title: Content-addressable holographic data storage system for invariant pattern recognition of gray-scale images.
abstract: Conventionally a holographic data storage system uses binary digital data as the input pages. We propose and demonstrate the use of a holographic data storage system for the purpose of invariant pattern recognition of gray-scale images. To improve the correlation accuracy for gray-scale images, we present a coding technique, phase Fourier transform (phase-FT) coding, to code a gray-scale image into a random and balanced digital binary image. In addition to the fact that a digital data page is obtained for incorporation into a holographic data storage system, this phase-FT coded image produces dc-free homogenized Fourier spectrum. This coded image can also be treated as an image for further processing, such as synthesis of distortion-invariant filters for invariant pattern recognition. A space-domain synthetic discriminant function (SDF) filter has been synthesized using these phase-FT coded images for rotation-invariant pattern recognition. Both simulation and experimental results are presented. The results show good correlation accuracy in comparison to correlation results obtained for SDF filter synthesized using the original gray-scale images themselves.
authors.affiliation: Photonics Group, Department of Physics, Indian Institute of Technology Delhi, New Delhi-16, India. joby@physics.iitd.ac.in
authors.forename: Joby
authors.initials: J
authors.lastname: Joseph
authors.forename: Alpana
authors.initials: A
authors.lastname: Bhagatji
authors.forename: Kehar
authors.initials: K
authors.lastname: Singh