Showing papers on "Night vision published in 1975"

Night Vision Laboratory Static Performance Model for Thermal Viewing Systems

Abstract: : The NVL thermal model predicts system noise equivalent temperature difference, minimum resolvable temperature, minimum detectable temperature and modulation transfer functions for any infrared imaging system. It also predicts detection and recognition as a function of range for a given atmosphere and target signature. This model is documented, and the validation from laboratory measurements and field experiments is also presented. The computer program and an in-depth user's manual are given in the appendices. This model can be and has been used in military systems analyses to direct component research, evaluate contractor proposals, and aid project manager decisions.

Influences of light on activity and phasing of carnivores

Abstract: Influences of light on the locomotor activity and phasing of 42 carnivores from 16 species were studied on four light regimes employing natural or artificial twilights: (1) outdoor light; (2) indoor, 24-h artificial light cycles with unvarying day and night illuminance and stepwise illuminance changes every 30 min during activity; and (3) indoor 3- or 4-h cycles. Responses to such tests may be the best available behavioral guide for assessing the overall state of adaptation of the visual system. Genets, kinkajous, and ringtails were strongly nocturnal. The behavior of kit foxes, long-tailed weasels, and red foxes suggests visual systems best adapted for dim light but also suitable for daylight. The arctic fox, gray fox, and striped skunk appear to be adapted for both day and night vision. Behavior of a juvenile coyote suggests optimal vision in twilights and moderate daylight, while that of a juvenile red wolf suggests better vision in moderate daylight than dim light. Animals that appear to be adapted be...

Apparatus for adding electronic display information to a night vision goggle display

Abstract: The described apparatus employs the image intensifier tube assemblies of ht vision goggles for nighttime viewing, but bypasses one of these assemblies in additionally injecting pictorial or electronically generated information at a comfortable light level.

Heterojunction III—V alloy photodetectors for high-sensitivity 1.06-µm optical receivers

Abstract: A new type of 1.06-µm solid-state detector is discussed, the inverted hetrojunction III-V alloy mesa photodiode, which offers quantum efficiencies near 1.00 percent, extremely low capacitance and transit time, and low dark currents. The characterstics of these detectors allow their use in sensitive 1.06-µm optical receivers which promise better signal-to-noise ratios in a number of applications than any other available 1.06-µm photodetector. In particular, an optimization procedure for selecting photodiode and preamplifier parameters to give the best signal-to-noise ratio under signal conditions is discussed and this technique is applied to a proposed system application. It is shown that in this laser-illuminated airborne night imaging system, a small area heterojunction III-V alloy photodiode detector in an optimized receiver should be able to give signal-to-noise ratios much higher than any other 1.06-µm detector approach, even though the other 1.06-µm detectors may have lower noise equivalent power (NEP) values than this receiver. This is an illustration of the fact that such "magic numbers" for detector comparision as NEP are applicable only to comparing similar types of detectors in certain specific types of applications (such as comparing IR photoconductors in a high background application), and are of very little value in determining the relative performance of different types of detectors for a given system application (such as comparing photomultipliers, avalanche photodiodes, and low-noise photodiodes for this application).

Visibility under night driving conditions: Part 2. Field measurements using disc obstacles and a pedestrian dummy

Abstract: The visibilities of a pedestrian dummy and disc objects of varying size and contrast were measured under dynamic night driving conditions on an unlit open road and in a road lighting situation for which the average pavement luminance was 0.8 cd/m2. The visibilities of the objects could largely be described by a standard luminous increment-visual area characteristic. Under road lighting conditions, negative contrasts (silhouette vision) were found to give slightly greater visibilities than positive contrasts. It was found that a contrast multiplier of 4 was required in applying laboratory 50% probability of detection thresholds to a 'just visible' criterion level of visibility in the field experiments, though in practical conditions contrast multipliers as large as 30 may be required. (a) for abstract of part I see IRRD no. 215842. /TRRL/

Driver search and scan patterns in night driving

Abstract: Because the rates of nighttime accidents are higher than daytime accidents, much research has been directed to the unique problems of night driving. Many researchers concur that the driver receives most of his or her information through the visual system. During night driving, the visual cues normally available during daytime are reduced. Whether this paucity of visual information is related to the higher night accident rate is not known. A basic approach to the problem is to identify through visual search patterns the driver's use of night driving cues. Identification of driver visual needs in night driving can eventually lead to improved night driving safety. This paper discusses and presents the results of two studies to investigate drivers' visual search patterns in night driving. The first study compares nighttime visual search behavior to daytime behavior on freeways and rural highways. The second study develops methods of using driver visual search data to evaluate illumination at rural highway intersections, which have high rates of nighttime accidents.

