Fourier-transform spectrometers

• US 20020097402A1
• Filed: 08/02/2001
• Published: 07/25/2002
• Est. Priority Date: 11/04/1998
• Status: Active Grant

• Current Assignee: Christopher J. Manning
• Original Assignee: Christopher J. Manning
• Inventors: Manning, Christopher J.
• Granted Patent: US 7,224,464 B2
• Time in Patent Office: Days
• US Class Current: 356/451
• CPC Class Codes: G01J 3/453 by correlation of the amplitudes

Abstract

A novel tilt-compensated interferometer geometry is described. The design uses tilt- and shear-compensation optics to simultaneously maintain high throughput and precise interferometric alignment, even in the presence of non-ideal scanning motions. The tilt-compensation mechanism consists of a novel beamsplitter/reflector assembly that produces two anti-parallel beams. A variety of enhancements to the basic design are described, providing a family of related interferometer designs. These interferometers have applications in spectrometry, spectral imaging and metrology.

Claims

1. A spectrometer, comprising:

a source of a primary beam of radiant energy;

a beamsplitter fixed in relation to the primary beam, for dividing primary beam into at least first and second energy beams which follow first and second optical paths;

a tunable solid-state reference laser coupled to the spectrometer through a filter;

at least one return reflector for reflecting the first beam back to the beamsplitter;

at least one radiant energy detector;

a control, data acquisition and processing electronic system;

4. the spectrometer of claim 1 where the filter is an etalon;

5. the spectrometer of claim 1 where the solid-state laser is a vertical cavity surface emitting laser;

6. the spectrometer of claim 1 where the solid state laser has a linewidth of less than 1 cm⁻

1;

11. the spectrometer of claim 1 where the signal generated by the diode laser is demodulated;

12. the spectrometer of claim 1 where an additional source of radiant energy is used to probe the transfer functions of the detector or detectors;

13. the spectrometer of claim 1 where the transfer function of the detector is inverted by the use of an adaptive filter;

15. the spectrometer of claim 1 where the detector signal is modified to correct for nonlinear response using the response to a probe signal;

2. A spectrometer, comprising:

a source of a primary beam of radiant energy;

a beamsplitter fixed in relation to the primary beam, for dividing primary beam into at least first and second energy beams which follow first and second optical paths;

at least one return reflector for reflecting the first beam back to he beamsplitting means;

at least one radiant energy detector;

a control, data acquisition and processing electronic system;

a roof reflector rigidly coupled to the beamsplitter for the purpose of folding the second beam by an angle;

7. the roof reflector assembly of claim 2 where the assembly is machined by wire EDM;

8. the roof reflector assembly of claim 2 where the assembly is fabricated from ceramic;

9. the roof reflector assembly of claim 2 where the reflective coating is prepared by replication;

16. the spectrometer of claim 2 where the detector signal is modified to correct for nonlinear response using the response to a probe signal;

3. A spectrometer, comprising:

a source of a primary beam of radiant energy;

a beamsplitter fixed in relation to the primary beam, for dividing primary beam into at least first and second energy beams which follow first and second optical paths;

at least one return reflector for reflecting the first beam back to the beamsplitting means;

at least one radiant energy detector;

a control, data acquisition and processing electronic system;

at least one flat compensator plate, having parallel faces, which may be scanned by nutation to vary the optical path difference;

10. the spectrometer of claim 3 where a second refractive scanning plate is interposed in the first or second beam;

17. the spectrometer of claim 3 where the detector signal is modified to correct for nonlinear response using the response to a probe signal.

14. the spectrometer of claim I where the radiation detector detects an optically subtracted beam;