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This article explains the design of an infrared-based human-machine interface using low cost components and infrared distance measuring sensors. This interface is targeted for people suffering from reduced mobility as well as specific professionals operating in constraining situations. This design allows using simple head movements to perform basic computer mouse operations, such as point and click. Existing solutions are briefly reviewed and advantages and disadvantages associated with these solutions are pointed out. In our design, special attention is given to two diferent infrared sensor layouts. We will also discuss the infrared sensors used as well as the way our design detects and processes a user's head movements. We will conclude by giving the achieved results as well as future perspectives for our design.

Linguistic minorities are confronted with particular pressures making it difficult to preserve and learn their language as well as their culture. Among these pressures, we may list the geographical scattering of minorities and the lack of necessary human and material resources to ensure this learning as well as to form educative staff and future assistance that will be needed. Remote education could present itself as an alternative if it shows performances as good as those of face-to-face education in terms of efficiency and formation quality. The present work deals with an experience using face-to-face and distant learning. Two courses offered by University de Moncton (Educ6122 and Educ6013) for French-speaking minorities in New Brunswick are considered. Our objective is not to favor the local student over the distant student. In addition to our approach and our achievements a statistical study of satisfaction will be presented.

In this paper we advance an optical JPEG color image compression algorithm and discuss its performance. Statistical metrics such as mean square error (MSE) and peak signal-to-noise ratio (PSNR) are used. These quality criteria quantify the difference between the original and reconstructed image. The time required for compression/decompression using our optical method is one of the considered performance factors. Simulation results are presented to illustrate the effect of the compression ratio on the reconstructed image quality.

Different methods of color image correlation are proposed. They are based on a "binary phase only filter" (BPOF) and the segmentation method. The objective of merging simultaneously "single-channel correlations" is to save computing time, to alleviate complexity and to reduce cost. These methods are investigated to determine the better match adaptive one to our applications. Multi-channel processing is applied to color images by decomposing the image into its three main color components "red, green and blue " (RGB). To each color components, one channel is assigned and processed separately. Then the respective outputs are combined. Our new contribution consists in putting together the respective spectra of the color channels to obtain a single spectrum. Instead of three spectral correlations, we perform only a grouped color correlation. After applying an optical Fourier transform (FT) on each channel, the three respective spectra are combined together. The correlation is carried out in the spectral domain and results in a compound spectrum. Indeed, relevant information should be selected from each spectrum of the three color components to form a unique spectrum which presents the core of the correlation. This resulting spectrum is then multiplied by the binary phase only filter (BPOF). Since a single phase filter is used, a significant reduction of the data base volume is achieved.

Ad hoc wireless networks can be described as dynamic multi-hop wireless networks with mobile nodes. However, the mobility condition can be relaxed, and we can consider an ad hoc wireless network as a reconfigurable network where all the nodes are connected to the local environment through wireless links, and where there is not a central or dominant node?as opposed to, for example, the case of cellular wireless networks where a base station is located in each cell. When ad-hoc networks are backboned by fibers, distortion of the optical link presents one of the major issues. In this paper, we will be addressing one of the fundamental problems, namely chromatic dispersion compensation in the fiber optic prior reaching the access points. This will ensure an adequate better quality of signal in the applied network.

"Anywhere" and, in particular, "anyhow": these are the two best words that can describe an ad hoc wireless network that is due to the increasing demand for connectivity in such an information society. Ad hoc wireless networks can be described as dynamic multihop wireless networks with mobile nodes. However, the mobility condition can be relaxed, and we can consider an ad hoc wireless network as a reconfigurable network where all the nodes are connected to the local environment through wireless links, and where there is not a central or dominant node—as opposed to, for example, the case of cellular wireless networks where a base station is located in each cell. When ad hoc networks are backboned by fibers, distortion of the optical link presents one of the major issues. In this paper, we will be addressing one of the fundamental problems, namely, chromatic dispersion in the fiber optic prior reaching the access points. This will ensure an adequate quality of service (QoS).

