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Acoustic, radio frequency (RF) and optical waves systems are the technologies that are used to carry out underwater wireless communications. In scientific, military and industrial sectors, the development of robust and efficient submarine wireless communication links is of enormous interest. To achieve secure short-range wireless communications, the Underwater Optical Wireless Communication (UOWC), which uses the 450-550 nm spectral range of the electromagnetic spectrum, is a good technology. Recently, UOWC applications have been proposed for environmental monitoring, offshore exploration, and military operations. There are many review articles published on this topic. However, research in this field evolves rapidly as does existing literature. The article deals with current and potentially available UWOC technologies in the near future. It is aimed at those who want to undertake studies in this field. Obviously, this paper does not attempt to cover every single aspect of UWOC.

Artwork counterfeiting is an historical problem, which has nowadays still ancient solution, not based on innovative technology, due to the intrinsic nature of the artworks themselves. In this paper an innovative system based on smartphone acquisition and mobile application is depicted to verify artwork authenticity based on typical craquelure patterns present in ancient painting. These patterns are unique and can be modified only via a complete and accurate artwork restoration process. This approach is based on like biometry paradigm (analogue fingerprinting) adapted to the painting pattern.

An important problem in industrial system, both working in low and medium power, is the possibility that some circuits have a current dispersion, with a subsequent increasing in local temperature. This situation, if not immediately corrected, can produce, in some cases, firing accidents, with a great amount of money loss and long period of out-of-order systems. Although procedures based on Infrared Thermography to analyze and find critical situations already exist, these are always based on long manual procedures and usually are used for analysis of complex industrial systems. In this paper, after a short review of the common manual thermograph investigation, an automatic system based on two infrared thermograph cameras and an image processing real time analysis is proposed. The device demonstrates the possibility to take under control some critical systems and preventing firing accident in automatic way. This solution can be easily integrated in a SCADA architecture for monitoring and alerting the supervisor about over-temperature or current dissipation cases.

The use of projected fringes for the measurement of surface profile is a well-developed technique. In this paper, we present a surface profile measurement method for micro-components based on the combination of digital fringe projection, phase stepping, temporal phase unwrapping, and digital image acquisition. In this paper, a cost-effective machine is proposed. In particular, the paper describes the hardware and software realization. A simple procedure is described, which enables calibration of the optical set-up for subsequent quantitative measurement of micro-components of unknown shapes. In this paper, some examples are presented to demonstrate the potentiality of the system in measurement of microscopic surface profile.

The relief of form is undoubtedly one of the most topical topics in the field of cultural heritage. Physical access to historic and artistic manufactures can be limited by a lot of factors. For example, the access to the collection of the ancient coins is difficult, especially for students. Indeed, for coins digital archive of high-quality three-dimensional model and remote fruition is of great interest. The use of projected fringes for the measurement of surface profile is a well-developed technique. In this paper, we present a surface profile measurement system for small objects of cultural heritage where it is important not only to detect the shape with good accuracy but also to capture and archive the signs due to ageing. The illustrated equipment is simple, reliable, and cheap. Furthermore, some examples of acquisitions are presented to demonstrate the potentiality of the proposed scheme for recovering 2.5D shape of cultural heritage objects.

Traditional wireless communication methods tend to saturate in terms of data rate, frequency spectrum and reliability. Visible Light Communication (VLC) integrated with the emerging technology of Internet-of-Things (IoT) opens up to a wide range of indoor applications. In this work we will describe the potential of an optical wireless communication infrastructure and we will make a comparison with the emerging 5G and 6G Wi-Fi (RF) technologies.

A new acquisition system for remote control of wall paintings has been realized and tested in the field. The system measures temperature and atmospheric pressure in an archeological site where a fresco has been put under control. The measuring chain has been designed to be used in unfavorable environments where neither electric power nor telecommunication infrastructures are available. The environmental parameters obtained from the local monitoring are then transferred remotely allowing an easier management by experts in the field of conservation of cultural heritage. The local acquisition system uses an electronic card based on microcontrollers and sends the data to a central unit realized with a Raspberry-Pi. The latter manages a high quality camera to pick up pictures of the fresco. Finally, to realize the remote control at a site not reached by internet signals, a WiMAX connection based on different communication technologies such as WiMAX, Ethernet, GPRS and Satellite, has been set up.

