Evan Schuman's StorefrontBacktalk

“Intentionally taking photos with the camera out of focus is somewhat unusual,” the document said. “The size of viewable barcode pattern is proportional to the camera aperture size. A relatively large lens aperture is required to see a reasonable part of the Bokode pattern. This explains why the Bokode pattern is effectively ‘invisible’ to the human eye, which has a relatively small pupil size of 2mm to 6mm.”

“With the Bokode’s optical setup, the information of the barcode is embedded in the angular and not in the spatial dimension. By throwing the camera out of focus, we capture this angular information in the defocus blur formed on the sensor,” the document said. “The pinhole is blurred, but the information encoded in the bokeh is sharp. This also means, for the same sized barcode we can potentially pack 1000 times more bits in both dimension, i.e. million times more data.”

This potentially means that the image can not only display a lot more total information, but it can show different information if the camera looks at the image differently.

“The requirements and constraints for the Bokode pattern design are quite different from a traditional 2D barcode. Unlike a traditional barcode, the camera only images a small region of the entire Bokode pattern at a time,” the MIT paper said. “This visible Bokode region depends on the distance of the camera from the Bokode and the relative view angle.”

“Our Bokode pattern consists of an array of tiled data matrices such that at least one tile is always imaged by the camera within the working angle and distance range. Instead of simply repeating the same information in each Data Matrix, we vary the data bits across the tiles so that the camera obtains view dependent information, something not possible with traditional barcodes.”

The report also raised the possibility of using bokodes in large signage. “With Bokodes in street billboards, the human eye will see the billboard information but an out of focus camera will capture the Data Matrix indicating a website link.” The full report is available at MIT’s site.