Barcode imaging using a light field camera

Abstract

We present a method to capture sharp barcode images, using a microlens-based light field camera. Relative to standard barcode readers, which typically use fixed-focus cameras in order to reduce mechanical complexity and shutter lag, employing a light field camera significantly increases the scanner’s depth of field. However, the increased computational complexity that comes with software-based focusing is a major limitation on these approaches. Whereas traditional light field rendering involves time-consuming steps intended to produce a focus stack in which all objects appear sharply-focused, a scanner only needs to produce an image of the barcode region that falls within the decoder’s inherent robustness to defocus. With this in mind, we speed up image processing by segmenting the barcode region before refocus is applied. We then estimate the barcode’s depth directly from the raw sensor image, using a lookup table characterizing a relationship between depth and the code’s spatial frequency. Real image experiments with the Lytro camera illustrate that our system can produce a decodable image with a fraction of the computational complexity.