Dollar bill visuals

When I tripped on LSD last, I saw a pattern. It just turned out that the pattern was the same pattern that was in the background of the US dollar bill. My trip buddy saw it, too. When I was wondering what it was, they were the one who pointed out that it was the pattern on the dollar bill. Is this normal? What could have caused this? Do you guys have any similar experiences? I've googled dollar patterns while trippi g and found nothing. Any insight would be appreciated!