PHOTO ACOUSTIC SAMPLE DETECTOR WITH LIGHT GUIDE

• US 20100192669A1
• Filed: 06/30/2008
• Published: 08/05/2010
• Est. Priority Date: 07/06/2007
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Vissenberg, Michel Cornelis Josephus Marie, Van Kesteren, Hans Willem, Presura, Cristian
• Application Number:
  US12/667,745
• Publication Number:
  US 20100192669A1
• Time in Patent Office: Days
• US Class Current: 73/23.3
• CPC Class Codes: G01N 2021/052 Tubular type; cavity type; multireflective
• CPC Class Codes: G01N 21/031 Multipass arrangements
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 33/0037 for NOx
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A photo acoustic sample detector (10) is provided for detecting a concentration of sample molecules in a sample mixture (1). The photo acoustic sample detector (10) comprises an input for receiving the sample mixture (1), an acoustic cavity (3) for containing the sample mixture (1), a light source (5) for sending light (50) into the acoustic cavity (3) for exciting the sample molecules and thereby causing sound waves in the acoustic cavity (3) and a pick up element (4) for converting the sound waves into electrical signals (12). The photo acoustic sample detector (10) also comprises a light guide (2) comprising a transparent inner wall (8) at an interface of the light guide (2) and the acoustic cavity (3) and a reflective outer wall (7) at an outside of the light guide (2). The light source (5) is arranged for illuminating the light guide (2). The light guide (2) serves for reflecting the light (50) back and forth through the light guide (2) and the acoustic cavity (3).

Claims

1. A photo acoustic sample detector (10) for detecting a concentration of sample molecules in a sample mixture (1), the photo acoustic sample detector (10) comprising,

an input for receiving the sample mixture (1),

an acoustic cavity (3) for containing the sample mixture (1),

a light source (5) for sending light (50) into the acoustic cavity (3) for exciting the sample molecules and thereby causing sound waves in the acoustic cavity (3),

a pick up element (4) for converting the sound waves into electrical signals (12), and

a light guide (2),

the light source (5) being arranged for illuminating the light guide (2), the light guide (2) comprising a transparent inner wall (8) at an interface of the light guide (2) and the acoustic cavity (3) and a reflective outer wall (7) at an outside of the light guide (2) for reflecting the light (50) back and forth through the light guide (2) and the acoustic cavity (3).

2. A photo acoustic sample detector (10) as claimed in claim 1, wherein the light source (5) comprises at least one light emitting diode with an emission spectrum, overlapping an absorption spectrum of the sample molecules.

3. A photo acoustic sample detector (10) as claimed in claim 2, further comprising an additional light emitting diode (6) with an emission spectrum that is mainly outside the absorption spectrum of the sample molecules.

4. A photo acoustic sample detector (10) as claimed in claim 3, further comprising a light modulator for providing an antiphase modulation of the intensities of the light emitting diode (5) and the additional light emitting diode (6).

5. A photo acoustic sample detector (10) as claimed in claim 1, wherein the light guide (2) comprises glass.

6. A photo acoustic sample detector (10) as claimed in claim 1, wherein the transparent inner wall (8) comprises an antireflective coating and the reflective outer wall (7) comprises a reflective coating.

7. A photo acoustic sample detector (10) as claimed in claim 1, wherein the pick up element (4) is a tuning fork.

8. A photo acoustic sample detector (10) as claimed in claim 1, wherein the pick up element (4) is optically shielded from the light from the light guide in order to reduce direct excitation of the pick up element (4).

9. A photo acoustic sample detector (10) as claimed in claim 1, wherein the pick up element (4) is thermally shielded from the light guide (2).

10. A photo acoustic sample detector (10) as claimed in claim 1, wherein the acoustic cavity (3) has an elongated shape and wherein the light guide (2) is arranged such that the light (50) passes the acoustic cavity (3) transversally.

11. A photo acoustic sample detector (10) as claimed in claim 1, wherein a cross section of the light guide (2) comprises two semicircles, situated at opposite sides of the acoustic cavity (3).

12. A photo acoustic sample detector (10) as claimed in claim 11, wherein a cross section of the light guide (2) is arranged to provide a spiral light path (11) for guiding the light (50) spirally through the light guide (2) and the acoustic cavity (3) from an outer radius of the light guide (2) to an inner radius.

13. A photo acoustic sample detector (10) as claimed in claim 12, wherein the spiral light path (11) is provided by reflective walls (9) inside the light guide (2).

14. A photo acoustic sample detector (10) as claimed in claim 12, wherein the spiral light path (11) is provided by air gaps inside the light guide (2).

15. A breath analysis device comprising a photo acoustic sample detector (10) as described in claim 1.