Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-06-07
2001-05-01
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S620000, C359S459000, C283S091000
Reexamination Certificate
active
06226127
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to substrates which provide one or more optical images which vary according to the angle of view in dependence upon microscopic reflection as opposed to diffraction.
There are many applications where such optically variable images are required or desirable: one important application is to provide a security identification on an article of value. Generally hitherto, relatively complicated methods of manufacture have been necessary in order to produce optically variable images, or alternatively these images have been of poor quality or relatively easy to counterfeit.
We have now devised substrates which provide an optically variable image of good quality, yet these substrates can be formed with a complex array of pixels which make them very difficult to counterfeit.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a substrate which is arranged to provide at least one optically variable image, the substrate being formed with a plurality of groups of elemental areas, the different groups forming respective image pixels, and the different elemental areas of each group being formed with respective grooves or ridges or sets of grooves or ridges, the grooves or ridges of the different elemental areas of each group being at different orientations.
The substrate may be arranged to be viewed under reflected light, the light being reflected from the grooves or ridges. Alternatively, the substrate may be formed of transparent or partially transparent material and arranged to be viewed by light transmitted through the substrate from its rear, the light being refracted (or refracted and reflected) by the grooves or ridges.
Each elemental area of each pixel directs light to the viewer only for a respective angle of view. Thus, for any given angle of view, the image seen by the viewer is made up of light reflected or refracted from the different pixels, but typically only from one elemental area of each such pixel. As the substrate is turned, different elemental areas of each pixel reflect or refract light to the viewer. In this way, a dynamically changing image is produced.
The grooves or ridges of each elemental area may be parallel to each other, or substantially parallel: in other words, the grooves or ridges may depart somewhat from being absolutely parallel to each other. Also, the grooves or ridges of each elemental area may be straight, or they may be curved. The elemental areas may be square, circular or of any other desired shape. Furthermore, the elemental areas of each group may be arranged in line (i.e. in a linear disposition, whether on a straight or on a curved line), or they may be closely packed together (e.g. in a square or circular zone). In any event, the substrate does not use diffraction effects and there is no interference between the light rays passing from the substrate to the viewer.
The arrangement so far described provides a two-dimensional, variable image. In a modification, a variable image which is at least partly three-dimensional is provided. In this modification, the teachings of our UK patent application No. 9617314.1 are used. Thus, at least some of the elemental areas of at least some of the pixels are each made up of two grooves or ridges, or series of grooves or ridges, forming a stereo pair, the two grooves or ridges or series of grooves or ridges being inclined to each other so as to be viewable by the respective eyes of the viewer (at the relevant angle of view for that elemental area), and thus forming an image of a point at a predetermined distance from the plane of the substrate: this distance is dependent on the spacing and relative angles of the two series of grooves or ridges.
A plurality of such “point” images is provided by those stereo pairs, of different pixels, which are seen by the viewer at the relevant angle of view: the plurality of such point images together form an overall three-dimensional image. As previously described, this image changes with different angles of view.
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Kettler, J. E., “The Compact Disk as a Diffraction Grating,”American Journal of Physics, vol. 59, No. 4, pp. 367-368 (Apr. 1991).
Dunn Paul
Rowe Andrew
Dang Hung Xuan
Fryco Limited
Schindler Edwin D.
Spector David N.
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