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Touch is our primary non-verbal communication channel for conveying intimate emotions and as such essential for our physical and emotional wellbeing. In our digital age, human social interaction is often mediated. However, even though there is increasing evidence that mediated touch affords affective communication, current communication systems (such as videoconferencing) still do not support communication through the sense of touch. As a result, mediated communication does not provide the intense affective experience of co-located communication. The need for ICT mediated or generated touch as an intuitive way of social communication is even further emphasized by the growing interest in the use of touch-enabled agents and robots for healthcare, teaching, and telepresence applications. Here, we review the important role of social touch in our daily life and the available evidence that affective touch can be mediated reliably between humans and between humans and digital agents. We base our observations on evidence from psychology, computer science, sociology, and neuroscience with focus on the first two. Our review shows that mediated affective touch can modulate physiological responses, increase trust and affection, help to establish bonds between humans and avatars or robots, and initiate pro-social behavior. We argue that ICT mediated or generated social touch can (a) intensify the perceived social presence of remote communication partners and (b) enable computer systems to more effectively convey affective information. However, this research field on the crossroads of ICT and psychology is still embryonic and we identify several topics that can help to mature the field in the following areas: establishing an overarching theoretical framework, employing better research methodologies, developing basic social touch building blocks, and solving specific ICT challenges.

High extraversion and conscientiousness and low neuroticism predict successful performance during and after stressful conditions. We investigated whether these personality factors are linked to stress sensitivity and to baseline physiology. Stress was induced through negative feedback on gaming performance. Stress sensitivity was determined as the difference in baseline physiological variables (skin conductance, heart rate and heart rate variability) before and after performing the game, as well as the difference in subjectively reported stress. While physiological results suggest that the game indeed induced stress, subjective reports do not. Maybe due to a low level of experienced stress, stress sensitivity (as indicated by the difference in heart rate) only correlates with conscientiousness and not with extraversion or neuroticism. The baseline measurements show the expected correlations between extraversion and both heart rate and heart rate variability-negative and positive respectively. The negative correlation between neuroticism and skin conductance is opposite to what we expected. While the exact mechanisms are not clear yet, the present results indicate that for healthy individuals, there are indeed measurable and consistent relations between physiology and personality. Hence, physiological indicators of personality may ultimately be of value as predictors of stress resiliency.

A study is presented in which several representations of polarimetric SAR data were evaluated for the purpose of obtaining land use classification. Two methods comprising visual interpretation and an automatic procedure were used. For the study, fully polarimetric SAR data with a resolution of 3m were obtained with the Dutch PHARUS sensor from a test area in the Netherlands showing various classes of land use. The land use classes consisted of bare soil, water, grass, urban areas, and forest. The visual inspection was performed by different groups of non-expert interpreters for each representation. It was found that people are quite successful by visual interpretation in performing land use classification using SAR data. Multi-polarized data are required for this purpose, although these data need not be fully polarimetric, since the best results were obtained with the hh- and hv-polarization combinations displayed in the red and green colour channels. The results show that land use classification by visual inspection is more effective than the automatic classification procedure.

Imperfections in binocular image pairs can cause serious viewing discomfort. For example, in stereo vision systems eye strain is caused by unintentional mismatches between the left and right eye images (stereo imperfections). Head-mounted displays can induce eye strain due to optical misalignments. We have experimentally determined the level of (dis)comfort experienced by human observers viewing brief presentations of imperfect binocular image pairs. We used a wide range of binocular image imperfections that are representative for commonly encountered optical errors (spatial distortions: shifts, magnification, rotation, keystone), imperfect filters (photometric asymmetries: luminance, color, contrast, crosstalk), and stereoscopic disparities. The results show that nearly all binocular image asymmetries seriously reduce visual comfort if present in a large enough amount. From our data we estimate threshold values for the onset of discomfort. The database collected in this study allows a more accurate prediction of visual comfort from the specification of a given binocular viewing system. Being able to predict the level of visual discomfort from the specification of binocular viewing systems greatly helps the design and selection process. This paper provides the basis.

We extend a recently introduced universal grayscale image quality index to a newly developed perceptually decorrelated colour space. The resulting colour image fidelity metric quantifies the distortion of a processed colour image relative to its original version. We evaluated the new colour image fidelity metric through observer experiments in which subjects ranked images according to perceived distortion. The metric correlates strongly with human perception and can therefore be used to assess the performance of colour image coding and compression schemes, colour image enhancement algorithms, synthetic colour image generators, and colour image fusion schemes.

