MXPA99004262A - Optical images - Google Patents

Abstract

A substrate 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. The different elemental areas (A1 to An) of each group are formed with respective grooves or ridges or sets of grooves or ridges (121 to 12n), which are at different orientations in the different elemental areas such that each elemental area of each pixel directs light to the viewer for a respective angle of view:for any given angle of view, the image seen by the viewer is made up of light reflected or refracted without interference from the different pixels, but only from a respective elemental area of each pixel.

Description

OPTICAL IMAGES The present invention relates to substrates, which provide one or more optical images, which vary according to the angle of observation depending on the microscopic reflection opposite to the diffraction. There are many applications where such optically variable images are required or desired: an important application is to provide a security identification on an article of value. In general, until now, relatively complicated manufacturing methods have been necessary to optically produce images. variables, or alternatively, those images have been of poor quality or relatively easy to falsify. Now we have devised substrates, which provide an optically variable image of good quality, even when those substrates can be formed with a complex arrangement of pixels, which makes them very difficult to falsify. According to the present invention, a substrate is provided, which is arranged to provide at least one optically variable image, the substrate is formed with a plurality of groups of fundamental areas, the different groups form respective image pixels, and the different ones elementary areas of each group are formed with grooves of flanges or sets of grooves or respective flanges, the grooves or ridges of the different elementary areas of each group are in different orientations. The substrate can be arranged to be observed under the reflected light, the light is reflected from the grooves or ridges. Alternatively, the substrate may be formed of transparent or partially transparent material, and arranged to be observed by the light transmitted through the substrate from its back, the light is refracted (or refracted and reflected) by the slots or flanges . Each elementary area of each pixel directs the light towards the observer only for a respective observation angle. Thus, for any given angle of observation, the image seen by the observer is constituted of the reflected or refracted light from the different pixels, but, typically, of an elementary area of each of said pixels. When the substrate is flipped, the different elementary areas of each pixel reflect or refract the light towards the observer. In this way, an image that changes dynamically is produced.

The grooves or ridges of each elementary area may be parallel to each other, or substantially parallel: in other words, the grooves or ridges may be somewhat offset from that which is absolutely parallel to each other. Also, the grooves or ridges of each elementary area can be straight, or they can be curved. The elementary areas can be square, circular or in any other desired way. In addition, the elementary areas of each group can be arranged in line (that is, in a linear arrangement, either on a straight or curved line), or they can be packed very close together (for example, in a square or circular area). In any case, the substrate does not use the effects of diffraction and there is no interference between the light rays that pass from the substrate to the observer. The arrangement just described provides a variable, two-dimensional image. In a modification, a variable image is provided, which is at least partially three-dimensional. In this modification, the teachings of our British patent application No. 9617314.1 are used. Thus, at least some of the elementary areas of at least some of the pixels are each constituted of two grooves or ridges, or series of grooves or ridges, which form a stereopar, the two grooves or ridges, or series of grooves. or flanges are inclined to each other so that they can be observed by the respective eyes of the observer (at the observation angle relevant to that elementary area), and thus forming an image of a point at a predetermined distance from the plane of the substrate: this distance It depends on the spacing and relative angles of the two series of grooves or ridges. A plurality of such 'point' images is provided by those stereopairs, of different pixels, which are viewed by the observer at the relevant angle of observation: the plurality of such point images together form a total three-dimensional image.

As described above, this image changes with the different viewing angles. The embodiments of the present invention will be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a diagram showing a set of reflecting slots on a substrate: FIGURE 2 is a diagram similar showing a set of reflecting slots on a substrate, but oriented at a different angle; and FIGURE 3 is a similar diagram showing a group of elementary areas having successively different orientations slots.

