Thermally compensated optical probe

• US 9,587,983 B1
• Filed: 09/21/2015
• Issued: 03/07/2017
• Est. Priority Date: 09/21/2015
• Status: Active Grant

• Current Assignee: Coherent Inc (Coherent Corp.)
• Original Assignee: Ondax Incorporated (Coherent Corp.)
• Inventors: Ho, Lawrence, Havermeyer, Frank, Carriere, James, Maye, Eric, Moser, Christophe, Heyler, Randy
• Primary Examiner(s): Nur, Abdullahi
• Application Number:
  US14/860,611
• Publication Number:
  US 20170082489A1
• Time in Patent Office: 533 Days
• US Class Current: 1/1
• CPC Class Codes: G01J 3/0227 using notch filters
• CPC Class Codes: G01J 3/0237 Adjustable, e.g. focussing
• CPC Class Codes: G01J 3/0286 Constructional arrangements for compensating for fluctuations caused by temperature, humidity or pressure, or using cooling or temperature stabilization of parts of the device; Controlling the atmosphere inside a spectrometer, e.g. vacuum
• CPC Class Codes: G01J 3/06 Scanning arrangements arrangements for order-selection
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G02B 27/4283 having a diffractive element with major temperature dependent properties
• CPC Class Codes: G02B 5/203 having holographic or diffractive elements diffraction gratings per se G02B5/18; holographic elements per se G02B5/32; generating the spectrum using diffraction elements G01J3/18
• CPC Class Codes: G02B 7/008 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G03H 1/0248 Volume holograms
• CPC Class Codes: G03H 2001/186 Swelling or shrinking the holographic record or compensation thereof, e.g. for controlling the reconstructed wavelength G03H2001/0033, G03H2250/44 take precedence
• CPC Class Codes: G03H 2001/2289 when reconstruction wavelength differs form recording wavelength
• CPC Class Codes: G03H 2227/03 Means for moving one component G03H1/0476, G03H2001/2695 take precedence

Abstract

Systems and methods are provided herein. An exemplary system may include a laser source, the laser source having a laser center wavelength; at least one narrowband optical element receiving light emitted by the laser, the narrowband optical element having a filter center wavelength, the narrowband optical element being arranged such that the filter center wavelength is initially spectrally aligned with the laser center wavelength, the filter center wavelength changing in response to a temperature change such that the filter center wavelength is not substantially aligned with the laser center wavelength; and a passive adjustment mechanism coupled to the narrowband optical element, the passive adjustment mechanism including an actuator, the actuator moving in response to the temperature change, the actuator motion rotating the narrowband optical element, the rotation compensating for the temperature change such that the filter center wavelength and laser center wavelength remain spectrally aligned.

Claims

1. An optical probe comprising:

a laser source, the laser source having a laser center wavelength;

at least one narrowband optical element receiving light emitted by the laser source, the narrowband optical element having a filter center wavelength, the narrowband optical element being arranged such that the filter center wavelength is initially spectrally aligned with the laser center wavelength, the filter center wavelength changing in response to a temperature change such that the filter center wavelength is not substantially aligned with the laser center wavelength; and

a passive adjustment mechanism coupled to the narrowband optical element, the passive adjustment mechanism including an actuator, the actuator moving in response to the temperature change, the actuator motion rotating the narrowband optical element, the rotation compensating for the temperature change such that the filter center wavelength and laser center wavelength remain spectrally aligned.

2. The optical probe of claim 1 wherein the filter center wavelength and the laser center wavelength are spectrally aligned when the filter center wavelength and the laser center wavelength are separated from each other by less than half a difference between a transition width of the narrowband optical element and a linewidth of the laser source.

3. The optical probe of claim 1 wherein the passive adjustment mechanism further comprises a rotating element, the rotating element being coupled to the actuator, the narrowband optical element being disposed on the rotating element.

4. The optical probe of claim 3 wherein the narrowband optical element is disposed on the rotating element such that a midpoint of the narrowband optical element is disposed approximately at a center of rotation of the rotating element.

