Anstis Stuart
Department of Psychology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0109, USA.
Vision Res. 2002 Oct;42(22):2485-91. doi: 10.1016/s0042-6989(02)00267-5.
In the Purkinje shift, the dark adapted eye becomes more sensitive to blue than to red as the retinal rods take over from the cones. A striking demonstration of the Purkinje shift, suitable for classroom use, is described in which a small change in viewing distance can reverse the perceived direction of a rotating annulus. We measured this shift with a minimum-motion stimulus (Anstis & Cavanagh, Color Vision: Physiology & Psychophysics, Academic Press, London, 1983) that converts apparent lightness of blue versus red into apparent motion. We filled an iso-eccentric annulus with radial red/blue sectors, and arranged that if the blue sectors looked darker (lighter) than the red sectors, the annulus would appear to rotate to the left (right). At equiluminance the motion appeared to vanish. Our observers established these motion null points while viewing the pattern at various retinal eccentricities through various neutral density filters.
The luminous efficiency of blue (relative to red) increased linearly with eccentricity at all adaptation levels, and the more the dark-adaptation, the steeper the slope of the eccentricity function. Thus blue sensitivity was a linear function of eccentricity and an exponential function of filter factor. Blue sensitivity increased linearly with eccentricity, and each additional log(10) unit of dark adaptation changed the slope threefold.
在浦肯野位移中，随着视网膜视杆细胞取代视锥细胞，暗适应的眼睛对蓝光比红光更敏感。本文描述了一种适合课堂使用的浦肯野位移的显著演示，其中观察距离的微小变化可以逆转旋转圆环的感知方向。我们使用一种最小运动刺激（安斯蒂斯和卡瓦纳，《颜色视觉：生理学与心理物理学》，学术出版社，伦敦，1983年）来测量这种位移，该刺激将蓝光与红光的表观亮度转换为表观运动。我们用径向红/蓝扇区填充一个等偏心圆环，并设置如果蓝色扇区看起来比红色扇区暗（亮），圆环将看起来向左（右）旋转。在等亮度时，运动似乎消失。我们的观察者在通过各种中性密度滤光片在不同视网膜偏心度下观察图案时确定了这些运动零点。
在所有适应水平下，蓝光（相对于红光）的发光效率随偏心度呈线性增加，暗适应程度越高，偏心度函数的斜率越陡。因此，蓝光敏感度是偏心度的线性函数和滤光系数的指数函数。蓝光敏感度随偏心度线性增加，每增加一个以10为底的对数单位的暗适应，斜率变化三倍。