Quick disconnect for night vision optics

Abstract: The invention provides a quick disconnect device for use between image insifier tubes and their power supply or their supporting apparatus.

Predictive validities of several clinical color vision tests for aviation signal light gun performance.

Abstract: Scores on the American Optical Company (AOC) test (1965 edition), Dvorine test, Farnsworth Lantern test, Color Threshold Tester, Farnsworth-Munsell 100-Hue test, Farnsworth Panel D-15 test, and Schmidt-Haensch Anomaloscope were obtained from 137 men with color-defective vision and 128 men with normal color vision. The validity of each of these tests in predicting scores on the aviation signal light gun was assessed by using daytime and nighttime administrations of the light gun as the criteria. Two "best sets" of plates from the AOC and Dvorine tests were selected by calculating a multiple regression equation in a stepwise manner with the nighttime and then the daytime administration of the signal light gun test as the criteria. Based on a graphic presentation of the miss and false alarm rates for each test at various possible cut scores, suggestions were made regarding the use of each test and the selection of optimal pass/fail scores.

Aviator Performance Measurement During Low Altitude Rotary Wing Flight with the AN/PVS-5 Night Vision Goggles

Abstract: : Aviators were required to fly a UH-1 helicopter at night with and without night vision goggles (AN/PVS-5). Three types of goggles were used: 40 deg field-of-view (FOV), 60 deg FOV, and 40 deg FOV with a 30% bifocul cut. During flight, data were acquired on over twenty aircraft status and control input variables. These data, for purposes of performance comparison, were subjected to both univariate and multivariate analyses. The six subjects (instructor pilots) also responded to a questionnaire regarding preference, training and estimated capabilities of each type intensification system. The major findings of both the subjective and objectives measures are provided.

Visibility under night driving conditions: Part 1. Laboratory background and theoretical considerations

Abstract: Comparison between studies of visibility under night driving conditions has been made difficult by the wide range of test objects and visibility criteria used. This study attempts to provide a model by which the visibilities of a range of items can be estimated for night driving conditions. This first of three papers discusses laboratory studies of the effects of size and shape on visibility and various theoretical interpretations of the findings. It is argued that, despite its limitations, a single-channel model of spatial vision based on measurements of contrast sensitivity with discs remains the most relevant and practical theoretical framework with which to relate the visibilities of objects that are of interest in the night driving environment. (A) /TRRL/

Driver screening for night driving

Abstract: A thorough review of the relevant literature was combined with a rigorous and systematic examination of the driving task to derive a set of visual functions important to the driving task. The functions included both static and dynamic measures, containing both sensory and perceptual aspects. A device was developed to test performance on these functions, including three measures related to night vision: static acuity under low levels of illumination, in the presence of veiling glare, and under spot glare. The battery of tests was administered to a total of 669 passenger car drivers and 235 truck and bus drivers. Three-year driving records were obtained for all subjects and were examined in relation to performance on the vision tests. Because no data on night accidents were available, an adequate evaluation of the night-vision-related-tests was not possible; however, the results showed a high degree of variability in visual acuity performance obtained under conditions similar to those encountered in night driving and also showed that acuity measured under normal light conditions does not adequately predict acuity under typical night driving conditions.

Selection of Individuals for Specific Duties Associated with Night Vision Proficiency

Abstract: : The human ability to see at night depends on the person's level of dark adaptation, his physiological state, as well as behavioral and environmental factors. There are major individual differences in night vision and the reasons for some differences are known; however, many are essentially unknown or unstudied. It is proposed that through the utilization of the refined techniques recently developed in the fields of vision, physiology, biochemistry and behavior, it may be possible to select individuals for specific duties requiring night vision proficiency. To meet this goal an in-depth study of the subject is required to fully develop the concepts and the opportunities for future research.

