Smartcard technologies, combined with biometric-enabled access control systems, are required for many high-security government ID card programs. However, recent field trials with some of the most secure biometric systems have indicated that smartcards are still vulnerable to well equipped and highly motivated counterfeiters. In this paper, we present the Kinegram Secure Memory Technology which not only provides a first-level visual verification procedure, but also reinforces the existing chip-based security measures. This security concept involves the use of securely-coded data (stored in an optically variable device) which communicates with the encoded hashed information stored in the chip memory via a smartcard reader device.
We present diffractive second-line security features based on the moiré phenomenon, that are designed for use in Optically Variable Devices (OVDs). After a short introduction of our 2D and 1D moire methods, we first present the integration of line-based, 1D animated moire patterns into OVDs. These covert features are verified using a printed, high-resolution screen, which causes the covert information to become visible. When the screen is moved back and forth, the covert information, for example a text, appears to move dynamically in a well defined way. We then present diffractive OVDs where specially designed 2D moire features have been integrated into graytone images. Such an integration has the advantage that the area in which the second-line security feature appears can be used simultaneously for a visually attractive first-line effect rather than just having a homogeneous background. The integrated diffractive
moire features are verified with a 2D microlens array through which the OVD is viewed; as the verifier or the OVD together with the verifier is moved, one observes dynamic visual effects. A special form of integrating a diffractive moire-feature into an OVD is shown in the last part of the paper, where the 2D microlens verifier is used in a fixed combination together with the information layer that consists of diffractive microstructures. Such a diffractive moire magnifier feature is characterized by the unique visual impression that it creates where projected images appear to move as the sample is tilted.
Optical effects in Optically Variable Devices (OVDs) are generally grouped in three different categories depending on how the effects can be verified: First-line features, second-line features, and third-line features. In this paper, we present novel examples for different classes of second-line security features designed for use in OVDs. The first class consists of features based on polarization effects. The second class consists of features which are based on special forms of very small text or images, that are invisible to the naked eye. The third class encompasses moire features that are based on engineered diffractive microstructures. These second-line security features can be checked by using simple verification devices like a polarizer, a magnifier glass, or a binary amplitude screen.
The simultaneous engineering of diffractive structures and amterial systems enables innovative appraoches for realizing iridescent color shifts for Optically Variable Devices (OVDs) for document secrity. In a first exmaple, we dmonstrate the interplay between a color-shifting coating, whichfunctions inreflection,a nd embossed gratings,w ith effects inthe first and hgher diffraction orders. In a second exmpale, we demosntrate novel surface-releif, zero-order gratingw hich show a color shift, e.g. green to red, uponrotation by 90 degrees. In a third example, we explore the use of combination gratings to realize color-shifting and color-contrast features. These color-shifting features are integrated within OVD designs in which an observer can easily check the behavior of the feature and verify the authenticity of the document.
We have studied the use of achromatic features in Optically Variable Devices (OVD) for document security applications. We present various forms of matt structures as we have implemented them in OVD designs. By tailoring the scattering characteristics of the surface relief, we have created OVDs which appear in various intensities of white or gray, and whose brightness can vary as the viewing conditions are changed. Furthermore, we have realized surface reliefs which appear bright and colorless when viewed within a predetermined solid angle and appears dark in all other viewing directions. The gratings appear bright and colorless when viewed from one side of the grating normal; however, when these gratings are rotated by 180 degrees in their plane, the gratings appear dark. We will show gratings of this type, where the surface reliefs have been engineered so that the bright and colorless appearance covers an enlarged solid angle.
We present the results of the application of zero-order diffraction gratings for optical variable devices (OVD's) for document security. Zero-order gratings have periods which are smaller than the wavelength of light; to describe accurately the optical properties of the zero-order gratings, we have applied rigorous electromagnetic theory, which we have compared to experimental measurements. We studied the diffractive behavior of zero-order grating varies locally in a predetermined manner. In the latter case, the resulting surface profile can exhibit variations in the diffraction properties, for example, a moire pattern. Furthermore, we have developed diffractive surface-reliefs which are a combination of a high-frequency, zero-order grating with large-period gratings, the addition of the zero-order grating to a large-period grating results in a surface relief with novel diffractive properties.
KEYWORDS: Diffraction, Diffraction gratings, Visualization, Holography, Structural engineering, Coherence (optics), Reflectivity, Light sources and illumination, Digital watermarking, Chemical elements
We will show various diffractive features which are easy to verify and highly secure against attempts to counterfeit. These features are based on engineered surface relief structures which allow one to tailor the diffraction properties to obtain the desired effects. The security is based on complex diffraction structures rather than on complex image content, allowing the realization of relative simple feature designs, which are favorable from an ergonomic point of view. The unique properties of the engineered diffraction structures can be visualized, if an appropriate reference is provided, against which the observer can compare. We follow the idea that the optical effects in a well designed security feature must be interdependent in the sense of coherence or self- referencing. Various examples are presented, showing unique self-referencing first-line security features for document applications, which are clearly recognizable and easy to communicate. The presented effects are resilient against attempts to counterfeit by holographic techniques.
