To bar code or to bokode?

The ubiquitous bar codes found on product packaging provide information to the scanner at the checkout counter, but that’s about all they do. Now there is a very tiny, very powerful alternative on the horizon.

Researchers at the Media Lab have come up with a new kind of very tiny bar code that could provide a variety of useful information to shoppers as they scan the shelves - and could even lead to new devices for classroom presentations, business meetings, video games or motion-capture systems.

The new system, called Bokode, is based on a new way of encoding visual information, explains Media Lab Associate Professor Ramesh Raskar, who leads the laboratory’s Camera Culture group. Until now, there have been three approaches to communicating data optically: through ordinary imaging (using two-dimensional space), through temporal variations such as a flashing light or moving image (using the time dimension), or through variations in the wavelength of light (used in fibre-optic systems to provide multiple channels of information simultaneously through a single fibre).

But the new system uses a whole new approach, encoding data in the angular dimension: rays of light coming from the new tags vary in brightness depending on the angle at which they emerge. “Almost no one seems to have used this method of encoding information,” Raskar says. “There have been three ways to encode information optically, and now we have a new one.”

The tiny labels are just 3 mm across - about the size of the @ symbol on a typical computer keyboard. Yet they can contain far more information than an ordinary bar code: thousands of bits. Currently, they require a lens and a built-in LED light source, but future versions could be made reflective, similar to the holographic images now frequently found on credit cards, which would be much cheaper and more unobtrusive.

“We’re trying to make it nearly invisible, but at the same time easy to read with a standard camera, even a mobile phone camera,” Mohan says.

One of the advantages of the new labels is that unlike today’s bar codes, they can be ‘read’ from a distance - up to a few metres away. In addition, unlike the laser scanners required to read today’s labels, these can be read using any standard digital camera, such as those now built in to about a billion mobile phones around the world.

The name Bokode comes from the Japanese photography term bokeh, which refers to the round blob produced in an out-of-focus image of a light source. The Bokode system uses an out-of-focus camera - which allows the angle-encoded information to emerge from the resulting blurred spot - to record the encoded information from the tiny tag. But in addition to being readable by any ordinary camera (with the focus set to infinity), it can also be read directly by eye, simply by getting very close (less than 2.5 cm away) to the tag.

As a replacement for conventional bar codes, the Bokode system could have several advantages, Mohan says. It could provide far more information (such as the complete nutrition label from a food product), be readable from a distance by a shopper scanning the supermarket shelves and allow easy product comparisons because several items near each other on the shelves could all be scanned at once.

In addition to conventional bar code applications, the team envisions some new kinds of uses for the new tags. For example, the tag could be in a tiny keychain-like device held by the user, scanned by a camera in the front of a room, to allow multiple people to interact with a displayed image, for example in a classroom or a business presentation. The camera could tell the identity of each person pointing their device at the screen, as well as exactly where they each were pointing. This could allow everyone in the room to respond simultaneously to a quiz, and the teacher to know instantly how many people, and which ones, got it right - and thus know whether the group was getting the point of the lesson.

The devices could also be used for the motion-capture systems used to create video games or computer-generated movie scenes. Typically, video cameras record a person or object’s motions using coloured dots or balls attached to various parts of the person’s body. The Bokode system would allow the camera to record very precisely not just the position but the angle of each tag - with an accuracy of a tenth of a degree. This is far more accurate than any present motion capture system.

“Bokode could enable a whole new range of applications,” Raskar says. In the future, they could be used in situations such as museum exhibit labels, where the tiny codes would be unobtrusive and not detract from the art or other exhibit, but could send a whole host of background information to viewers through the use of their mobile phone cameras. Or a restaurant could make its menu available to a passer-by on the footpath.

It could also replace RFID systems in some near-field communication applications, Mohan suggested. For example, while RFIDs, now used in some ID cards, can provide a great deal of information, that information can be read from a distance, even when the card is inside a wallet. That makes them inappropriate for credit cards, for example, because the information could be retrieved by an unauthorised observer. But the Bokode could encode just as much information, but require an open line-of-sight to the card to be read, increasing security.

The prototype devices produced at the Media Lab currently cost about $5 each, most of that cost due to use of an off-the-shelf convex glass lens, but Raskar says that price could easily drop to 5 cents once they are produced even in volumes of a few hundred units.

The new concept was presented in August in New Orleans at SIGGRAPH, the leading international conference and exhibition on computer graphics and interactive techniques.

The work was supported by grants from Nokia, Samsung and the Alfred P Sloan Foundation.