Human scene recognition performance was tested with images of night-time outdoor scenes. The scenes were registered both with a dual band (visual and near infrared) image intensified low-light CCD camera (DII) and with a thermal middle wavelength band (3–5 mm) infrared (IR) camera. Fused imagery was produced through a grayscale pyramid image merging scheme, in combination with two different colour mappings. Observer performance was tested for each of the (individual and fused) image modalities. The results show that DII imagery contributes most to global scene recognition (situational awareness), whereas IR imagery serves best for the detection and recognition of targets like humans and vehicles. Grayscale fused imagery yields appreciable performance levels in most conditions. With an appropriate colour mapping, colour fused imagery yields the best overall scene recognition performance. However, an inappropriate colour mapping significantly decreases observer performance compared to grayscale image fusion. The deployment of a DII system in addition to a 3-5 mu IR system through image fusion can increase the performance of human observers when the colour mapping relates to the nature of the visual task and the conditions (scene content) at hand.

Previous research has shown that odorants consistently evoke associations with textures and their tactile properties like smoothness and roughness. Also, it has been observed that olfaction can modulate tactile perception. We therefore hypothesized that tactile roughness perception may be biased towards the somatosensory connotation of an ambient odorant. We performed two experiments to test this hypothesis. In the first experiment, we investigated the influence of ambient chemosensory stimuli with different roughness connotations on tactile roughness perception. In addition to a pleasant odor with a connotation of softness (PEA), we also included a trigeminal stimulant with a rough, sharp or prickly connotation (Ethanol). We expected that - compared to a No - odorant control condition—tactile texture perception would be biased towards smoothness in the presence of PEA and towards roughness in the presence of Ethanol. However, our results show no significant interaction between chemosensory stimulation and perceived tactile surface roughness. It could be argued that ambient odors may be less effective in stimulating crossmodal associations, since they are by definition extraneous to the tactile stimuli. In an attempt to optimize the conditions for sensory integration, we therefore performed a second experiment in which the olfactory and tactile stimuli were presented in synchrony and in close spatial proximity. In addition, we included pleasant (Lemon) and unpleasant (Indole) odorants that are known to have the ability to affect tactile perception. We expected that tactile stimuli would be perceived as less rough when simultaneously presented with Lemon or PEA (both associated with softness) than when presented with Ethanol or Indole (odors that can be associated with roughness). Again, we found no significant main effect of chemosensory condition on perceived tactile roughness. We discuss the limitations of this study and we present suggestions for future research.Previous research has shown that odorants consistently evoke associations with textures and their tactile properties like smoothness and roughness. Also, it has been observed that olfaction can modulate tactile perception. We therefore hypothesized that tactile roughness perception may be biased towards the somatosensory connotation of an ambient odorant. We performed two experiments to test this hypothesis. In the first experiment, we investigated the influence of ambient chemosensory stimuli with different roughness connotations on tactile roughness perception. In addition to a pleasant odor with a connotation of softness (PEA), we also included a trigeminal stimulant with a rough, sharp or prickly connotation (Ethanol). We expected that—compared to a No-odorant control condition—tactile texture perception would be biased towards smoothness in the presence of PEA and towards roughness in the presence of Ethanol. However, our results show no significant interaction between chemosensory stimulation and perceived tactile surface roughness. It could be argued that ambient odors may be less effective in stimulating crossmodal associations, since they are by definition extraneous to the tactile stimuli. In an attempt to optimize the conditions for sensory integration, we therefore performed a second experiment in which the olfactory and tactile stimuli were presented in synchrony and in close spatial proximity. In addition, we included pleasant (Lemon) and unpleasant (Indole) odorants that are known to have the ability to affect tactile perception. We expected that tactile stimuli would be perceived as less rough when simultaneously presented with Lemon or PEA (both associated with softness) than when presented with Ethanol or Indole (odors that can be associated with roughness). Again, we found no significant main effect of chemosensory condition on perceived tactile roughness. We discuss the limitations of this study and we present suggestions for future research.

In this project we adapted the newly developed Phase-Based Video Processing (PBVP) algorithm to enhance the visibility of subtle temporal changes (movement or temperature fluctuations) in multiband (visual, near-, shortwave- and longwave-infrared) imagery while simultaneously reducing dynamic noise. We successfully applied the adapted algorithm to enhance the visibility of small movements in the Visual, Near-Infrared and Thermal (LWIR) bands of multiband video sequences registered by the TNO TRI-band Color Low-light OBServation System (TRICLOBS), and in dynamic short-wave infrared (SWIR) sequences provided by AFRL/711HPW/RHCV. In addition, we applied the method for the early detection of change processes, for the estimation of a person s heart rate from facial videos, and to enhance the visibility of landmines in polarized SWIR sequences. In the course of the project we also developed a simple Power-Logarithm (Pow-Log) histogram modification operator to enhance image contrast, and a new color-to-gray conversion algorithm that retains both the overall appearance and the discriminability of a three channel color image when represented as a single band (grayscale) image.