For any wireless network based on mm-wave radio systems to be viable, the cost of the infrastructure must be much lower than is currently the case. One approach that promises this cost reduction is the radio over fiber, where radio signals at the carrier frequency are delivered over an optical network to the radio access point. Benefits of this centralized approach are that expensive and delicate pieces of equipment can be located in a beginning environment and costs can be shared between a number of radio access point. However, the integration of such systems is conditioned by the development of low cost radio components, antennas, the packaging as well as the optic/radio transductors. The paper explores therefore the areas of strategic importance in integration of new antenna array topologies, which are appropriated for use as a building block for the millimeter wave fiber wireless system that employs an intelligent multi-beam antenna where the direction of each sharp beam can be adoptively controlled. Thereby, the objective of truly monolithic array with integrated planar antennas and phase shifters was the driving force behind the development of the aperture coupled patch element, which is especially relevant for these systems. The effectiveness of this antenna array has been experimentally confirmed. Finally, it is worthy to note that the small wavelengths allow miniaturize of the size of components such as antennas which are very important for portable sets as well as base station (BS) facilities, which need to be readily installed.

We present an approach to analyze the Talbot effect caused by chromatic dispersion up to the third order. A new method for compensation of chromatic dispersion up to the third order caused by propagation through the optical fiber is advanced. To the best of our knowledge, this method is the first that uses an optical post-equalization stage based on the temporal Talbot effect. Moreover, using this approach, we can easily implement a system doubling, tripling, ... the pulse rate of an initial periodic signal.

A versatile numerical tool simulating the spectral and temporal behaviour of fibre gratings operating in reflection or in transmission is designed. Several constraints and geometries are handled by this user-friendly numerical tool including uniform, apodized, chirped, discrete phase-shifted, and superstructure gratings; short-period and long-period gratings. The versatility and extensibility of the tool allows straightforwardly handling further forms and constraints.

Driven by the world's growing need for communication bandwidth, progress is constantly being reported in building newer fibers that are capable of handling the rapid increase in traffic. However, building an optical fiber link is a major investment, one that is very expensive to replace. A major impairment that restricts the achievement of higher bit rates with standard single mode fiber is chromatic dispersion. This is particularly problematic for systems operating in the 1550 nm band, where the chromatic dispersion limit decreases rapidly in inverse proportion to the square of the bit rate. For the first time, to the best of our knowledge, this document illustrates a new optical technique to post compensate optically the chromatic dispersion in fiber using temporal Talbot effect in ranges exceeding the 40G bit/s. We propose a new optical post equalization solutions based on the self imaging of Talbot effect.

Light propagation trough dispersive media was the object of intensive research. Split-step methods such as optical fibers based on Fourier transform were among the most interesting methods. This method shows well the interplay between the dispersion and nonlinear effects in the optical fiber. We provide here some results of the split-step Fourier method applied to the simulation of wave propagation in a dispersive medium.

In the present paper, we take a closer look at the design of long period fiber gratings (LPFG) which present several advantages compared to similar components. In fact, the LPFG has stronger wavelength stability when opposed to temperature variations and a better resistance against mechanical strength. These qualities offer them more importance in the industry. We use an electric arc to change the fiber characteristics and to create a fringe which presents a very thin section of the fiber that has a different refractive index. We use a computer based setup which allow us the control of the arc intensity and the discharge time and the gap between two neighbor fringes for the LPFG varies in the range of 400 to 700μm. A various optical fiber components designs and implementations are possible using electrical arc. In this paper we will expose the use of electrical arc and micro deformations for writing the Long Period Fiber Gratings (LPFG) on a single mode fiber. We take a closer look at the design of this component which present several advantages compared to similar components.

One of the most important vehicles for providing dynamic learning is interaction combined to animation. We designed a dynamic e-learning environment for teaching optics. In spite of the fact that the teacher and the learner do not share neither space nor time, dynamic teaching is implemented aiming at reducing passivity, engaging and motivating the learner, empowering him with responsibility for his own learning experience, allowing collaborative learning, popularizing complex aspects in optics, and enabling the learner to easily access and interact with the environment content at his own pace, in his own time and from wherever he might be. Audio-visual tools are used for real-time assistance. The degree of complexity is customized by supervising and interpreting the interactions of the learner so that laypeople can readily follow the course. The course is adapted to people with a modest background in physics such as clinicians, optometrists and ophthalmologists. However, the learning environment is useful for advanced topics in optics as well as for research. Index — E-learning, dynamic teaching, interaction, optics.

