Optical subroutine
The optical subroutine was a function of the EMH that allowed it to perceive objects visually.

In 2376, The Doctor dismissed Tom Paris's suggestion that he not blink while Neelix performed a sleight-of-hand magic trick, asserting, "You have to get up pretty early in the morning to fool my optical subroutines." ()

de: Optische Subroutine
Holographic technology
Subroutines