We tested the hypothesis that, either through training or selection, military personnel is more resilient to stress than civilians, as indicated by several subjective and physiological measures. In addition, we examined the effect of stress on the perceived trustworthiness of faces in these two groups. Stress was induced in 45 civilian participants and 45 army participants through the Sing-a-Song Stress Test (SSST). In this paradigm seven neutral sentences are presented, each followed by a 60-s interval. An eighth sentence asks participants to sing a song aloud after the next (eighth or stress) interval. Participants rated the trustworthiness of five neutral faces, both before and after the SSST. Pupil size, heart rate, and skin conductance were adopted as physiological stress correlates. Stress response was calculated as the difference between the mean values over the last neutral interval and the stress interval. Subjective stress ratings were obtained before and after the SSST. The baseline levels of all physiological and subjective measures were the same in the army and civilian groups, while all measures showed a significant increase following the stressor. However, compared with the civilian group, army participants reported significantly less stress and showed significantly attenuated heart rate and skin conductance responses to the SSST. These results indicate higher stress resilience in the army compared with the civilian group. In addition, we found that perceived facial trustworthiness decreased after presentation of the stressor, suggesting that the effect of a stressor can influence in principle unrelated social judgments based on facial information. © The Author(s) 2017.

Simulated test protocols are used to investigate the effectiveness of a novel and non-lethal approach for the degradation of human performance.

We recently presented a color transform that produces fused nighttime imagery with a realistic color appearance (Hogervorst & Toet, 2010, Information Fusion, 11-2, 69-77). To assess the practical value of this transform we performed two experiments in which we compared human scene recognition for monochrome intensified (II) and longwave infrared (IR) imagery, and color daylight (REF) and fused multispectral (CF) imagery. First we investigated the amount of detail observers can perceive in a short time span (the gist of the scene). Participants watched brief image presentations and provided a full report of what they had seen. Our results show that REF and CF imagery yielded the highest precision and recall measures, while both II and IR imagery yielded significantly lower values. This suggests that observers have more difficulty extracting information from monochrome than from color imagery. Next, we measured eye fixations of participants who freely explored the images. Although the overall fixation behavior was similar across image modalities, the order in which certain details were fixated varied. Persons and vehicles were typically fixated first in REF, CF and IR imagery, while they were fixated later in II imagery. In some cases, color remapping II imagery and fusion with IR imagery restored the fixation order of these image details. We conclude that color remapping can yield enhanced scene perception compared to conventional monochrome nighttime imagery, and may be deployed to tune multispectral image representation such that the resulting fixation behavior resembles the fixation behavior for daylight color imagery.

Variable scale displays which combine a highly detailed representation of regions of interest with a less detailed representation of their context can be effective visualisation aids. This paper presents a concise review of the principles of conformal digital image warpings that can be used to construct variable scale displays like global fisheye views or multifocal image representations (a `looking glass' effect). It is argued that a backward warping transform is most suitable for this purpose. Pilot studies indicate that these variable scale displays may serve to optimize observer performance in surveillance and navigation tasks.

A simple power-logarithm histogram modification operator is proposed to enhance digital image contrast. First a logarithm operator reduces the effect of spikes and transforms the image histogram into a smoothed one that approximates a uniform histogram while retaining the relative size ordering of the original bins. Then a power operator transforms this smoothed histogram into one that approximates the original input histogram. Contrast enhancement is then achieved by using the cumulative distribution function of the resulting histogram in a standard lookup table based histogram equalization procedure. The method is computationally efficient, independent of image content, and (unlike most existing contrast enhancement algorithms) does not suffer from the occurrence of artifacts, over-enhancement and unnatural effects in the processed images. Experimental results on a wide range of different images show that the proposed method effectively enhances image contrast while preserving overall image brightness, and yields results that are comparable or even of higher quality than those provided by previous state-of-the-art methods.

We present a color-to-gray conversion algorithm that retains both the overall appearance and the discriminability of details of the input color image. The algorithm employs a weighted pyramid image fusion scheme to blend the R, G, and B color channels of the input image into a single grayscale image. The use of simple visual quality metrics as weights in the fusion scheme serves to retain visual contrast from each of the input color channels. We demonstrate the effectiveness of the method by qualitative and quantitative comparison with several state-of-the-art methods. © 2014 SPIE and IS&T.

