Apparatus and a method for testing documents

• US 5,280,333 A
• Filed: 07/10/1991
• Issued: 01/18/1994
• Est. Priority Date: 07/11/1990
• Status: Expired due to Fees

• Current Assignee: GAO Gesellschaft Fur Automation und Organisation mbH
• Original Assignee: GAO Gesellschaft Fur Automation und Organisation mbH
• Inventors: Wunderer, Bernd
• Primary Examiner(s): McGraw, Vincent P.
• Assistant Examiner(s): KEESEE, LACHARLES
• Application Number:
  US07/727,629
• Time in Patent Office: 923 Days
• Field of Search: 356/71, 356/317-318, 250/481, 250/341, 250/337, 250/338.1, 250/458.1, 250/556, 209/534, 235/491
• US Class Current: 356/71
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07D 7/121 Apparatus characterised by sensor details

Abstract

In an apparatus for testing documents, the optical illuminating unit comprises at least one light guide provided with fluorescent substance for directing at least two light fractions of different wavelengths onto a common area of the document. The light fractions are switched on and off by the time-division multiplex method. Special switching regulators are provided for regulating not only the switch-on and switch-off operation of the illumination sources but also the brightness thereof.

Claims

1. An apparatus for testing documents having an optical means for illuminating the document in at least one spectral range and a means for taking up the light diffusely reflected by the document and/or transmitted through the document, the apparatus comprising:

a light guide including a fluorescent substance for directing first and second light fractions having different spectral ranges onto a common area of the document, the light guide having an excitation band, the first light fraction being fluorescent light which arises by excitation of the light guide from a light source directed onto the light guide having a spectral range in the excitation band, and the second light fraction being from a further light source guided through the light guide, the further light source having a further spectral range outside the excitation band.

2. The apparatus of claim 1, wherein the light guide is a plastic plate having flat or curved surfaces and narrow edges, and the first light fraction is the fluorescent light which arises by excitation of radiation from a light source directed onto at least one of the surfaces and which exits at an exit edge of the plastic plate facing the document.

3. The apparatus of claim 2, wherein the second light fraction enters via an edge opposite the exit edge and exits at the exit edge facing the document.

4. The apparatus of claim 2, wherein the second light fraction is the fluorescent light of a further light guide which is coupled optically to a first light guide.

5. The apparatus of claim 2, wherein the second light fraction comprises the light of at least one light-emitting diode.

6. The apparatus of claim 2, wherein the exit edge of the light guide is provided with certain optically reflective areas to influence the form of an exit light lobe.

7. The apparatus of claim 2, further comprising an optical unit provided between the exit edge of the light guide and the document for imaging the exit edge of the light guide on the document.

8. The apparatus of claim 1, wherein the light source and the further light source are connected with switching regulators that regulate both the switch-on and switch-off phases of the light sources and the brightness thereof.

9. An apparatus for testing documents having an optical means for illuminating the document in at least one spectral range and a means for taking up the light diffusely reflected by the document and/or transmitted through the document, comprising:

first and second light guides each including a fluorescent substance for directing at least two light fractions having differing spectral ranges onto a common area of the document;

whereby the at least two fractions are fluorescent light which arise by excitation of radiation from first and second sources directed onto the at least two light guides.

10. A method for testing documents which are illuminated with light of different spectral ranges and scanned to take up the light diffusely reflected and/or transmitted by the document, comprising the step of:

directing first and second light fractions having first and second spectral ranges, respectively, onto a common area of the document via at least one light guide including a fluorescent substance, the at least one light guide having an excitation band, the first light fraction being fluorescent light, which arises by excitation of radiation from a light source directed onto the at least one light guide and the second light fraction being light from at least one further light source guided through the at least one light guide, the light source and at least one further light source being switched on and off by a time-division multiplex method.

11. The method of claim 10, wherein the directing step is carried out with the light source having a spectral range within the excitation band of the at least one light guide.