Laboratory Assessment of the AN/PVS-5 Night Vision Goggle

Abstract: : Laboratory assessment of the AN/PVS-5 Night Vision Goggle was conducted. Visual fields, goggle infrared source, useable range, and detectability of targets with the goggle were measured. Illumination levels of -5.4 and -6.22 log foot candles were adequate for 90 percent detection of 0.14 and 0.07 acuity targets respectively. Calculations of distances at which various surface and airborne targets subtended comparable visual angles and tables of natural brightness conditions are presented to permit translation of laboratory values into field conditions. While further field evaluation is anticipated, the laboratory assessment indicates that the goggle can significantly facilitate aircrew night visual performance.

Heterojunction III-V alloy photodetectors for high-sensitivity 1.06-micrometers optical receivers

Abstract: It is pointed out that currently promising technical developments related to the Nd-YAG laser technology at 1.06 micrometers cannot be implemented because of the absence of a suitable detector. Such a detector could possibly be provided in connection with new advances related to the development of the heterojunction III-V alloy photodiode. Details of detector requirements for the considered applications are discussed along with approaches to satisfy these requirements by an appropriate detector design.

Electronic aids to night vision

Abstract: In the past, `seeing in the dark? has always been achieved by means of artificial light. Today, with the help of electronic aids, such as image-intensifier tubes and thermal-imaging systems, a human form can be discriminated in moonlight at a distance of up to 1500 m

Natural and Artificial Illumination in Optically Thick Atmospheres

Abstract: : In the analysis of target signatures it is essential that the illumination level be defined and determined for a variety of environmental conditions. This report deals primarily with two important sources of illumination, the moon and man-made flares. The illumination due the moon is calculated using an atmospheric-radiative-transfer model which includes multiple scattering by gases and particulates in the atmosphere but does not include absorption due to gases. A variety of atmospheric states is considered, from very clear atmospheres to very hazy. A detailed analysis of fogs was carried out and density profiles were calculated to represent different kinds of fogs. A mathematically exact formula was developed which allows one to calculate the surface illumination due to one or more point sources (flares). Calculations were performed to determine surface illumination in terms of distance from source, source height, height of fog layer, and visibility. Contours were plotted which illustrate the surface illumination for various flare configurations.

Vision and driving: a report on research

Abstract: Information on vision test performance and personal and driving habits was obtained for 17,769 California drivers and was compared with their driving records, i.e., accidents and convictions for traffic citations. Of the vision tests evaluated, dynamic visual acuity is by far the one most closely related to driving record, followed by static visual acuity, visual field, and 'night vision'. The results show that mileage, age, and sex are also important factors influencing driving record, and that conviction experience is a much more stable driving record variable than accident experience.

Wet night visibility study

Abstract: Issued as Interim report phase I, Planning report, Materials requirements, Work program and cost estimate, Quarterly progress report no.1-19, Annual progress report, Interim reports, [1-2], and Final report, Project no. A-1033

Installation and Operation of an Atmospheric Particulate Collector.

Abstract: : The Atmospheric Sciences Laboratory (ASL) at White Sands Missile Range (WSMR) NM, has an active program to measure the optical absorption coefficient of atmospheric particulate matter collected from a variety of world wide geographic locations as part of a mission objective to determine the potential adverse effects of such dust on military night vision, target designation, remote sensing, and other systems relying on propagation of light in the atmosphere. To insure that the samples collected from different localities can be directly compared, the sampling equipment and procedure must be standardized. This report describes the design details of the collector and procedure developed for this purpose. The collector uses a 47-millimeter-diameter 0.45-micrometer pore size membrane filter through which air is pulled by means of an auxiliary vacuum pump. Illustrations of operational details of the collector are included.

Reduction of veiling glare in electro-optical image tubes

Abstract: : Using an image dissector scanner as an electronic microphotometer, the absolute magnitude of veiling glare was measured in a series of production image tubes In general, the measured total veiling glare levels varied from 1 to 5% (1 to 5% of the true image flux appearing in non-image areas at the output) In addition, significant differences were observed between tube types in the distribution of this veiling glare over the image field Interpretation of the results indicated that second generation microchannel plate wafer tubes could be expected to show markedly superior performance under 'bright source' interfering conditions, whereas first generation electrostatic and magnetic image tubes should be superior for reconnaissance photography, where maximal system contrast transfer is required The sources of veiling glare were sufficiently well-determined so that recommendations could be made as to appropriate procedures for reducing veiling glare (Author)

