Optical displacement sensor element

Patent metadata

Field	Value
Publication number	US-2016138906-A1
Application number	US-201414899701-A
Country	US
Kind code	A1
Filing date	Jun 20, 2014
Priority date	Jun 21, 2013
Publication date	May 19, 2016
Grant date	—

Abstract

The present invention relates to an optical displacement sensor comprising a first at least partially reflective surface and a second surface having a diffractive pattern, the surfaces being provided on elements having a variable distance between them, each surface pair defining a cavity between them. The sensor also comprising at least one light source transmitting light at least one a chosen wavelength range into said cavities and at least one light detector receiving light from the cavities, wherein said diffractive patterns are adapted to direct light toward at least one detector provided in a known position relative to said diffractive surfaces.

First claim

1 . An optical displacement sensor comprising:
a first at least partially reflective surface and a second surface having at least two diffractive patterns, the first and second surfaces being provided on elements having a variable distance between them, each pair constituting the partially reflective surface and diffractive pattern defining a cavity between them, at least one light source transmitting light in at least one chosen wavelength range into said cavities; and at least one light detector receiving light from the cavities, wherein each pair is adapted to provide a maximum diffractive efficiency at chosen wavelengths within said range, said diffractive patterns being adapted to direct light toward at least one detector provided in a known position relative to said diffractive surfaces, the detector being adapted to measure the diffraction efficiency phase corresponding to each pair.

2 . The sensor according to claim 1 , comprising three diffraction patterns and three pairs having cavity lengths providing phase offsets of 0°, 120° and 240°, respectively at the chosen wavelengths.

3 . The sensor according to claim 1 , comprising two diffraction patterns and two pairs having cavity lengths, the first diffractive pattern providing phase offsets of 0° and 180°, respectively, between the diffracted and reflected signal from the first pattern, the second diffractive pattern providing phase offsets of 90° and 270° between the diffracted and reflected and at the chosen wavelengths.

4 . The sensor according to claim 1 , wherein the diffractive patterns are diffractive lenses focusing the light toward the respective sensors.

5 . The sensor according to claim 4 , wherein each diffractive lens is constituted by circular patterns having an optical axis being shifted relative to the beam centre.

6 . The sensor according to claim 5 , wherein a central area of each diffractive lens is provided with a surface treatment so as to avoid direct reflections from the light source to the detectors.

7 . The sensor according to claim 1 , wherein a difference in cavity lengths is chosen so as to provide a chosen phase differences between the light directed from said gratings diffractive gratings.

8 . The sensor according to claim 1 , wherein the light source emits a light beam covering a certain area, the cavities size across the beam cross section covering essentially equal area in the beam, so as to be subject to essentially the same amount of light.

9 . The sensor according to claim 1 , wherein said surfaces are treated so as to avoid direct reflections back to the light source.

10 . The sensor according to claim 1 , wherein the light source is positioned coaxially with said reflective surfaces, said cavities and detectors being distributed around said axis.

11 . The sensor according to claim 10 , wherein said cavities constitute equally sized sections around said axis.

12 . The sensor according to claim 10 , wherein said light source is positioned outside said axis, said cavities covering essentially equal areas and essentially sections of the circumference relative to the distance from the centre of said centre.

13 . The sensor according to claim 1 , wherein said light source illuminates said cavities through an optical fibre transmitting light at several chosen wavelengths, and wherein each diffractive pattern directing light at one of the chosen wavelengths toward one or several optical fibres, which are transmitting the signal to one or several detectors.

14 . The sensor according to claim 1 , wherein said light source illuminates said cavities through an optical fibre transmitting light at several chosen wavelengths, and wherein each diffractive pattern directing light back toward said optical fibre being adapted to transmit the signal to one or several detectors.

15 . The sensor according to claim 13 , further comprising a dispersive element between the optical fibre and the diffractive patterns that directs different wavelengths to different diffractive patterns.

16 . The sensor according to claim 1 , wherein the cavities define different cavity lengths.

17 . The sensor according to claim 1 , wherein the cavities are illuminated with light at different wavelengths.

18 . A microphone comprising a sensor according to claim 1 , wherein one of said surfaces is mounted on a membrane.

19 . The sensor according to claim 14 , further comprising a dispersive element between the optical fibre and the diffractive patterns that directs different wavelengths to different diffractive patterns.

Assignees

• Sintef Tto As

Inventors

• Lacolle Matthieu
• Johansen Ib-Rune
• Bakke Thor
• Bjor Ole-Hermann

Classifications

• H04R23/008

  using optical signals for detecting or generating sound · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title