp. 83-90, 2007) recently introduced the target structural similarity (TSSIM) clutter metric, which deploys the SSIM to quantify the similarity of a target to its background in terms of luminance, contrast en structure. They showed that the TSSIM correlates significantly with mean search time and detection probability. However, it is not immediately obvious to what extent each of the three TSSIM components contributes to this correlation. Here we evaluate the TSSIM by deploying it to a set of natural images for which human visual search data are available: the Search_2 dataset. By analyzing the predictive performance of each of the three TSSIM components, we find that it is predominantly the structural similarity component which determines human visual search performance, whereas the luminance and contrast components of the TSSIM show no relation with human performance. Since the structural similarity component of the TSSIM is equivalent to a matched filter, it appears that matched filtering predicts human visual performance when searching for a known target.

The problem solved in this paper is easily stated: given search parameters (p∞, τ) that are known functions of time, calculate how the probability a single observer acquires a target grows with time. This problem has been solved analytically. In this paper we describe the analytical solution and provide derivations of the results. Comparison with perception experiments will be reported in a future publication and hopefully will support the results presented here. The provided solution is applicable to any scenario where the search parameters are changing with time and are specified. In particular, the solution can be used to estimate the probability of target acquisition as a function of time: (1) when the sensor-target range is changing, (2) for a slewed sensor where the target is alternately in and out of the field of view, and (3) for a sensor that switches between wide and narrow fields of view.

We investigate a dim-target-detection approach for pixellated focal-plane-arrays based on differential correlation detection. The change in the temporal correlation of the output signals between an illuminated pixel and a dark reference pixel is measured in real time over some number of samples and may enable more sensitive detection of dim targets whose signal amplitudes are on the order of the noise levels of the sensor. If successful, target detection may be possible with target signal-to-noise-ratios of less than 1 under practical conditions where dark drift may occur.

Modern infrared imaging seekers can nowadays deal with higher resolution and less noisy sensor images. The testing of new image processing or tracking algorithms requires a fitted set of relevant sensor images. When no actual recordings are available, when experimental benches are not adapted or at an early stage of development, one can require a simulation tool to generate synthetic infrared sensor images. This paper presents the first version of ISISserver (Infrared Sensor Image Simulation Server) a software library developed at TNO and used for infrared (IR) imaging seeker applications. Based on the EOSTAR Pro (Electro-Optical Signal Transmission And Ranging) model suite, the set of functions offered by this toolkit allows analysis of synthetic sensor images generated for various synthetic environments and targets. Typical targets from a database can be used as well as externally user designed 3D targets. Simulation results using ISISserver toolkit with test data (not realistic or physical data) will be shown.

In this paper we address these problems. 1) Two stationary observers with two sensors independently search for a stationary target. Each sensor is characterized by individual search parameters (p∞, τ) which are different either because the sensors are at different ranges or are different because the sensors are at the same range but have different properties. The target is said to be detected when the first observer detects the target. Using this definition for time to detect, we derive an analytical expression for the mean detection time. 2) If multiple observers independently search an image obtained from a single sensor how does the mean time until the first observer detects the target vary with the number of observers. 3) If multiple observers independently search an image obtained from a single sensor how does the probability of detection vary with the number of observers. Here the target is said to be detected if any of the observers detect the target. 4) For the problem of two stationary observers searching independently for a stationary target we found the probability density function for the time to detect.

The physical model for long wave infrared (LWIR) thermal imaging through a dust obscurant incorporates transmission loss as well as an additive path radiance term, both of which are dependent on an obscurant density along the imaging path. When the obscurant density varies in time and space, the desired signal is degraded by two anti-correlated atmospheric noise components-the transmission (multiplicative) and the path radiance (additive)-which are not accounted for by a single transmission parameter. This research introduces an approach to modeling the performance impact of dust obscurant variations. Effective noise terms are derived for obscurant variations detected by a sensor via a forward radiometric analysis of the imaging context. The noise parameters derived here provide a straightforward approach to predicting imager performance with existing NVESD models such as NVThermIP.

