Apple has been granted a couple of patents (here and there) on linking two devices using a moving graphic on the display of a watch. A camera on the device which is being paired reads an “invisible” image.
The technology apes the 1994 Timex Datalink which employed flashing bars on the CRT of a computer running Windows 95 to send data to a watch.
The new Apple patent uses limitations in human vision to tinker with the colours, but crucially not the luminance of the image so that the camera can see the codes while a person cannot.
The patent claim says:
The present disclosure is directed to using an optical label, such as a Quick Response (QR) code for transmitting information between computing devices. More specifically, the present disclosure is directed to generating and displaying a label on one computing device that is invisible or otherwise not perceptible by a human eye but is visible to a second computing device that is to receive information from the first computing device.
The method is to take two colours which look pretty much the same to a human eye and flash between them so fast the eye cannot see them changing. The receiving device looks at the pattern and the movement of the changing dots and decodes that as data.
Taking your watch off to wave it at the screen of your computer is perhaps more useful as a way to get some relief from a painful rash. Several Apple Watch owners have complained that their skin has been irritated by the watch straps on Sport models. The fruity firm has jumped to the usual defence and issued technical advice on how to wear a watch. It employs the “goldilocks principle” of too loose, too tight and just right.
Still Apple watch users might not have to put up with their annoying sport band watch strap for much longer because Cupertino has also released developer guidelines(PDF) for how to make a watch strap. The rules specifically prohibit interference with the heart rate sensor, Apple Pay NFC or adding magnetic charging. They don’t say that straps can’t irritate the skin of users.
So - that’s alright then. ®