The fractional Talbot effect brings into play a superimposition of shifted and complex weighted replicas of the original object. This phenomenon can be used to replicate images of nonperiodic objects by means of Talbot array illuminators. These diffractive elements can also be used to concentrate replicas into a single image. These techniques are useful for several applications such as beam shaping.

Vanadium dioxide (VO(2)) is used to implement an electrically addressable beam splitter with continuously variable splitting ratios. The electrical control of temperature in a thin VO(2) layer is used to vary its transmission/reflection behavior. The technique is characterized for various incidence angles, s- and p-polarizations, and the wavelength range of 400-2000 nm. Splitting ratios continuously tunable over four orders of magnitude are reported.

A steganographic method offering a high hiding capacity is presented in which the techniques of digital holography are used to distribute information from a small secret image across the larger pixel field of a cover image. An iterative algorithm is used to design a phase-only or complex hologram from a padded version of the secret image, quantizing this data according to the carrier data bits that are available within the intended cover image. By introducing the hologram data only into low-order bits of larger amplitude cover pixels, the change in the cover image remains imperceptible to the casual observer, with a peak signal-to-noise ratio of >40dB.

We propose an iterative method to optimize the phase profile of the initial field so that its intensity profile is observed periodically along the longitudinal (propagation) axis. The new method is inspired from the Gerchberg–Saxton technique, where the Fresnel transform is used, instead of the Fourier transform, for retrieving the phase profile of several light distributions (for example, 15 planes), instead of a Fourier pair of distributions. The additional challenge, with respect to the conventional Gerchberg–Saxton technique, is that the planes where constraints are applied number more than two. It turned out that when the number of periods increased, the spectrum of the obtained initial field converges toward including Montgomery’s rings (self-imaging condition).

An ad hoc network is a set of wireless mobile nodes that communally form a network without specific user administration or configuration. There are several scenarios that do not have an available network infrastructure and could benefit from the creation of an ad hoc network as rescue/emergency operations, law enforcement activities, tactical/military missions, commercial projects, educational classrooms.

An approach for designing Talbot array illuminators that produce quasi-arbitrary numbers of spots and quasi-arbitrary distributions of these spots in the output plane is proposed. The approach consists in combining elementary Talbot array illuminators. In addition to the quasi-arbitrary topology of the output spots, the resulting compound array illuminator shows several advantages such as its ability to be used for both coherent and incoherent imaging. Compared with elementary array illuminators, the compound illuminator does not add any specific technological complication.

Spatial coherence can be created by appropriate spatial arrangements of incoherent point sources. Lau used a source of extended light and two amplitude gratings of identical periods, separated by the quarter Talbot distance, to provide coherent light. Because of the two successive amplitude gratings, most of the power is lost. By modifying the geometry of the second grating, I designed an array illuminator, providing several compression ratios and various topologies of the output plane, with significantly reduced losses. To further improve the power efficiency of the system, I used a longitudinal mirror system to collect the light rays that are lost in the initial Lau setup. Both one- and two-dimensional geometries are considered.

