Sensor for gases or ions

• US 4,872,759 A
• Filed: 07/07/1988
• Issued: 10/10/1989
• Est. Priority Date: 07/07/1987
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Dohnke, Karl-Otto, Stich-Baumeister, Eva-M., Winnacker, Albrecht
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US07/216,134
• Time in Patent Office: 460 Days
• Field of Search: 356/5, 356/28.5, 356/432
• US Class Current: 356/432
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B
• CPC Class Codes: G01N 21/783 for analysing gases
• CPC Class Codes: G01N 2201/0622 Use of a compensation LED
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/42 Coupling light guides with opto-electronic elements
• CPC Class Codes: G02B 6/4295 coupling with semiconductor devices activated by light through the light guide, e.g. thyristors, phototransistors

Abstract

A sensor for gases or ions with a light source, a detector and a sensor layer all of which are attached to a carrier. A thin sensor film, the absorptivity of which changes through the action of the measurement medium, is arranged on a light waveguide, the one flat side of which covers a flat end face of the light source, the end face of the carrier and a plane receiving surface of the detector. Thus, a sensitive sensor, especially for gases, is obtained in which the sensor layer, the light source and the detector form an integrated structural unit.

Claims

1. A sensor for detecting gases and ions comprising:

carrier means with at least one flat surface;

light source means with a light emitting surface for generating light and attached to the carrier means so that the light emitting surface of the source is in the same plane as the flat surface of the carrier;

light detector means with a flat detecting surface for detecting and quantifying light falling thereon, attached to the carrier means on the side of the carrier means opposite that to which the source means is attached, the detector being mounted so that its flat detecting surface is in the same plane as the flat surface of the carrier;

light wave guide means with at least one flat side mounted on the flat surface of the carrier, covering the light means, the detector means, and the flat surface with the waveguide'"'"'s flat side, conveying light of various intensities from said source means to said detector means; and

thin sensor layer means attached to the waveguide means on the side of the waveguide opposite to the side attached to the carrier for analyzing the gases and ions by changing its absorptivity, and thereby altering light flow through the light waveguide means.

2. The sensor of claim 1 further comprising a matching layer placed between the light source means and the light waveguide means for improving the light coupling between the waveguide and the source.

3. The sensor of claim 2 wherein the matching layer is comprised of an ultraviolet-hardening adhesive.

4. The sensor of claim 1 further comprising a matching layer placed between the light waveguide means and the detector means for improving the light coupling between the waveguide means and the detector.

5. The sensor of claim 4 wherein the matching layer is comprised of an ultraviolet-hardening adhesive.

6. The sensor of claim 1 wherein the waveguide means is comprised of a III-V semiconductor compound.

7. The sensor of claim 6 wherein the waveguide is further comprised of gallium phosphide.

8. The sensor of claim 1 wherein the waveguide means is provided with a mirror surface on the side of the waveguide which is attached to the flat surface of the carrier, in the region where the waveguide contacts the carrier.

9. The sensor of claim 8 wherein the waveguide means is provided with a mirror surface on the side of the waveguide which is not attached to the flat surface of the carrier in the region where the light source contacts the waveguide and where the detector contacts the waveguide.

10. The sensor of claim 1, further comprising a second light detector means for monitoring the variability of the light source attached to the light waveguide means on the opposite side of the light waveguide and in the same region where the light source contacts the waveguide.

11. The sensor of claim 1 wherein the light source applies light to the waveguide at a oblique angle.

12. The sensor of claim 1 wherein the thin sensor layer is between 50 and 200 nanometers in thickness.

13. The sensor of claim 1 wherein the thin sensor layer comprises an optical filter with a reversible color change having at least one alkaline or acid color pigment.

14. The sensor of claim 13 wherein the color pigment contains the triphenylmethane system.

15. The sensor of claim 13 wherein the pigment contains malachite-green or crystal-violet lacton.

16. The sensor of claim 13 wherein the sensor layer contains phthaleins or sulfonephthaleins as the pigment.

17. The sensor of claim 13 where the acid color pigment contains bisphenol-A and salicic acid.

18. The sensor of claim 13 wherein the sensor layer contains p-toluidin or p-chloroanilin.

19. The sensor of claim 1 wherein the thin sensor layer comprises an optical filter with a reversible color change having at least one alkaline or acid color pigment and at least one complementary acid or alkaline compound.

20. The sensor of claim 19 wherein the pigment and compound are embedded in a matrix substance.

21. The sensor of claim 1 wherein the sensor layer is comprised at least partially of a chemosensitive material.

22. The sensor of claim 1 wherein the waveguide is between 100 and 400 micrometers thick.

23. The sensor of claim 1 wherein the light source means is a light-emitting diode, the diode and the waveguide both comprising a III-V semiconductor and being fabricated as one unit.

24. The sensor of claim 1 wherein the detector and the waveguide are fabricated as one unit.

25. The sensor of claim 1 wherein the detector contains a pn junction.

26. The sensor of claim 1 wherein the detector contains a metal-semiconductor schottky-type junction.

27. The sensor of claim 1 wherein the light waveguide is of the multimode type.

28. The sensor of claim 1 wherein two moats are etched into the III-V semiconductor material between the light source and the detector for optical insulation.