Showing papers on "Night vision published in 1968"

The ability to see a pedestrian at night: the effects of clothing, reflectorization and driver intoxication

Abstract: AN EXPERIMENT WITH EIGHT MALE STUDENTS SHOWED THAT AT LOW LEVELS OF ILLUMINATION, AN INDIVIDUAL'S SENSITIVITY TO CONTRAST DECREASES AS HIS BLOOD ALCOHOL LEVEL INCREASES. ALL SUBJECTS EXHIBITED A SIGNIFICANT DECREASE IN CONTRAST SENSITIVITY AT BLOOD ALCOHOL LEVELS GREATER THAN 0.04 PERCENT. IN A ROAD TEST STUDY, VISIBILITY DISTANCES WERE FOUND TO BE UNACCEPTABLY SHORT FOR DUMMY PEDESTRIANS COVERED WITH BLACK OR GREY FABRIC. DUMMIES COVERED WITH WHITE FABRIC WERE SAFELY VISIBLE FOR A DRIVER TRAVELLING UP TO A SPEED OF 50 MPH. HOWEVER, ONLY REFLECTORIZED DUMMIES WERE SAFELY VISIBLE ABOVE THAT SPEED. AT BLOOD ALCOHOL LEVELS GREATER THAN 0.04 PERCENT ALL FOUR OBJECTS EXHIBITED A SIGNIFICANT DECREASE IN THE MEAN VISIBILITY DISTANCE FOR EACH OF THE SIMULATED PEDESTRIAN CONDITIONS.

Choroideremia. Visual defects in a heterozygote.

Abstract: This disease has always been considered to affect men only. Women, who represent the carrier state, may show fundus changes but have never been considered to have functional disease. A case history of a female patient with choroideremia is presented, showing not only the typical fundus changes but also marked impairment in night vision, constriction of visual fields, limited dark adaptation, and electroretinographic extinction. It is suggested, genetically, that this is an extreme example of Lyonization or the result of modifying genes which are, at present, not clearly understood.

Two-flash thresholds as a function of flash luminance and area

Abstract: Two-flash thresholds were obtained from three dark-adapted Ss by means of a two-interval, temporal forced-choice technique involving foveally fixated circular targets varying in luminance and area. The Ss were instructed to report the temporal position of the longer of two pairs of I-msec flashes. a comparison pair with an interflash interval of 1 msec, and a test pair with a varying interflasn interval. The Ss were informed about the accuracy of their responses after each response. For all three Ss the results replicated a previous finding that two-flash thresholds are a negatively accelerated function of flash luminance. but the function was shown to be dependent on area. a greater threshold change occurring at smaller areas. Two-flash thresholds were also found to be a decreasing function of stimulus area. with the greatest threshold change occurring at low luminances.

Image intensifiers for night vision

Abstract: An image intensifier suitable for night vision which employs a channel intensifier, i.e., a plate-shaped resistive matrix provided with conductive coatings on opposite major faces which constitute input and output electrodes respectively connected by elongated passageways in the matrix which constitute secondary emissive channels. A photocathode responsive to infrared and near infrared radiation is positioned opposite the input electrode while a luminescent screen is positioned opposite the output electrode and luminesces under electron impact in the visible spectrum adjoining the infrared portion of the spectrum, i.e., in the red wavelengths.

The effectiveness of night driving glasses under part-task simulation.

Abstract: THIS IS A REPORT OF TWO PILOT STUDIES WITH SMALL SAMPLES, A SERIES OF PART-TASK SIMULATION EXPERIMENTS WITH 121 SUBJECTS, AND A FOLLOW-UP STUDY, ON THE EFFECTS OF WEARING NIGHT DRIVING GLASSES. THE FINDINGS IN ALL CASES ARE CONTROVERSIAL, WITH SOME SUBJECTS DEMONSTRATING MORE EFFECTIVE PERFORMANCE WITH THE GLASSES AND OTHERS WITHOUT, ALTHOUGH NO GROUP TRENDS WERE STATISTICALLY SIGNIFICANT. SIMILARLY CONFLICTING DATA WERE OBTAINED WHEN SUBJECTS WERE INTERVIEWED AS TO THE EFFECTS OF THE GLASSES. THE NEED FOR MORE SOPHISTICATED RESEARCH IS SUGGESTED. /AUTHOR/

Backscatter Limitations in Active Night-Vision Systems

Abstract: : This study explores atmospheric backscatter as a fundamental limitation in using an artificial light source for night viewing. A mathematical model of an active night-vision system is constructed, and formulas are derived for the signal received from a target and the backscatter caused by the intervening atmosphere. Signal-to-noise ratio is defined, and its use as a measure of system performance is discussed. Several hypothetical systems are evaluated, and graphs of the signal-to-noise ratio as a function of range are presented. Additional graphs show the power that would be required by the systems to achieve a given signal-to-noise ratio as a function of range. (Author)

Statistical brightness gain of a channeltron image intensifier.