Despite the advent of remotely operated and autonomous targeting systems, human (direct) vision is still critical for the successful performance of many tasks on the battlefield. Since high intensity light sources have the potential to generate a variety of disturbing visual effects, ranging from short-term disruption to lasting eye damage, they may offer a simple and cost-effective method to deny operators the possibility to successfully fulfill their tasks. Here we describe the full range of different effects that result from stimulation of the human visual system with high intensity (visible) light, and their associated potential operational impact. To systematically investigate the capability of high intensity light sources to disturb human vision and degrade human task performance we designed test protocols involving a range of military relevant tasks. The effectiveness of optical countermeasures is quantified both through their impact on task performance and through subjective reports on the experienced level of discomfort. We also derived a model that predicts normal driving behavior during exposure to a high intensity light source. These predictions can be directly related to operational requirements and can thus be used to assess the operational effectiveness of optical countermeasures. Unexpectedly, the results from our tests indicate that severe light insults have only very limited effect on human performance, even when the associated levels of visual discomfort are extremely high. Together with the limited window of operation (only during darkness) and other operational limitations (e.g., the difficulty of pointing a beam straight at the adversary) these findings question the effectivity of high intensity light sources as robust countermeasures against human operators. Further research should focus on the stimulus characteristics and methods of delivery to optimize the effectiveness of these countermeasures. © 2014 SPIE.

Systematic biases have been found when matching haptic and visual locations. In this demo we can show two things; first we can show that these biases are similar when pointing at a visual target with the index finger or with a handle in a power grip. Second, we show that intermodal biases are not simply the result of a mismatch between the senses and that the transformations of the position information between modalities (and hands) are not simply reversible.

This report results from a contract tasking TNO Defence, Security and Safety as follows: The grantee will acquire and register a multimodal dynamic target image test set that can be used to assess the operational effectiveness of static and dynamic image fusion techniques for a range of relevant military tasks. TNO originally developed the TOD (Triangle Orientation Detection) method to predict human target detection and identification performance from static imagery. The TOD method produces a TOD-curve that resembles an MTF or MRTD (commonly used to evaluate thermal sensors). However, the TOD-method is more directly related to the target recognition task, and is better suited at capturing nonlinear effects of the kind that typically occur in image fusion methods, such as sampling and (local) contrast enhancement. In the proposed project grantee collected dynamic nighttime and daytime imagery using sensors with various spectral sensitivities. The sensors were thermal, SWIR, NIR, and visible wavelength cameras that will be mounted on a common base plate. The sensor suite as a whole will be placed in a vehicle, allowing one to register approach sequences to the targets. The targets were military relevant targets such as personnel or, if possible, military vehicles. Included with each target sequence will also be triangles with a range of different sizes, thermal and visual contrasts. This will allow TOD-measurements (characterizing object recognition performance) on the resulting set of multimodal images that can be compared with human task performance using the same imagery. At total of 16 runs were successfully registered, partly in dry and partly in rainy conditions. The imagery collected during this study, together with the GPS data and all other documentary material, was made available to the Air Force Research Laboratory organization at the end of the field trials. Researchers from both the Air Force Research Laboratory and TNO Human Factors will write a joint pa

Touch is an essential channel in interpersonal and affective communication, yet most social agents currently lack the capability to touch the user. In this paper we show the credibility of three premises that make the case that providing touch capability to social robots will increase their effectiveness in communicating emotions, building trust and achieving behavioral changes. The first premise is that humans can communicate distinct emotions through touch only, the second is that this is also possible through mediated (virtual) touch, and the third is that social agents can use the same mediated touch technology as effectively as humans. Based on a literature review, we also formulate ten design rules as guidance for the development of social agents that can touch. These rules concern parameters that regulate the meaning of touch cues like context and familiarity, the implicit and explicit meanings of touch, user characteristics, and parameters that can be communicated through affective touch.