In this study, an educational tool has been prepared for obtaining short-term and more economic training on digital speckle shearography (DSS). Shearography non-destructive testing (NDT) has gained wide acceptance over the last decade, providing a number of important and exciting inspection solutions in aerospace, electronics and medical device manufacturing. For exploring these motivations, it is important to develop didactic tools to understand the potential of digital shearography through training and didactic courses in the field of NDT. In this paper we describe a simple tool for making one familiar with the potential of DSS in the area of education and training. The system is realized with a simple and economic optical setup and a virtual instrument based on the LabVIEW™ and DAQ.

For legal purposes there is a requirement for the validation of signatures and handwritten documents. A helpful method in this respect is the so-called superposed strokes analysis, based on the observation of some characteristics in the writing, such as some letters and their dynamics. This paper introduces a promising new technique for superposed strokes analysis based on conoscopic holography. Through a non-contact 3D measure a 3D profile is created of the superposed strokes that allows the writing dynamics to be determined, such as, for example, if a stroke was drawn clockwise or counterclockwise. We propose a 3D analysis by an opto-electronic system, in order to improve the graphology analysis for off-line signature verification.

The artwork market is plenty of unauthorized reproduction of original products. One of the most varies filed is the counterfeiting of Authenticity Certificate related to paints, lithography, sculptures, etc., with the aim to create an illegal market of reproduced copies. To resolve this problematic, it is possible change the current paper certificate, related to a single artwork, with a digital version, which will contain some specific information, related to the artwork itself. In this paper, starting with the well-known advantages given by the biometry paradigm in human authentication, we propose a method able to distinguish the single “non-living” objects. In other words, we propose an approach that, by using the random inimitably characteristics, is able to uniquely identify artworks such as painting, lithographs, sculptures, etc. In this way it could be possible creating a secure digital certificate of authenticity (digital COA). Due to the high density information available in modern acquisition media, it is possible using a Speckle Metrology approach. During verification phase, the same area has to be acquired, to extract embedded verification data. It is possible to secure this data using a private key, necessary for accepting the digital signature. The presence of possible geometrical distortions between image present in the certificate and acquired during the verification phase, it is necessary applying geometrical corrections based on affine transformation, before executing the correlation methodologies, used in speckle metrology.

Conoscopic holography is a fringe generation method widely used to reconstruct surface profiles with high precision. By means of linear fringe method, it is possible obtaining a depth analysis with resolution better than 1 μm. This depth allows utilizing conoscopic holography also to aid the forensic handwriting expert. In fact manuscripts have 3D characteristics, which can be acquired only with systems having a high level of details in the z dimension. In particular, this peculiarity has been used for analyzing line crossing cases, some of the more controversy during signature association in trials. Sometimes the analysis of the only 3D profile is not sufficient to clearly associate a signature to a specific person. In this article, a method to generate a pressure profile by means of a linear conoscopic holography System, which can identify a person from a template generated by this profile, in a way similar to biometric voice recognition systems is proposed.

Actually, two-dimensional (2D) barcodes are readable not only by scanners, but also by camera phones. A number of common problems are encountered in the process of scanning and decoding barcode, such as various types of noise, blur, uneven lighting, and in particular the presence of extraneous information surrounding the image. In this paper we introduce a new 2D barcode namely HoloBarcode. The proposed barcode is developed as a computer generated hologram (CGH). Exploiting the ownerships of the holography, this new 2D barcode is able to provide the embedded information even in the presence of damaged surface. In particular, HoloBarcode is particularly robust in presence of extraneous information overlapping the image. For these reasons, this new barcode can be a valid alternative in all those applications where we have possibility of "important" damages of the code itself. Measurements of robustness to such manipulations were made, on 2D HoloBarcode against the popular Data Matrix code. Comparisons between the two different 2D Barcodes are highlighted.

