西元1230年–1235年:羅伯特·格羅斯泰斯特描述光的應用:在他的著作De Iride提到, "...將小物體放在一個距離上會出現我們所期望的任何大小,在這個令人難以置信的距離上有可能閱讀最小的字母..." ("Haec namque pars Perspectivae perfecte cognita ostendit nobis modum, quo res longissime distantes faciamus apparere propinquissime positas et quo res magnas propinquas faciamus apparere brevissimas et quo res longe positas parvas faciamus apparere quantum volumus magnas, ita ut possible sit nobis ex incredibili distantia litteras minimas legere, aut arenam, aut granum, aut gramina, aut quaevis minuta numerare.")[10]
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