5. The optical probe of claim 3 wherein the actuator comprises at least one of a bimetallic or memory metal component, the bimetallic or memory metal component contorting in a predefined manner in response to the temperature change, the contortion effecting a rotation of the narrowband optical element turning the rotating element.

6. The optical probe of claim 3 wherein the actuator comprises an arm, the arm comprising a substantially homogeneous material having a coefficient of thermal expansion such that the arm expands or contracts in response to the temperature change, the expansion or contraction turning the rotating element.

7. The optical probe of claim 3 wherein the actuator has a spiral or curved shape and a known movement path with respect to temperature changes, such that the actuator moves in response to the temperature change, the movement turning the rotating element.

8. The optical probe of claim 1 wherein an optical beam path angle is maintained by using at least one pair of rotating optical elements.

9. The optical probe of claim 1 wherein at least one pair of rotating optical elements is mounted to a common rotating element.

10. The optical probe of claim 1 wherein the narrowband optical element is a narrowband diffractive volume holographic grating (VHG) comprising at least one of photosensitive glass, photosensitive polymers, and other photosensitive optical materials.

11. The optical probe of claim 1 wherein the light from the laser source has a wavelength approximately in the range of 300-2,000 nanometers (nm).

12. The optical probe of claim 1 wherein optical feedback from at least one of the narrowband optical elements within the optical probe is optically coupled back to the laser source in order to stabilize and synchronize the laser center wavelength to the filter center wavelength of the narrowband optical element.

13. The optical probe of claim 1 wherein optical feedback from the at least one narrowband optical element is optically coupled to a detector external to the optical probe, the optical feedback including parameters for stabilizing and synchronizing the laser center wavelength to the filter center wavelength of the narrowband optical element.

14. An optical system comprising:

the optical probe of claim 1;

a narrowband laser; and

a detection system, the narrowband laser and detection system being optically coupled via a fiber-optic cable to the optical probe.

15. The optical system of claim 14 further comprising:

a computer, the computer analyzing an optical output of the detection system.

16. An optical system comprising:

a laser source, the laser source having a laser center wavelength;

a first narrowband optical element receiving light transmitted by the laser source, the first narrowband optical element having a first filter center wavelength, the first filter center wavelength being initially spectrally aligned with the laser center wavelength, the first filter center wavelength changing in response to a temperature change such that the first filter center wavelength is not spectrally aligned with the laser center wavelength;

a first passive adjustment mechanism coupled to the first narrowband optical element, the first passive adjustment mechanism including a first actuator, the first actuator moving in response to the temperature change, the first actuator motion rotating the first narrowband optical element, the rotation compensating for the temperature change such that the first filter center wavelength and laser center wavelength remain spectrally aligned;

at least one additional narrowband optical element having a respective filter center wavelength, the respective filter center wavelength being initially spectrally aligned with the laser center wavelength, the respective filter center wavelength changing in response to the temperature change such that the respective filter center wavelength is not spectrally aligned with the laser center wavelength;

an additional passive adjustment mechanism coupled to each additional narrowband optical element, each passive adjustment mechanism including a separate actuator, each separate actuator moving in response to the temperature change, each separate actuator motion rotating an additional narrowband optical element, the rotation compensating for the temperature change such that all the filter center wavelengths and laser center wavelength remain spectrally aligned; and

an optically coupled detection system and computational means for analyzing the filtered optical signals.

17. The optical system of claim 16 wherein an optical beam path angle is maintained by using at least one pair of rotating optical elements.

18. The optical system of claim 16 wherein

a second narrowband optical element and the first narrowband optical element are initially positioned such that their reflective surfaces are approximately parallel to each other;

and

respective rotations of the first and second narrowband optical elements are such that the reflective surfaces of the first and second narrowband optical elements remain approximately substantially parallel to each other.

19. The optical system of claim 16 wherein at least one pair of rotating optical elements is mounted to a common rotating element.

