At present, the progress in optics is associated with wide use of diffractive optical elements (DOEs). In this paper we present a DOE design method, which not use computer iterative methods. Starting from the knowledge of the expression of the propagated field on image plane, we use simple formulas to obtain the entire information necessary to characterize the desired DOE. The DOE designed with the proposed method can equate an arbitrary complex amplitude transmission T(r) and has higher imaging accuracy than other DOEs. Even if it is possible studying any level combination, the aim of this paper is to summarize the results of simulation experiments which were carried out only to test the binary level diffractive optical elements (DOEs).
When we buy an artwork object a certificate of authenticity contain specific details about the artwork. Unfortunately,
these certificates are often exchanged between similar artworks: the same document is supplied by the seller to certificate
the originality. In this way the buyer will have a copy of an original certificate to attest that the "not original artwork" is
an original one. A solution for this problem would be to insert a system that links together the certificate and a specific
artwork. To do this it is necessary, for a single artwork, to find unique, unrepeatable, and unchangeable characteristics. In
this paper we propose a new lithography certification based on the color spots distribution, which compose the
Due to the high resolution acquisition media available today, it is possible using analysis method typical of speckle
metrology. In particular, in verification phase it is only necessary acquiring the same portion of lithography, extracting
the verification information, using the private key to obtain the same information from the certificate and confronting the
two information using a comparison threshold. Due to the possible rotation and translation it is applied image correlation
solutions, used in speckle metrology, to determine translation and rotation error and correct allow to verifying extracted
and acquired images in the best situation, for granting correct originality verification.
In order to measure small diffusion coefficients of miscible fluids, in this paper we propose an improved version of digital projection moiré. The system uses a simple and flexible fringe generator realized by means of a video projector with a modification of projection optic. The fringe patterns are projected on the bottom of a ground glass plate. The phase object (diffusion cell) is placed in front of the ground glass (in other words, in front of the fringe pattern), which is imaged by a digital video camera. Grating patterns, during the evolution of diffusion phenomena, are captured by a CCD camera and stored in a computer at different times. With the aid of signal demodulating techniques, the images are processed to obtain the diffusion coefficients. The theoretical aspects of the method are presented and the relationship between the fringe shift and the diffusion coefficient is derived. Furthermore, we report some experiments conducted for demonstrating the usefulness of the system.
The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. This paper presents the potentiality of the 3D micro-topography to resolve the writing order of signatures (if partially superimposed), to detect the tampering of manuscripts (if the added inscription superimposes itself on parts already written), to analyze pressure variation, and to identify strokes in handwritten. The system used, in this paper for creating 3D micro-topography, is based on conoscopic holography. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (which is usual on the surface of the handwritten document). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft do not be physically or chemically modified, allowing the possibility of multi-analysis in different time, also in case of forensic analysis with the necessity to preserving the original sample. The experiments performed with line crossings data base show that the proposed method is able of "positive identification" of writing sequence in the majority of the tests. When we have not had a positive identification, the result has been "inconclusive". The proposed technique, if correctly used, does not supply "false positive" or "probable" identifications. The possible results are only: "positive identification" and "inconclusive".
KEYWORDS: Image compression, 3D image reconstruction, Digital holography, Image processing, Digital watermarking, Computer programming, Medical imaging, Computer generated holography, Digital imaging, Image filtering
In this paper we propose a fragile marking system based on Computer Generated Hologram coding techniques, which is able to detect malicious tampering while tolerating some incidental distortions. A fragile watermark is a mark that is readily altered or destroyed when the host image is modified through a linear or nonlinear transformation. A fragile watermark monitors the integrity of the content of the image but not its numerical representation. Therefore the watermark is designed so that the integrity is proven if the content of the image has not been tampered. Since digital images can be altered or manipulated with ease, the ability to detect changes to digital images is very important for many applications such as news reporting, medical archiving, or legal usages. The proposed technique could be applied to Color Images as well as to Gray Scale ones. Using Computer Generated Hologram watermarking, the embedded mark could be easily recovered by means of a Fourier Transform. Due to this fact host image can be tampered and watermarked with the same holographic pattern. To avoid this possibility we have introduced an encryption method using a asymmetric Cryptography. The proposed schema is based on the knowledge of original mark from the Authentication
In this article is presented an application of synthetic hologram as fragile watermarking. The proposed technique is a frequency domain watermarking, based on computer generated hologram. Our technique, named Fragile Synthetic Holographic Watermarking (F-SHW), is suitable for ID Cart image authentication. In this paper, the F-SHW is applied to Color Images as well as to Gray Scale ones. The proposed schema is based on the knowledge of original mark from the Authentication Entity, for applying Image Correlation between this and the extracted one. Due to the application the mark is encrypted using a private key (symmetric schema).