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PubMed1982

PAVE LOW III: interior lighting reconfiguration for night lighting and night vision goggle compatibility.

The PAVE LOW III aircraft is a modified HH-53H helicopter that has a low altitude--below 30.48 m (100 ft)--night/day rescue mission. The desired night flying configuration is for the pilot to wear night vision goggles (NVGs) to fly the aircraft while the copilot, without NVGs, observes the video display and monitors the aircraft instruments. The problems of NVG incompatibility in the cockpit were successfully countered using several light control techniques. The light control modifications were evaluated on the ground in the PAVE LOW III helicopter at Kirtland AFB in April, 1980, by PAVE LOW instructor pilots. The evaluation results were extremely positive.

Aircraft↗

PubMed1997

Color Night Vision: Opponent Processing in the Fusion of Visible and IR Imagery.

We describe here a means of fusing registered low-light visible and thermal infrared (IR) imagery to support realtime color night vision. Opponent processing, in the form of feedforward center-surround shunting neural networks, is used to contrast enhance and adaptively normalize both visible and IR imagery separately. Both positive and negative polarity ("on" and "off") enhanced IR imagery is then combined with the enhanced visible imagery to create two single-opponent color-contrast grayscale images. The opponent processed visible and opponent-color images (forming a set of three grayscale images) are then assigned directly to the red, green, blue (RGB) color space. Final manipulation of both hue and saturation is achieved in the hue, saturation, value (HSV) color space. Remarkably realistic color renderings of night scenes are obtained which may support perceptual "pop-out" of extended navigation cues and compact targets. Psychophysical testing on low contrast targets in natural dynamic scenes is called for in order to assess human performance using fused visible and IR imagery at night. Copyright 1996 Elsevier Science Ltd.

Journal Article↗

PubMed1994

Switching from forward-looking infrared to night vision goggles: transitory effects on visual resolution.

Helmet-mounted displays under development for rotary- and fixed-wing aircraft will allow the user to switch electronically between forward-looking infrared (FLIR) and night vision goggle (NVG) sensors. These sensor transitions potentially involve large changes in display luminance which could transiently impair visual resolution and performance. The purpose of this study was to identify the display luminances which produce a transient reduction in vision when switching from a higher luminance (i.e., FLIR) to a lower luminance (i.e., NVG) display. A letter recognition task was used to assess the effect of luminance adaptation on visual resolution in five subjects. A significant reduction in letter recognition was observed in the first second after switching from simulated FLIR to simulated NVG's when the FLIR luminance was > or = 10 fL. By varying letter size, contrast, and exposure time, the magnitude and duration of visual loss after switching from a bright (49.2 fL) FLIR display were determined. The visual loss lasted up to 4 s, and included a 2x reduction in visual acuity, and a 3x reduction in contrast sensitivity. Large differences in sensor display luminance should be avoided to maintain high levels of visual performance and aviation safety. Design features or training may be necessary to achieve a proper balance between FLIR and NVG luminances which optimize performance and safety without sacrificing the quality of the sensor image.

Adult↗

PubMed2000

The Night Vision Threshold Test (NVTT): a simple instrument for testing dark adaptation in young children.

It is estimated that 41 per cent of the population aged under 5 in the developing world has an inadequate vitamin A dietary intake resulting in increased morbidity and mortality. Half a million children go blind each year as a result of vitamin A deficiency. Thirteen and a half million have night blindness, the first sign of vitamin A deficiency. Unfortunately, there is no simple, sensitive and inexpensive means to identify the child who has marginal levels of vitamin A and thus institute means to prevent their development of severe deficiency. A low cost, simple, easy-to-use instrument designed to detect a young child's ability to adapt to darkness was tested in children admitted to the Mwanamugimu Nutrition Unit at Makerere Medical School in Kampala, Uganda. Despite the severe degree of malnutrition found in these children, Night Vision Threshold Test results and serum retinol levels were related (r = 0.41, p < 0.05). Further efficacy trials for this instrument are planned at community sites in Nepal.