The applicability of two theories that account for aliasing artifacts, introduced by spatial sampling, on target acquisition performance is addressed. Currently the Army's imager performance model, the Targeting Task Performance (TTP) metric uses a parameterized model, based upon a fit to a number of perception experiments, called MTF squeeze. MTF squeeze applies an additional degradation to the TTP metric based upon the amount of spurious response in the final image. While this approach achieves satisfactory results for the data sets available, it is not clear that these results extend to a wider variety of operating conditions. Other models treat the artifacts arising from spurious response as a target-dependent noise. Modeling spurious response as noise allows proper treatment of sampling artifacts across a wider variety of systems and post-processing techniques. Perception experiments are used to assess the performance of both the MTF squeeze and aliasing as noise methods. The results demonstrate that modeling all of the aliased frequencies as a target-dependent noise leads to erroneous predictions; however, considering only aliased signals above the Nyquist rate as additive noise agrees with experimental observations.

The ability of observers to identify human activities in noise is expected to differ from performance with static targets in noise due to the unmasking that is provided by target motion. At a minimum, the probability of identification should increase when the temporal bandwidth of the noise is less than that of the system. Results from a human activities identification experiment are presented in this paper, along with results from a moving character experiment that is intended to provide better understanding of basic motion in noise with varied temporal bandwidth. These results along with further experiments and analysis will eventually be used to improve performance predictions derived from the Targeting Task Performance (TTP) metric.

Wide field-of-view infrared sensor and data acquisition and exploitation systems are being developed and tested for detecting activity and threats over extended areas. Limitations on the total number of pixels available in infrared arrays precipitate sensor design discussions on achieving the widest total field-of-view while achieving small ground sample distance to allow automated tracking and activity detection. In order to allow accurate imagery geo-location, the sensors optical characteristics as well as its location and orientation must be accurately recorded with each image. This paper will discuss system considerations of infrared imaging sensors for wide area persistent surveillance. We will present some uses of an advanced day/night sensors for wide area persistent surveillance that use large, high quality mid-wave infrared (MWIR) staring arrays in a fast step-stare stabilized mount and a Windows based data acquisition and exploitation system.

The TTP (Targeting Task Performance) metric, developed at NVESD, is the current standard US Army model to predict EO/IR Target Acquisition performance. This model however does not have a corresponding lab or field test to empirically assess the performance of a camera system. The TOD (Triangle Orientation Discrimination) method, developed at TNO in The Netherlands, provides such a measurement. In this study, we make a direct comparison between TOD performance for a range of sensors and the extensive historical US observer performance database built to develop and calibrate the TTP metric. The US perception data were collected doing an identification task by military personnel on a standard 12 target, 12 aspect tactical vehicle image set that was processed through simulated sensors for which the most fundamental sensor parameters such as blur, sampling, spatial and temporal noise were varied. In the present study, we measured TOD sensor performance using exactly the same sensors processing a set of TOD triangle test patterns. The study shows that good overall agreement is obtained when the ratio between target characteristic size and TOD test pattern size at threshold equals 6.3. Note that this number is purely based on empirical data without any intermediate modeling. The calibration of the TOD to the TTP is highly beneficial to the sensor modeling and testing community for a variety of reasons. These include: i) a connection between requirement specification and acceptance testing, and ii) a very efficient method to quickly validate or extend the TTP range prediction model to new systems and tasks.

The standard model used to describe the performance of infrared imagers is the U.S. Army imaging system target acquisition model, based on the targeting task performance metric. The model is characterized by the resolution and sensitivity of the sensor as well as the contrast and task difficulty of the target set. The contrast of the target is defined as a spatial average contrast. The model treats the contrast of the target set as spatially white, or constant, over the bandlimit of the sensor. Previous experiments have shown that this assumption is valid under normal conditions and typical target sets. However, outside of these conditions, the treatment of target signature can become the limiting factor affecting model performance accuracy. This paper examines target signature more carefully. The spatial frequency dependence of the standard U.S. Army RDECOM CERDEC Night Vision 12 and 8 tracked vehicle target sets is described. The results of human perception experiments are modeled and evaluated using both frequency dependent and independent target signature definitions. Finally the function of task difficulty and its relationship to a target set is discussed.