Most studies on physiological effects of emotion inducing images and sounds examine stimulus locked variables reflecting a state of at most a few seconds. We here aimed to induce longer lasting emotional states using blocks of repetitive visual, auditory and bimodal stimuli corresponding to specific valence and arousal levels. The duration of these blocks enabled us to reliably measure heart rate variability as a possible indicator of arousal. In addition, heart rate and skin conductance were determined without taking stimulus timing into account. Heart rate was higher for pleasant and low arousal stimuli compared to unpleasant and high arousal stimuli. Heart rate variability and skin conductance increased with arousal. Effects of valence and arousal on cardiovascular measures habituated or remained the same over 2-minute intervals whereas the arousal effect on skin conductance increased. We did not find any effect of stimulus modality. Our results indicate that blocks of images and sounds of specific valence and arousal levels consistently influence different physiological parameters. These parameters need not be stimulus locked. We found no evidence for differences in emotion induction between visual and auditory stimuli, nor did we find bimodal stimuli to be more potent than unimodal stimuli. The latter could be (partly) due to the fact that our bimodal stimuli were not optimally congruent.

There are many weapon systems in which a human operator acquires a target, tracks it and designates it. Optical countermeasures against this type of systems deny the operator the possibility to fulfill this visual task. We describe the different effects that result from stimulation of the human visual system with high intensity (visible) light, and the associated potential operational impact. Of practical use are flash blindness, where an intense flash of light produces a temporary “blind-spot” in (part of) the visual field, flicker distraction, where strong intensity and/or color changes at a discomfortable frequency are produced, and disability glare where a source of light leads to contrast reduction. Hence there are three possibilities to disrupt the visual task of an operator with optical countermeasures such as flares or lasers or a combination of these; namely, by an intense flash of light, by an annoying light flicker or by a glare source. A variety of flares for this purpose is now available or under development: high intensity flash flares, continuous burning flares or strobe flares which have an oscillating intensity. The use of flare arrays seems particularly promising as an optical countermeasure. Lasers are particularly suited to interfere with human vision, because they can easily be varied in intensity, color and size, but they have to be directed at the (human) target, and issues like pointing and eye-safety have to be taken into account. Here we discuss the design issues and the operational impact of optical countermeasures against human operators.

In this study we investigated the effectiveness of high power illuminators that are intended to be used as warning devices or non-lethal weapons to deny car drivers their view on the outside world through windscreens. The test is based on a measurement of the amount of veiling glare resulting when a high intensity light source hits a windscreen. We measured the veiling glare for new, used and colored windscreens that were either clean or dirty. We found no significant difference between the scatter function for new, used and colored windows. The scatter function for dirty windscreens is a factor 14 larger than for clean windscreens. We also derived a method to assess the impact of the illumination of a windscreen by a high intensity light source on driving behavior. The method is based on the assumption that drivers reduce their speed when veiling glare reduces the detection distance of objects on the road. Estimates of respectively the detection distance for objects on the road and the maximum safe driving speed are directly related to operational requirements, and can therefore be used to assess the operational effectiveness of high intensity light sources as powerful warning devices or non-lethal weapons.

In the current study participants explored a desktop virtual environment (VE) representing a suburban neighborhood with signs of public disorder (neglect, vandalism, and crime), while being exposed to either room air (control group), or subliminal levels of tar (unpleasant; typically associated with burned or waste material) or freshly cut grass (pleasant; typically associated with natural or fresh material) ambient odor. They reported all signs of disorder they noticed during their walk together with their associated emotional response. Based on recent evidence that odors reflexively direct visual attention to (either semantically or affectively) congruent visual objects, we hypothesized that participants would notice more signs of disorder in the presence of ambient tar odor (since this odor may bias attention to unpleasant and negative features), and less signs of disorder in the presence of ambient grass odor (since this odor may bias visual attention toward the vegetation in the environment and away from the signs of disorder). Contrary to our expectations the results provide no indication that the presence of an ambient odor affected the participants' visual attention for signs of disorder or their emotional response. However, the paradigm used in present study does not allow us to draw any conclusions in this respect. We conclude that a closer affective, semantic, or spatiotemporal link between the contents of a desktop VE and ambient scents may be required to effectively establish diagnostic associations that guide a user's attention. In the absence of these direct links, ambient scent may be more diagnostic for the physical environment of the observer as a whole than for the particular items in that environment (or, in this case, items represented in the VE).