Comparison of two head-up displays in simulated standard and noise abatement night visual approaches

Abstract: Situation and command head-up displays were evaluated for both standard and two segment noise abatement night visual approaches in a fixed base simulation of a DC-8 transport aircraft. The situation display provided glide slope and pitch attitude information. The command display provided glide slope information and flight path commands to capture a 3 deg glide slope. Landing approaches were flown in both zero wind and wind shear conditions. For both standard and noise abatement approaches, the situation display provided greater glidepath accuracy in the initial phase of the landing approaches, whereas the command display was more effective in the final approach phase. Glidepath accuracy was greater for the standard approaches than for the noise abatement approaches in all phases of the landing approach. Most of the pilots preferred the command display and the standard approach. Substantial agreement was found between each pilot's judgment of his performance and his actual performance.

New hazards in penetrating wounds of the eye

Abstract: Since the mid 1960's phototropic spectacles and sunglasses have been widely sold. These contain highly active and photo reactive silver halides. In additions to silver chloride, fluoride and bromide, some of these lenses contain small percentages of copper and cobalt. These active and toxic elements significantly increase the x-ray density of such lenses or their fragments and slightly increase the specific gravity of the glass. Infrequently patients complain of added weight of such lenses. Skiers on bright, sunny slopes and particularly cold days are enthusiastic concerning such lenses especially when skiing mogul courses. Market place popularity has also placed millions of such lenses before the eyes of warm weather wearers and others hoping for some advantage inside automobiles on bright days. Inherently slow clearing, compounded by the further delaying effect of high ambient temperature makes these lenses an impediment to twilight and night driving. Maximum clearing requires shielding from all light for many hours. Filters such as these worn under mesopic conditions as in night driving reduce needed incident light on the retina and are progressively more severe impediments with advancing age of the wearer. MacFarland has demonstrated a need for essentially doubled ambient light every thirteen years of adult life to maintain recognition capabilities under mesopic illumination. Drivers with tinted windshields face compounded reduction of necessary luminous cues when wearing such lenses for mesopic driving tasks. When fragmented, these lenses, like lead glass, are easier to identify by x-ray even when less than 2 mm in size. Conventional crown glass fragments must be larger than 2 mm in size for usual x-ray identification. Active silver and cobalt ions are leached from this glass. Chronic experiment with glass fragments implanted into the vitreous of albino rabbits over 6-8 months shows a tri-phasic reaction consisting of a few days of post insertional inflammation followed by 7-14 days of relative inflammatory quietude and then progressive low grade inflammation over months. This is complicated by vitreous strands and localized hemorrhage about the fragments particularly when they are in contact with the retina. Fragments suspended in mid vitreous evoke lesser localized reaction. Established concepts of minimal extraction efforts for glass fragments may now need to be revised toward more prompt or heroic efforts to remove phototropic elements.

Night vision aiming system for tanks - has TV camera and screen with data superposed by optical system

Abstract: The night vision system for tanks has a television camera which is coupled to a gun. The camera operates in conjunction with a target marking projector and the system has an image display with data for given ammunition and range. This information is superimposed optically on the image and not electronically, in order to improve reliability. The optical system consists of two transparent plates with conventional markings which are arranged in front of the image screen. The first plate is fixed in front of the screen and it has scales for range and ammunition varieties. The second plate can be adjusted relative to the first one and it has reference scales and target aiming system markings. The scales on the plates are adjusted automatically by a control system.

A data acquisition system for research studies of driver performance in real traffic situations

Abstract: This paper describes a real-time data acquisition system and instrumentation installed in a full-size North American automobile for the purposes of research studies of driver performance in real traffic situations and under various conditions of driver stress. The basic parameters recorded are distance travelled and three primary control movements - sterring wheel, accelerator and brake. Provision is also made for vehicle yaw measurement, driver's pulse rate and perceived illumination level in night-driving tasks. Other parameters may be recorded as dictated by project requirements. The paper presents summaries of the test conditions and principal findings of the various projects carried out at the National Research Council of Canada during the past three years, in which the frequency and magnitude of steering wheel movements have formed the basis for assessment of driver performance and task difficulty. The application of power spectral analysis techniques appears most promising, and it is in this content that the advantages of a highly flexible real-time data acquisition system are most apparent.