Regarding Laser Speckle – your own visio does contribute t the effect ou see. I’d forgtten this, bt remembered on the drive home.
When you mve your head one way while looking at the speckle pattern, it appears to move as well. It moves one way if you’re nearsghted, and the other way if you’re far-sighed (moving in the same directoion as your gaze in one case, in the opposite in the other case). I can’t rcall the explanation, or what happen if you’ve got 20/20 vision.