The fusion and enhancement of multiband nighttime imagery for surveillance and navigation has been the subject of extensive research for over two decades. Despite the ongoing efforts in this area there is still only a small number of static multiband test images available for the development and evaluation of new image fusion and enhancement methods. Moreover, dynamic multiband imagery is also currently lacking. To fill this gap we present the TRICLOBS dynamic multi-band image data set containing sixteen registered visual (0.4–0.7μm), near-infrared (NIR, 0.7–1.0μm) and long-wave infrared (LWIR, 8–14μm) motion sequences. They represent different military and civilian surveillance scenarios registered in three different scenes. Scenes include (military and civilian) people that are stationary, walking or running, or carrying various objects. Vehicles, foliage, and buildings or other man-made structures are also included in the scenes. This data set is primarily intended for the development and evaluation of image fusion, enhancement and color mapping algorithms for short-range surveillance applications. The imagery was collected during several field trials with our newly developed TRICLOBS (TRI-band Color Low-light OBServation) all-day all-weather surveillance system. This system registers a scene in the Visual, NIR and LWIR part of the electromagnetic spectrum using three optically aligned sensors (two digital image intensifiers and an uncooled long-wave infrared microbolometer). The three sensor signals are mapped to three individual RGB color channels, digitized, and stored as uncompressed RGB (false) color frames. The TRICLOBS data set enables the development and evaluation of (both static and dynamic) image fusion, enhancement and color mapping algorithms. To allow the development of realistic color remapping procedures, the data set also contains color photographs of each of the three scenes. The color statistics derived from these photographs can be used to define color mappings that give the multi-band imagery a realistic color appearance.

Object recognition can be formulated as an optimization problem. The objective function measures for instance the evidential support for any particular projection of the parameterized object contour model onto the input image. A genetic algorithm can be used to find a set of parameters which provide an optimal interpretation of the image in terms of the model. Preliminary test results demonstrate the feasibility of the proposed approach.

The objective of image fusion is to represent relevant information from multiple individual images in a single image. Some fusion methods may represent important visual information more distinctively than others, thereby conveying it more efficiently to the human observer. Here, we propose to rank order images fused by different methods according to the computational attention value of their regions of interest (ROI). To achieve this aim, we compute a multi-bitrate attention map for each of the fused images, following a rational model of computational attention. From this attention map, we then calculate the average attention score within areas of interest for each bitrate while using a prioritisation scheme. Here, the prioritisation protocol is used to simulate the basic cognitive process of visual information acquisition by human users. A huge computed mean attention value within the areas of interest at any reconstruction fidelity corresponds to a high-computational saliency of the areas of interest. The novelty of our approach to image fusion evaluation is the use of rate-attention curves, which are given by the normalised mean attention score within the areas of interest across bitrates while using a prioritisation protocol, and where the detection of ROI is achieved either interactively through human user intervention or by the use of automated detection. © 2012 Copyright Taylor and Francis Group, LLC.

We present the design and evaluation of a new demonstrator rifle sight viewing system containing direct view, red aim point and fusion of an (uncooled, LWIR) thermal sensor with a digital image intensifier. Our goal is to create a system that performs well under a wide variety of (weather) conditions during daytime and nighttime and combines the advantages of the various sensor systems. A real-time colour image with salient hot targets is obtained from the night vision sensors by implementing the Colour-the-Night fusion method (Hogervorst & Toet, 2010) on the on-board processor. The prototype system was evaluated in a series of field trials with military observers performing detection and identification tasks. The tests showed that during daytime the addition of a thermal image to direct vision is advantageous, e.g. for the detection of hot targets. At nighttime, the fusion of thermal and image intensified imagery results in increased situational awareness and improved detection of (hot) targets. For identification of small (handheld) objects, the technology needs to be further refined.

A real-time mapping technique enables full-color rendering of multi-spectral nighttime images, making them as clear and colorful as daylight ones

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. © 2011 SPIE.

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. © 2011 SPIE.

The increasing availability and deployment of imaging sensors operating in multiple spectral bands has led to a requirement for methods that combine the signals from these sensors in an effective and ergonomic way for presentation to the human operator. Effective combinations of complementary and partially redundant multispectral imagery can provide information that is not directly evident from the individual input images. Image fusion for human inspection should combine information from two or more images of a scene into a single composite image that is more informative than each of the input images alone, and that requires minimal cognitive effort to understand. The fusion process should therefore maximize the amount of relevant information in the fused image, while minimizing the amount of irrelevant details, uncertainty and redundancy in the output. Thus, image fusion should preserve task relevant information from the source images, prevent the occurrence of artifacts or inconsistencies in the fused image, and suppress irrelevant features (e.g. noise) from the source images (Smith & Heather, 2005). The representation of fused imagery should optimally agree with human cognition, so that humans can quickly grasp the gist and meaning of the displayed scenes. For instance, the representation of spatial details should effortlessly elicit the recognition of known Gestalts, and the color schemes used should be natural (ecologically correct) and thus agree with human intuition. Irrelevant details (clutter) should be suppressed to minimize cognitive workload and to maximize recognition speed. Some potential benefits of image fusion are: wider spatial and temporal coverage, decreased uncertainty, improved reliability, and increased robustness of the system. Image fusion has applications in defense for situation awareness (Toet et al., 1997b), surveillance (Riley & Smith, 2006), target tracking (Zou & Bhanu, 2005), intelligence gathering (O'Brien & Irvine, 2004), and person authentication (Kong et al., 2007). Other important applications are found in industry and medicine (for a recent survey of different applications of image fusion techniques see Blum & Liu, 2006). The way images are combined depends on the specific application and on the type of information that is relevant in the given context (Smith & Heather, 2005). By examining the effects of several image fusion methods on different cognitive tasks, Krebs et al. (Krebs & Ahumada, 2002) showed that the benefits of sensor fusion are task dependent. However, until now the human end user has not been involved in the design process and the development of image fusion algorithms to any great extent. Mostly, image fusion algorithms are developed in isolation, and the human end-user is little more than an

