Optics: measuring and testing – Document pattern analysis or verification
Patent
1995-08-17
1998-05-12
Font, Frank G.
Optics: measuring and testing
Document pattern analysis or verification
359 2, 235457, 283 86, 283 91, G06K 974, G06K 710, G03H 100, B42D 1500
Patent
active
057514127
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to devices to aid in authenticating a diffraction surface attached to an object, to thereby aid in authenticating and identifying the origin of the object.
BACKGROUND OF THE INVENTION
The present invention relates to optical authentication and identification technology and more particularly but not exclusively to the application thereof to credit and security cards, bank notes, cheques, and products of various types. More particularly, the present invention relates to devices to aid in authentication and identification of diffraction surfaces.
Diffracted images can be used to confirm visually (as well as electronically) the authenticity of a diffraction surface. A disadvantage of using a collimated laser beam to produc such diffracted images is that such a beam may not produce sharp, clear diffracted images and may not provide the ability to differentiate between a genuine optically diffractive surface and a counterfeit surface produced from a genuine surface by a process of holographic remastering (sometimes known as holographic reorigination).
OBJECT OF THE INVENTION
It is the object of the present invention to overcome or substantially ameliorate the above disadvantage.
SUMMARY OF THE INVENTION
There is disclosed herein a viewing device to aid in authenticating an optical surface, which surface is adapted to produce a projected image from an incident light beam, said device comprising;
a base;
a laser light source mounted on the base to provide a light beam and to project the light beam along a predetermined path, said laser light source being provided to illuminate said optical surface to produce a diffracted beam;
an image surface mounted on said base to receive said diffracted beam from said optical surface so that the projected image is received on said image surface and may be viewed by an observer; and
an optical lens system positioned along said path said configured so as to focus said beam on said image surface if a mirror is placed along said path, in a preferred position of said optical surface, to direct said beam at said image surface.
Preferably the image surface is provided by an image member through which light can pass, so that said image can be observed on said member from either side thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will now be described by way of non-limiting example with reference to the accompanying drawings, wherein:
FIGS. 1a and 1b are schematic illustrations of a viewing apparatus;
FIG. 2 is a schematic illustration of the spot of light produced at an optical surface by a preferred embodiment of the viewing apparatus of FIG. 1;
FIG. 3 is a schematic illustration of a hand held viewing device incorporating the viewing technique employed in the apparatus of FIG. 1.
It should be noted that the laser diode and lens system shown in FIGS. 1 and 3 are internal components which are included in the figures for clarity of explanation.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
In FIG. 1 there is a schematically illustrated (in side elevation of FIG. 1(a) and in top view in FIG. 1(b)) a device for viewing an optical surface 100. The optical surface 100 is designed to produce projected images, when correctly illuminated, via a process of optical diffraction.
The output of a laser diode 101 is passed through a lens system 102 to produce a beam of light 103. The beam 103 is reflected by a mirror 104 onto the optical surface 100. The mirror 104 is used in order to enable convenient location and housing of the laser 101 and lens system 102 while also enabling an optimum angle of incidence--in this case slightly off perpendicular--of the beam 103 onto the optical surface 100.
The optical surface 100 causes specular reflection of part of the incident beam 103 into the beam 105, and diffraction of part of the incident beam 103 into the diffracted beam 106. The mirror 104 is positioned such that the beam 103 is not perpendicular to the optical surface 100, thereby creatin
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Atherton Peter Samuel
Bullock Graeme
Duell Graham
Flynn Daphne
Martinuzzo Steven
Font Frank G.
Mikoh Technology Limited
Viena-Eisenberg Jason D.
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