First reference will be made to Figures 1 and 2 to explain the principles used in the substrates according to the present invention. Figure 1 shows a set of parallel grooves 12 formed in a substrate 10, which is intended to be observed under reflected light: because the grooves 12 run parallel to the upper and lower edges of the substrate 10, the observer will only see the light reflected from these grooves when the substrate 10 is oriented so that the grooves are horizontal. Figure 2 shows a set of parallel grooves 22, which are inclined toward the upper and lower edges of the substrate 20: the observer will only see light reflected from those grooves when the substrate 20 is rotated through a corresponding angle (about of an axis perpendicular to its plane), to bring the slots 22 to a hori-zonal orientation. Figure 3 shows a group of successive elementary areas Ax to An, each formed with a set of parallel slots 12? up to 12n, but with the slots of each such element oriented at an angle towards the slots of the preceding element of the group. In this way, when the substrate, on which this group of elements is formed, is rotated through 180 ° in a counter-clockwise direction, the successive elements Ai to An become visible to the observer, to his time. The group of elements can be used to form a pixel of an image, and the effect is that the rotation of the substrate produces, in effect, a dynamic movement of that pixel. In this way, a substrate is formed according to the invention, with a plurality of groups of elementary areas, the different groups form respective image pixels: the different elementary areas of each group are formed with respective sets of slots, with the slots of the different elementary areas of the group being at different orientations within the plane of the substrate. For any given angle of observation, the image seen by the observer is made up of the reflected light of the different pixels, but only of one elementary area of each of such pixels: the substrate does not use the effects of the diffraction and there is no interference between the rays of light that pass from the substrate to the observer. When the substrate is rotated or viewed from a changing angle, the different elementary areas of each pixel reflect the light to the observer, so that a dynamically changing image is produced. The resolution of the individual slots can be as low as 2 microns. Each elementary area can have any desired number of slots, although as few as one or two slots can be provided in each of such elementary areas. In general, each elementary area can be as small as 5 microns, although there is no upper limit to its size. Although elementary square areas are shown, they can, in principle, be of any desired shape and size. Also, although straight slots are shown, they can instead be curved or in any other way. Furthermore, the grooves of each elementary area need not be absolutely parallel to each other, and may vary in orientation within that elementary area. In other words, the slot may have the property of a vector or image image oriented by pixels or any combination of the two. In a modification, at least some of the elementary areas of at least some of the pixels may be arranged to contribute to the three-dimensional image, in accordance with the teachings of our British patent application No. 9617314.1. Each of such elementary areas is constituted by two series of grooves that form a stereopar, the two series of grooves are inclined to each other to be observed by the respective eyes of the observer, and in this way, form an image from a point to a predetermined distance from the plane of the substrate. A plurality of such point images is provided by those stereopairs of different pixels, which are seen at the relevant observation angle: the plurality of such point images together form a total three-dimensional image. Although the principles of the invention have been described with reference to a substrate formed with grooves, and to be seen under reflected light (the light that is being reflected from the grooves themselves), the substrate can instead be transparent and formed with ridges instead of grooves, to be seen by the light transmitted through the substrate and refracted (or refracted and reflected) by the ridges. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the one conventional for the manufacture of the objects to which it relates.

Claims (18)

1. REGVINDICATIONS
2. Having described the invention as above, the content of the following claims is claimed as property. 1. A substrate, characterized in that it is arranged to provide an optically variable image composed of a plurality of pixels, the substrate has a front surface, which is formed by a plurality of groups of elementary areas, the different groups form respective image pixels , and the different elementary areas of each group are formed with grooves or ridges or with respective groove or flange assemblies, the grooves or ridges of the different elementary areas of each group are at different orientations, and the grooves or ridges are arranged to direct the light towards the observer, reflecting the incident light on the frontal surface, without interference occurring between the rays of light directed towards the observer from the substrate. The substrate according to claim 1, characterized in that at least some of the elementary areas comprise a plurality of grooves or ridges, which are parallel or substantially parallel to each other.
3. 3. The substrate according to claim 1 or 2, characterized in that the grooves or ridges of at least some elementary areas are rectilinear.
4. The substrate according to any of the preceding claims, characterized in that the grooves or ridges of at least some of the elementary areas are curved.
5. The substrate according to any of the preceding claims, characterized in that at least some of the elementary areas are square-shaped.
6. The substrate according to any of the preceding claims, characterized in that at least some of the elementary areas are circular in shape.
7. The substrate according to any of the preceding claims, characterized in that in at least some of the groups, the elementary areas are arranged in a linear arrangement.
8. The substrate according to any of the preceding claims, characterized in that, in at least some of the groups of elementary areas, the elementary areas are packed very close together.
9. The substrate according to any of the preceding claims, characterized in that at least some of the elementary areas of at least some of the groups, comprise two grooves or ridges, or two series of grooves or ridges, forming a stereoptic, the two slots or ridges, or the two series of slots or ridges, are inclined relative to each other to direct light towards the respective eyes of the observer, when the observer sees the substrate from a predetermined viewing angle.
10. 10. A substrate, characterized in that it is arranged to provide an optically variable image composed of a plurality of pixels, the substrate is formed of transparent material and has a front surface, which is formed with a plurality of groups of elementary areas, the different groups that form respective image pixels, and the different elementary areas of each group are formed with respective slots or flanges or with respective slots or flange assemblies, the slots or ridges of the different elementary areas of each group, are in different orientations and the slots or ridges are arranged to direct the light towards the observer, refracting the light transmitted through the substrate from its back, without interference occurring between the rays of light directed towards the observer from the substrate.
11. The substrate according to claim 10, characterized in that at least some of the elementary areas comprise a plurality of grooves or ridges that are parallel or substantially parallel to each other.
12. The substrate according to claim 10 or 11, characterized in that the grooves or ridges of at least some of the elementary areas are rectilinear.
13. 13. The substrate according to any of claims 10 to 12, characterized in that the grooves or ridges of at least some of the elementary areas are curved.
14. The substrate according to any of claims 10 to 13, characterized in that at least some of the elementary areas are square in shape.
15. 15. The substrate according to any of claims 10 to 14, characterized in that at least some of the elementary areas are circular in shape.
16. 16. The substrate according to any of claims 10 to 15, characterized in that, in at least some of the groups, the elementary areas are arranged in a linear arrangement.
17. 17. The substrate according to any of claims 10 to 16, characterized in that, in at least some of the groups of elementary areas, the elementary areas are packed very close together.
18. 18. The substrate according to any of claims 10 to 17, characterized in that at least some of the elementary areas of at least some of the groups, comprise two grooves or ridges, or two series of grooves or ridges, forming a stereopar, both slots or ridges or two series of slots or ridges, are inclined to each other to direct the light towards the respective eyes of the observer, when the observer sees the substrate from a predetermined viewing angle.