Visual Acuity Under Dim Light with and Without Night Vision Goggles
Author: Liang Cai
Publisher:
Published: 1994
Total Pages: 118
ISBN-13:
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Night Vision Goggle Field-expedient Visual Acuity Adjustment Procedures
Author:
Publisher:
Published: 1996
Total Pages: 54
ISBN-13:
DOWNLOAD EBOOKEvaluation of Visual Acuity with Gen 3 Night Vision Goggles
Author:
Publisher:
Published: 1994
Total Pages: 46
ISBN-13:
DOWNLOAD EBOOKMedicinal Herbs in Primary Care
Author: Jean M. Bokelmann
Publisher: Elsevier Health Sciences
Published: 2021-07-20
Total Pages: 713
ISBN-13: 0323846777
DOWNLOAD EBOOKWritten specifically for the conventional medical healthcare provider, Medicinal Herbs in Primary Care forms an integral part of the primary care tool belt. Through a series of system-based disease tables, this unique title provides quick, authoritative guidance for the busy practitioner whose patient is requesting guidance on medicinal herbs. The disease tables are supported by herbal monographs that provide expanded details of the available preclinical and clinical evidence laid out in a system-based sequence. Together with the section on herbal basics, this practical reference contains the information today’s medical healthcare providers need to develop familiarity with and confidence in the prescription of medicinal herbs. Provides quick answers and evidence-based prescribing guidance for medicinal herbs while also addressing complexities and co-morbidities in patient care. Features 48 system-based disease tables that identify herbs based on strength of evidence and indicate the scope of potential benefits for other conditions the patient may have. Includes 55 monographs for the most common medicinal herbs, with safety and precaution guidelines, summaries of preclinical and clinical trials, chemical constituents and actions, and prescription options for each. Contains an introductory section on the basics of medicinal herbs that dispels common misconceptions regarding herbal medicine. Discusses key topics such as herb-drug interactions, and includes information on SARS-COV-2 where appropriate. Uses typical medical abbreviations throughout for ease of use, and provides a glossary of terms for non-medical and alternative health care providers. Helps conventional medical practitioners partner with patients to determine safe herbal options when appropriate, and ensure safety and efficacy of herbal use.
Mild Hypoxia and Visual Performance with Night Vision Goggles
Author: Leray Lyle Leber
Publisher:
Published: 1985
Total Pages: 92
ISBN-13:
DOWNLOAD EBOOKPilots have frequently reported an apparent darkening of the visual field while flying at high altitude without supplemental oxygen, and subsequent exposure to oxygen resulted in marked increases in the brightness of lights. Likewise, at low light intensities visual acuity is greatly decreased during oxygen deprivation. In contrast, at high light intensities, the effect of moderate oxygen deprivation on visual acuity is slight. Even though the Night Vision Goggles (NVGs) amplify low night illumination, the interaction between amplified illumination and high altitude effects may prove to be important factors in visual performance. The objective of this research was to investigate the effects of mild hypoxia on monocular visual performance with NVGs. This study revealed that mild oxygen deprivation significantly affects unaided square-wave grating visual acuity but does not significantly affect NVG-augmented performance. Large differences between visual sensitivities at different spatial frequencies were not differentially affected by mild hypoxia. Supplemental oxygen did significantly improve naked-eye but not NVG-augmented night resolution acuity up to an altitude of 13,000 feet (3,692 m) above sea level (ASL).
Visual Acuity Versus Field-of-View and Light Level for Night Vision Goggles (NVG).
Author: Harry L. Task
Publisher:
Published: 1994
Total Pages: 21
ISBN-13:
DOWNLOAD EBOOKParameters typically used to characterize night vision goggles (NVG) are visual acuity (resolution) and field-of-view (FOV). An increase in FOV is accomplished by providing higher magnification of the image intensifier tube. However, increased magnification means that the pixels will subtend a larger angle, thus leading to lower NVG visual acuity. An inverse relationship between visual acuity and field-of-view is expected based upon this optical/geometrical relationship. This relationship should be examined as production of NVG resolution quality increases. A trade-off study examining FOV and resolution was conducted with three observers having 20/20 corrected Snellen acuity. The NVGs had fields-of-view of 40, 47, and 52 degrees, respectively. Five levels of ambient scene illumination (corresponding to output luminance levels of 0.01, 0. 03, 0.08, 0.26, and 1.4 ft-L) were provided by a 2856K light source. The targets used in the study were 95+% contrast square wave targets ranging in size from 45 cycles/degree to 5 cycles per degree. A walk-back method of adjustment was employed. The results indicate that the geometric relationship between field-of-view and visual acuity is valid. Night vision devices, Visual acuity, Night vision goggles.
