Optical: systems and elements – Holographic system or element – Authentication
Patent
1994-12-08
1998-09-22
Dzierzynski, Paul M.
Optical: systems and elements
Holographic system or element
Authentication
359 15, 359 32, 283 86, G03H 100, G02B 532
Patent
active
058122877
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of light diffracting patterns, such as diffraction gratings and surface-relief holograms. The invention is specifically directed, although not restricted to, rainbow holograms and diffraction gratings used to form decorative or graphic compositions, wherein an image is formed of two or more colours by means of contrasting areas of diffracted light. The invention is directed to a method of using holographically generated diffraction patterns or holograms with multiple spectral colours wherein a "key-colour" (Magenta) is provided which permits the identification of the correct viewing position from which an observer must examine the image in order to see all the other colours in they correct hues.
2. Description of Related Art
Use of diffraction gratings to compose patterns and multi-coloured designs without the use of any conventional inks or pigments has been described, for example U.S. Pat. No. 1,354,471 wherein jewellry, signs and other articles are decorated by colours derived by the diffraction of incident white-light into iridescent spectral colours. Light diffracting patterns such as those described in the above said US Patent are formed by mechanically ruling fine parallel lines into a suitable substrate, the different combinations of shades and colours being attained by varying the number and direction of the lines. A method of making diffraction gratings by optical means is described in the U.S. Pat. No. 3,578,845 using two beams of coherent light from a laser to form a holographic diffraction grating.
The use of holographically formed diffraction gratings to produce decorative patterns which may be embossed into plastic is described by M. C. Hutley in the Spring 1979 issue of the National Physical Laboratory Newsletter pages 6-7. By this method a plurality of complimentary photographic masks are used to form several surface-relief gratings in a photo-resist, to produce the desired decorative pattern. A more elaborate method is described in U.S. Pat. No. 4,629,282 wherein a rainbow hologram (as disclosed in U.S. Pat. No. 3,633,989) is made of a diffusing surface (such as a piece of ground glass) to produce diffractive colour effects. A variation of this method is described in U.S. Pat. No. 4,998,785 wherein the slit laser transmission hologram is replaced by a lens array. In both these methods a diffraction grating is formed in a photo-resist by means of the mutual interference of two or more coherent monochromatic beams of light from a laser to provide a surface relief pattern for subsequent embossing into plastic or other embossable materials. The process of replicating surface-relief holograms formed in photo-resist to form nickel stamping dies which are subsequently used to emboss holograms into plastic materials has been described in detail by a number of authors (see for example Bartolini et al. Applied Optics Vol. 9-10 October 1970, pages 2283-2290. These methods have been improved upon to provide embossed holograms and diffraction gratings for decorative and security purposes, for example U.S. Pat. No. 4,913,504 describes a process for embossing holograms to form a security device for marking documents or articles of value.
Embossed holograms and diffraction gratings provide a high degree of security relative to conventional printed markings or designs, because the diffractive rainbow colours of embossed holograms and diffraction gratings can not be reproduced by conventional printing techniques or by photocopying or photographic methods.
Rainbow holograms and diffraction grating compositions provide an inexpensive means of guaranteeing the authenticity of a document or marking a product as being genuine, rather than counterfeit goods.
Because of their utility as a security device for documents and product marking, the use of embossed holograms has increased worldwide, whilst the general public have little comprehension of holograms and are unused to discerning multi-colour hologram
REFERENCES:
patent: 1354471 (1920-10-01), Doner
patent: 3578845 (1971-05-01), Brooks
patent: 3633989 (1972-01-01), Benton
patent: 4629282 (1986-12-01), McGrew
patent: 4913504 (1990-04-01), Gallagher
patent: 4998785 (1991-03-01), Ridout
patent: 5153751 (1992-10-01), Ishikawa et al.
Optics and Laser Technology, vol. 23, No. 6, Dec. 1991, Haywards Heath, GB, pp. 341-344, E.H. Hogert et al., Alignment and/or Tilting Measurement by Means of Conical Diffraction Phenomena.
Bartolini et al., Embossed Hologram Motion Pictures For Television Playback, Oct. 1970, Applied Optics, vol. 9, No. 10, pp. 2283-2290.
M.C. Hutley, National Physical Laboratory, 1979, pp. 6-7.
N.G. Vlasov et al., Production of Color Specimens by Rainbow Holography, Opt. Spectrosc. (USSR) 67(2), Aug. 1989, pp. 243-245.
Dzierzynski Paul M.
Istituto Poligrafico e Zecca Dello Stato
Schuberg Darren E.
LandOfFree
Holograms having a standard reference color does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Holograms having a standard reference color, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Holograms having a standard reference color will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1628000