This paper presents a simple, fast, and robust method to estimate the blur kernel model, support size, and its parameters directly from a blurry image. The edge profile method eliminates the need for searching the parameter space. In addition, this edge profile method is highly local and can provide a measure of asymmetry and spatial variation, which allows one to make an informed decision on whether to use a symmetric or asymmetric, spatially varying or non-varying blur kernel over an image. Furthermore, the edge profile method is relatively robust to image noise. We show how to utilize the concepts behind the statistical tools for fitting data distributions to analytically obtain an estimate of the blur kernel that incorporates blur from all sources, including factors inherent in the imaging system. Comparisons are presented of the deblurring results from this method to current common practices for real-world (VNIR, SWIR, MWIR, and active IR) imagery. The effect of image noise on this method is compared to the effect of noise on other methods.

Hodgkin (SPIE 6207(2006)) extended NVThermIP to be applicable to cold weather conditions. We also (IRPhys&Technol.51 (2008)520) later published an analysis of the effect of varying ambient temperature (Tamb) by modifying the inputs to NVTherm2002, and by using spectrally-weighted atmospheric transmission calculated from MODTRAN at different ambient temperatures and relative humidities (RH). We took into account the effects on the integration time and NETD, and we now account for the variation of ▵T with varying Tamb, as Hodgkin has done. The overall trends are similar, but we have NVTherm, not NVThermIP. We vary the parameters associated with Johnson's criteria to obtain similar results. Note that diurnal, seasonal, climatic and microclimatic variations of relative humidity (RH) significantly impact the performance of thermal imagers, especially LWIR ones. We compare the performance of thermal imagers a horizontal mean-sea-level path in clear weather conditions for terrestrial imagers and ground targets/scenes in both LWIR and MWIR bands, as a function of the ambient temperature from -40°C to +40°C and also as a function of RH (30%, 50% and 70%). To understand the differences in the results reported by Hodgkin and our paper, we do a sensitivity analysis as a function of system and environmental parameters (f/#, RH, detection probability, spectral width etc). For one set of parameters, we observe that the range curves RLW and RMW intersect at more than one value of Tamb and suggest an analogy to a 're-entrant phase'. We also analyze how motion blur affects the two bands, at different Tamb.

Most existing platform signature models use semi-empirical correlations to predict flow convection on internal and external surfaces, a key element in the prediction of accurate skin signature. Although these convection algorithms are capable of predicting bulk heat transfer coefficients between each surface and the designated flow region, they are not capable of capturing local effects such as flow stagnation, flow separation, and flow history. Most computational fluid dynamics (CFD) codes lack the ability to predict changes in background solar and thermal irradiation with the environment and sun location, nor do they include multi-bounce radiative surface exchanges by default in their solvers. Existing interfaces between CFD and signature prediction typically involve a one-directional mapping of CFD predicted temperatures to the signature model. This paper describes a new functional interface between the NATO-standard ship signature model (ShipIR) and the ANSYS Fluent model, where a bi-directional mapping is used to transfer the thermal radiation predictions from ShipIR to Fluent, and after re-iteration of the CFD solution, transfer the wall and fluid temperatures back to ShipIR for further refinement of local-area heat transfer coefficients, and re-iteration of the ShipIR thermal solution. Both models converge to an RMS difference of 0.3 °C within a few successive iterations (5-6). This new functional interface is described through a detailed thermal/IR simulation of an unclassified research vessel, the Canadian Forces Auxiliary Vessel (CFAV) Quest. Future efforts to validate this new modelling approach using shipboard measurements are also discussed.

