Download or read book Evaluation of Visual Acuity with Gen 3 Night Vision Goggles written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using 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 ...
Download or read book Evaluation of Visual Acuity with Gen 3 Night Vision Goggles written by and published by . This book was released on 1994 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Visual Acuity with Gen III Night Vision Goggles written by Arthur Bradley and published by . This book was released on 1994 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Night Vision Goggle Field expedient Visual Acuity Adjustment Procedures written by and published by . This book was released on 1996 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Night Vision Goggle Field Expedient Visual Acuity Adjustment Procedures Initial Experiment written by and published by . This book was released on 1996 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 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.
Download or read book 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 written by and published by . This book was released on 1992 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 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.
Download or read book Night Vision Goggle Assessment Techniques with Incompatible Cockpit Lighting and a Modified Class B Goggle written by Randall William Gibb and published by . This book was released on 1996 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proc s verbaux des secines de l enquete agricole written by and published by . This book was released on 1890 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Signal to Noise Ratio on Visual Acuity Through Night Vision Goggles written by Joseph T. Riegler and published by . This book was released on 1991 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since 1971, night vision goggles (NVGs) have been used by the military to enable personnel to perform visual operations in a nighttime environment. The key component of these devices is the image intensifier tube. Currently, no studies were identified which relate the signal-to-noise ratio (SNR) of image intensifiers to human visual acuity. The purpose of the present research was to determine the effect of NVG intensifier tube SNR on visual acuity. Visual acuity, using PVS-7 third generation NVGs, was measured for twelve participants at quarter moon and starlight illumination levels for four intensifier tubes with different SNRs. The range of SNR examined was 11.37 to 17.92. Visual acuity was assessed using Landolt C charts with target contrasts of 20 to 95 percent. The distance at which the acuity targets were resolved was recorded for each of the four illumination and contrast conditions. The results showed that increases in image intensifier tube SNR, illumination level, and contrast affected visual acuity. Regression analyses were performed to obtain estimated equations relating SNR to visual acuity for each experimental condition. The results were used to develop predictive guideline tables to provide approximate percent degradation/ improvement in visual acuity based upon intensifier tube signal-to-noise ratio ... Visual acuity, Night vision goggles, Signal-to-noise ratio, Image intensifier tubes.
Download or read book Visual Acuity Under Dim Light with and Without Night Vision Goggles written by Liang Cai and published by . This book was released on 1994 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Project No 7 Night Vision from Tanks written by Armored Medical Research Laboratory (U.S.) and published by . This book was released on 1944 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measuring Observers Visual Acuity Through Night Vision Goggles written by and published by . This book was released on 1998 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 observer's psychometric function when viewing through NVGs (percent correct detection as a function of spatial separation) to determine their visual acuity using probit analysis.
Download or read book Image Contrast and Visual Acuity Through Night Vision Goggles written by Jeff C. Rabin and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to investigate effects of display contrast and luminance on visual resolution through NVGs. Computer-generated letter charts were used to measure visual acuity across the range of luminances and contrasts one can encounter when viewing an NVG display. The results indicate that display luminance cannot, in itself, account for the level of acuity achieved through NVGs. Understanding the contrast and luminance transfer of NVGs is important for predicting human visual performance, and for developing improved night vision devices.
Download or read book Visual Acuity Versus Field of View and Light Level for Night Vision Goggles NVG written by Harry L. Task and published by . This book was released on 1994 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Parameters 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.
Download or read book Prospective Evaluation of Mesopic Night Vision and Night Vision Goggle Visual Acuity After Photorefractive Keratectomy PRK written by and published by . This book was released on 2005 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: The US Air Force PRK Study involved 98 non-flying, active duty volunteer personnel. All study subjects underwent a comprehensive array of vision tests. Baseline and post-operative data were collected at the Ophthalmology Branch of the Clinical Sciences Division of the USAF School of Aerospace Medicine, in partnership with the Air Force Research Laboratory and Wilford Hall Medical Center. This report covers results from pre- and post-operative night vision goggle (NVG) visual acuity testing. 65 treated subjects and 15 untreated controls completed all post-op visits through 12 months, and 52 treated subjects and 14 untreated controls through 24 months. NVG acuities were collected on a high contrast letter chart (Bailey-Lovie), and custom made grating charts. There was a statistically significant loss of letter acuity at the 4- and 6-month post-op visits for treated subjects but not controls. Acuity returned to baseline levels by 12 months. Mean loss of acuity for groups was typically only a few letters; however, treated subjects were more likely to lose than gain acuity beyond that predicted from repeatability studies with controls.
Download or read book Visual Acuity and Stereopsis with Night Vision Goggles written by and published by . This book was released on 1989 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of visual performance (stereopsis and visual resolution) were acquired to compare results achieved using unaided monocular and binocular viewing, monocular and binocular viewing with the AN/PVS-5A night vision goggles, and models A and B of the AN/PVS-7 biocular night vision goggles. All of the goggles were equipped with 2nd generation tubes. Using a modified Howard- Dolman apparatus to assess stereopsis, all of the goggle-assisted thresholds were very much larger than stereoscopic thresholds achieved with unaided binocular vision. Statistical analysis of the results indicated that stereopsis through night vision goggles, regardless of the model or viewing condition, is essentially eliminated and equivalent to the threshold obtained with unaided monocular viewing. In comparison, spatial resolution capability with all of the goggle systems is superior to performance with unaided vision. In agreement with previously published data, visual acuity with the goggles is approximately 20/ 50, but only for high contrast targets and simulated full moon ambient light levels. As light levels decrease to quarter moon conditions or target contrasts are reduced to more realistic values, visual spatial resolution with the goggles is much poorer. For infantry use, any differences in visual performance between monocular, biocular, and binocular designs probably are not operationally meaningful.
