US 5,784,200 AGranted

Difraction grating recording medium, and method and apparatus for preparing the same

AssigneeDai Nippon Printing Co., Ltd.

InventorToshio Modegi

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Abstract

A hologram seal for security is prepared in pseudo manner by using a diffraction grating pattern. A picture data of a plurality of motifs is inputted to a computer. Within the computer, there are prepared in advance plural kinds of pixel patterns in which grating lines are arranged within one pixel at a predetermined line width, a pitch and an arrangement angle. These pixel patterns are arranged in a matrix form like tiles by making reference to the inputted picture data to represent respective motifs. The picture data in which the motifs are represented is given to an electron beam picture drawing apparatus to prepare a diffraction grating original block. This original block is used to mass-produce pseudo hologram seals by press device. By varying an arrangement angle of grating lines, it is possible to carry out gradation representation, or to record a plurality of motifs in an overlapping manner.

Claims8

Dependent claims

A diffraction grating recording medium in which plural motifs are represented by diffraction gratings, comprising:

a plurality of pixel patterns arranged on a planar surface of a medium, each of said pixel patterns having grating lines of a predetermined width arranged within a predetermined closed area at a predetermined pitch and a predetermined angle with respect to a reference axis defined on said planar surface,
at least one of three parameters of line width, pitch and angle of said pixel patterns being different from the others,
each of said pixel patterns belonging to one of a plurality of groups, respectively, and pixel patterns belonging to the same group having grating lines with different angles within a given angle range relative to each other, such that at least one motif is represented with tones by the pixel patterns belonging to the same group thereof, and
wherein given angle ranges for the respective groups are set so that a difference between boundary angle values of adjacent ranges is greater than a predetermined minimum value, and
wherein pixel patterns belonging to different groups represent different motifs respectively thereby to represent plural motifs on the same planar surface in an overlapping manner.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/784,724Filed 16 Jan 1997 · continuation
Priority: JP 5-14868027 May 1993
Granted: 21 Jul 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G03H 1/30
Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique: discrete…
G02B 5/1847
Diffraction gratings: manufacturing methods
G03H 1/0011
Adaptation of holography to specific applications: for security or authentication
G03H 2001/048
Holographic printer: parallel printer, i.e. a fringe pattern is reproduced