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

A new C++ library for radiative transfer calculations in the visible and infrared bands which uses MODTRAN as a primary source for atmospheric optical parameters has been developed at Defense R&D Canada, Valcartier (DRDC Valcartier). The main benefit of the library is its capability to perform fast wide spectral band calculations with an appreciably high accuracy. Coherent calculations on wide bands are made possible by using a modified version of the correlated-k theory. The main features of the library are discussed, and comparisons with conventional spectral MODTRAN 4 calculations are presented. It is shown that the library is capable of producing band results that are usually within 5% of MODTRAN 4 with computation times that are thousands of times faster.

Active imaging systems, including laser range-gated short wave infrared (LRG SWIR) systems, are currently being developed to increase the identification range performance of electro-optical targeting systems. This paper reports on the development of an end-to-end simulation of a LRG SWIR imaging system that includes the principle phenomena of beam broadening, beam jitter, scintillation, atmospheric turbulence blur and distortion, laser speckle and camera blur. Although the simulation is restricted to weak turbulence conditions, it is much less computationally expensive than the classical the split-step Fourier-transform algorithm.

The development and implementation of a computer model to simulate the impact of atmospheric turbulence on image quality for a passive imaging system is presented. The presented model is an empirical one based upon the analysis of imaging distortions in real image sequences recorded under different atmospheric conditions. Only horizontal views are considered, which are typical for a ground to ground application. The computer simulation uses pristine, single images (showing no turbulence effects) as input and produces image sequences that are degraded by the specified turbulence. The implemented method can be applied for instance to the images calculated by any existing imaging simulation tool of a passive camera in a post processing step. Imagers with high frame rates can be simulated. The simulation results for a medium and a strong turbulent condition are compared to field data collected by Germany during the NATO-RTG40 White Sands Missile Range field trials of November 2005. An important feature of the presented simulation method is the consideration of the range information, which is the viewing distance to an object, or in other words, the length of the optical propagation path. In contrast to the usual way how turbulence is included into imaging simulations by assuming only a single viewing distance for all parts of a scene, different range information for different image areas can be used in our simulation. Such spatially high resolved range information can be for instance easily calculated for synthetic scenarios by computer graphics tools. Examples are presented showing the advantages of the range dependent turbulence simulation. The presented simulation method is fast in terms of computing time and well suited for real-time simulations using the computing power of nowadays graphics processors.

It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band between 0.9 and 1.7 μm wave length. This phenomenon, often referred to as airglow, has been demonstrated as an effective illumination source for passive low light level night time imaging applications. It addition it has been shown that observation of the spatial and temporal variations of the illumination can be used to characterize atmospheric tidal wave actions in the airglow region. These spatio-temporal variations manifest themselves as traveling wave patterns whose period and velocity are related to the wind velocity at 85 km as well as the turbulence induced by atmospheric vertical instabilities. In this paper we present nearly a year of airglow observations over the whole sky, showing long term and short term fluctuations to characterize SWIR night time image system performance.

We use a rigorous Markov approximation-based propagation model to calculate statistical properties of the instantaneous turbulent Point Spread Function (PSF) for the weak and strong turbulence condition. Long-Term PSF is well known and is currently widely used for the estimates of the optical system performance and simulation of the image distortions caused by turbulence. We discuss some peculiarities of the Long-Term PSF that are related to the specifics of the propagation in turbulence, and are often overlooked in the recent literature. Models for the Short-term PSF have been used since mid-1960's, and were the subject of some recent publications. We review the recently published model and present sample calculations of the Short-term PSF. We calculate the variances of the power in the instantaneous PSF and the Strehl ratio at the average PSF center, and correlation between the total power and the Strehl ratio. This information allows modeling the instantaneous PSF with random width and height. Analysis of the calculation results shows that for the most practical situations random Strehl ratio is a product of two uncorrelated random variables - power and axial directivity.

