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The authors present an empirical investigation and a system dynamics model of human decision priming. Decision priming occurs when initial information creates the expectation that a given decision is appropriate, which speeds up or slows down decision making. A conjunction benefits-and-costs paradigm was used to collect the empirical data, whereas system dynamics techniques were used to create a computational model of decision priming. Decision priming occurred with simulated naturalistic stimuli (i.e., models of military tanks in a desert scene presented in perspective view), the results of which were modeled in a parallel-channels coactive architecture. Simulation revealed that the basic features of decision priming in humans could be simulated with this architecture. Decision priming likely occurs in naturalistic settings. Predictions derived from the model could provide useful information for the design of multimodal or multichannel displays.

Implicit learning involves the largely unconscious learning of dynamic statistical patterns and features, which leads to the development of tacit knowledge. This kind of learning is a ubiquitous, robust phenomenon that likely occurs in most, if not all, tasks in which individuals engage throughout their lives. In this paper, we argue that implicit learning and its end state, tacit knowledge, may assist in the acquisition, retention, and transfer of expertise and thus provide a form of tacit scaffolding for expertise development. The notion of tacit scaffolding represents a novel and interesting area of future research for the field of naturalistic decision making and naturalistic cognition.

We provide a review and analysis of much of the published literature on decision making that is relevant to the design of immersive environments. This review draws from the basic and applied literature in order to provide insight for the design of such synthetic environments. Included in this review are articles and books cited in other works, and articles and books obtained from an Internet search. Issues discussed are (a) an overview of immersive decision environments; (b) dual-process decision making; (c) training robust intuitive decision making; (d) combining analytical and intuitive processing in immersive environments; and (e) concluding remarks. For the development of robust decision making in immersive environments, intuitive reasoning should be emphasized by creating an immersive situation and by providing for the development of automatic processing through implicit learning, with the latter reinforced by explicit thought processes. Considerations of the literature on decision making will provide insight for future design solutions for immersive decision environments.

Two types of decision-making processes have been identified in the literature: an analytical process and an intuitive process. One conceptual model of the latter is the recognition-primed decision (RPD) model (e.g., Klein, 2008). According to this model, decision making in naturalistic contexts entails a situational pattern-recognition process that, if subsequent expectancies are confirmed, leads the decision maker to render a decision to engage in a given course of action. In this paper, we describe a system dynamics model of Klein's RPD framework that focuses upon the dynamics of the decision-making process. The structure of our RPD model is based on a model of a set of laboratory phenomena called conjunction benefits and costs (e.g., L. R. Fournier, Patterson, Dyre, Wiediger, & Winters, 2007), which was extended to encompass the RPD framework. The results of our simulations suggest that decision priming (a bias toward rendering a given decision based on prior information) is a phenomenon that should occur in many naturalistic settings.

Objective: We provide a review and analysis of much of the published literature on binocular rivalry that is relevant to the design and use of head-worn displays (HWDs). Background: This review draws heavily from both the basic vision literature and applied HWD literature in order to help provide insight for minimizing the effects of binocular rivalry when HWDs are worn. Method: Included in this review are articles and books found cited in other works as well as articles and books obtained from an Internet search. Results: Issues discussed and summarized are (a) characteristics of binocular rivalry, (b) stimulus factors affecting rivalry, (c) cognitive variables affecting rivalry, and (d) tasks affected by rivalry. Conclusion: This paper offers a set of recommendations for minimizing the effects of binocular rivalry when HWDs are used as well as recommendations for future research. Application: Considerations of the basic vision literature on binocular rivalry will provide insight for future design solutions for HWDs.

