Do you really think this is a photo of your palm they're storing?

No doubt there are 3D scanners (to map the elevation of your palms, the depth of the lines, etc.), infrared imaging and a slew of other minor sensors. To make this fast, they need to effectively correlate enough of the data to identify you without relying solely on a single thing.

We already know there are solid theoretical basis for rebuilding 3d spaces from photos. Infrared imaging doesn't dramatically get different data from a regular camera except maybe picking up your veins a bit more clearly.

There aren't a bunch of other sensors available.. probably some heat/temperature just to make sure it's a real palm but that's not for uniqueness.

The photo of your palms out doesn't include an image of your veins because it wasn't taken with an infrared camera.

“ One reason was that palm recognition is considered more private than some biometric alternatives because you can’t determine a person’s identity by looking at an image of their palm.”

Wow. Never thought of that. But is it easy to reconstruct veins?