Spatial frequency, phase, and the contrast of natural images
Spatial frequency, phase, and the contrast of natural images
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DOI：
10.1364/josaa.19.001096
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发表时间：
2002-06-01
影响因子：
1.9
通讯作者：
Makous, W
中科院分区：
文献类型：
--
作者：
Bex, PJ;Makous, W
我们检查了对比敏感度和阈上明显对比度与自然图像。图像的单个倍频程内的空间频率分量被去除（陷波滤波），它们的相位被随机化，或者图像的极性被反转。在迈克尔逊对比度、均方根（RMS）对比度和限带对比度中，RMS对比度是最好的可检测性指标。负像的明显对比度低于正像。对比度检测阈值显示陷波滤波和相位随机化后的空间频率依赖性升高。空间频率调谐函数的峰值约为0.5-2个周期/度（c/deg）。超阈值对比度匹配函数也显示了陷波滤波和相位随机化图像的空间频率依赖性对比度损失。空间频率调谐函数的峰值约为1-3 c/deg。相位随机化和陷波滤波对对比敏感度的影响之间没有可检测到的差异。我们认为，这些观察结果是一致的，在空间频率通道内的活动所造成的高阶相位结构的自然图像，是负责的边缘和镜面反射的存在下的变化。(C)2002年美国光学学会。
We examined contrast sensitivity and suprathreshold apparent contrast with natural images. The spatial-frequency components within single octaves of the images were removed (notch filtered), their phases were randomized, or the polarity of the images was inverted. Of Michelson contrast, root-mean-square (RMS) contrast, and band-limited contrast, RMS contrast was the best index of detectability. Negative images had lower apparent contrast than their positives. Contrast detection thresholds showed spatial-frequency-dependent elevation following both notch filtering and phase randomization. The peak of the spatial-frequency tuning function was approximately 0.5-2 cycles per degree (c/deg). Suprathreshold contrast matching functions also showed spatial-frequency-dependent contrast loss for both notch-filtered and phase-randomized images. The peak of the spatial-frequency tuning function was approximately 1-3 c/deg. There was no detectable difference between the effects of phase randomization and notch filtering on contrast sensitivity. We argue that these observations are consistent with changes in the activity within spatial-frequency channels caused by the higher-order phase structure of natural images that is responsible for the presence of edges and specularities. (C) 2002 Optical Society of America.