Evaluation of Visual Acuity with Gen 3 Night Vision Goggles
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-07-02
Total Pages: 42
ISBN-13: 9781722214555
DOWNLOAD EBOOKUsing laboratory simulations, visual performance was measured at luminance and night vision imaging system (NVIS) radiance levels typically encountered in the natural nocturnal environment. Comparisons were made between visual performance with unaided vision and that observed with subjects using image intensification. An Amplified Night Vision Imaging System (ANVIS6) binocular image intensifier was used. Light levels available in the experiments (using video display technology and filters) were matched to those of reflecting objects illuminated by representative night-sky conditions (e.g., full moon, starlight). Results show that as expected, the precipitous decline in foveal acuity experienced with decreasing mesopic luminance levels is effectively shifted to much lower light levels by use of an image intensification system. The benefits of intensification are most pronounced foveally, but still observable at 20 deg eccentricity. Binocularity provides a small improvement in visual acuity under both intensified and unintensified conditions. Bradley, Arthur and Kaiser, Mary K. Ames Research Center ...
Attenuating the Luminous Output of the AN/PVS-5A Night Vision Goggles and Its Effects on Visual Acuity
Author: Richard R. Levine
Publisher:
Published: 1989
Total Pages: 36
ISBN-13:
DOWNLOAD EBOOKAviators 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.
Night Vision Goggle Field-Expedient Visual Acuity Adjustment Procedures: Initial Experiment
Author:
Publisher:
Published: 1996
Total Pages: 46
ISBN-13:
DOWNLOAD EBOOKThe third-generation image intensification technology in night vision goggles (NVGs) used by ground forces provides at best 20/40 or 20/45 visual acuity. These acuity levels cannot be achieved unless soldiers adjust their NVGs properly. Documentation available to soldiers does not address optimum adjustment techniques developed by the aviation community nor does it address what can be used in the field to achieve a good setting. We examined the effectiveness and utility of 15 different objects commonly available to soldiers to determine which provided the best visual acuity readings with the AN/PVS-713 NVGs. After training and practice acuity improved by 25% over the baseline assessment. No large differences in readings occurred among the objects. However, a more definitive picture emerged when the average readings were combined with measures of variability and soldier preferences. The initial recommendation is to use one of the following objects for NVG adjustment: trec trunk, vehicle, vehicle trail, stars, blue chem light, or an infrared chem light. Not recommended are bright and/or red light sources, white paper, and trees silhouetted against the night sky. Problems in assessing acuity with NVGs are also discussed.
Visual Acuity with Second and Third Generation Night Vision Goggles Obtained from a New Method of Night Sky Simulation Across a Wide Range of Target Contrast
Author:
Publisher:
Published: 1992
Total Pages: 43
ISBN-13:
DOWNLOAD EBOOKThe purpose of this investigation was to study the primary factors which influence visual acuity (VA) with night vision goggles (NVGs). These factors are: night sky condition, target contrast, and NVG generation. Improved methods were used to simulate the night sky and to control for differences in target contrast which result from dissimilarities in spectral sensitivity between NVG generations. The new simulation method used combinations of spectrally flat (neutral density) and wavelength selective (blue glass) filters to reproduce the spectral distribution of the night sky across the entire NVG response range. Between-generation differences in target contrast were eliminated by weighting the incident radiant flux by the sensitivity of the detector. It was found that the difference in VA between the two generations widens under two conditions: (1) when target contrast is constant and night sky irradiance decreases, and (2) when night sky irradiance is constant and target contrast decreases. Furthermore, it was found that for a given NVG generation, VA falls off more rapidly for a low contrast target than for one of high contrast when night sky irradiance decreases.