Adaptation, Ocular↗

PubMed2001

Use of night vision goggles and low-level light source in obtaining intravenous access in tactical conditions of darkness.

OBJECTIVE: The tactical environment of the nighttime battlefield precludes the use of white light to perform medical procedures. This study sought differences between two alternatives to white light used to facilitate intravenous access. A comparison was made between night vision goggles (NVG) and a low level light source (Fingerlite). METHODS: Fifty-eight volunteers were paired. Each member of the pair attempted intravenous access on his or her partner in darkness using both techniques. One attempt per method was allowed. Success was confirmed by the free flow of blood from the catheter. RESULTS: Of the 58 attempts using NVG, 32 were successful and 26 failed. In the Fingerlite group, there were 46 successful attempts and 12 failures. These differences reached statistical significance (p < 0.02). CONCLUSION: This study suggests that in conditions requiring darkness, a Fingerlite offers a clinical advantage over NVG in obtaining intravenous access.

Chi-Square Distribution↗

PubMed2000

A new, simple, inexpensive means of testing functional vitamin A status: the night vision threshold test (NVTT). A preliminary field-test report.

Vitamin A deficiency is the leading cause of preventable childhood blindness in developing countries. Each year, an estimated 13.5 million children world-wide are unable to adapt to the dark and half a million children progress to complete blindness annually from lack of vitamin A. Most of the currently available methods for assessing vitamin A status are expensive, require sophisticated instrumentation and are not efficacious in field conditions. A simple, inexpensive method was developed to identify children with defective dark-adaptability, thereby providing a reflection of marginal vitamin A stores. The purpose of this preliminary study was to test the field-efficacy of the Night Vision Threshold Tester (NVTT). Thirty-nine middle-school children with a mean age of 13.5 +/- 1.37 years were initially tested for their ability to adapt to the dark using the

Child↗

PubMed2003

Use of a night vision intensifier for direct visualization by eye of far-red and near-infrared fluorescence through an optical microscope.

We describe the design, construction and testing of a prototype device that allows the direct visualization by eye of far-red and near-infrared (NIR) fluorescence through an optical microscope. The device incorporates a gallium arsenide (GaAs) image intensifier, typically utilized in low-light or 'night vision' applications. The intensifier converts far-red and NIR light into electrons and then into green light, which is visible to the human eye. The prototype makes possible the direct, real-time viewing by eye of normally invisible far-red and NIR fluorescence from a wide variety of fluorophores, using the full field of view of the microscope to which it is applied. The high sensitivity of the image intensifier facilitates the viewing of a wide variety of photosensitive specimens, including live cells and embryos, at vastly reduced illumination levels in both fluorescence and bright-field microscopy. Modifications to the microscope are not required in order to use the prototype, which is fully compatible with all current fluorescence techniques. Refined versions of the prototype device will have broad research and clinical applications.

Animals↗

PubMed1991

Errors in distance appreciation and binocular night vision.

Studying binocular vergence in relation to luminance levels, we isolated two types of behaviour which may explain differences in distance appreciation: 1. Underestimation of distances in subjects with overconvergence in darkness. 2. Overestimation of distances in subjects with underconvergence in darkness. Progression towards the limiting value of convergence varies from one individual to another for each mesopic and scotopic luminance level and for different experimental conditions: variable discrepancy between the observation distance and the tonic vergence distance; accommodative or fusional stimuli at varying degrees of eccentricity; mobile stimuli in the observer's peripheral field. The study of bipartition in depth of a given interval for different observation distances confirms the existence of two major categories of individuals. Over- or underestimation of the nearer subjective half correlates to the binocular dark convergence capacity of each individual. These findings may explain errors in distance appreciation for road users in night vision.

Convergence, Ocular↗

PubMed1954