Method and device for detecting soiling

• US 8,334,972 B2
• Filed: 09/07/2010
• Issued: 12/18/2012
• Est. Priority Date: 09/07/2009
• Status: Active Grant

• Current Assignee: Pepperl + Fuchs GmbH
• Original Assignee: Pepperl + Fuchs GmbH
• Inventors: Thien, Marcus
• Primary Examiner(s): Toatley, Gregory J
• Assistant Examiner(s): Alli, Iyabo S
• Application Number:
  US12/876,788
• Publication Number:
  US 20110085161A1
• Time in Patent Office: 833 Days
• Field of Search: 340/601, 340/602, 340/901, 340/438, 340/425.5, 356/237.3, 356/342, 356/436, 356/432, 356/442, 356/448, 356/445
• US Class Current: 356/237.3
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence

Abstract

A device for detecting soiling, having a light source, which emits a light beam, and a layer having a first boundary surface and a second boundary surface, whereby the light beam emitted by the light source first impinges on the first boundary surface, and part of a light beam fraction, which is scattered at the second boundary surface, impinges on a receiver and forms a measuring signal, and hereby the first boundary surface is set up to scatter part of the incident light beam, and the part impinging on the receiver of the light beam, scattered at the first boundary surface, forms a reference signal, and the device is set up further to determine a measure for the soiling of the second boundary surface from the comparison of the reference signal and measuring signal.

Claims

1. A device for detecting soiling comprising:

a light source which emits a light beam;

a layer having a first boundary surface and a second boundary surface,

a receiver for receiving light scattered from said first and secondary boundary surface wherein the light beam emitted by the light source first impinges on the first boundary surface with a scattered portion of the light beam being scattered at the first boundary surface and received by said receiver as a reference signal and a second portion of the light beam passing through said layer and impinging on said second boundary and another scattered portion of the light beam scattered at said second boundary surface and received by said receiver as a measuring signal; and

an evaluator for comparing the reference signal and the measuring signal to determine a measure of the soiling of the secondary boundary surface.

2. The device according to claim 1, wherein the surface of the first boundary surface is roughened.

3. The device according to claim 1, wherein a scattering film is arranged on the first boundary surface.

4. The device according to claim 1, wherein the receiver has a first receiving surface and a second receiving surface.

5. The device according to claim 1, wherein the light scattered at the first boundary surface and the light scattered at the second boundary surface substantially impinge on different receiving surfaces.

6. The device according to, claim 1, wherein the optical axis of the light beam is selected so that in the case of a direct reflection of the light beam at the boundary surfaces, the reflected fraction substantially does not impinge on the receiver directly.

7. The device according to claim 1, wherein the receiver has a reference signal output, connected to an inverting input of an operational amplifier, and a measuring signal output, connected to a noninverting input of the operational amplifier.

8. The device according to claim 7, wherein a controllable voltage divider is provided between the inverting input and the reference signal output.

9. The device according to claim 1, wherein a control device for controlling the light source and the voltage divider is provided and the control device has an output for outputting a signal for the extent of soiling.

15. The device according to claim 1 wherein the soiling is on surfaces of solar collectors and/or solar cells and/or glass panes.

10. A method for detecting soiling on a layer, which has a first boundary surface and a second boundary surface, the method comprising:

directing a light beam from a light source unto said first boundary surface;

directing a scattered portion of light scattered from said first boundary surface onto a receiver to provide a reference signal wherein a potion of light from the beam passes through said layer and impinges on said secondary boundary surface;

directing another scattered portion of light scattered by said second boundary surface onto said receiver to provide a measuring signal; and

measuring a soiling of said layer by comparing the reference signal and the measuring signal.

11. The method according to claim 10, wherein substantially only the scattered light fractions of the two boundary surfaces are transmitted to the receiver.

12. The method according to claim 10 wherein soiling is detected when the measuring signal is greater than the reference signal.

13. The method according to claim 10, wherein the comparison of the reference signal with the measuring signal is carried out at time intervals by a control device and the result of the comparison is transmitted wirelessly or hard-wired to a host device.

14. The method according to claim 13, wherein the control device is supplied with the energy of a solar cell and in the event of soiling a signal is provided by the control device by means of an open collector circuit.

16. The method according to claim 10 wherein the soiling is on surfaces of solar collectors and/or solar cells and/or glass panes.