返回Google圖書搜尋

Effects of Light Transmittance and Scatter by Windshields on Nighttime Visual Performance

出版	University of Michigan Transportation Research Institute, 1992
URL	http://books.google.com.hk/books?id=yqWxSgAACAAJ&hl=&source=gbs_api

註釋A laboratory study investigated the effects on night vision of windshield transmittance and light-scattering properties in relation to the effects of reduced contrast, glare, night myopia, and age. Three groups of subjects included: (1) ten elder drivers, (2) ten younger drivers who were susceptible to low levels of night myopia, and (3) ten younger drivers who were not susceptible to night myopia. Visual acuity of all subjects was measured for high- and low-contrast targets viewed through five windshields with and without glare that simulated opposing low-beam headlights at 50 m distance. To assess night myopia, visual accommodation of younger subjects was measured objectively under each of the ten windshiled-by-glare conditions while they viewed four realistic low-luminance targets. The transmittance of three clean windshields, with different tints and rake angles (ranging from 45° to 75° from the vertical) varied from 0.86 to 0.43. Two additional conditions were created by mounting a dirty windshield at rake angles of 45° and 75°, which produced light transmittances similar to two of the clean windshileds but now with a higher degree of light scatter. The main results are as follows: (1) Reduced transmittance of clean glass elevated low-contrast resolution thresholds by 0.09 log units, but had no effect on high-contrast thresholds. (2) Light-scatter of dirty windshields elevated low-contrast thresholds to unmeasurable leves. (3) Glare elevated low-contrast threshold by 0.18 log units. (4) Resolution thresholds were 0.28 log units higher for low-contrast than for high-contrast targets. (5) Thresholds for low-contrast targets were 0.31 log units higher for elder than for younger subjets. (6) Tests of accommodation showed significant increases of night myopia with glare and reduced target luminance, as well as a tendency toward greater night myopia for higher luminance targets with the dirty windshileds as compared with the clean windshield...