Objective: We sought to determine the optimal focal distance for a semitransparent monocular head-mounted display (HMD) integrated with a flight simulator display and to investigate whether observers experienced visual discomfort or impaired target recognition when using an HMD set at the optimal distance. Background: When an observer wears a monocular HMD and views a simulator display, focal distances of both displays must be within the observers' depth of focus to prevent blurred imagery. Because focal distance can vary by as much as 0.5 m in U.S. Air Force multifaceted simulator displays, we determined whether a monocular HMD could be integrated with a simulator display without blurred imagery or discomfort. Method: Depth of focus and visual recognition were measured with a staircase procedure, and visual discomfort was measured with a questionnaire. Results: Depth of focus was 0.64 diopters in one condition tested, but it was affected by luminance level and display resolution. It was recommended that HMD focal distance equal the optical midpoint of the range of viewing distances encountered in the simulator. Moreover, wearing an HMD produced a decline in recognition performance for targets presented on the simulator display despite both displays being within observers' depth of focus and producing no visual discomfort. Conclusion: Monocular HMDs can be integrated with multifaceted simulator displays without blurred imagery or visual discomfort, provided that the correct focal distance is adopted. Application: For situations involving simultaneously viewed visual displays.

Air-to-ground target identification was used to select simulated target characteristics that resulted in performance similar to that found in real-world tasks. for a wide variety of ground target-vehicles, it was found that simulated-target identification levels could be matched to any desired real-world level by making visually realistic modifications to target contrast.

Perceptual motion blur was studied using imagery presented on an LCoS projector equipped with a mechanical shutter to reduce pixel hold-time. Perceptual measures of image blur were obtained with a simple test stimulus, as well as imagery similar to that used in Air Force flight simulation and training. Measured pixel hold-time was found to accurately predict perceived blur.

With increased reliance on head-mounted displays (HMDs), such as the Joint Helmet Mounted Cueing System and F-35 Helmet Mounted Display System, research concerning visual performance has also increased in importance. Although monocular HMDs have been used successfully for many years, a number of authors have reported significant problems with their use. Certain problems have been attributed to binocular rivalry when differing imagery is presented to the two eyes. With binocular rivalry, the visibility of the images in the two eyes fluctuates, with one eye’s view becoming dominant, and thus visible, while the other eye’s view is suppressed, which alternates over time. Rivalry is almost certainly created when viewing an occluding monocular HMD. For semi-transparent monocular HMDs, however, much of the scene is binocularly fused, with additional imagery superimposed in one eye. Binocular fusion is thought to prevent rivalry. The present study was designed to investigate differences in visibility between monocularly and binocularly presented symbology at varying levels of contrast and while viewing simulated flight over terrain at various speeds. Visibility was estimated by measuring the presentation time required to identify a test probe (tumbling E) embedded within other static symbology. Results indicated that there were large individual differences, but that performance decreased with decreased test probe contrast under monocular viewing relative to binocular viewing conditions. Rivalry suppression may reduce visibility of semi-transparent monocular HMD imagery. However, factors, such as contrast sensitivity, masking, and conditions such as monofixation, will be important to examine in future research concerning visibility of HMD imagery.

As monocular head-mounted displays (HMDs) are introduced into existing flight simulators for training and mission rehearsal it will be important to determine whether binocular rivalry affects the visibility of HMD presented symbology or the out-the-window (OTW) flight simulator display imagery. In the present study, we examined whether rivalry suppression could be objectively measured under conditions that simulated a monocular HMD and OTW display, and whether voluntary attention and moving imagery influenced the strength of rivalry suppression. The results indicated that strength of suppression under these conditions was less than that found under classic dichoptic viewing conditions, and that attention had little influence on performance.

In two experiments, we manipulated the properties of 3-D objects and terrain texture in order to investigate their effects on active heading control during simulated flight. Simulated crosswinds were used to introduce a rotational component into the retinal flow field that presumably provided the visual cues used for heading control. An active control task was used so that the results could be generalized to real-world applications such as flight simulation. In Experiment 1, we examined the effects of three types of terrain, each of which was presented with and without 3-D objects (trees), and found that the presence of 3-D objects was more important than terrain texture for precise heading control. In Experiment 2, we investigated the effects of varying the height and density of 3-D objects and found that increasing 3-D object density improved heading control, but that 3-D object height had only a small effect. On the basis of these results, we conclude that the vertical contours improved active heading control by enhancing the motion parallax information contained in the retinal flow.

