CONTRAST SENSITIVITY AS A FUNCTION OF SPATIAL-FREQUENCY, VIEWING DISTANCE AND ECCENTRICITY WITH AND WITHOUT SPATIAL NOISE
CONTRAST SENSITIVITY AS A FUNCTION OF SPATIAL-FREQUENCY, VIEWING DISTANCE AND ECCENTRICITY WITH AND WITHOUT SPATIAL NOISE
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DOI：
10.1016/0042-6989(92)90179-m
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发表时间：
1992-04-01
期刊：
影响因子：
1.8
通讯作者：
NASANEN, R
中科院分区：
文献类型：
--
作者：
ROVAMO, J;FRANSSILA, R;NASANEN, R
利用计算机图形学和两种可选的强制选择方法，我们测量了具有和不具有附加的二维白色空间噪声的光栅的阈值对比度作为观看距离、空间频率和偏心的函数。我们的实验表明，在空间噪声中，只要有噪声的对比敏感度低于没有噪声的对比敏感度，对比敏感度就不受观察距离的影响。随着空间频率(F)的增加，为了保持相对栅格尺寸(AF2)不变，栅格面积(A)减小。因此，在所有空间频率下，测试光栅具有相同数量的细节和轮廓。为了保持物理信噪比恒定，噪声谱密度与栅格面积成正比。因此，空间频率的增加伴随着栅格面积和噪声谱密度的减少，类似于由相应的观看距离增加所产生的减少。一致地，空间噪声中的对比度检测被发现与空间频率无关，只要有噪声时的对比敏感度低于没有噪声时的对比度灵敏度。偏心率增加对视觉性能的影响可以通过减小观看距离(M缩放)来补偿。因此，在没有M缩放的情况下，增加偏心率的效果与增加观看距离的效果相似。一致地，我们发现空间噪声中的对比敏感度与偏心率无关，只要有噪声的对比敏感度低于没有噪声时的对比敏感度。
Using computer graphics and a two-alternative forced-choice method we measured threshold contrast as a function of viewing distance, spatial frequency, and eccentricity for gratings with and without added, white two-dimensional spatial noise. Our experiments showed that in spatial noise contrast sensitivity was independent of viewing distance as long as contrast sensitivity was lower with noise than without. With increasing spatial frequency (f) the grating area (A) was reduced in order to keep the relative grating size (Af2) constant. At all spatial frequencies the test gratings thus had the same amount of detail and contour. Noise spectral density was reduced in direct proportion to grating area in order to keep the physical signal-to-noise ratio constant. An increase in spatial frequency was thus accompanied with reductions in grating area and noise spectral density similar to those produced by a corresponding increase in viewing distance. In agreement, contrast detection in spatial noise was found to be independent of spatial frequency as long as contrast sensitivity was lower with noise than without. The effect of increasing eccentricity on visual performance can be compensated for by reducing the viewing distance (M-scaling). Hence, without M-scaling the effect of increasing eccentricity is similar to that of increasing viewing distance. In agreement, we found that contrast sensitivity in spatial noise was independent of eccentricity as long as contrast sensitivity was lower with noise than without.