Unperturbed by Google's inability to make smart glasses a commercial success, Apple is busy working on a wearable computer with a semi-transparent display and augmented reality of its own.

Patents recently filed by the computer giant detail a pair of smart glasses which use augmented reality to add a user interface over what the wearer can already see of the real world. This is interacted with by raising a finger and tapping on thin air.

The device builds on what Apple has already demonstrated in public with its new ARKit, a tool for developers to create augmented reality applications for use on the iPhone and iPad. Although the patent covers this, its inclusion of sketches showing how a pair of smart AR glass would work is of most interest.

The patent states: "The head-mounted display is a video-see-through, head-mounted display. It is typically not possible for the user to touch the head-mounted screen in a manner like a touchscreen. However, the camera that captures an image of the real environment may also be used to detect image positions of the user's finger in the image."

Patent language is often quite difficult to follow, as it covers every possible eventuality of a given product or feature. What this patent appears to suggest is a Google Glass-style device which would display a user interface over the top of the real-world environment already visible to the wearer. Then, by raising a finger and tapping on something in their field of vision - either real or a part of the AR interface - they can interact with the device's operating system.

Such a device could be used to show more information about points of interest ahead of the wearer, such as the opening times of a shop, the menu of a restaurant, or the history of an old building.

Also mentioned is a hybrid system where the glasses project an augmented display into the wearer's eyes, while their iPhone acts as an interactive controller, giving the user more than a pointed finger to control the AR interface.

As with any patents, it is worth stating that companies like Apple patent new innovations all the time to prevent them being copied by rivals. Just because a product is shown working in these sketches, it doesn't mean a pair of Apple smart glasses will definitely go on sale in the future. What it does show, is that Apple is indeed experimenting behind closed doors on augmented reality glasses.