The United States Patent Office has published a patent from Apple, filed December 18 of last year and not yet granted, for a "sunscreen detector" that could be incorporated into the Apple Watch or the iPhone and could even include augmented reality functionality.

"Disclosed herein is a [ultraviolet-ifrared (UV-IR)] spectrometer for mobile and/or wearable devices," Patent Application 0202927, published July 19, reads. "The UV-IR spectrometer may be a sunscreen detector that is configured to identify the degree of sunscreen coverage in exposed areas of the skin of a user or subject and may provide information about regions that may be at elevated UV exposure risk. The sunscreen detector may be configured to indicate areas of skin or entire body parts where sunscreen protection is missing or inadequate. Based upon the detected sunscreen coverage, the detector may provide notifications or instructions to the user about where to apply or re-apply sunscreen, and/or how much and how often to apply sunscreen."

Sunscreen works by forming a protective layer on the skin that reflects UV radiation rather than letting the skin absorb it. In the patent, Apple is proposing a sensor that could detect the UV rays being deflected by the skin, thus guaging the effectiveness of the sunscreen. The sensor would be built into an iPhone or Watch, allowing the user to scan different areas of their skin.

"The sensor module may be located in a portable multifunction device, such as a cell phone, or a watch, including but not limited to a band of a watch," the application says. "The controller may be configured to overlay a graphic corresponding to the sensor field onto a camera image."

The latter point suggests some kind of augmented reality overlay that would visually indicate where sunscreen needs to be re-applied. The patent also talks about using push notifications to remind or instruct the user to reapply.

Apple files a lot of patents, and Apple filing a patent doesn't necessarily mean it's actively developing a product or that that product will ever see the light of day (no pun intended). All that said, it's always interesting to see the company investigating new directions, especially when it comes to health sensors. 

This space hasn't seen much high-profile innovation: In 2016, wearable patch company MC10 partnered with L'Oreal to develop a UV-detecting patch, and another Cambridge, Massachusetts-based company, GoodLux, makes a sun-detecting clip-on wearable called SunSprite. That company announced today plans for a new version of the device out this fall.