Low-altitude flight performance was used to evaluate the effectiveness of the texture density cues used in high fidelity flight simulators. Observers were asked to maintain a constant above ground level (AGL) altitude over textured terrain whose elevation was varied. All combinations of two texture densities (0.13 and 0.43 elements/meter) and three airspeeds (50, 150, and 300 m/sec) were tested. Observers maintained a higher AGL altitude as speed increased, suggesting that higher optical flow rates interfered with the ability to maintain the target AGL altitude. However, when a single airspeed was used in a given block of trials, the effect of airspeed was eliminated, indicating that the original airspeed effect was due to perceptual averaging of the optical flow rate at each airspeed tested. Texture density was a significant factor only in the blocked-airspeed condition, suggesting that the blocking procedure eliminated measurement error that initially obscured the effect of this factor on altitude maintenance.

The ratio (τ) of a moving target's angular size to the rate of change in its angular size can be used by observers to judge the time remaining before they will collide with the target. We consider here whether optical flow information, consistent with simulated observer motion, affects observers' estimates of time-to-contact (TTC). Estimates of TTC were obtained when either the observer approached a stationary target or the target approached a stationary observer. The visual information for τ was the same in both conditions, whereas the visual information for observer self-motion was varied. For the low closing velocities, (3 and 6 eyeheights/sec) there was no significant difference in the estimated TTC for observer motion versus target motion. However, there was a significant difference for the highest closing velocity (12 eyeheights/sec). This result suggests that visual information, specifying self-motion, may be used either in combination with or in place of τ to estimate TTC during simulated locomotion. The present findings have practical implications for both the use of τ in judging TTC and the rendering of terrain texture detail in high-fidelity flight simulators.

The ratio (τ) of a target's angular size to the rate of change in its angular size can be used by observers to judge the time remaining before they will collide with the target. We consider here whether texture flow rates (i.e., optical flow rates), consistent with simulated observer motion, affect judgments of time-to-collision (TTC). TTC was estimated for various relative velocities of the observer and a circular target. Relative velocity was varied such that the proportion of the total closing velocity attributable to the observer was either 0.0, 0.33, 0.67, or 1.0. Since the closing velocity between the observer and target was held constant, visual information for τ was the same under all test conditions. However, visual information (i.e., texture flow rate) for simulated self-motion was varied. The Weber fraction for estimated TTC progressively decreased as the proportion of observer motion increased, indicating that estimated TTC decreased as texture flow rate increased. This result has practical implications for judging TTC in high-fidelity flight simulators, since the rendering of terrain texture detail directly affects both texture flow rates and the perception of self-motion, either of which may effect estimated TTC.

There is some question as to whether non-collimated (i.e., real) imagery viewed at one meter or less provides sufficiently realistic visual cues to support out-the-window flight simulator training. As a first step toward answering this question, we have obtained perceived size and velocity estimates using both simple stimuli in a controlled laboratory setting and full simulator imagery in an apparatus consisting of optically combined collimated and real-image displays. In the size study it was found that real imagery appeared 15-30% smaller than collimated imagery. In the velocity studies, the laboratory data showed that the perceived velocity of real imagery was less than that of collimated imagery. No perceived velocity effects were found with the simulator imagery. Results support the position that for training tasks requiring accurate perception of spatial and temporal aspects of the simulated visual environment, misperceptions of size, but not velocity, need to be considered when real-image displays are used.

