scopophile

Etymology
From + English.

Noun

 * 1)  One with a sexual dependency on openly observing genitalia and sexual acts, as opposed to a voyeur, who watches in secret.
 * Caligula was a scopophile who was not ashamed of his irregular desire to watch others making love, while Mr. Hoover, as a voyeur, favored the keyhole and wiretap as methods of observation.