KEYWORDS: Holograms, Receivers, Digital holography, 3D image processing, 3D acquisition, 3D modeling, Holography, Phase shifting, Charge-coupled devices, Diffraction
We propose a statistical approach to detect a three-dimensional object using digital holography. The proposed algorithm uses the statistical properties of the speckle noise to find a probabilistic model for the likelihood function of the presence of the three-dimensional object in the scene. Phase shifting holography is used to generate the optical hologram of the 3D object and inverse Fresnel diffraction is used to reconstruct the 3D object. The complex wave generated from the inverse Fresnel integral is used as an input to the proposed algorithm. We show that the reconstructed 3D scene can be modeled as an object buried in a background complex Gaussian noise and the object is multiplied by a complex Gaussian noise. Analytical analysis and simulations show that the proposed technique is able detect the three dimensional coordinates of the distorted target object.
We present a 2-D barcode technique that can be used to authenticate documents. The proposed system holds much more information than one-dimensional barcode. It is robust against different types of noises and distortions. We use double phase encoding to encode information into the 2-D binary barcode. As a result, the technique is secure against unauthorized detection. We present analysis for the system performance using the statistical properties of double-phase encoding. The algorithm is tested under several types of noise and distortions, for example, additive noise, geometric distortion, fading, scratches, and occlusion. We compare the performance of amplitude-based double phase encoding and fully phase double phase encoding with that of an ordinary 2-D barcode with error-correcting code. Computer simulations and optical experiments are presented to test the robustness of the proposed method.
KEYWORDS: Digital watermarking, Holograms, Digital holography, 3D image processing, 3D image reconstruction, Image restoration, Digital imaging, Computer programming, Charge-coupled devices, Digital image correlation
We present an optical method for information watermarking of 3D objects using digital holography and authenticating the hidden image. A hidden image is embedded using double phase encoding in a phase shift digital hologram of the 3D object. The watermarked hologram is decoded to reconstruct the hidden image and the 3D object. We use either the entire hologram or a part of it to decode the hidden image. The recovered hidden image is authenticated using non-linear correlation. Experiments are presented to illustrate the ability to recover both the 3D object and the decoded hidden image.
The performance of nonlinear joint transform correlators (JTCs) are experimentally tested with respect to in-plane and out-of-plane rotation distortions. Optical experiments are presented for both linear and nonlinear joint transform correlators. The robustness of these systems to rotation distortions is investigated. The results show that nonlinear JTCs perform similarly to linear JTCs in the presence of out- of-plane rotation distortions, but that nonlinear JTCs are more sensitive than linear JTCs to in-plane rotation distortions. However, it is well known that nonlinear JTCs have the desirable properties of illumination tolerance and discrimination sensitivity. To reduce the sensitivity of nonlinear JTCs to in-plane rotation distortions, the nonlinear joint power spectrum is multiplied by a circularly symmetric Gaussian function. This is equivalent to applying a Gaussian filter to the nonlinear JTC output. The experimental results show that using such a Gaussian filter provides nonlinear JTCs with similar in-plane rotation tolerance to that of linear JTCs.
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