12. The method of claim 10, wherein the light from the further light source is produced using light-emitting diodes connected with a switching regulator which produces pulse width modulated control signals in synchronism with the switch-on and switch-off operation of the light-emitting diodes, the further light source having a second spectral range being outside the excitation band.

13. A method for testing documents which are illuminated with light of different spectral ranges and scanned to take up the light diffusely reflected and/or transmitted by the document, comprising the step of:

directing light fractions of different spectral ranges onto a common area of the document via at least two light guides each including a fluorescent substance, the light fractions of the different spectral ranges being switched on and off by a time-division multiplex method, whereby both fractions are fluorescent light which arise by excitation of radiation from at least two light sources directed onto the at least two light guides.

14. An apparatus for testing documents by observing light directed onto the documents, the apparatus comprising:

a light guide including a fluorescent substance and an edge positioned to direct light onto the document, the light guide having an excitation band;

first and second light sources for directing light onto the light guide so that the light exits the body at said edge, the first light source emitting light of a spectral range within the excitation band which excites the fluorescent substance so that a first light fraction emitted at the edge of the body is of the wavelength of light emitted by the fluorescent substance when excited, and the second light source emitting light having a second spectral range outside the excitation band, the light from the second light source being guided through the body and exiting the body at said edge.

15. Apparatus according to claim 14 wherein the light guide includes two spaced apart outer surfaces, and the first light source directs light against one of the outer surfaces and the second light source directs light onto another edge of the body.

16. A method of testing document by observing light directed onto the document, the method comprising the steps of:

forming a light transmissive light guide including a fluorescent substance;

positioning the light guide relative to the document so that light directed against the light guide reaches the document;

directing a first light having a wavelength selected to excite the fluorescent substance against the body so that light emitted by the excited fluorescent substance reaches the document; and

directing light of another spectral range against the light guide so that light of such other spectral range reaches the document.

17. An apparatus for testing a document having an optical means for illuminating the document in at least one spectral range and a means for taking up the light diffusely reflected by the document and/or transmitted through the document, comprising:

at least one light guide including a fluorescent substance for directing first and second light fractions of different spectral ranges onto a common area of the document, the first light fraction being fluorescent light which arises by excitation of the light guide from a light source directed onto the light guide, and the second light fraction being from a further light source guided through the light guide, the wavelength of at least one light fraction being the wavelength of light emitted by the fluorescent substance when excited; and

a further light guide, the light guide and the further light guide being oriented at an angle of about 45°

based on the normal of the document and positioned relative to the document such that the document is located in the superposed area of emitted lobes.

18. A method for testing documents which are illuminated with light of different spectral ranges and scanned to take up the light diffusely reflected and/or transmitted by the document, comprising the steps of:

providing at least one light guide including a fluorescent substance, the light guide having an excitation band;

directing first and second light fractions having first and second spectral ranges, respectively, onto a common area of the document via the at least one light guide, the first light fraction being fluorescent light which arises by excitation of radiation from a light source directed onto the light guide, the second light fraction being the light from at least one further light source guided through the light guide, the light source having a spectral range within the excitation band of the light guide and comprising a fluorescent lamp;

connecting the light source and the at least one further light source to a time-division multiplex apparatus, the light source and the at least one further light source being turned on and off by the time-division multiplex apparatus; and

connecting the fluorescent lamp to a switching regulator which produces control pulse sequences (bursts) dependent on the brightness of the fluorescent lamp in synchronism with the switch-on and switch-off operation of said fluorescent lamp.

19. An apparatus for testing documents by observing light directed onto the documents, the apparatus comprising:

a light guide including relatively large, opposing and spaced apart outer surfaces and an edge between the surfaces positioned to direct light onto the document;

first and second light sources for directing light onto the light guide so that the light exits the body at said edge, the light guide including a fluorescent substance, the first light source emitting light of a wavelength which excites the fluorescent substance so that at least one light fraction emitted at the edge of the body is of the wavelength of light emitted by the fluorescent substance when excited, the first and second light sources emitting light of differing wavelengths.