PURPOSE. To describe monochromatic optical aberrations of the eye as a function of age. METHODS. One hundred fourteen subjects with a spherical equivalent within 3.50 D from emmetropia, corrected visual acuity of 20/40 or better, and normal findings in an ophthalmic examination were enrolled. The mean age was 43.2 24.5 years (range, 5.7‐ 82.3). Monochromatic optical aberrations were measured with a Hartmann-Shack wavefront sensor after pharmacological dilation and cycloplegia. RESULTS. For a 5-mm pupil and for third- to seventh-, third-, fourth-, and fifth- to seventh-order aberrations, as well as for coma and spherical aberrations, the root mean square (RMS) error as a function of age was modeled by a second-order polynomial regression. It decreased progressively through childhood, adolescence, and early adulthood; reached a minimum level during the fourth decade of life, then increased progressively with age, to age 82. For a 5-mm pupil, the mean modulation transfer function (MTF) was reduced in both the child- teenage (5‐20 years; n 29) and the elderly (61‐ 82 years; n 37) groups versus the middle-aged adult group (41‐ 60 years; n 24; P 0.05). In young adults (21‐ 40 years; n 23) and elderly subjects, the MTF curves were very close and almost superimposed at spatial frequencies higher than 38 cyc/deg. CONCLUSIONS. Aberrations of the whole eye were objectively measured from early childhood to an advanced age, and the relationship between monochromatic aberrations and age has been shown to fit a quadratic model. The results suggest that the definition of emmetropization should be broadened to include the reduction of higher order aberrations. (Invest Ophthalmol Vis Sci. 2003;44:5438‐5446) DOI:10.1167/iovs.02-1042

A multimedia teaching aid based on animated Java applets can help users visualize the behavior of complex optical systems.

Although the technology of fixed optical interconnects has shown rapid progress, the programmability requirements remain a difficulty that has not yet been definitively solved. A new configuration of diffractive optical elements is presented that takes full advantage of the progress made in the field of fixed elements and also offers the possibility of programmability. The idea consists of serially combining a few elementary diffractive elements that might be spatially separated. One or some of these elements should be programmable. Configurations that make use of the assets of fixed elements are proposed that overcome the limitations, such as low resolution, that are associated with programmable elements. For illustration, an experiment is described.

I present a general approach for designing Talbot array illuminators (TAIL's). Beyond the scope of conventional TAIL's, in which each period of the replay field contains only one bright spot, I examine complex configurations ensuring various topologies of the output spots. The synthesis problem is stated in terms of constraints and degrees of freedom. Both the one-dimensional and two-dimensional cases are treated, and an example of constraints, namely the binarization of the TAIL, is discussed. For illustration, an application is proposed in which I consider a dynamic multilayer interconnection architecture involving a programmable TAIL.

We describe a Talbot array illuminator made of cascaded binary phase plates located at fractional Talbot distances. We compare the performance of such an illuminator with a conventional single-layer Talbot array illuminator in terms of compression ratio and technical feasibility.

The efficient Fresnel-transform algorithm (EFTA) is a computational tool that facilitates diffracted field analysis. The computational improvement that is achieved with the EFTA relative to the conventional double fast-Fourier-transform (FFT) algorithm results from the properties of fractional Fresnel diffraction. Some programming simplicities are shown to appear at numerous locations along the propagation axis. The number of those locations is determined by the fractional order. Some computational aspects of the method are presented and compared with those of the FFT algorithm.

Multilevel phase holograms can be obtained from the combination of two binary phase-only holograms set up in a fractional joint Talbot configuration. Among possible solutions, the quarter-Talbot location is of particular interest because it permits the generation of four-level phase holograms from the combination of two binary {0, π} phase holograms. At the same time recent advances in electrically addressed ferroelectric liquid-crystal spatial light modulators for producing binary pure phase-only holograms make possible the implementation of programmable high-diffraction-efficiency computer-generated holograms. An extension of computer generation of holograms is proposed that includes spatial constraints related to the fractional Talbot effect.

We propose a new technique for generating a four-level reconfigurable phase-only hologram, using two binary phase {0,pi} ferroelectric liquid-crystal spatial light modulators. The principle is based on the self-imaging properties of periodic structures operating in a Fresnel field double-diffraction system. Fractional Talbot planes are shown to be of particular interest. The problem of hologram bandwidth reduction that results from the holographic pattern replication is addressed. A trade-off between diffraction efficiency and hologram coding capacity is considered.

We address free-space optical interconnections based on cascaded multifacet holographic elements, including an intermediate regeneration of the optical signals. Particular attention is paid to digital hologram encoding in the case of highly interconnected planes. Degrees of freedom selected in the reconstruction plane are used for satisfying both holographic-encoding and signal constraints. An iterative Fourier-transform algorithm is chosen because of its ability to incorporate constraint considerations.

