A sheet of glass can distinguish between drawings of 0 to 9, because light waves reflected off the images are bent differently as they pass through the glass
Source:
https://www.newscientist.com/article/2208975-ai-made-from-a-sheet-of-glass-can-recognise-numbers-just-by-looking/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home