In order to facilitate systematic, computer aided improvements of camouflage and concealment assessment methods, the software system CART (Camouflage Assessment in Real-Time) was built up for the camouflage assessment of objects in multispectral image sequences (see contributions to SPIE 2007-2010 [1], [2], [3], [4]). It comprises a semi-automatic marking of target objects (ground truth generation) including their propagation over the image sequence and the evaluation via user-defined feature extractors as well as methods to assess the object's movement conspicuity. In this fifth part in an annual series at the SPIE conference in Orlando, this paper presents the enhancements over the recent year and addresses the camouflage assessment of static and moving objects in multispectral image data that can show noise or image artefacts. The presented methods fathom the correlations between image processing and camouflage assessment. A novel algorithm is presented based on template matching to assess the structural inconspicuity of an object objectively and quantitatively. The results can easily be combined with an MTI (moving target indication) based movement conspicuity assessment function in order to explore the influence of object movement to a camouflage effect in different environments. As the results show, the presented methods contribute to a significant benefit in the field of camouflage assessment.

We show how to simulate realistic turbulent imagery using only two scalar fields, from which we derive a Gaussian and non-isoplanatic Point-Spread Function (PSF). The first field controls mainly scintillation effects, while the second principally controls image displacements. The model is designed for weak turbulence and is based on the first-order Rytov theory for propagation through turbulence. We explain the physical principles behind the model and justify them using empirical evidence.

MATISSE (Advanced Modeling of the Earth for Environment and Scenes Simulation) is an infrared background scene generator developed for computing natural background spectral radiance images. The code also provides atmospheric radiatives quantities along lines of sight. Spectral bandwidth ranges from 0.4 to 14 μm. Natural backgrounds include atmosphere, sea, land and high and low altitude clouds. The new version MATISSE-v2.0, released this year, has been designed to treat spatial multi resolution in the generated images in order to be able to reach metric spatial variability in pixels footprints. Moreover, MATISSE-v2.0 includes a new sea surface radiance model (water waves and surface optical properties) which depends on wind speed, wind direction and fetch value. Preliminary validations using radiometric measurements have been conducted concerning sea radiances and give promising results. In order to go further in the validation process of MATISSE-v2.0, comparisons with MODIS satellite images have been led. The results of comparing the simulated MATISSE images radiances with the MODIS observations show that the code is performing well. This paper gives a description of MATISSE-v2.0 new functionalities and focus on first results on comparison between MATISSE/MODIS images radiances.

The 3d-noise components are used for describing detector noise, especially for infrared focal-plane array (FPA) detectors, where individual pixel variations and the read-out-process of pixel values will give rise to detector-induced intensity variations. For consistency of actual and anticipated system performance it is essential that detector noise is measured and estimated in a way that is consistent with how noise is modeled in system simulations. This paper describes how to efficiently obtain bias-free estimates of the 3d-noise components in the frequency domain. Frequency domain representation of the noise also allows application-tailored detector noise requirements. Intensity variations caused by e.g. optics should not be allowed to influence the detector noise estimation, frequency domain estimation can easily avoid influence from such non-uniformity. An alternative approach is to use pre-filtering as a means to suppress non-uniformity; the effect of filter choice on estimated 3d-detector noise values is examined and filter choice discussed. Finally, we demonstrate that low pixel operability, requiring replacement by interpolation from neighboring pixels for many of the pixels in the array, will lead to under-estimation of the detector noise of the operable pixels.

MR-i is an imaging version of the ABB Bomem MR Fourier-Transform spectroradiometer. This field instrument generates spectral datacubes in the MWIR and LWIR. It is designed to be sufficiently fast to acquire the spectral signatures of rapid events. The design is modular. The two output ports of the instrument can be populated with different combinations of detectors (imaging or not). For instance to measure over a broad spectral range, one output port can be equipped with a LWIR camera while the other port is equipped with a MWIR camera. No dichroics are used to split the bands, hence enhancing the sensitivity. Both ports can be equipped with cameras serving the same spectral range but set at different sensitivity levels in order to increase the measurement dynamic range and avoid saturation of bright parts of the scene while simultaneously obtaining good measurement of the faintest parts of the scene. Various telescope options are available for the input port. Overview of the instrument capabilities will be presented. Test results and results from field trials for a configuration with two MWIR cameras will be presented. That specific system is dedicated to the characterization of airborne targets. The two MWIR cameras are used to expand the dynamic range of the instrument and simultaneously measure the spectral signature of the cold background and of the warmest elements of the scene (flares, jet engines exhausts, etc.).

