This paper discusses a new type of holographic overlay, FLASHPRINT, which may be used in both security and packaging applications. Unlike the more common embossed holograms currently used, FLASHPRINT leads to reduced set-up costs and offers a simpler process. This reduces the long lead times characteristic of the existing technology and requires the customer to provide only two-dimensional artwork. The overlay material contains a covert 2-D image. The image may be switched on or off by simply tilting the overlay in a light source. The overlay is replayed in the 'on' position to reveal the encoded security message as a highly saturated gold colored image. This effect is operable for a wide range of lighting conditions and viewing geometries. In the 'off' position the overlay is substantially transparent. These features make the visual effect of the overlay attractive to incorporate into product design. They may be laminated over complex printed artwork such as labels and security passes without masking the printed message. When switched 'on' the image appears both sharp and more than seven times brighter than white paper. The image remains sharp and clear even in less favorable lighting conditions. Although the technique offers a low set-up cost for the customer, through its simplicity, it remains as technically demanding and difficult to counterfeit as any holographic process.
This paper reports new possibilities for increasing the information capacity of 3-D holograms. It is based on the application of the speckle wave as a reference under the volume hologram recording. Such hologram has the translational selectivity (the sensitivity of the diffracted wave amplitude to the mutual translational shift of the hologram and the reconstructing beam) and the angular selectivity which doesn't depend on the changing of the rotational axis. All these possibilities arise due to the space mismatch between the recorded structure and the reconstructing speckle wave. The theoretical analysis and experimental study of this problem under the volume holograms recording at the LiNbO3:Fe crystals were carried out.
A brief survey of the theoretical, physical, and psychophysical background of surveillance, the basis of security, is given, especially, in those cases when the signal carriers are electromagnetic waves. The concept of flat cylinder perspective (FCP) is introduced, allowing an undistorted 360-degree panoramic view. Technical considerations of designing such an optic, called PAL, satisfying these criteria are presented. Examples are given regarding how to use some instruments based on PAL-optic in surveillance and security related panoramic inspection tasks.
In this paper several methods for making holographically protected printwork (HPP) are discussed. This article refers to work of other people as well as work done in the author's own laboratory. In this booming field, successes as well as flops have been made. At this moment several holographic products such as dichromated gelatin holograms and embossed pvc- or polyester foils, for self adhesive stickers or hot-foil application, are used to create HPP.
A method for generating half-tone images on binary (i.e., paper and ink) systems using different (frequency-) modulation techniques is described. Security gratings and patterns are designed to generate 'alias' images or detectable codes, due to undersampling by the digital scanner.
This paper highlights the problems a Dutch bank has in choosing the security measures it takes for valuable documents. The various types of fraud for which the security measures are intended are dealt with. The magnitude of fraud and its subsequent effects are examined, leading to the conclusion that security is necessary for more than just financial reasons. Security procedures and measures that are possible elsewhere are examined. After that, the application of security possibilities to value documents will be elaborated on, particularly from the point of view of effectiveness and costs. It is assumed that security and science can serve the interests of the criminal and consequently, to some extent, harm the interests of the bank and its customers
This paper discusses security applications of reversible photosensitivity that resulted from a search in SECURIDAT--viz. dual fluorescence with longwave remanence, thermochroism, stimulation of mixed inorganic phosphors, and photochroism.
This paper will discuss the state of the art of optical variable devices (OVDs) as security elements, and the possibilities of fraud-criminals to counterfeit OVDs. The activities of criminals in this field will be reviewed. A few practical cases will be presented, and feasible solutions to protect OVDs against counterfeiting will be proposed.