A study is reported of (i) the perceived inclination of a textured surface in depth about a horizontal axis as a function of disparity magnitude for horizontal-shear disparity, vertical-shear disparity, and rotation disparity; and (ii) interactions between patterns with shear or rotation disparity and superimposed or adjacent patterns or lines with zero disparity. Horizontal-shear disparity produced strong inclination which was enhanced by superimposed or adjacent zero-disparity stimuli. It produced little or no inclination contrast in superimposed or adjacent zero-disparity stimuli. Vertical-shear disparity produced inclination in the opposite direction (induced effect) which was reduced to near zero by a superimposed zero-disparity pattern. Adjacent vertical-shear and zero-disparity patterns appeared inclined at slightly different angles with a wide curved boundary. This suggests that vertical-shear disparities are averaged over a wide area. Rotation disparity produced minimal inclination. A superimposed or adjacent zero-disparity line appeared strongly inclined. A superimposed or adjacent zero-disparity pattern appeared vertical and caused the pattern with rotation disparity to appear inclined. Four mechanisms are proposed to account for the results: depth contrast, depth enhancement, deformation-disparity processing, and disparity transfer arising from cyclovergence.

Depth interactions between a frontal test surface and an adjacent induction surface were measured as a function of the type of disparity in the induction surface and of the vertical/horizontal orientation of the boundary between the surfaces. The types of disparity were 4 degrees horizontal-shear disparity, 4 degrees vertical-shear disparity, and 4 degrees rotation disparity; 4% horizontal-size disparity, 4% vertical-size disparity, and 4% overall-size disparity. Depth contrast in a frontal surface was produced by surfaces containing horizontal-size disparity but not by those containing horizontal-shear disparity. Vertical-shear and vertical-size disparities produced induced effects in both the induction and the test surface, which is here explained in terms of deformation-disparity processing. Effects of rotation disparity on the test surface can be accounted for in terms of cyclovergence, deformation disparity, and perhaps also depth contrast. The fact that horizontal-size disparity produced more depth contrast than horizontal-shear disparity is due to an anisotropy of disparity processing rather than the relative orientation of the surfaces. Ground surfaces appeared more slanted than ceiling surfaces. Surfaces containing horizontal disparities produced a sharp boundary with the test surface because horizontal disparities are processed locally. Surfaces with vertical disparities produced a gradual boundary with the test surface because vertical disparities are processed over a wider area.

Subjects made trend and difference estimates in an experiment with three display types: two-dimensional (2D), three-dimensional with monocular cues (3D mono), and three-dimensional with monocular cues and stereopsis (3D stereo). The results showed a general accuracy advantage for 2D displays, even for global trend estimates. Binocular stereopsis appeared to provide a slight advantage in accuracy for trend estimation. The data are partially consistent with the predictions of the Proximity Compatibility Principle. Possible mental operations used with the various displays are discussed.

Digital projectors based on liquid crystal or micro-mirror technologies provide higher spatial resolution than the CRTs typically used in flight-simulator applications. However, their temporal response is limited by long hold-times. Hold-time is the interval that pixels are activated during each frame, and it is related to both the design of the driver circuitry and the display itself. Long hold-times result in the blurring of moving imagery, which can affect the detection and identification of simulated targets as well as the perceived realism of simulated scenes. Described here are the results of an evaluation of several digital projectors that implement various techniques for reducing pixel hold-time. The evaluation included estimates of both spatial and temporal resolution, as well as perceptual tests used to assess the validity of those estimates. The techniques described here can be used to assess the potential utility of candidate projectors for a given simulator application. The following projectors were tested: ferro-electric liquid crystal on silicon (FLCoS), liquid crystal on silicon (LCoS), liquid crystal (LCD), digital light projector (DLP, a digital micro-mirror device, or DMD), and cathode ray tube (CRT). The hold-time of the FLCoS and LCD projectors was varied using mechanical shutters, and the hold-time of the DLP projector was varied using an electronic shutter. The CRT and LCD projectors were used mainly for comparison and so their hold-times were not varied.