Application-specific integrating sphere-based, integral veiling glare measurement systems are described. The sources use the integral method for measuring the veiling glare (VG) index of various lens-based imaging systems. The calibration source has provisions in the form of a collimating lens holder to simulate a situation where the black target and bright surround are at a sufficiently great distance to give measurements of VG index which are the same as that which would result if the distance where infinite. The design criteria for the integral VG test source are presented. Included is a summary of the end-user specifications in regards to spectral radiance, levels of attenuation, irradiance stability, and aperture uniformity and contrast. Spectral radiometric predictions and actual output levels are compared.

A compact low-cost LWIR test station has been developed that provides real time MTF testing of IR optical systems and EO imaging systems. The test station is intended to be operated by a technician and can be used to measure the focal length, blur spot size, distortion, and other metrics of system performance. The challenges and tradeoffs incorporated into this instrumentation will be presented. The test station performs the measurement of an IR lens or optical system's first order quantities (focal length, back focal length) including on and off-axis imaging performance (e.g., MTF, resolution, spot size) under actual test conditions to enable the simulation of their actual use. Also described is the method of attaining the needed accuracies so that derived calculations like focal length (EFL = image shift/tan(theta)) can be performed to the requisite accuracy. The station incorporates a patented video capture technology and measures MTF and blur characteristics using newly available lowcost LWIR cameras. This allows real time determination of the optical system performance enabling faster measurements, higher throughput and lower cost results than scanning systems. Multiple spectral filters are also accommodated within the test stations which facilitate performance evaluation under various spectral conditions.

The infrared test equipment industry has matured over the past half century and has historically offered test equipment that met and often exceeded the capabilities of the units under test. This may seem to be a moot or trivial point. However, in the past decade infrared imagers have begun to press the limits of infrared test equipment. Today, infrared imagers incorporate focal plane arrays that offer a significantly higher resolution and sensitivity than their predecessors. Additionally, current infrared imagers are expanding their role in the field and are being developed for a wide variety of applications. These applications demand that optical infrared test equipment begin to expand their capability. Roles such as: larger emitting surface areas, temperature ranges from cryogenic to sunlight, wide ambient temperature ranges, vacuum ambient conditions, vehicle installation, field portability, computer interface compatibility, applications level software integration, and high off-axis uniformity and emissivity. Therefore, how does infrared test equipment meet these demands while maintaining excellent uniformity and stability, two of the traditionally most scrutinized specifications? This paper will present methods for achieving the rigorous demands for test equipment outlined above, it will present an outline of the development and technology trends of blackbody/infrared test equipment over the past 50 years, and finally this paper will discuss the expected development of blackbody/infrared test equipment for the years to come.

Usage of image intensified (I²) and other low light level devices have grown considerably over the past decade^1,2 As the systems have become more common place, the demand for production line test equipment has also grown. Accurate measurements of device response are a key part of determining acceptable system operation. However, differences in the spectral response of the unit under test (UUT) devices and the control detector; and the spectral distribution of the source, can lead to errors in test accuracy. These errors can be compounded by spectral variation in the source (or color temperature shifts) as a function of attenuation. These issues are often further confused by test system requirements that are not consistent with the desired parameter to be measured. For example, source requirements are often specified in illuminance while the UUT actually measures irradiance. We report on the calibration of a large dynamic range light source test system (> 7 orders), and discuss output compensation approaches for systems which control in a band different than the UUT being tested.

