Tracking shopping carts using mobile cameras viewing ceiling-mounted retro-reflective bar codes

"Shopping Buddy" is a wireless multi-media terminal that clips onto a conventional shopping cart that allows customers to scan items as they shop, providing self-checkout at the cart, Cart tracking technology enables delivery of real-time location-based content, including "you are here" navigation map, coupons and recipes. A new cart tracking technology is developed using a cart-mounted camera viewing ceiling-mounted retro-reflective bar codes. Tag acquisition and decoding is designed to run on an inexpensive microprocessor to meet stringent system cost, size and power constraints. The image is quantized and compressed "on-the-fly" to minimize memory and processing requirements. Field testing in a retail store demonstrates system robustness under a variety of lighting conditions, delivering 5 cm spatial resolution accuracy. © 2006 IEEE.