Networked flight simulators facilitate team training by creating exercise environments and simulations representative of real-world operations. However, networked simulators are often plagued by connectivity issues, such as constant and variable network delay. Network delay can cause positional discrepancies or visual jitter in the flight path of a moving model which could effect pilots overall perception of fidelity of motion. To reduce the visibility effects of network delay, image generator algorithms, such as model position smoothing, can be enabled. The use of smoothing however, can also contribute to error in the motion path of an entity. This research aims to determine the detection threshold of visual displacement for a typical flight task, formation flight, as a function of simulated distance (100, 200, & 400 meters) and smoothing (no smoothing or smoothing across 1 second). The results show a significant increase in detection threshold with increases in distance. The addition of model position smoothing also increased the amount of visual displacement required for detection. The implications of these results, as well as plans for future research on network transport delay will also be discussed in this paper.

Motivation-Two decision-making processes have been identified: an analytical process and an intuitive process. One conceptual model of the latter is the Recognition Primed Decision (RPD) model (Klein, 2008). According to this model, decision making in naturalistic contexts entails a situational pattern-recognition process which, if subsequent expectancies are confirmed, lead the decision maker to render a decision to engage in a given course of action. Research approach-In this paper, we describe a system dynamics model of Klein's RPD framework, focusing upon the dynamics of the decision process. Findings/Design-Our framework is based on a model of a set of laboratory phenomena called conjunction benefits and conjunction costs, which was extended to encompass the RPD framework. Research limitations/Implications-Our simulations suggest that decision priming (bias in decision making) should occur in many naturalistic settings. Originality/Value-Originality comes from system dynamics modeling. Take away message-Robust decision making based on pattern recognition may be susceptible to priming.

Motivation - Validate a System Dynamics model of decision speed for a scenario relevant to an Air Force mission task. Research approach - Extend a decision priming basic research paradigm to a more applied case. Findings/Design - Decision priming was found to occur with more complex stimuli relevant to an air-to-ground target identification scenario. A system dynamics model was developed to predict those results. Research limitations/Implications - While decision delays of approximately 100 milliseconds were found here, it remains to be determined whether decision priming extends to decision processes extending over seconds or minutes. Originality/Value - A temporally-based method of modeling a decision process has been validated for an applied air-to-ground target identification scenario. Many other decision models lack this time component and are therefore of limited use in time-critical situations. Take away message - Tactical situations where information is processed rapidly and sequentially can result in decision priming.

An array of moving circular stimuli was used to determine whether perceived speed is affected by the oculomotor responses associated with changes in viewing distance. The perceived speed of stimuli viewed at either 0.33 or 1.33 m was compared to the perceived speed of a similar stimulus viewed at a distance of 5.5 m. In addition, a control condition was run in which changes in perceived speed were compared for monocular viewing of the 0.33 m and 5.5 m stimuli. In the binocular condition, there were statistically significant decreases in perceived speed of about 11% for the 0.33 m viewing distance, and about 6.5% for the 1.33 m viewing distance. There was no significant decrease in perceived speed in the monocular condition. This latter finding, along with the similar appearance of the near and far stimuli in the monocular condition, suggests that ocular vergence (as opposed to accommodation or vergence-accommodation) was the primary determinant of the change in perceived speed with changes in binocular viewing distance. Although the change in perceived speed with fixation distance was relatively small, the data from all observers were in the direction of speed constancy. Thus, to the extent that vergence is a cue to egocentric distance, the present data suggest that egocentric distance is used to scale the perceived speed of targets moving at different distances from the observer.

The research performed under Task Order 24 of Air Force Contract F41624-97-D-5000 for the period 1 June 2002 through 30 November 2005 is summarized in this technical report. The summaries includes citations and associated abstracts of published research, as well as a more complete description of seven of the major research projects conducted as part of this Task Order.