The three dimensional noise model (3D noise) is a widely used model for characterizing noise in thermal imaging system. In this model, a sequence of images of a uniform background are acquired, and organized in a three dimensional matrix. This matrix is then decomposed into eight orthogonal noise components that can be assessed individually to yield an understanding about the magnitude and source of noise in a given system. In a previous paper we showed that the operators used to estimate the magnitude of the 3D noise in a system are biased statistical estimators that lead to systematic errors when measuring system noise. Here we provide new definitions for the noise estimators that enable removal of the statistical bias, and accurate estimation of system noise using the 3D noise model.

Test Program Set (TPS) software development for Electro-Optical (EO) testing has traditionally been an expensive and lengthy process. A major cause of this has been the development of new test executive software on an ad hoc basis for each program. Furthermore, there have typically been different needs for production versus lab environments with production needing a set of standard tests, while users in a lab environment requiring the capability to modify certain aspects of their tests as needed. At Santa Barbara Infrared, a new architecture for TPS development has been engineered that addresses these concerns. The new architecture can host a complete TPS development environment that eliminates the need for a separate test executive. It supports EO testing in both engineering development and production testing through the use of user editable test scripts along with distinct user accounts and privileges. The new architecture is unit under test (UUT) centric, allowing a user to define UUT parameters once and easily share the results between tests. In this article we will review the new architecture and give examples of TPS development under that architecture.

As far as we know, CI has been the only manufacturer in the world of commercial visible/infrared spectroradiometers for remote sensing applications for many years. In this paper we describe the new design and some performance improvements that we are developing to renew and modernize the system. Simultaneous visible and infrared spectroradiometry, field of view flatness of response and scan speed are only some aspects of the system which have undergone significant improvement. The challenge is to achieve these functional improvements without losing any of the advantages of the traditional system as far as ruggedness for field use, interchangeability of spectral range and field of view and aiming and image recording facility. Important factors in the success of this endeavor are: i) the development of a new electronic signal processing package, ii) a modular optical concept that mechanically separates modules for small, medium and large field of view ranges, and iii) a compact overall shape for convenience of use. Actual instrument performance results will be reported in a future paper.

Pyroelectric radiometers with noise-equivalent-power (NEP) close to 1 nW/Hz^1/2 have been developed to measure less than 1 μW radiant power levels at room temperature to 25 μm. The radiometers will be used as transfer standards for routine spectral responsivity calibrations in the infrared range at the output of a traditional monochromator. Dome inputoptics are used with multiple beam reflections to increase absorptance and to minimize structures in the spectral responsivity function. The temperature of the pyroelectric detector is stabilized with a thermoelectric cooler/heater. Spectral power responsivity calibrations were performed with two different methods. A Fourier Transform Spectrometer using it's Infrared Reference Integrating Sphere System based method was validated with a continuously variable filtermonochromator based detector-comparison method using earlier developed pyroelectric radiometer standards. A responsivity uncertainty of 1.4 % (k=2) was obtained between 2 μm and 14 μm.

We present the application of Quadri-Wave Lateral Shearing Interferometry (QWLSI), a wave front sensing technique, to characterize optical beams at infrared wavelengths from 2 to 16μm with a single instrument. We apply this technique to qualify optical systems dedicated to MWIR (λ within 3 and 5μm) and LWIR (λ within 8 and 14μm) wavelength ranges. The QWLSI offers the crucial advantage that it yields an analyzed wave front without the use of a reference arm and consequent time consuming alignment. The qualification of an optical system with QWLSI gives a complete diagnostic, from the aberration cartography to the PSF and MTF curves for every direction in one single measurement. In this paper, we first present the QWLSI technology and its main features, we also detail an experimental comparison between our MTF measurement and the results given by a classical MTF test bench. We finally show the experimental analysis of an infrared lens at two different wavelengths, one in the MWIR range (λ=3.39μm) and the other in the LWIR range (λ=10.6μm).

