Abstract

We previously proposed a novel technology with which the images of real objects with no copyright protection could contain invisible digital watermarking, using spatially modulated illumination. In this “optical watermarking” technology, we used orthogonal transforms, such as a discrete cosine transform (DCT) or a Walsh-Hadamard transform (WHT), to produce watermarked images, where 1-b binary information was embedded into each pixel block. In this paper, we propose an optimal condition for a technique of robust optical watermarking that varies the size of pixel blocks by using a trade-off in the efficiency of embedded watermarking. We conducted experiments where ${\hbox{4}}\times{\hbox{4}}$, ${\hbox{8}}\times{\hbox{8}}$, and ${\hbox{16}}\times{\hbox{16}}$ pixels were used in one block. A detection accuracy of 100% was obtained by using a block with ${\hbox{16}}\times{\hbox{16}}$ pixels when embedded watermarking was extremely weak, although the accuracy did not necessarily reach 100% by using blocks with ${\hbox{4}}\times{\hbox{4}}$ or ${\hbox{8}}\times{\hbox{8}}$ pixels under the same embedding conditions. We also examined the effectiveness of using a Haar discrete wavelet transform (Haar DWT) as an orthogonal transform under the same experimental condition, and the results showed that the accuracy of detection was slightly inferior to DCT and WHT under very weak embedding conditions. The results from experiments revealed the effectiveness of our new proposal.

© 2012 IEEE

PDF Article

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription