The demands to connect between paper media and digital worlds are increasing, and an "electronic clipping system", which overprints an invisible barcode into analog media, is an example of connecting these worlds. However, depending on the combination of the target paper media, the ink used in the media, and the invisible ink, we cannot always correctly decode the information. In this paper, we introduce a new 2D barcode encoding and decoding method which overcomes such problems. In our method, we divide the 2D code data area into several blocks, and do not use for encoding the blocks where many of the bits in the block have high probabilities of bit errors. The decoder determines the skipped blocks from the image itself. The experimental results proved that our method greatly improved the probability of correct information decoding for the invisible barcode.

The Internet, digital television, and similar technologies have accelerated the speed of digitalization. Nevertheless, paper media forms, such as newspapers and magazines, still have large market shares, and the authors believe that these two worlds, digital and analog, will coexist even in the future, with their own market areas. However, the demands to connect between these two worlds are increasing, and barcodes and watermarking are examples of technologies used to connect them. However, a barcode occupies space and disrupts the layout of an article, and watermarking has limited capacity for embedding data.In this paper, we propose an "electronic clipping system with invisible barcodes", which connects the analog and digital worlds, addressing these problems. In this system, we overprint invisible 2D barcodes on printed articles using invisible ink, then take pictures of them using a camera equipped with a special LED (Light Emitting Diode)that the invisible ink responds to, decode the encoded data of the 2D barcode after the image is processed, and extract the information. We developed a code extraction system which can extract the information from invisible 2D barcodes even if the barcodes are overprinted on the articles in media such as newspapers, and even if the article is in color. We also made a prototype cell phone which includes both the barcode extraction code and the LED, and confirmed that we can correctly extract the information from the pictures taken by the phone.