Use of night vision goggles (NVGs) for military applications has grown steadily over the past 30 years Each successive NVG model represents some kind of improvement in terms of size, weight, ruggedness, gain, noise, spectral sensitivity, field-of-view or resolution The primary focus of this paper is the determination of NVG resolution Many methods have been devised to measure the resolving power of NVGs and each method has with it an associated variance or accuracy of measurement This variance is most likely caused by several sources including observer visual capability (since most methods involve visual observations and judgement to assess NVG resolution) The main purpose of this paper is to present the different methods that have been used to assess NVG resolution and to determine to what extent observer visual capability limits the accuracy of NVG resolution measurement This study uses a methodology that measures an observerOs psychometric function when viewing through NVGs (percent correct detection as a function of spatial separation) to determine their visual acuity using probit analysis

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Measuring Observers' Visual Acuity Through Night Vision Goggles

In 1973, the Development of the Army adopted night vision devices for use in aviation. Known as the AN/PVS-5 night vision goggle (NVG), these devices, which are based on the principle of image intensification (I2), have become the mainstay for the aviator's capability to operate during periods of low illumination, i.e., at night. In the 2 years that have followed, a number of engineering the advancements have improved greatly the performance of these devices. The current version, using third generation I2 technology, is known as the Aviator's Night Vision Imaging Systems (ANVIS). The performances histories of NVGs and ANVIS are presented with an emphasis on visual and biodynamic issues which have, and do, affect aviator mission effectiveness and safety.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Performance history of AN/PVS-5 and ANVIS image intensification systems in U.S. Army aviation

: The Canadian Forces have recognized the importance of simulator training as a cost-effective alternative to real training; yet the effect of display simulation on visual perception is not fully understood. Fighteen subjects participated in an experiment to determine if training, in the form of immediate feedback, improved distance estimation to muzzle flashes in a simulated NVG environment. Testing was performed on a PC desktop computer using software that simulated a large open grassy field. Subjects were exposed to three flash types; five flashes, single flash, and a prolonged flash. Flashes were presented to the subjects both above and below the horizon. Significant improvement was shown in the experimental group's accuracy; this accuracy persisted over two weeks but with notable deterioration. Contrary to expectation the perception of a single flash resulted in significantly greater accuracy than the prolonged flash. This experiment reinforces the effectiveness of simulation as a tool in preparing soldiers. A bibliography of the topic is included.

Distance Estimation to Flashes in a Simulated Night Vision Environment

The image quality of night vision goggles is often expressed in terms of visual acuity, resolution or modulation transfer function. The primary reason for providing a measure of image quality is the underlying assumption that the image quality metric correlates with the level of visual performance that one could expect when using the device, for example, target detection or target recognition performance. This paper provides a theoretical analysis of the relationships between these three image quality metrics: visual acuity, resolution and modulation transfer function. Results from laboratory and field studies were used to relate these metrics to visual performance. These results can also be applied to non-image intensifier based imaging systems such as a helmet-mounted display coupled to an imaging sensor.

Theoretical and applied aspects of night vision goggle resolution and visual acuity assessment

: Many factors which could affect visual acuity (VA) with night vision goggles (NVGs) already have been studied, e.g., night sky condition and target contrast (Levine and Rash, 1989a and 1989b; Wiley, 1989; Kotulak and Rash, 1992) , NVG generation (Miller et al., 1984; Kotulak and Rash, 1992), nuclear flashblindness protection (Levine and Rash, 1989a and 1989b), chemical protective masks (Miller et al., 1989; Donohue-Perry, Riegler, and Hausman, 1990), signal-to-noise ratio (Riegler et al., 1991), interpupillary distance misadjustment (King and morse, 1992), and instrument myopia (Kotulak and Morse, 1992, 1994a, and 1994b; Kotulak, Morse, and Wiley, 1993). Another factor which could influence NVG VA is decreased unaided VA, i.e., VA without NVGs; however, relatively little is known about it.

Factors That Determine Visual Acuity through Night Vision Goggles for Emmetropes

: Aviators in combat may be subjected to a variety of noxious light stimuli. Filters and other eye protective devices may be used to counter these threats. At night, filters may be used in conjunction with image intensification devices (e.g., night vision goggles) to provide useful low-light vision as well as protection from deleterious light sources (e.g., lasers, pyrotechnics, nuclear fireballs, etc.). Technologies may be combined in a single, integrated head gear unit. The present study was performed in order in consider the effects on visual acuity after reducing night vision goggle luminous output from 0-99 percent. A range of target contrasts and ambient illumination levels was investigated. AN/PVS-5A goggles were selected based upon their compatibility with current phosphor display technology and their current ubiquity within aviation units. Visual acuity was assayed behaviorally because of its critical importance in flying performance. The results of the study provide normative acuity data with goggles alone and document the effects on goggle visual acuity with reduce goggle luminances as might be produced by protective materials placed between the goggles and the eyes. Keywords: Light filters; Human factors engineering; Night vision devices.

Richard R Levine

Papers

Attenuating the Luminous Output of the AN/PVS-5A Night Vision Goggles and Its Effects on Visual Acuity