The automatic identification of objects at a distance, using an applied device or tag, is a very powerful application of technology. While radio frequency identification (RFID), optical coding, and robust character recognition are all used for this, many applications are limited by factors such as size or cost of the tag, radio frequency interference, and optical challenges. In this paper, Mohan et al. introduce a creative alternative that is based on the blurring or bokeh--the out-of-focus portions of an image.

The authors describe a system that takes advantage of this effect by essentially splitting the optical system between an imager and a small lens affixed to the front of a barcode, to form a bokode--a data tag--that can be attached to an object. When the object is imaged crisply, the tag is out of focus, due to the additional lens element in front of it. This addresses the appearance of bar codes--to some extent; it should be mentioned that the out-of-focus tag would likely appear as an anomalous bright spot. When the imaging camera is defocused to the proper degree, the barcode within the bokode tag is visible and occupies a larger portion of the image than the tag area, due to defocus effects. The resulting tag image is quite readable at surprising distances--two to three meters for a small tag. Mohan et al. describe possible strategies for designing the barcode contained within the bokode tag. For example, it may be a tiled arrangement of data matrix codes that contain slightly different information; from this, the relative angle of the tag to the optic axis may be determined.

While the concept is creative, the experimental results are currently limited. There are still usability issues to be resolved. Most notably, the useful bokode tags that are currently active contain a light source that makes them undesirably large and costly. Passive bokode tags that are based on retroreflectivity lack necessary contrast at this time, although research continues. Once a good passive bokode design is in place, extensive testing across a range of distances, angles, and conditions should be conducted to confirm the usefulness of this exciting concept.

Bokodes have received extensive coverage in the popular press. While this paper describes some of the optical properties of the tag, it is not the first publication related to the concept.