Optical spectrometer and method

• US 20050175362A1
• Filed: 02/21/2004
• Published: 08/11/2005
• Est. Priority Date: 01/22/2004
• Status: Abandoned Application

• Current Assignee: Bookham Incorporated (Lumentum Holdings Inc.)
• Original Assignee: Bookham Incorporated (Lumentum Holdings Inc.)
• Inventors: Wilson, Gordon
• Application Number:
  US10/784,081
• Publication Number:
  US 20050175362A1
• Time in Patent Office: Days
• US Class Current: 398/212
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01J 3/0294 Multi-channel spectroscopy
• CPC Class Codes: G01J 3/1804 Plane gratings
• CPC Class Codes: G01J 3/32 Investigating bands of a spectrum in sequence by a single detector

Abstract

An optical apparatus and associated method(s) that utilize zeroth-order feedback to provide precise positional information about optical components comprising the optical apparatus.

Claims

1. In an optical device having at least one movable element, a method of operating the optical device comprising the steps of:

receiving an optical signal from an optical input aperture;

diffracting the optical signal into one or more chromatically dispersed non-zeroth-order components and a non-chromatically dispersed zeroth-order component; and

directing one of the non-zeroth-order components to an optical output;

CHARACTERIZED IN THAT;

positional feedback information about the movable element is determined. from the zeroth-order optical signal.

2. The method according to claim 1 further comprising the step of:

directing the zeroth-order component to a position detector.

3. The method according to claim 2 further comprising the step of:

directing the optical signal to the movable element.

4. The method according to claim 3 wherein the optical-signal directing, the zeroth-order-component directing, and the non-zeroth-order-component directing is performed by a common optical element.

5. The method according to claim 4 wherein the common optical element is a lens.

6. The method according to claim 1 wherein the diffracting step is performed by the action of the movable element and that movable element is a diffraction grating.

7. The method according to claim 1 further comprising the step of:

positioning the movable element based upon the positional feedback information.

8. The method according to claim 1 wherein the movable element is a mirror.

9. The method according to claim 1 wherein the optical input aperture comprises a plurality of input apertures.

10. The method according to claim 1 wherein the optical output comprises a tapered slit.

11. The method according to claim 1 further comprising the step of:

chopping the non-zeroth order components such that desirable signal/noise characteristics are realized.

13. The optical device according to claim 7 wherein the movable reflector is responsive to control signals determined from the positional feedback information.

14. The optical device according to claim 7 wherein the diffractor is a diffraction grating.

15. The optical device according to claim 7 wherein the diffractor and the movable reflector are the same optical element and that same optical element comprises a grating.

16. The optical device according to claim 8 further comprising an optical element for directing the input optical signal to the diffractor.

17. The optical device according to claim 8 further comprising an optical element for directing the input optical signal to the diffractor and a non-zeroth-order component to the output.

19. The optical device according to claim 13 wherein the input optical signal director element, the non-zeroth-order directing element and the zeroth-order directing element are a common optical element.

20. The optical device according to claim 14 wherein the common optical element comprises a lens.

24. The optical device according to claim 16 further comprising a means for directing the zeroth-order component to the position determining means.

25. The optical device according to claim 17 wherein the zeroth-order component directing means and the non-zeroth order directing means are lenses.

26. The optical device according to claim 17 wherein the zeroth-order component directing means and the non-zeroth order directing means comprise a common lens.

12. An optical device comprising:

an input for receiving an optical signal;

a diffractor, for diffracting the optical signal into a one or more chromatically dispersed non-zeroth-order components and a non-chromatically-dispersed zeroth-order component;

a movable reflector, for selectively directing one of the non-zeroth order components to an output; and

a position detector;

responsive to the zeroth-order component;

for providing positional feedback information about the movable reflector.

18. The optical device according to claim 12 further comprising an optical element for directing the zeroth-order component to the position detector.

21. The optical device according to claim 12 wherein the input comprises one or more apertures.

22. The optical device according to claim 12 wherein the output comprises a tapered slit.

23. An optical device comprising:

means for inputting an optical signal;

means for diffracting the optical signal into one or more chromatically dispersed non-zeroth-order components and a non-chromatically dispersed zeroth-order component;

means for directing, one of the non-zeroth components to an output; and

means for determining, a position of the directing means from information derived from the zeroth-order component.

27. The optical device according to claim 23 further comprising:

means for chopping the output directed components.