20. The optical system of claim 16 wherein the first filter center wavelength, a second filter center wavelength, and the laser center wavelength are spectrally aligned when the filter center wavelengths and the laser center wavelength are separated from each other by less than half a difference of a transition width of the narrowband optical elements and a linewidth of the laser source.

21. The optical system of claim 16 wherein at least one of the first and second passive adjustment mechanisms each further comprises a rotating element, the rotating element being coupled to the actuator, the narrowband optical element being disposed on the rotating element.

22. The optical system of claim 21 wherein at least one of the first and second narrowband optical elements is disposed on the rotating element such that a respective midpoint of at least one of the first and second narrowband optical elements is disposed approximately at a center of rotation of the rotating element.

23. The optical system of claim 21 wherein at least one of the first and second actuators comprises a bimetallic component, the bimetallic component comprising two metals having different coefficients of thermal expansion such that the bimetallic component contorts in response to the temperature change, the contortion turning the rotating element.

24. The optical system of claim 21 wherein at least one of the first and second actuators comprises an arm, the arm comprising a homogeneous material having a known coefficient of thermal expansion such that the arm expands or contracts in response to the temperature change, the expansion or contraction turning the rotating element.

25. The optical system of claim 21 wherein at least one of the first and second actuators has a spiral shape and a known movement path with respect to temperature changes, such that the actuator moves in response to the temperature change, the movement turning the rotating element.

26. The optical system of claim 16 wherein at least one of the first and second narrowband optical elements is a narrowband diffractive volume holographic grating (VHG) comprising at least one of photosensitive glass, photosensitive polymers, or other photosensitive materials.

27. The optical system of claim 16 wherein a bandwidth of at least one of the narrowband optical elements in an excitation beam path is less than a bandwidth of the narrowband optical elements disposed in a path of reflected light.

28. A method for temperature compensated spectroscopy comprising:

initially arranging a narrowband optical element such that a filter center wavelength of the narrowband optical element is initially spectrally aligned with a laser center wavelength of a laser source;

receiving light emitted by the laser source;

filtering the light by the narrowband optical element;

undergoing a temperature change, the filter center wavelength changing in response to the temperature change such that the filter center wavelength is not substantially aligned with the laser center wavelength; and

passively rotating the narrowband optical element by an actuator in response to the temperature change, the rotation compensating for the temperature change such that the filter center wavelength and laser center wavelength remain spectrally aligned.

29. The method of claim 28 wherein the filter center wavelength and the laser center wavelength are spectrally aligned when the filter center wavelength and the laser center wavelength are separated from each other by less than half a difference between a transition width of the narrowband optical element and a linewidth of the laser source.

30. The method of claim 28 wherein the rotating the narrowband optical element is rotating a rotating element, the actuator being coupled to the rotating element, and the narrowband optical element being disposed on the rotating element.

31. The method of claim 30 wherein the narrowband optical element is disposed on the rotating element such that a midpoint of the narrowband optical element is disposed approximately at a center of rotation of the rotating element.

32. The method of claim 30 wherein the actuator comprises at least one of a bimetallic or memory metal component, the bimetallic or memory metal component contorting in a predefined manner in response to the temperature change, the contortion effecting a rotation of the narrowband optical element turning on the rotating element.

33. The method of claim 30 wherein the actuator comprises an arm, the arm comprising a substantially homogeneous material having a coefficient of thermal expansion such that the arm expands or contracts in response to the temperature change, the expansion or contraction turning the rotating element.

34. The method of claim 30 wherein the actuator has a spiral or curved shape and a known movement path with respect to temperature changes, such that the actuator moves in response to the temperature change, the movement turning the rotating element.

35. The method of claim 28 further comprising:

maintaining an optical beam path angle using at least one pair of the rotating optical elements.

36. The method of claim 28 further comprising:

providing optical feedback from the narrowband optical element to a detector, the optical feedback including parameters for stabilizing and synchronizing the laser center wavelength to the filter center wavelength of the narrowband optical element.