In this study, the authors investigated how restriction of the vertical viewing angle influences obstacle-crossing behavior. Twelve participants stepped over obstacles of different dimensions while wearing visual-field-restricting goggles. Using full-body motion capture, several kinematic measures were extracted and analyzed. Results indicate that both a 40° and 90° vertical viewing angle yielded increased step length and toe clearance as compared to an unrestricted view (i.e., 135°), whereas speed remained unaltered. A further decrease (to 25°) caused participants to slow down in addition to a further increase of step length and toe clearance. These results are discussed in terms of a change in priorities, from conservation of energy and time to safety.

An international group consisting of several NATO nations participated in a trial in which urban camouflage was developed and compared. First, photographs were taken in and around a small town (arid climate). Next, the different groups derived urban camouflage patterns from these photographs. We applied our method for deriving a camouflage pattern from a set of (characteristic) background images to the imagery. Eleven different patterns were made into prototype camouflage suits. Panoramic images of all prototype suits were taken on 36 locations in the environment in which the background images were taken. We used these images in a search experiment with human observers for evaluating camouflage performance of the various patterns. The pattern we developed featured among the two best performing patterns, with good performance indicated by low chance of detection and long search times. The results show that our method for deriving a camouflage pattern from background imagery works well. © 2010 Copyright SPIE - The International Society for Optical Engineering.

We present the design and first field trial results of the all-day all-weather INVIS Integrated Night Vision surveillance and observation System. The INVIS augments a dynamic three-band false-color nightvision image with synthetic 3D imagery in a real-time display. The night vision sensor suite consists of three cameras, respectively sensitive in the visual (400-700 nm), the near-infrared (700-1000 nm) and the longwave infrared (8-14 μm) bands of the electromagnetic spectrum. The optical axes of the three cameras are aligned. Image quality of the fused sensor signals can be enhanced in real-time through Dynamic Noise Reduction, Superresolution, and Local Adaptive Contrast Enhancement. The quality of the longwave infrared image can be enhanced through Scene-Based Non-Uniformity Correction (SBNUC), intelligent clustering and thresholding. The visual and near-infrared signals are used to represent the resulting multiband nightvision image in realistic daytime colors, using the Color-the-Night color remapping principle. Color remapping can also be deployed to enhance the visibility of thermal targets that are camouflaged in the visual and near-infrared range of the spectrum. The dynamic false-color nighttime images can be augmented with corresponding synthetic 3D scene views, generated in real-time using a geometric 3D scene model in combination with position and orientation information supplied by the GPS and inertial sensors of the INVIS system. © 2010 SPIE.

We present the design and first field trial results of the INVIS integrated night vision surveillance and observation system, in particular for the image enhancement techniques implemented. The INVIS is an all-day-andnight all-weather navigation and surveillance tool, combining three-band cameras. We present a processing pipeline for this system. The image quality of all individual sensor signals is enhanced through Dynamic Noise Reduction and Dynamic Super Resolution. The quality of the thermal image can be enhanced through Scene-Based Non-Uniformity Correction (SBNUC). The images are fused using natural tone mapping techniques. The contrast in the image can be improved using Local Adaptive Contrast Enhancement, applied before or after the tone mapping. These results show that the image enhancement techniques have an added value for image fusion systems. © 2010 SPIE.

