I thought I'd pass this on.  It's a moire fringe technique to check for front/back focus.  Pull the 1000x1000 image up on your screen, center your camera on a tripod looking at the screen, and adjust your fine tune until the pattern looks correct.  Front/back focus will look weird, and if you're high/low/sideways you'll get odd patterns showing you to adjust the centering of your camera vs display.

http://www.northlight-images.co.uk/camera-af-microadjustment/#AF_test_image

Correct focus and then front focus:

Here I was thinking you took those shots and wondering how the sun could possibly be lighting up those curtains.

But I'll have to try this out.

Looks interesting.  I've always used the focus ramp test.  At the fastest aperture it's pretty darned effective.