神经对比敏感度的亮度变化机制研究

Luminance Effects on Neural Contrast Sensitivity Function at Photopic Level

研究了明视觉下亮度变化对神经对比敏感度函数(NCSF)的影响。分别测量人眼的对比敏感度函数(CSF)和调制传递函数(MTF),而后通过计算的方法获得白光的NCSF。运用这种方法对4只人眼进行白光(15,210和310cd/m2)下的NCSF测定。测试结果表明:白光的NCSF均随着亮度的增加有较大幅度的提高,并且曲线向着高空间频率方向移动,提高的幅度和移动的大小存在个体上的差异。CSF的变化趋势类似于NCSF的变化趋势,但在亮度的影响下,CSF的相对增长幅度要高于NCSF的相对增长幅度,这种情形在高频部分尤为突出。由于NCSF反映的是排除了眼屈光系统的从视网膜到大脑的视觉特性,因此NCSF随亮度的变化才是视觉的神经系统对亮度敏感特性的客观反映。

The influence of the luminance at photopic level on the neural contrast sensitivity function（NCSF） of visual system is studied.The contrast sensitivity function（CSF） of the visual system and the modulation transfer function（MTF） of the eye′s optical system are firstly measured.Then the NCSF is gotten through the calculation method.NCSFs of four individual eyes are respectively determined in the cases of white light（with the luminance of 15,210 and 310 cd/m2）.The results show that,the NCSF of white light mounts up considerably and the curves shift toward higher spatial frequency as the luminance increases.However,the change of NCSF is somehow different from individual to individual.With the increase of luminance,the variation tendency of the CSF is similar to that of the NCSF,while the gain is much larger than that of the NCSF,especially in the region of higher spatial frequency.It is the NCSF,rather than CSF,that reflects the luminance sensitivity in the retina-brain neural system,because the influence of the eye′s optical system is excluded.