平方毫米的用法和樣例：
例句
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光度視網(wǎng)膜亮度單位，相當于每平方米有一燭光亮度的表面，通過(guò)一平方毫米的瞳孔區域，到達視網(wǎng)膜的光線(xiàn)數量
A unit of retinal illumination, equal to the amount of light that reaches the retina through 1 square millimeter of pupil area from a surface having a brightness of 1 candela per square meter.