When wearing a monocular head-mounted display (HMD), one eye views the HMD symbology while both eyes view an out-the-window scene. This may create interocular differences in image characteristics that could disrupt binocular vision by provoking visual suppression, thus reducing visibility of the background scene, monocular symbology, or both. However, binocular fusion of the background scene may mitigate against the occurrence of visual suppression, a hypothesis that was investigated in the present study. Observers simultaneously viewed a static background scene and HMD symbology while performing a target recognition task under several viewing conditions. In a simulated HMD condition observers binocularly viewed a background scene with monocular symbology superimposed. In another condition, viewing was dichoptic (i.e. completely different images were presented to the left and right eyes). Additionally, one control condition was implemented for comparison. The results indicate that for continuously presented targets binocular rivalry did not have significant effects on target visibility. However, for briefly presented targets, binocular rivalry was shown to increase thresholds for target recognition time in HMD and dichoptic viewing conditions relative to the control. Impairment was less in the HMD condition. Thus, binocular fusion of a background scene can partially mitigate against the occurrence of visual suppression. However, some suppression still exists which occurs between monocular pathways. Implications for the integration of monocular HMDs into Air Force training environments will be discussed.

This report provides a review and analysis of the published literature on head-mounted displays (HMDs). In particular, we discuss several key perceptual issues that are relevant to the use of HMDs. The issues discussed are: (1) brightness and contrast; (2) accommodationvergence synergy; (3) field of view; (4) binocular input; and (5) head movements. This review of the literature is intended to anticipate and solve perceptual issues associated with two particular HMD applications: (1) simulation of off-bore sight (OBS) targeting and (2) full fieldof- view out-the-window (OTW) simulation for deployable flight training. Additionally, several technology issues important to the continued development of HMDs are discussed. This report concludes with a set of recommendations for the design and use of HMDs for OBS and OTW flight training applications.

The Joint Helmet Mounted Cueing System (JHMCS),is being considered for integration into the F-15, F-16, and F-18 aircraft. If this integration occurs, similar monocular head-mounted displays (HMDs) will need to be integrated with existing out-the-window simulator systems for training purposes. One such system is the Mobile Modular Display for Advanced Research and Training (M2DART), which is constructed with flat-panel rear-projection screens around a nominal eye-point. Because the panels are flat, the distance from the eye point to the display screen varies depending upon the location on the screen to which the observer is directing fixation. Variation in focal distance may create visibility problems for either the HMD symbology or the out-the-window imagery presented on the simulator rear-projection display screen because observers may not be able to focus both sets of images simultaneously. The extent to which blurring occurs will depend upon the difference between the focal planes of the simulator display and HMD as well as the depth of focus of the observer. In our psychophysical study, we investigated whether significant blurring occurs as a result of such differences in focal distances and established an optimal focal distance for an HMD which would minimize blurring for a range of focal distances representative of the M2DART. Our data suggest that blurring of symbology due to differing focal planes is not a significant issue within the range of distances tested and that the optimal focal distance for an HMD is the optical midpoint between the near and far rear-projection screen distances.

ELECTRONIC FILE CHARACTERISTICS: 5 files; Adobe Acrobat (.PDF), MS Excel (.XLS), Rich Text Format (.RTF), and Color Display Test Excecutable. PHYSICAL DESCRIPTION: 1 CD-ROM; 4 3/4 in.; 1.10 MB. SYSTEMS DETAIL NOTE: ABSTRACT: This paper documents a technique for assessing the spatial resolution of visual display systems like those currently used for flight simulation at the Air Force Research Laboratory (AFRL), Mesa, Arizona. The introduction defines spatial resolution, and how best to apply the concept in the context of visual display evaluation. The measurement technique is described in detail, as are the CCD-based light measurement device and the techniques developed to calibrate it. Typical spatial resolution data are presented for a variety of display systems. The various steps required for data analysis, and suggested methods for implementing these steps using standard application programs are presented. The computer programs used to generate and display the test patterns and to estimate spatial resolution are described and are available from Defense Technical Information Center (DTIC).

