Spectrum analyzer for reading authentication marks

• US 6,274,873 B1
• Filed: 05/14/1999
• Issued: 08/14/2001
• Est. Priority Date: 11/18/1998
• Status: Expired due to Fees

• Current Assignee: Polestar LTD
• Original Assignee: DNA Technologies Incorporated
• Inventors: Outwater, Chris, Helmick, Mark
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US09/311,896
• Time in Patent Office: 823 Days
• Field of Search: 250/458.1, 250/459.1, 250/472.1, 250/473.1, 250/483.1, 250/484.2, 250/271, 235/468, 235/469, 235/491, 283/92
• US Class Current: 250/458.1
• CPC Class Codes: G01J 3/14 using refracting elements, e.g. prisms G01J3/18, G01J3/26 take precedence prisms per se G02B5/04
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/4406 Fluorescence spectrometry

Abstract

A spectrum analyzer determines the light emission characteristics of an authentication mark that is invisible when illuminated with visible light but is visible when illuminated with IR light. The spectrum analyzer includes an IR light source, a mirror positioned to deflect light from the IR light source in a direction that is substantially perpendicular to a surface of the authentication mark, a first lens for collimating light that is emitted by the authentication mark in response to an illumination by the light from the IR light source, an optical element comprising a prism or a hologram for generating a spectrum from the collimated light, a second lens for imaging the spectrum, an IR light blocking filter, a detector positioned to receive light components of the spectrum after the spectrum has been imaged by the second lens and filtered by the IR light blocking filter, and a control unit connected to the detector and programmed to read the authentication mark based on intensities of the light components received by the detector.

Claims

1. A device for reading an authentication mark having an IR mark that is visible when illuminated with IR light but not visible when illuminated with visible light, said device comprising:

an optical system for producing an IR beam oriented in a substantially perpendicular direction to a surface of the authentication mark;

a first lens for collimating light that is emitted by the authentication mark in response to an illumination by the light from the IR beam;

an optical element for generating a spectrum of physically separated light frequency components from the collimated light;

an IR light blocking filter;

a detector positioned to receive light frequency components of the spectrum after the spectrum has been filtered by the IR light blocking filter; and

a control unit connected to the detector and programmed to read the authentication mark based on intensities of the light components received by the detector.

2. The device according to claim 1, wherein the optical system includes an IR light source for generating the IR beam and a mirror that deflects the IR beam in the substantially perpendicular direction to the surface of the authentication mark.

3. The device according to claim 1, further comprising a second lens for imaging the spectrum from the optical element, wherein the IR light blocking filter is positioned to filter the IR light from the light components imaged by the second lens.

4. The device according to claim 1, further comprising a second lens for imaging the spectrum from the optical element, wherein the IR light blocking filter is positioned to filter the spectrum from the optical element, and the second lens images the IR-filtered spectrum onto the detector.

5. The device according to claim 1, wherein the optical element comprises a hologram.

6. The device according to claim 1, wherein the optical element comprises a prism.

7. The device according to claim 6, wherein the detector comprises an array of photodiodes each photodiode positioned to receive a different portion of said physically separated light frequency components.

8. The device according to claim 6, wherein the detector comprises an array of CCDs each positioned to receive different portion of said physically separated light frequency components.

9. The device according to claim 6, wherein the detector comprises an aperture-photodiode assembly that is movable to a plurality of positions, the photodiode receiving different portions of the physically separated light components through the aperture at each of the plurality of positions of the assembly.

10. The device according to claim 6, wherein the detector comprises an aperture-photodiode assembly and the prism is rotatable about a fixed axis to a plurality of positions, the photodiode receiving different light components through the aperture at each of the plurality of positions of the prism.

11. The device according to claim 6, further comprising:

a beam splitter positioned between the collimating lens and the prism;

a reticle positioned to image light deflected by the beam splitter; and

a movable stage on which the authentication mark is mounted, the movable stage being controlled in accordance with the image formed by the reticle.

12. A device for generating a plurality of visible light components from an authentication mark having an IR mark that is visible when illuminated with IR light but not visible when illuminated with visible light, said imaging device comprising:

an IR light source;

means for deflecting light from the IR light source in a direction that is substantially perpendicular to a surface of the authentication mark;

a first lens for collimating light that is emitted by the authentication mark in response to an illumination by the light from the IR light source;

means for generating a spectrum of physically separated light frequency components from the collimated light;

means for imaging the spectrum to have visible light components but no IR light components.

13. The device according to claim 12, wherein the means for imaging includes an IR light blocking filter and an imaging lens.

14. The device according to claim 13, wherein the IR light blocking filter is positioned to filter the IR light from the imaged light components after the light components have been imaged by the imaging lens.

15. The device according to claim 13, wherein the IR light blocking filter is positioned to filter the IR light from the spectrum and the imaging lens generates the visible light components from the IR-filtered spectrum.

16. The device according to claim 12, wherein the means for generating the spectrum comprises a hologram.

17. The device according to claim 12, wherein the means for generating the spectrum comprises a prism.

18. A method for reading an authentication mark having an IR mark that is visible when illuminated with IR light but not visible when illuminated with visible light, said method comprising the steps of:

exposing the IR mark with an IR light beam that is substantially perpendicular to a surface of the authentication mark;

collecting light that is emitted by the authentication mark;

generating a spectrum of physically separated light frequency components from the collected light; and

determining features of the IR mark based on intensities of spectral components of the spectrum,

wherein said IR light beam is IR filtered at some point before said step of determining.

19. The method according to claim 18, further comprising the steps of imaging the components of the spectrum onto a detector, producing signals proportional to the intensities of the components, and amplifying the signals before the step of determining.

20. The method according to claim 19, wherein the detector comprises an array of photodiodes and the step of producing signals includes the step of producing an intensity signal at each of the photodiodes.

21. The method according to claim 19, wherein the detector comprises a movable aperture-photodiode assembly and the step of producing signals includes the step of producing intensity signals as the assembly is moved to different positions.

22. The method according to claim 19, wherein the spectrum is generated using a rotatable prism and the detector comprises a aperture-photodiode assembly, and wherein the step of producing signals includes the step of producing intensity signals as the prism is rotated to different positions.

23. A method for verifying an authentication mark having an IR mark that is visible when illuminated with IR light but not visible when illuminated with visible light, said method comprising the steps of:

illuminating the IR mark with an IR light beam to cause the IR mark to emit visible light;

imaging spectral components of the emitted visible light, said spectral components being physically separated from one another;

detecting intensities of the spectral components to obtain an intensity signature of the emitted visible light; and

comparing the intensity signature of the emitted visible light with a reference intensity signature to verify the authentication mark.

24. The method according to claim 23, further comprising the step of positioning the IR mark to be aligned with the IR light beam.

25. The method according to claim 24, further comprising the step of filtering IR light from the emitted visible light.

26. The method according to claim 23, wherein the step of illuminating includes the steps of generating the IR light beam and deflecting the IR light beam in a direction that is perpendicular to a surface of the IR mark.