GB2159268A

GB2159268A - Device for producing and detecting a gapshaped pencil of light rays

Info

Publication number: GB2159268A
Application number: GB08412442A
Authority: GB
Inventors: Bengt Akerstrom; Bo Goran Eklund
Original assignee: ESSELTE SECURITY SYST AB; Esselte Security Systems AB
Current assignee: ESSELTE SECURITY SYST AB; Esselte Security Systems AB
Priority date: 1982-11-18
Filing date: 1984-05-16
Publication date: 1985-11-27
Also published as: SE8206585L; GB8412442D0; SE434090B; GB2159268B; DE3418055C2; DE3418055A1; SE8206585D0

Abstract

A device for producing and detecting a gap-shaped parallel pencil of light rays, including a light source (1) and detecting members (9) of a suitable known kind, such as phototransistors for detecting the rays which may have passed through an object to be measured (18), comprises a first shielding member (2) having a mirroring layer (4) facing the light source (1), and a gap (5) where said mirroring layer (4) has been removed. A further characterizing feature is that a second shielding member (8) is located between said first shielding member (2) and said detecting members (9), said second shielding member (8) having at least one shielding layer (10,11) with at least one gap (12,14), substantially aligning with the gap (5), of the layer (4) of the first shielding member (2), and said detecting members (9), and that the shielding members (2,8) are spaced from each other, so that a space (17) is formed therebetween, into which space (17) an object to be measured (18), for example a banknote (18), is intended to be inserted. <IMAGE>

Description

SPECIFICATION Device for producing and detecting a gapshaped pencil of light rays This invention relates to a device for producing and detecting a gap-shaped parallel pencil of light rays, where a light source is provided, from which light is intended to incide to a gap formed in a shielding member, and detecting members are provided to detect the gap and, for example, light having passed through an object to be measured.

At many measuring or detecting methods one or more gap-shaped pencils of light rays are utilized where each ray pencil is caused to light an object with varying light permeability.

By detecting light having passed through the object it is possible, for example, to detect a pattern in respect of permeability which is comprised in the object. One example thereof is the detection of watermarks at the checking of banknotes. One problem in this connection is to produce a well-defined, narrow and gapshaped pencil of rays in order to obtain good dissolution. The object is both to produce well-defined gaps and to eliminate the effect of scattered light. For obtaining the densest possible scanning, the photo-diode is arranged in zig-zag configuration, in such a manner, that two ray pencils are located tightly adjacent one another. This implies great risks of light scattering.

The present invention has the object to produce a device, which renders it possible to obtain a well-defined ray pencil in a very simple and inexpensive way. The device also reduces substantially the effect of heat radiation from the light source.

The invention, thus, relates to a device for producing and detecting a gap-shaped parallel pencil of light rays, where a light source is provided, from which light is intended to incide to at least one gap formed in a shielding member, which gap is intended to be passed through by the light, and detecting members of a suitable known kind, such as photo-transistors, are provided to detect the gap and, for example, light having passed through an object to be measured.

The device is especially characterized in that it comprises a first shielding member, which consists of a mirror where mirroring layers arranged on a pane of glass or corresponding material are mirroring to the light source, that every gap consists of a score where said mirroring layer has been removed, that a second shielding member is provided between said first shielding member and said detecting member, where also said second shielding member comprises at least one shielding layer with at least one score, gap, substantially aligning with a score, gap, of the layer of the first shielding member and said detecting member, and that the shielding members are located spaced from each other, so that a gap is formed therebetween, in which gap an object to be measured, for example a banknote, is intended to be inserted.

The invention is described in greater detail in the following, with reference to an embodiment thereof and to the accompanying drawing, in which Figure 1 is a schematically shown section through an embodiment of the device according to the invention perpendicularly to the longitudinal direction of the gap-shaped ray pencil, Figure 2 is a view A-A according to Fig. 1, Figure 3 is a view B-B according to Fig. 1, Figure 4 shows a first shielding member according to the invention with two scores in the mirroring layer of the shielding member, and Figure 5 shows a zigzag configuration, a first row and a second row, of photo-detectors for detecting two ray pencils.