The National Institute of Standards and Technology (NIST) and the Naval Surface Warfare Center - Corona Division (NSWC) have jointly developed a dual-wavelength extended-sensitivity radiometer (D-ESR) that functions as a portable transfer standard for measuring laser pulses at wavelengths of 1.06 μm and 1.55 μm. The peak-power irradiance range is from 500 pW/cm² to 50 μW/cm² within the wavelength range of 1.54 μm to 1.58 μm. A similar peak-power range is covered at a wavelength of 1.06 μm. The measurement range is covered by using smaller apertures or a neutral-density filter to reach the highest peak powers. The D-ESR radiometer is based on an InGaAs avalanche photodiode (APD) detector that is integrated with a transimpedance preamplifier module. The light-collecting optical system has a maximum aperture of approximately 125 cm². The D-ESR is able to measure Gaussian pulse duration from 4 ns to 400 ns. The output is a negative-going pulse waveform that is measured with an oscilloscope. The total expanded uncertainty of a calibrated peak-power measurement with a D-ESR radiometer is approximately 9 % (k=2).

The conversion methodology for field performance of HFLIR (Heliborne FLIR) systems has been in phenomenon established to get reasonable evaluation for its detection and identification ranges. On the basis of the field performance model with Johnson criterion, the contribution factors affecting on the HFLIR performance are derived as follows: the bar target size, the temperature difference between the black and white in target, the atmospheric transmittance (the visibility, the atmospheric temperature and the humidity), the background temperature, and the instability in the system MRT requirement. Then, by considering those factors, the test and evaluation procedures are set up where the conversion process from the performance measured under real test condition to that at the evaluation criterion is implemented, which is newly devised in this paper. With the help of this methodology, the field performances (the detection and recognition ranges) of HFLIRs on S-LYNX, UH-60 and HH-47 helicopters have been measured and reasonably evaluated to check whether or not their performances meet the requirement of capability (ROC). As for the HFLIR on S-LYNX, the converted detection and recognition ranges are proved to be elongated respectively +10% and -9.2%, compared with the measured ranges. They for the HFLIR on UH-60 turn out to be respectively better +6.2% and +12.4% than the measured ones, and they for HFLIR on HH-47 show performances with conversion rate of +0.4% and +1%. The difference between the converted and the measured ranges, of course, comes from the difference in the real weather conditions at test day and at ROC. This methodology gives so fair and reasonable judgment that it may be very useful for the case that the measured values are comparable to those at ROC within the experimental error.

A modern laboratory capable to carry out expanded tests of all types of electro-optical surveillance systems (thermal imagers, TV/LLLTV cameras, night vision devices, laser range finders/designators/illuminators, multi-sensor surveillance systems) and basic modules of such surveillance systems (IR FPA/CCD/CMOS/EBAPS sensors, image intensifier tubes, optical objectives) was developed and is presented in this paper. The laboratory can be treated as a both scientific and technical achievement due to its several features. First, all important parameters of modern electro-optical surveillance systems or parameters of basic modules of such systems can be measured. Second, the laboratory is built using a set of semi-independent modular test stations. This modular concept enables easy creations of many versions optimized for different applications. Third, interpretation of the measurement data is supported by a set of specialized computer simulation programs. Fourth, all tests stations in the laboratory were developed by the same design team and are based on similar test concepts.. Because of these features the laboratory of electro-optical surveillance technology presented in this paper can be an optimal solutions for scientific centers or industrial companies who plan to enter and make quick progress in all main areas of surveillance technology.

Laser illumination systems for high brightness imaging through the self-luminosity of explosive events, at Aberdeen Proving Ground and elsewhere, required complex pulse timing, extensive cooling, large-scale laser systems (frequencydoubled flash-pumped Nd:YAG, Cu-vapor, Q-switched ruby), making them difficult to implement for range test illumination in high speed videography. A Vertical Cavity Surface-Emitting Laser (VCSEL) array was designed and implemented with spectral filtering to effectively remove self-luminosity and the fireball from the image, providing excellent background discrimination in a variety of range test scenarios. Further improvements to the system are proposed for applications such as imaging through murky water or dust clouds with optimal penetration of obscurants.