Proposal of multi-value cell structure for high-density two-dimensional codes and evaluation of readability using smartphones

In the now-popular two-dimensional code, bits are expressed using white and two black colors in the cell, which forms the element. However, such codes do not have confidentiality. Since confidentiality may be needed according to the use, a large-capacity and high-density two-dimensional code with compatibility and confidentiality can be realized by adding a secrecy part in addition to the existing part. To enlarge capacity, it is necessary to form a cell using many bits, which requires a multicolor method. The read verification of the compatible area and the additional area was carried out using a smartphone, and the code was verified to confirm its practicality.