A new method of optical encrypted color images based on a spectral fusion (segmented) of information has been proposed. Color images are decomposed into three basic color components. Pertinent information fusion is considered as segmentation. Encrypting consists in modulating each of these three components of the image spectrum by a corresponding phase mask. This phase mask includes pertinent information collected from various encrypted color keys according to a fusion criterion. As encrypting keys are formed by real images, it becomes an impossible task to get the target image by any trial and error random images techniques. For decrypting, a simple algorithm based on composite correlation filters is proposed. Simulation results corroborate the effectiveness of our algorithm.

This paper introduces an alternative fuzzy clustering method that does not require fixing the number of clusters a priori and produce reliable clustering results. This newly proposed method empowers the existing Improved Artificial Fish Swarm algorithm (IAFSA) by the simulated annealing (SA) algorithm. The hybrid approach can prevent IAFSA from unexpected vibration and accelerate convergence rate in the late stage of evolution. Computer simulations are performed to compare this new method with well-known fuzzy clustering algorithms using several synthetic and real-life datasets. Our experimental results show that our newly proposed approach outperforms some other well-known existing fuzzy clustering algorithms in terms of both accuracy and robustness.

In this paper, we implement a numerical tool for the simulation of the spectral and temporal characteristics that can be achieved in fiber reflection and transmission gratings. Both principles for understanding and techniques for manufacturing fiber gratings are emphasized. Examples of possible utilization are presented. The types of gratings considered by this numerical tool include uniform, apodized, chirped, discrete phase-shifted, and superstructure gratings; short-period and long-period gratings

The rapid spread in digital data usage in many real life applications have urged new and effective ways to ensure their security. Efficient secrecy can be achieved, at least in part, by implementing steganograhy techniques. Novel and versatile audio steganographic methods have been proposed. The goal of steganographic systems is to obtain secure and robust way to conceal high rate of secret data. We focus in this paper on digital audio steganography, which has emerged as a prominent source of data hiding across novel telecommunication technologies such as covered voice-over-IP, audio conferencing, etc. The multitude of steganographic criteria has led to a great diversity in these system design techniques. In this paper, we review current digital audio steganographic techniques and we evaluate their performance based on robustness, security and hiding capacity indicators. Another contribution of this paper is the provision of a robustness-based classification of steganographic models depending on their occurrence in the embedding process. A survey of major trends of audio steganography applications is also discussed in this paper.

Wavelength division multiplexing (WDM) is a data transmitting technology, which allows the sending of a several optical signals from different sources over the same optical fiber. Today, WDM technologies allow maximizing the use of both the existing and the new fiber optic infrastructures. According to the International Telecommunication Union (ITU) for the WDM standards, optical multiplexers and demultiplexers must handle closely wavelengths for the optical data channels. The use of WDM has reduced the fabrication cost and eased the process of realization. Optical fiber components have very low insertion losses to insert or to extract a specific optical data channel from a WDM network. Various optical fiber components designs and implementations are possible. In this paper we expose the use of electrical arc and micro deformations for writing the long period fiber gratings (LPFG) on a single mode fiber. We take a closer look at the design of this component which has several advantages compared to similar components. In fact, the realized LPFG has stronger wavelength stability when opposed to temperature variations and a better resistance against mechanical strength. These advantages makes the LPFG so important in the industry.

By using Lau effect, we generate an array of spatially coherent point sources from incoherent light. Spatial coherence can be generated by periodic selection of the input light sources. Lau used a source of extended light and two amplitude gratings of identical periods, separated by a distance of the quarter Talbot distance, to provide coherent light. Because of the two successive blocking elements, most of power is lost. To significantly reduce these power losses, we introduce three modifications. First, the losses caused by the first grating are totally eliminated when we use a periodic structure of incoherent point sources. Such structures can be offered by vertical cavity surface emitting lasers or by a microlens array illuminated by an extended light source. Second, to further improve the power efficiency of the system, we modify the geometry of the second grating. Finally, we use a mirror system to collect the light rays that are lost in the initial Lau setup. This approach is of nature to open the perspectives towards all the applications of the coherent spatial Talbot effect.