James Gaska

Laser‐speckle properties and their effect on target detection

Laser projectors are currently being developed for use in high-fidelity wide-field-of-view displays. In order to assess the effects of laser speckle on target detection, contrast thresholds as a function of target spatial frequency on both a laser-speckle background and a uniform-luminance field have been measured. For all spatial-frequency targets tested, speckle increased contrast thresholds relative to those obtained on the uniform field. In addition, a power-spectral-density metric for char- acterizing laser speckle and predicting its effect on target detection has been developed. To evaluate the metric, contrast-energy thresholds on both a laser-speckle background and backgrounds consisting of randomly modulated pixel luminance (i.e., pixel noise) have been measured. The results of previous studies, concerned with the detection of targets in wideband noise, suggest that these thresholds should be the same when the power spectral densities of the backgrounds are equated. It was found, however, that, for the same background power spectral density, energy thresholds on pixel noise were slightly higher than those obtained with laser-speckle noise. This small difference could be accounted for, however, by the well-documented individual differences in the optical parameters of the eye, particularly pupil size.

P‐76: Perceptual Tests of the Temporal Properties of a Shuttered LCD Projector

Abstract : 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.

59.5L: Late‐News Paper: Evaluation of a Prototype Grating‐Light‐Valve Laser Projector for Flight Simulation Applications

An evaluation of a prototype grating light valve laser projector indicates it has properties well-suited to flight-simulation applications. Full-field luminance and contrast, spatial resolution, temporal resolution, and color stability were equal to or better than those of CRT projectors typically used in flight-simulator applications. In addition, this projector is capable of providing refresh rates greater than 60 Hz. The higher refresh rates eliminate perceived flicker, and greatly reduce (120 Hz) or eliminate (240 Hz) motion artifacts over the range of target speeds tested.

HMD distortion characterization and alignment toolset for precision-critical applications

Head-mounted displays (HMDs) generally exhibit significant image distortion, which must be reduced/eliminated prior to effective use. Additionally, biocular or binocular near-eye displays must be carefully aligned to enable overlapping two- or three-dimensional image synthesis without causing eye strain, fatigue, or performance loss. Typically, HMDs include distortion correction maps supplied by the manufacturer that are often generated by theoretical calculations that do not precisely match the as-built optical system or account for manufacturing variance. However, HMD users often assert that manufacturer-supplied distortion maps are not accurate enough for some alignment-critical applications. In this work we present the design and validation of a relatively low cost alignment and distortion characterization toolset (hardware and software) for characterization of biocular HMDs. This toolset is able to replicate the ocular alignment of most human observers by emulating a user’s ocular position to examine both on- and off-axis distortion and alignment over a wide range of viewing angles and eye positions. This enables accurate characterization of distortion changes experienced as a user’s eyes move to view different regions of the display (e.g., viewing off-boresight symbols in a well-aligned HMD or viewing a new alignment after an HMD has “slipped” to a slightly different position). The toolset characterizes distortion through image registration of distorted patterns displayed in the HMD to undistorted reference patterns. This work is intended to be of interest to HMD manufacturers, vision scientists, and operators of biocular HMDs for use in precision-critical applications.

Color Vision and Performance on Color-Coded Cockpit Displays.

INTRODUCTION Although there are numerous studies that demonstrate that color vision deficient (CVD) individuals perform less well than color vision normal (CVN) individuals in tasks that require discrimination or identification of colored stimuli, there remains a need to quantify the relationship between the type and severity of CVD and performance on operationally relevant tasks. METHODS Participants were classified as CVN (N = 45) or CVD (N = 49) using the Rabin cone contrast test, which is the standard color vision screening test used by the United States Air Force. In the color condition, test images that were representative of the size, shape, and color of symbols and lines used on fifth-generation fighter aircraft displays were used to measure operational performance. In the achromatic condition, all symbols and lines had the same chromaticity but differed in luminance. Subjects were asked to locate and discriminate between friend vs. foe symbols (red vs. green, or brighter vs. dimmer) while speed and accuracy were recorded. RESULTS Increasing color deficiency was associated with decreasing speed and accuracy for the color condition (R2 > 0.2), but not for the achromatic condition. Mean differences between CVN and CVD individuals showed the same pattern. DISCUSSION Although lower CCT scores are clearly associated with lower performance in color related tasks, the magnitude of the performance loss was relatively small and there were multiple examples of high-performing CVD individuals who had higher operational scores than low-performing CVN individuals. Gaska JP, Wright ST, Winterbottom MD, Hadley SC. Color vision and performance on color-coded cockpit displays. Aerosp Med Hum Perform. 2016; 87(11):921-927.

A practical definition of eye-limited display system resolution

Over the past few decades the term “eye-limited resolution” has seen significant use. However, several variations in the definition of the term have been employed and estimates of the display pixel pitch required to achieve it differ significantly. This paper summarizes the results of published evaluations and experiments conducted in our laboratories relating to resolution requirements. The results of several evaluations employing displays with sufficient antialiasing indicate a pixel pitch of 0.5 to 0.93 arcmin will produce 90% of peak performance for observers with 20/20 or better acuity for a variety of visual tasks. If insufficient antialiasing is employed, spurious results can indicate that a finer pixel pitch is required due to the presence of sampling artifacts. The paper reconciles these findings with hyperacuity task performance which a number of authors have suggested may require a much finer pixel pitch. The empirical data provided in this paper show that hyperacuity task performance does not appear to be a driver of eye-limited resolution. Asymptotic visual performance is recommended as the basis of eye-limited resolution because it provides the most stable estimates and is well aligned with the needs of the display design and acquisition communities.

Detection Threshold of Visual Displacement in a Networked Flight Simulator

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.

Evaluation of the Spatial and Temporal Resolution of Digital Projectors for use in Full-Field Flight Simulation

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.

P-216: Comparison of a Local Contrast Metric with Flight-Simulator Target-Identification Data

We used a visible contrast metric developed by Ahumada and colleagues [1, 2] to predict behavioral data gathered in our lab [3]. We found that the metric, augmented with an empirically determined psychometric function provides a reasonable prediction of left-right identification data, and should prove useful in characterizing the influence of target and background resolution on target identification in flight simulators.

P-30: Target Identification on Simulated Terrain Imagery Varying in Resolution

Abstract 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,