Biometry is gaining popularity as a physical security approach in situations where a high level of security is necessary. Currently, biometric solutions are embedded in a very large and heterogeneous group of applications. One of the most sensible is for airport security access to boarding gates. More airports are introducing biometric solutions based on face, fingerprint or iris recognition for passenger identification. In particular, fingerprints are the most widely used biometric, and they are mandatorily included in electronic identification documents. One important issue, which is difficult to address in traditional fingerprint acquisition systems, is preventing contact between subsequent users; sebum, which can be a potential vector for contagious diseases. Currently, non-contact devices are used to overcome this problem. In this paper, a new contact device based on laser speckle decorrelation is presented. Our system has the advantage of being compact and low-cost compared with an actual contactless system, allowing enhancement of the sebum pattern imaging contrast in a simple and low-cost way. Furthermore, it avoids the spreading of contagious diseases.

Protecting pharmaceutical products against counterfeiting or the fraudulent importation of donated and discounted drugs will remain a permanent challenge in light of the increased frequency of counterfeiting. The increasing complexity of the supply chain in today's global economy complicates certification of each individual supply source. This complexity is a key factor in the rapid increase of counterfeiting attacks, including those in countries where the supply chains are well established and trustworthy. In this article, an innovative solution based on the white-light speckle theory (visible speckle obtained as ultraviolet fluorescence) is applied to an ultraviolet source, which allows drug packages to be linked with a barcode. The basis of the proposed method is the biometric paradigm, applied to nonliving matter, which requires the identification of a unique distinctive matter characteristic for the unique identification of the related object. The identified characteristic is not an inherent characteristic of the object itself; instead, a white-light speckle pattern will be artificially added. This speckle pattern becomes a sort of fingerprint for the drug package. Starting from this pattern, drug packages can be authenticated by a biometric-like approach. This paper presents a concise review of pharmaceutical product anti-counterfeiting and introduces our white-light speckle method.

Biometry is a wide-used and pervasive approach to verify people identity, based on the presence of some unique characteristics, having precise properties (i.e. biometric characteristics). On the other hand, optical detection of random features is widely used for recognizing object authenticity. In this paper we explain how these two approaches are similar; random features can be seen as "fingerprint" of inanimate objects. Some parallelisms with well-known biometrics solutions are reported, to emphasize the similarity of the two approaches.

A diffractive optical elements (DOEs), permits to change a wave front by means of diffraction. The proposed method has the advantage of not requiring complex computation and programming. In particular the designed process is made without computer iterative methods. The DOE, implemented by the proposed algorithm, consists of cells of equal size. Each cell is subdivided into appropriate parts. The average phase of these parts is related to the phase of the complex amplitude. The DOE phase can be easily computed according to simple formulas. In the paper designing phases and numerical simulation are reported. In particular the effect of the DOE structure quantization is considered.

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 paper we present a content fragile watermarking based on a computer generated hologram coding technique. Content fragile watermarking techniques aim to prevent tampering and fraudulent use of modified images. A content 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 with. However, if parts of the image are replaced, the watermark information should indicate evidence of forgery. Using computer generated hologram watermarking, the embedded mark could be easily recovered by means of a Fourier transform. Due to this fact the host image can be tampered with and watermarked with the same holographic pattern. To avoid this possibility we have introduced an encryption method using a private key. The proposed technique is suitable for use for freelancers' photography authentication. It could be applied to colour images as well as to grey-scale ones. The proposed schema is based on the knowledge of the original mark from the authentication entity, to apply image correlation between this and the extracted one.

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".

Banknote security is an issue that has led in the last decades to insert, inside the banknote itself, a very high number of controlling methods with the aim of verifying possible tampering attempts. In order to distinguish the false banknotes, sophisticated means (i.e. watermark, feel of the paper, raised print, metallic threads, quality of the printing, holograms, ultraviolet features, micro-lettering, etc) are often used. The purpose of this paper is to show a new approach and related method to protect banknotes and to verify their originality, based on the idea of hylemetry (methodology conceptually similar to biometry) applied to banknotes. Specifically, the hylemetric feature used in this paper is the random distribution pattern of the metallic security fibers set into the paper pulp. The outcome of the proposed solution is to identify an original banknote using a binary sequence derived from the banknote itself.