Perhaps you've been in a situation where you noticed that your reflection in a window looked like it was actually standing amongst the items that were visible through that window. Now, scientists at the University of Bristol have taken that phenomenon and incorporated it into an experimental new interactive display. Among other things, it lets users select objects seen through a pane of glass, using the reflection of their finger on that glass.
When you view an item's reflection in a mirror, that reflection appears to be sitting in an actual three-dimensional physical location on the other side of the glass. That location remains consistent for that item, independent of the angle from which the mirror is being viewed – if you move over and look at the mirror from off to one side, for instance, the "location" of the item's reflection won't change from your perspective. The U Bristol display utilizes that principle.
It incorporates semi-transparent glass that both acts as a mirror, and allows the viewer to see objects located on the other side of it – such a setup is known as a "combining glass." Sensors track both the location of the user's hand relative to the viewing side of the glass, along with a displayed object's location relative to the opposite side of the glass. By combining that data, it can ascertain where the reflection of the hand will appear in relation to the object.
This means that the system can tell (for example) when the reflection of a user's index finger is "touching" a museum artifact in a display case. Using an overhead-mounted projector, it can then spotlight that object, or project a pop-up box that contains information.
If the projector is facing towards the user, then it can project content directly onto their hand or something that they're holding, which they'll be able to view in the reflection. For example, they can hold up a piece of paper and pass its reflection "through" an item on the other side of the glass. As they do so, the projector will project a corresponding view of the inside of the item, onto that paper.
Additionally, the system is able to work in two directions at once. This means that users could be located on both sides of a combining glass, collaboratively working with projected data, or with an object located on either side.
Along with its possible use in places like museums, the Bristol team believes that the technology could also have applications in things like art installations, medical imaging and airport security. It could even be used in storefront windows, allowing after-hours shoppers to select items of clothing, see them projected onto themselves, then purchase them and arrange for home delivery.
The system can be seen in use, in the video below.