Following the development of the Catpix I diffraction gratings structure first used on the 1988 Australian plastic $DLR10 banknote and more recently on the Singapore plastic $DLR50 banknote, the CSIRO Australia, Division of Materials Science & Technology has developed a new optical security and anti-counterfeiting technology known as Pixelgram (or Catpix 2). The Pixelgram, which is subject to patent, is an optically variable device based on a computerized procedure for producing an optically variable version of any given input picture, e.g., a photograph. When a Pixelgram is observed under a given source, such as a fluorescent tube, the image of the original input picture appears at particular angles of view. At other angles, the image varies in both contrast and brightness and can even appear as the photographic negative of the original input picture at some angles of view. As well as its ability to generate optically variable text and graphical images, Pixelgram has the unique capability of being able to display easily recognizable small scale optically variable images of the human face of near photographic clarity. Pixelgram optical security device master plates are produced by a technique borrowed from the microelectronics industry and known as electron beam lithography. In this technique, millions of microscopic grooves are written individually by a finely focused electron beam scanning across a glass plate coated with an electron sensitive material. On a typical Pixelgram there are approximately 2,000 million individual polygons etched into the plate by the electron beam. This corresponds to more than 10,000 megabytes of binary data. The only known electron beam lithography systems that have been able to write such large data files with the required precision are the Cambridge Instruments EBMF 10.5 and EBML 300 electron beam systems.
As the range of materials and applications for holographic and diffractive features grows, so manufacturers can provide customers with a host of options and formats. Increasingly customers are specifying what they require in more detail. This includes material specifications, residual chemical levels, release and adhesion properties, as well as the more obvious image details. To date one feature vital to any buyer that is poorly defined is the optical or diffractive properties of their hologram or diffractive element. The problem is confounded by those manufacturers that do measure or assess the diffractive properties of their products, as there is no agreement on what should be measured and how these measurements should be interpreted. This paper presents a technique that will form the basis of an assessment technique that will allow standardisation, should the industry decide it need it.
The discovery of high-temperature superconductors (HTS) has opened new opportunities for applications of superconductors in optoelectronics. The HTS perovskites represent a new class of solid-state materials, exhibiting many very interesting and potentially useful electronic, optical, and electro-optical properties. They also operate in the 30—80 K temperature range, where refrigeration is cheap and the parameters of semiconducting devices are optimal. A review of the substrate materials and deposition techniques suitable for fabrication of high-quality epitaxial HTS films for electronic and optoelectronic applications is given. Laser processing techniques of HTS films are presented, with a special emphasis put on the laser writing method, which enable to define superconducting and nonsuperconducting regions in the same, epitaxial HTS film. Two possible approaches for the development of a complete optoelectronic system with the elements based on the HTS films and operational at liquid-nitrogen temperatures are presented. The first approach consists of manufacturing the devices made of conventional electro-optic materials and containing HTS transmission lines and electrodes. Design and properties of ultrafast HTS interconnects are discussed, and a new concept of the Mach-Zehnder-type YBa2Cu3O7.-on-LiNbO3 optical modulator is introduced. The second, more futuristic approach, is to exploit contrasting properties of the oxygen-poor and oxygen-rich HTS phases to fabricate novel, monolithic devices. We discuss recent experiments, which reveal intriguing optical properties of FITS films, and are most relevant for the development of all-HTS optoelectronic devices. Several practical devices, such as high-frequency modulators, ultrafast-pulse generators, and sensitive photodetectors will be presented
This interferometer is designed to measure 75x40 cm laser glass. The entire surface is measured
at a Brewsters angle, 56.57°, with an s-polarization beam. The reflected beam is retro-reflected
by a highly reflective mirror. Thus, a 75x40 cm surface can be tested with a 60-cm aperture.
The most troublesome problem is the ghost reflection from the rear surface of a flat while the
front surface is being measured. After the second surface is polished, both surfaces are reflective
and their beams can interfere. However, the second surface of a flat is to be polished to ensure
the transmitted wavefront quality, not the quality of the surface itself. Therefore, the second
surface does not need to be measured directly. To avoid reflection from both surfaces, the laser
is switched to a p-polarization after the first surface is measured while the flat is still at a
Brewster's angle. Thus, the transmitted wavefront is not affected by the reflection.
We believe that a 60-cm clear aperture, Fizeau phase-shifting interferometer is the most practical
and accurate instrument for testing 75x40 cm optical flats. In this paper, we briefly summarize
the important design factors, and show in theory that the design can meet the required