I've confirmed this on two different iPads. If you turn off your iPad and then power it on (full power-off/power-on), mid-way through the boot cycle (Apple logo on black), a part of the screen flashes. It's really odd, like a collection of pixels flash white. 
Doesn't mean anything of course. I just thought it was bizarre! It's easier to see the flash in a dark room.
Doesn't mean anything of course. I just thought it was bizarre! It's easier to see the flash in a dark room.