A novel opto-electronic system has been developed using a diffractive code for the machine verification of the contents of the electronic memory of integrated-circuit (IC) cards to impeded attacks against IC card security. Through engineering of the diffractive microstructures, the intensity distribution of the diffracted light can be tailored for optical codes of high security, uniqueness and unambiguous identification. By measuring the diffraction properties of the optical code, the authenticity of the IC card can be checked. The diffractive code further provides a link to the information stored in the IC memory. The demonstrated diffractive-optical code is of the WORM type; that is, it is a write-once, read-many times memory. The data recorded in the diffractive optical code are compared to the data of the IC-card electronic memory using an encryption algorithm and are used to prevent tempering and alteration of the data stored in the IC-card electronic memory.
Experimental and theoretical results for linear surface- relief grating structures of locally varying depth are presented. The studied gratings result from the superposition of two linear gratings of uniform depth, an example of which is the superposition of two gratings of slightly different k-vectors. The resulting surface profile can exhibit a relatively large-period modulation in profile form and, thus, in diffraction efficiency having especially interesting polarization properties. This periodic variation in diffraction efficiency yields a typical Moire pattern which is seen to alter as the interrogation conditions are varied. For the case of two combined gratings whose individual surface-relief profiles are described by functions f1 and f2, the resultant surface-relief profile is described by f1 + f2. The basis functions f1 and f(subscript 2#/ have periods between 0.5 micrometers and 5 micrometers and uniform depths of several hundred nanometers. The basis functions which we studied include sinusoidal, blazed and rectangular gratings.
We demonstrate the use of diffractive surface-relief profiles for the machine verification of official documents. The microstructures are engineered to yield a prescribed intensity distribution of the diffracted light which can be measured to insure unambiguous verification and authentication. We have developed a palette of machine-verifiable features, offering various capacities of information, ranging from a feature which is easily verified through visual inspection using a special aid, to a feature capable of representing hundreds of bits of information in a read-only diffractive optical memory. The proposed features which we will present here are the hidden-information features, the diffractive area code and the diffractive linear code. For each of the three proposed features, we present prototype systems demonstrating the use of machine-verifiable diffractive optical features incorporated into optically variable devices (OVDs) for document security. Specially engineered diffractive structures are used which are extremely resilient against counterfeit, reorigination or imitation. The machine-readable feature is combined with a visual security device, such as the products known under the tradename KINEGRAMR.
We have developed a palette of visual features based on non- standard diffraction structures, where the profile-shape and the profile depth are determining the intended effects. The target is to provide features with increased security inherent to the diffractive structures. Since the exact reconstruction of the profile is the basis of the effects, these features are very resilient against counterfeiting by standard holographic techniques. Three different types of grating structures and their use as security-feature are described.
A combination grating is the diffractive relief structure resulting from the superposition of at least two gratings. For the case of two combined gratings, whose individual profiles are described by function f1 and f2, the resultant surface relief profile is described by f1 + f2. Typical examples are crossed gratings. Experimental and theoretical results for different combination gratings are presented, including examples which cannot be produced using standard holographic or ruling techniques. The applications include diffractive optical variable devices, which are applied to documents as visual high-security features.
The criteria by which optically variable devices are judged are aesthetic, semantic, security, ergonomic, and physical/chemical. This paper addresses ergonomic aspects which relate to the human vision and perceptual-cognitive system. Applying some pertinent rules may help greatly to improve the image visual information for easier, more straight-forward reception of a persistent security message. We consider two important aspects of the human visual system that help to determine the ergonomic response to visual displays created using optical diffraction. The human visual system aspect treats the retinal source of information, which is the retinal signal produced when an image of the external world is projected on the retina. The other aspect is the underlying information-processing mechanism of our brains and its constructive operations, which yields the final perceptual information. In this paper we consider information processing methods hidden in the biology of our cognition system. Findings on the relationship between physiology and psychology, sensory results and the activities of the optic pathway and subjective brightness sensations can be applied directly in designing images. Some effects are demonstrated by video tape.
We demonstrate the use of diffractive optical memories for official documents, such as machine-readable identity or fiduciary papers. Through engineering of the diffractive micro- structures, the direction and intensity distribution of the diffracted light can be tailored to optical memories for high security, uniqueness and unambiguous verification. The proposed optical memory is of the WORM-type, that is, write-once, read-many times. In order to write in the optical memory, the diffractive structure is changed irreversibly through the interaction of the diffractive surface with a beam of laser light. We demonstrate optical memories based on diffractive structures with a memory capacity of up to 100 kBits/cm2 which are appropriate for use in securing official documents.
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