Quadrature detection for optical mems pressure gauge

Patent metadata

Field	Value
Publication number	US-2019376861-A1
Application number	US-201816002752-A
Country	US
Kind code	A1
Filing date	Jun 7, 2018
Priority date	Jun 7, 2018
Publication date	Dec 12, 2019
Grant date	—

Abstract

A method and apparatus for measuring a pressure. A pressure gauge includes a first plate having a resonant frequency related to a pressure at the pressure gauge. The first plate is thermally-excited at a selected frequency, and a sensor measures a first power level of a first light having a first wavelength reflected from the first plate and a second power level of a second light having a second wavelength reflected from the first plate. A processor determines a thermal drift in the resonant frequency of the first plate due to the thermal excitation of the first plate from the first power level and the second power level, corrects a pressure measurement determined from the resonant frequency of the first plate for the thermal drift of the resonant frequency, and operates a device based on the pressure measurement.

First claim

What is claimed is:

1 . A method of measuring a pressure, comprising:
thermally exciting a first plate of a Fabry-Perot interferometer to oscillate at a selected frequency; measuring a first power level of a first light reflected from the first plate, the first light having a first wavelength; measuring a second power level of a second light reflected from the first plate, the second light having a second wavelength; and determining a thermal drift in a resonant frequency of the first plate due to the thermal excitement of the first plate from the first power level and the second power level; and correcting a pressure measurement related to the resonant frequency of the first plate for the thermal drift in the resonant frequency; and operating a device based on the pressure measurement.

2 . The method of claim 1 , further comprising determining the thermal drift from a ratio of the first power level and the second power level.

3 . The method of claim 2 , further comprising determining a change in an optical phase between the first light and the second light from the ratio of the first power level and the second power level, and determining the thermal drift from the optical phase.

4 . The method of claim 1 , wherein the Fabry-Perot interferometer includes the first plate and a second plate separated from the first plate by the gap, the method further comprising passing the first light and the second light through the second plate to reflect off of the first plate.

5 . The method of claim 1 , further comprising thermally exciting the first plate using an excitation laser.

6 . The method of claim 5 , further comprising one of: (i) toggling the excitation laser toggled on and off at the selected frequency; and (ii) sinusoidal modulation of an amplitude of the excitation laser.

7 . The method of claim 1 , wherein a phase difference between the first wavelength and the second wavelength is mπ/4 where m is an odd integer.

8 . An apparatus for measuring a pressure, comprising:
a first interrogation light source for generating a first light having a first wavelength; a second interrogation light source for generating a second light having a second wavelength; a pressure gauge including a first plate having a resonant frequency related to a pressure at the pressure gauge; a sensor for measuring a first power level of the first light reflected from the first plate of the pressure gauge and a second power level of the second light reflected from the first plate, wherein the first plate is thermally-excited at a selected frequency; and a processor configured to:
determine a thermal drift in the resonant frequency of the first plate due to the thermal excitation of the first plate from the first power level and the second power level,
correct a pressure measurement determined from the resonant frequency of the first plate for the thermal drift of the resonant frequency, and operate a device based on the pressure measurement.

9 . The apparatus of claim 8 , wherein the processor is further configured to determine the thermal drift from a ratio of the first power level and the second power level.

10 . The apparatus of claim 9 , wherein the processor is further configured to determine a change in an optical phase between the first light and the second light from the ratio of the first power level and the second power level, and determine the thermal drift from the optical phase.

11 . The apparatus of claim 8 , wherein the pressure gauge includes a Fabry-Perot interferometer having the first plate and a second plate separated from the first plate by the gap, wherein the first light source and the second light source direct their respective light onto the first plate through the second plate.

12 . The apparatus of claim 8 , wherein the second plate includes an anti-reflective coating on a surface.

13 . The apparatus of claim 8 , further comprising an excitation light source configured to thermally excite the first plate.

14 . The apparatus of claim 13 , wherein one of: (i) the excitation light source is toggled on and off at the selected frequency and (ii) an amplitude of the excitation light source is modulated in a sinusoidal pattern.

15 . The apparatus of claim 1 , wherein a phase difference between the first wavelength and the second wavelength is mπ/4 where m is an odd integer.

Assignees

• Johnston William Albert
• Barry Alexander Michael
• Baker Hughes A Ge Co Llc

Inventors

• Johnston William Albert
• Barry Alexander Michael

Classifications

• G01L9/0079 Primary

  with Fabry-Perot arrangements · CPC title

• G01L19/04 Primary

  Means for compensating for effects of changes of temperature {, i.e. other than electric compensation} · CPC title