Previous studies showed that orange odor reduces the anticipatory anxiety and improves the mood of patients waiting for scheduled appointments in small dental practices. We replicated these previous studies in the setting of three large dental clinics. In addition, we investigated whether another pleasant fruity smell (apple odor) is similarly associated with reduced anxiety. We included 219 patients (117 males, 102 females) between the ages of 18 and 81 in this study. While they were waiting for dental treatment, the participants were either exposed to the ambient odor of orange (N = 81) or apple (N = 69), or they received no stimulation. State anxiety, mood, and perceived level of pain of the participants were assessed using questionnaires. Statistical analysis showed no significant difference between the responses of patients in each of the three experimental groups. We therefore conclude that orange and apple odors have no effect on the anticipatory anxiety or mood of patients waiting for scheduled appointments in large dental clinics.

This paper presents a systematic theory for the construction of morphological operators on graphs. Graph morphology extracts structural information from graphs using predefined test probes called structuring graphs. Structuring graphs have a simple structure and are relatively small compared to the graph that is to be transformed. A neighborhood function on the set of vertices of a graph is constructed by relating individual vertices to each other whenever they belong to a local instantiation of the structuring graph. This function is used to construct dilations and erosions. The concept of the structuring graph is also used to define openings and closings. The resulting morphological operators are invariant under symmetries of the graph. Graph morphology resembles classical morphology (which uses structuring elements to obtain translation-invariant operators) to a large extent. However, not all results from classical morphology have analogues in graph morphology because the local graph structure may be different at different vertices.

This effort we acquired and registered a multi-spectral dynamic image test set with the intent of using the imagery to assess the operational effectiveness of static and dynamic image fusion techniques for a range of relevant military tasks. This paper describes the image acquisition methodology, the planned human visual performance task approach, the lessons learned during image acquisition and the plans for a future, improved image set, resolution assessment methodology and human visual performance task. © 2009 SPIE.

We present the design and first test results of the TRICLOBS (TRI-band Color Low-light OBServation) system The TRICLOBS is an all-day all-weather surveillance and navigation tool. Its sensor suite consists of two digital image intensifiers (Photonis ICU's) and an uncooled longwave infrared microbolometer (XenICS Gobi 384). The night vision sensor suite registers the visual (400-700 nm), the near-infrared (700-1000 nm) and the longwave infrared (8-14 m) bands of the electromagnetic spectrum. The optical axes of the three cameras are aligned, using two dichroic beam splitters: an ITO filter to reflect the LWIR part of the incoming radiation into the thermal camera, and a B43-958 hot mirror to split the transmitted radiation into a visual and NIR part. The individual images can be monitored through two LCD displays. The TRICLOBS provides both digital and analog video output. The digital video signals can be transmitted to an external processing unit through an Ethernet connection. The analog video signals can be digitized and stored on on-board harddisks. An external processor is deployed to apply a fast lookup-table based color transform (the Color-the-Night color mapping principle) to represent the TRICLOBS image in natural daylight colors (using information in the visual and NIR bands) and to maximize the detectability of thermal targets (using the LWIR signal). The external processor can also be used to enhance the quality of all individual sensor signals, e.g. through noise reduction and contrast enhancement. © 2009 SPIE.

We designed and evaluated a dual-band Night Vision Goggles sensor system. The sensor system consists of two optically aligned NVGs fitted with filters splitting the sensitive range into a visual and a near-infrared band. The Color-the-night technique (Hogervorst & Toet, FUSION2008) was used to fuse the images of the two sensors, using a color scheme optimized for the detection of camouflaged targets. The added value of this system was established in an experiment in which observers detected targets (green and blue tubes). Performance was measured for daytime imagery and nighttime imagery: each of the two individual bands, standard NVG, and the color fused sensor system. We found that some of the targets were detected in the individual bands, but most targets were detected in the dual-band system. The fact that performance in the dual-band condition is comparable to the sum of the two individual bands indicates that the fusion method is (close to) optimal. An experiment in which subjective reports were gathered shows that the colored dual-band images are easier to grasp and give a better sense of depth. Our evaluation shows the added value of dual-band over single band NVG for the detection of targets, situational awareness, and perceived depth.

Field-of-view (FOV) restrictions are known to affect human behaviour and to degrade performance for a range of different tasks. A proposed cause for this performance impairment is the predominant activation of the ventral cortical stream as compared to the dorsal stream. This may compromise the ability to control heading as well as degrade the processing of spatial information [Patterson et al. 2006]. Furthermore, the peripheral visual field is important in maintaining postural equilibrium [Turano et al. 1993]. These are all significant factors when manoeuvring through complex structured environments. We discuss here two experiments investigating the influence of horizontal FOV-restriction on manoeuvring performance through real-world structured environments. The results can help determine requirements for the selection and development of FOV limiting devices such as Head-Mounted Displays (HMDs).