Abstract: A mathematical calculation of the statistical brightness gain of a postulated image intensifier is achieved. Two general cases for the signal-to-noise ratio are formulated: (1) owing to an inevitable nonadditive quantum noise, and (2) owing to the sum of a quantum noise and a postulated additive Poisson noise. The former is found to be somewhat higher than the latter. However, if either the brightness gain of the imaging system or the input photon rate increases, the signal-to-noise ratio of the latter case will asymptotically approach that of the former case. The minimum required scintillation for the two general cases is also determined and is found to be directly proportional to the brightness gain of the imaging system. The illumination of the image screen for the two cases is also calculated. Finally, it is concluded that the brightness gain does not improve the signal-to-noise ratio of the imaging system, which is due to the inevitable quantum noise. However, if the gain of the image illumination could affect the integration time and the perceptive area of the human eye, a substantial change of the signal-to-noise ratio and the required minimum scintillation would be expected.

[Forty-seven years of interest in insulin].

Abstract: While my interest in insulin has been practically continuous since its discovery, there have been periods when my attention was concentrated on choline, histamine and heparin. In the War years the subjects for research were, of course, quite different. The highlights in the development of insulin, from the chemical wiewpoint, have been its purification, crystallization, determination of structure and synthesis. Physiologists have been fascinated by studies of thelocus and mechanism of action of insulin. A great deal has been learned about the action on many different tissues and insulin has been shown to be the chief anabolic hormone. The clinical developments are mentioned only briefly since my own research interests have been exclusively experimental.

Some Tests of Night and Day Vision

Abstract: : The report introduces some tests of night and day vision which, though devised for a special purpose, are potentially useful in a much wider variety of applications. The tests are mostly of binocular visual acuity for far vision, measured either during the course of dark adaption or after adaption to various light levels has been completed. In addition, a special form recognition test has been developed to investigate the relationship between visual acuity data and the visibility of a 'real-life' shape, namely, the silhouette of a man. The test are implemented via specially developed slides to be used in a commercial vision test instrument. The latter has been adapted to provide a range of discrete nighttime and daytime light levels (through the use of neutral density filters). Unlike the slides normally provided with this instrument, those specially developd cover a wide range of contrast values. Thus, acuity may be tested over a wide range of contrasts at each of the nighttime and daytime light levels. (Author)

Use of image intensifiers for real-time multispectral viewing

Abstract: : An experimental program has investigated the practicality of synchronized rotating filter wheels at the input and output of an image intensifier to produce a field-sequential color image. Both military and commercial intensifier tubes were used. Reasonably true-color rendition was obtained, even with the limitations imposed by crude equipment and far-from- optimum filters. Fundamental limitations result in rather large energy losses and hence preclude full-color operation at very low light levels (such as starlight). At intermediate light levels, color viewing may be practical and may be valuable in enhancing target contrast. With appropriately chosen sets of input and output filters, the spectral response of camouflage detection film can be duplicated.

The spiral aftereffect: influence of stimulus size and viewing distance on the duration of illusory motion,

Abstract: : The study examined some effects of stimulus size and distance on the persistence of one type of illusory motion, viz., the spiral aftereffect (SAE). Duration of SAE was investigated with stimuli of 2, 4, 8, 12, and 16 inches in diameter. The distance between the observers and the rotating spirals was varied to produce visual angles between 1 deg. 12 min. and 18 deg. 56 min. of arc. Data indicate that the duration of illusory motion reaches peak values between approximately 2 deg. -4 deg. of visual angle. (Author)

Assessment of the broca-sulzer phenomenon via inter- and intra modality matching procedures: studies of signal-light brightness,

Abstract: : Signal lights are presented to an observer as flashes with finite duration; thus, the effect of flash duration on the apparent brightness of the signal is important. The relation of effective signal brightness to flash duration and luminance finds expression in the Broca-Sulzer phenomenon. This study was concerned with the effect of method of measuring brightness and with the effect of adaptive state of the eye on the Broca-Sulzer phenomenon. Subjects adjusted the luminance of test flashes 1 to 1000 msec. in duration to match either the loudness of a 500 msec. comparison tone (1000 Hz) or the brightness of a 500 msec. comparison flash. Comparison tone loudness were 75, 86, and 97 dB. Comparison flash luminances were 10, 100, and 1000 mL. In the light-adapted condition, a 1.5 sec. adapting flash was presented 2.5 sec. before the comparison flash. No adapting flash was presented in the dark-adapted condition. The Broca-Sulzer effect appeared only with the highest comparison stimulus intensities in both crossmodality matching and brightness matching conditions. This finding conflicts with the hypothesis that the Broca-Sulzer effect is obtained only when the procedure for measuring brightness involves a visual comparison stimulus. An interaction found between method of measuring brightness and adaptive state was also discussed. The findings are pertinent to the prediction of effective brightness of a signal since, under some conditions, apparent brightness does not increase steadily with increased duration but, rather, evidences a peaking effect. (Author)