In Fig. 1 the numeral 1 designates a light source, such as a row of lamps extending perpendicularly to the plane of the Figure, from which lamps light is intended to incide to first shielding member 2, which is shown in detail in Fig. 4 and consists of a mirror in the form of a preferably planeparallel pane of glass or corresponding material, one side of which, 3, the remote side in relation to the light source 1, is coated with a mirroring layer 4 mirroring to the light source, and on said layer with a layer (not shown) of preferably black heat-resistant paint. In the mirror-paint layer two scores 5, 6 parallel to each other, a first score 5 and a second score 6, are located where the layers are removed. Said scores 5, 6 constitute two gaps 5, 6, through which light can pass.According to a preferred embodiment, the coated side 3 is covered by a protective anti-reflex coated layer 7 in the form of a protective glass, the two sides of which, which are in parallel with the shielding member 2, are anti-reflex coated.

The numeral 8 designates a second shielding member located preferably in parallel with the first shielding member 2 and between the same and detecting members 9, which will be dealt with in detail later on. According to one embodiment, the second shielding member comprises a first mirroring layer 10 located closest to the light source 1 and provided with scores, which layer 10 mirrors on the remote side in relation to the light source. The second shielding member further comprises a second mirroring layer 11 located between the first layer and said detecting members 9, which layer 11 is provided with scores and mirrors to the light source 1. The layers 10, 11 preferably are in parallel with each other and comprise adjacent scores, a first one and a second one, 12, 1 3 and respectively, 14, 1 5.

The scores 5, 1 2 and 14 align with each other, and a first row or corresponding ar rangement of detecting members 9 and the scores 6, 1 3 and 1 5 align with each other and a second row or corresponding arrangement of detecting members 9.

The layers 10, 11 preferably are coated with black heat-resistant paint in a way corresponding to the layer 4.

According to another preferred embodiment, substantially the entire layer 10 is covered by a protective anti-reflex coated layer 1 6 in the form of a protective glass, both sides of which, which are in parallel with the shielding member 8, are anti-reflex coated.

The shielding members 2, 8 at the embodiment shown here are located spaced from each other, so that a gap 1 7 is formed between them, into which gap 1 7 an object to be measured 18, for example a banknote 18, is intended to be inserted.

The detecting members 9 for detecting the gap 17 and the scores 5, 6, 12, 13, 14, 15 and light having passed through the object to be measured consist, for example, of phototransistors 9 connected to a recording unit 1 9. For obtaining a compact arrangement with small division, Fig. 5, the photo-transistors 9 are arranged in a zigzag configuration, whereby two rows are formed.

The mode of operation of the device according to the invention should have become apparent substantially from the above. Light from the light source 1 incides to the first shielding member 2, and only light meeting the scores 5, 6 passes through the mirroring layer 4. The remaining radiation is reflected, which is essential, because in this way the heating of the device is reduced. Light having passed through the scores 5, 6 thereafter passes through the gap 1 7 between the shiel ding members 2, 8 and a possible object to be measured 18. By means of the scores 12, 14 and, respectively, 13, 1 5 scattered light having passed through the scores 5, 6 is shielded effectively, and through the opposed mirroring layers 1 0, 11 scattered light is reflected out to the right and left in Fig. 1.

Through each of the scores 14, 1 5 an especially well-defined gap-shaped pencil of light rays passes out, which pencils can be detected by the detecting members 9.

At the checking of the watermarks of banknotes, for example, the banknotes 1 8 are caused to pass through the gap 17, and the variations in intensity of light having passed through a banknote, which variations are detected by the detecting members 9, yield a very good picture of the watermark. The device can also be used, for example, for checking the safety thread of banknotes. At the checking of banknotes the gap 1 7 has a thickness of about 1.5 mm, so that the banknotes passing therethrough clean the protective glass etc. from dust and the like.

