DETECTION APPARATUS AND METHOD

• US 20090152468A1
• Filed: 12/18/2006
• Published: 06/18/2009
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Essentra Filter Holdings Limited (Frank Acquisition Four Ltd.)
• Original Assignee: Filtrona PLC
• Inventors: Gilbert, Andrew John, Allen, Philip John
• Granted Patent: US 8,076,643 B2
• Time in Patent Office: Days
• US Class Current: 250/339.60
• CPC Class Codes: B41M 3/14 Security printing securities B42D25/29
• CPC Class Codes: G01V 8/12 using one transmitter and one receiver
• CPC Class Codes: G07D 7/1205 Testing spectral properties

Abstract

A technique and apparatus for detection of infrared radiation emitted from a taggant material sample following the excitation of the sample are described. The decay time of the radiation is a function of the particular taggant being used and so, if the decay characteristic or signature is accurately measured, the particular taggant can be accurately identified. The apparatus comprises an electronic controller (10), a pair (12) of illuminating light-emitting diodes, a photo-detector (14), a first amplifier (16), a three-way sampling switch (18), filter/stores (20)(a-c), second amplifiers (22)(a-c) and an output display (26). The infrared emission is excited by repeatedly illuminating the material for a period of microseconds every few milliseconds using a very intense source of infrared light. This light is supplied by the pair of 940 nm, light-emitting diodes (12). Once this light source has been turned off, the sample continues radiating infrared light for a few milliseconds. The emission is detected by photo-detector (14) that is only sensitive to infrared light in the 800 to 1000 nm waveband. This helps to reject interference from visible light sources.

Claims

1. Detection apparatus for determining the presence, absence or characteristic of a security ink on a sample, the apparatus comprising:

a radiation source for providing excitation radiation to the sample;

a detector for detecting radiation emitted from the sample; and

processing means arranged in use to determine the presence, absence or characteristic of ink on the sample according to analysis of the detected radiation emitted from the sample;

wherein the processing means is arranged to measure radiation emitted from the sample, in the same part of the spectrum as the frequency of excitation, following its excitation.

2. Detection apparatus according to claim 1, wherein the processing means is arranged to measure radiation emitted from the sample at substantially the same frequency as the frequency of excitation.

3. Detection apparatus according to claim 1, wherein the processing means is arranged to measure a decay characteristic of said radiation.

4. Detection apparatus according to claim 1, wherein the excitation radiation is in the infrared part of the spectrum.

9. Detection apparatus according to claim 1 wherein the excitation radiation source emits radiation in the non-visible spectrum.

10. Detection apparatus according to claim 9 wherein the detector senses radiation of substantially the same spectrum as the radiation emitted by the source.

11. Detection apparatus according to claim 1 wherein said processing means comprises a first intensity measurement device for measurement of a reference signal during a first time increment, a second intensity measurement device for measurement of a sample signal during a second time increment subsequent to the first time increment, and a third intensity measurement device for measurement of a baseline background signal during a third time increment subsequent to the second time increment.

12. Detection apparatus according to claim 11 wherein said processing means further includes a device for adjusting the intensity of the radiation source.

5. A method of determining the presence, absence or characteristic of security ink on a sample, the method comprising:

irradiating the sample with excitation radiation;

detecting radiation emitted from the sample; and

processing an electronic signal derived from the detected radiation;

wherein the step of processing includes measuring radiation emitted from the sample, in the same part of the spectrum as the frequency of excitation, following its excitation.

6. A method according to claim 5, wherein the step of processing comprises measuring radiation emitted from the sample at substantially the same frequency as that of the excitation radiation.

7. A method according to claim 5, wherein the step of processing includes measuring a decay characteristic of said radiation.

8. A method according to claim 5, wherein the excitation radiation is in the infrared part of the spectrum.