The level of detail in flight-simulator images depends upon the resolutions of the database, the image generator (IG), and the display. In response to the need for greater detail, resources are being devoted to increasing the spatial resolution of each of these system components. Next-generation flight-simulator visual systems will thus be capable of representing smaller environmental features and of representing a given feature at a greater distance. However, flight-simulator imagery is more than a sequence of static, spatial images. The visual system of a simulator creates three-dimensional space-time images, and the quality of these images depends on the temporal as well as the spatial characteristics of both the IG and the display. Here we discuss how the spatial resolutions of the database and the IG affect the temporal frequencies in an image and thus the extent of temporal aliasing likely with a standard, 60-Hz image-update rate. We also discuss how the spatial and temporal resolutions of a display system limit the spatiotemporal-frequency spectrum of the display image. We conclude with a brief description of some perceptual effects of temporal aliasing.

Head and helmet mounted displays (HMDs) can benefit greatly from new wide field-of-view, compact visor optics to project very high resolution (e.g., 5k X 4k) imagery. Physical Optics Corporation (POC) is developing novel, compact, lightweight wide field-of-view optics based on three-color multiplexed aberration-compensated holographic optical elements (MAC-HOEs). Taking advantage of the flexibility of holography, the HMD optics can be made compact using waveguide projection through the curved visor substrate, so that the see-through visor can have a wide field-of-view without large, bulky optical components. Using narrowband red-green-blue hologram multiplexing, MAC-HOEs can significantly reduce the chromatic and geometrical aberration introduced by conventional HOEs and refractive optics. In the initial phase of development, POC demonstrated the feasibility of the HMD optics through computer design and analysis, and by fabricating and demonstrating a MAC-HOE component.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This report describes an experiment to compare the perceived size of collimated and uncollimated aircraft targets presented on typical flight simulator background imagery. It has recently been suggested that magnifying the size of imagery might improve the spatial detail of simulated targets. Such a magnification would also render uncollimated targets perceptually more similar in size to collimated targets. It has been questioned, however, whether a magnification using a viewing distance of 44 inches should be applied to a visual display system whose viewing distance is only 28 inches. The present experiment was performed to answer this question.

Observers estimated differences in the apparent size and distance of simulated objects viewed on collimated and real-image displays. High-resolution target aircraft that remained stationary relative to the observer were superimposed on moving simulator background imagery. The aircraft were slide projections of F-15s viewed either from the side as during formation flight, or from behind and above, as during a gun pass. Both pilots and nonpilots were tested during simulated passive flight. For both the size and distance estimates, differences of 15-30% were found for formation flight at distances of 2,500; 6,000; and 9,000 ft; and differences of 10-20% were found for gun passes at distances of 1,000 and 2,000 ft. No significant differences were found in the data obtained from the pilots and nonpilots under any of the conditions tested. The data generally confirm, for simulator imagery, that both perceived size and perceived distance are significantly reduced when imagery is displayed at viewing distances of less than about 1 m as compared to when it is displayed at or near optical infinity. The implications of magnifying real imagery displayed within about 1 m of the observer, in order to correct for the perceptual size and distance effects reported here, are discussed.

We examined (i) perceived slant of a textured surface about a vertical axis as a function of disparity magnitude for horizontal-size disparity, vertical-size disparity, and overall-size disparity; and (ii) interactions between patterns with various types and magnitudes of size disparity and superimposed or adjacent zero-disparity stimuli. Horizontal-size disparity produced slant which increased with increasing disparity, was enhanced by superimposed zero-disparity stimuli, and induced contrasting slant in superimposed or adjacent zero-disparity stimuli. Vertical-size disparity produced opposite slant (induced effect) which was reduced to near zero by a superimposed zero-disparity pattern and both patterns appeared as one surface. Adjacent vertical-size-disparity and zero-disparity patterns appeared as separate surfaces with a wide curved boundary. Overall-size disparity produced slant which was enhanced by a superimposed zero-disparity pattern and less so by a zero-disparity line, and induced more slant in a zero-disparity line than in a zero-disparity pattern. The results are discussed in terms of depth underestimation of isolated surfaces, depth enhancement, depth contrast, and the processing of deformation disparity.