As should have become clear from the aforesaid, the invention implies that a detecting device with very good dissolution by using gap-shaped pencils of light rays can be brought about with high precision as well as simply and inexpensively. A suitable score width at the checking of banknotes is about 0.1 mm. The mirroring layer 4, 10, 11 and possible paint layers are removed by a simple tool, so that a well-defined gap with uniform width is obtained. The mirroring layers also have the function of reflecting away heat radiation and scattered light.

The invention has been described above with reference to substantially one embodiment. Several more embodiments and minor alterations, of course, can be imagined without abandoning the invention idea.

In certain cases, for example, it may be sufficient with only one row of scores 5, 12, 14 or 6, 13, 1 5 and one row of detecting members 9 for obtaining satisfactory dissolution. In a corresponding manner more rows than two can be imagined. In certain cases, furthermore, only one layer provided with scores may be sufficient, for example layer 10, for achieving the required accuracy. In certain cases the protective layers 7, 1 6 can be imagined omitted. The score width, of course, is to be adapted to the demand, and it, therefore, can vary substantially compared to the one stated above, i.e. about 0.1 mm.

The layers 10, 11 of the second shielding member 8 need not be mirroring. Each layer 10, 11 can consist, for example, of a mirroring layer, which by oxydation has been made non-mirroring. The layers 10, 11 also may consist of a material other than such as used for producing mirroring layers. The material, however, in respect of composition and structure shall be of such condition that at its scoring well-defined, i.e. not serrated, score edges are obtained.

Of course, the gaps in the shielding layers 4, 10, 11 can be provided by any suitable means, even by forming a layer with a gap ab initio

Claims

1. A device for producing and detecting a gap-shaped parallel pencil of light rays, where a light source is provided, from which light is intended to incide to at least one gap formed in a shielding member, which gap is intended to be passed through by the light, and where detecting members are provided for detecting the gap and, for example, light having passed through an object to be measured, characterized in that it comprises a first shielding member, which consists of a mirror, the mirroring layer(s) of which arranged on a pane of glass or corresponding material are mirroring to the light source, that each gap consists of a score where said mirroring layer(s) are removed, that a second shielding member is located between said first shielding member and said detecting members, and also said second shielding member consists of a pane of glass or corresponding material with at least one shielding layer with at least one score, gap, substantially aligning with a score gap, of the layer of the first shielding member and said detecting mmbers, and that the shielding members are located spaced from each other, so that a gap is formed therebetween, into which gap an object to be monitored, for example a banknote, is intended to be inserted.

2. A device as defined in claim 1, characterized in that said second shielding member comprises a first mirroring layer located closest to the light source and provided with scores and mirroring on the remote side in relation to the light source, and a second mirroring layer located between the first layer and said detecting members and provided with scores and mirroring to the light source, which first and second layers preferably are in parallel with each other and comprise scores aligning with said detecting members and a score of said first shielding member.

3. A device as defined in claim 1 or 2, characterized in that each shielding member on its surface facing to the gap located between the shielding members is covered by a protective anti-reflex coated layer, for example a protective glass which is anti-reflex coated on on its two sides in parallel with the shielding members.

4. A device as defined in claim 1, 2 or 3, characterized in that each shielding layer comprises at least two adjacent parallel scores a first one and a second one, which first scores align with each other and a first row or corresponding arrangement of detecting members, and which second scores in a corresponding way align with each other and a second row or corresponding arrangement of detecting members.

5. A device as defined in any one of the preceding claims, where said second shielding members comprise at least one shielding layer on the surface facing to the gap located between the shielding members, characterized in that at least the layer of said first shielding member and the layer of said second shielding member facing to the gap between the shielding members on their surface facing to the gap are covered with heat-resistant, preferably black, paint.

6. A device for producing and detecting a shaped pencil of light rays substantially as any herein described with reference to and/or as illustrated in the accompanying drawings.