Recently the use of Hermite functions in vision and image analysis has gained interest in the image processing community. Hermite functions are related to Gaussian functions through a differential operator. In the search for a suitable spatially localized, but not-redundant, alternative to the Gabor approach, Gaussian derivatives as basis functions were introduced. The literature reports that Hermite functions fit the profiles of many cells in the striate cortex very well. We will present some results on texture analysis using Hermite functions.

Perceptual motion blur was studied in imagery presented on an LCD projector equipped with a mechanical shutter to reduce pixel hold-time. Perceptual measures of image blur were obtained with both a simple test stimulus, as well as real-world imagery. Both were found to correlate well with the measured pixel hold-time.

Air-to-ground target identification was found to improve with decreases in background resolution as defined by a satellite-imaging metric. This metric was then compared to a more conventional measure of target and image spatial resolution based on gaussian blur. 1. Introduction Photorealistic flight-simulator databases are produced by mapping satellite imagery onto a terrain height-map. The resolution of these databases is typically defined by the inverse of the spacing of the pixels representing the satellite imagery. This definition assumes that the imaging optics are sufficient to resolve the individual image pixels. Based as it is on an optical criterion, database resolution, as defined above, is not directly comparable to resolution measures typically used to evaluate imagery used in, for instance, flight-simulation (Geri, et al. , 2004) and night-vision (Driggers, et al. , 1999) applications. One way to relate the two measures is to compare performance using flight-simulator imagery derived from each of them. It has previously been shown (Geri

Simulated imagery was used to determine the effect of target and background blur on target identification performance. An interaction between these two variables was found, indicating that greater image detail may not improve performance, and hence may not be required in applications for which high-resolution databases are not readily available.

— In this study, the effects of manipulating the properties of 3-D objects and terrain texture on the control of altitude in simulated flight has been investigated. 3-D objects were found to be as effective as terrain texture for controlling altitude, and this result was interpreted as suggesting that both terrain texture and 3-D objects can serve as effective carriers of information about motion parallax and optical expansion and contraction. The present results, which were obtained using a vertically defined flight task, are inconsistent with the findings of Patterson et al., who reported that 3-D objects were more effective than terrain texture for controlling a horizontally defined heading task. The present results indicate that, when terrain texture is present, the motion parallax or optical expansion associated with the presence of 3-D objects does not improve altitude control.

The effects of terrain texture type and the height and density of 3D objects on heading control were studied in two experiments conducted in a high-performance flight simulator. The results suggest an orthogonal-extension principle which relates performance to the number and length of contours that are perpendicular to the ground plane, and also begin to define the stimulus conditions for which the principle is valid.

Increasing Display line rate did not improve aspect angle recognition performance beyond a level predicted by measured display resolution. Image antialiasing improved performance even though it did not increase the measured spatial resolution. Finally, the threshold for aspect angle recognition was found to be consistent with that obtained for other visual tasks dependent on target spatial detail.

— Stereoscopic perception of tilt about a vertical or horizontal axis is influenced by size and shear disparities, respectively. Other researchers have reported that, under certain conditions, stereoscopic perception deficits occur when the dots in a random-dot stereogram move at a velocity that produces optokinetic nystagmus. Here we examine how size disparity and shear disparity affect stereoscopic tilt perception under various motion conditions. We hypothesized that visual stimulus motion may interact with these disparities to affect tilt perception. Our results indicate that shear disparity and size disparity effects under static conditions are maintained under motion conditions. A possible explanation for the conflict between the current and previous results is discussed, as are implications for binocular head-mounted display applications.