초록 ▼

A critical wavelength refractometer is provided. A broadband light source (413) is optically coupled to a sensor (401), the sensor having at least one sensing surface (407). As the light from the broadband light source passes through the sensor, it undergoes multiple internal reflections against the

A critical wavelength refractometer is provided. A broadband light source (413) is optically coupled to a sensor (401), the sensor having at least one sensing surface (407). As the light from the broadband light source passes through the sensor, it undergoes multiple internal reflections against the sensing surface. Due to the index of refraction of the material in contact with the sensing surface, a portion of the light passing through the sensor is reflected while a second portion of the light is transmitted through the sensing surface and into the material. A detector (421) coupled to the sensor measures the spectral intensity of the light that passes completely through the sensor after having undergone the multiple internal reflections against the sensing surface. A microprocessor (423) coupled to the detector determines the critical wavelength based on the spectral intensity measurement, thereby allowing the index of refraction of the material to be determined.

대표청구항 ▼

What is claimed is: 1. A critical wavelength refractometer comprising: a broadband light source; a sensor, wherein an entrance face of said sensor is optically coupled to said broadband light source, said sensor comprised of at least one sensing surface, wherein light emitted by said broadband ligh

What is claimed is: 1. A critical wavelength refractometer comprising: a broadband light source; a sensor, wherein an entrance face of said sensor is optically coupled to said broadband light source, said sensor comprised of at least one sensing surface, wherein light emitted by said broadband light source and optically coupled to said sensor undergoes a plurality of internal reflections within said sensor, wherein a portion of said plurality of internal reflections are against said at least one sensing surface, wherein said portion is comprised of multiple reflections, and wherein for each of said multiple reflections a first fraction of said light is reflected from said sensing surface and a second fraction of said light passes through said sensing surface, wherein said first and second fractions of said light are a function of an index of refraction of a material in contact with said at least one sensing surface; a detector optically coupled to an exit face of said sensor, said detector measuring spectral intensity for said first fraction of said light passing through said sensor and exiting through said exit face of said sensor; and a microprocessor coupled to said detector, said microprocessor determining a critical wavelength for said material and said index of refraction for said material from said spectral intensity. 2. The critical wavelength refractometer of claim 1, said sensor further comprising a sensor window, wherein said at least one sensing surface comprises a lower surface of said sensor window, and wherein an upper surface of said sensor window and said lower surface are parallel to within 10 arc seconds. 3. The critical wavelength refractometer of claim 1, said sensor further comprising a sensor window, a first prism and a second prism, wherein said broadband light source is optically coupled to said entrance face of said sensor via said first prism, and wherein said detector is optically coupled to said exit face of said sensor via said second prism. 4. The critical wavelength refractometer of claim 1, said sensor further comprising a sensor probe, wherein said at least one sensing surface comprises a lower surface and an upper surface of said sensor probe, wherein an end surface of said sensor probe is mirrored, wherein said entrance face of said sensor is comprised of a first portion of a front surface of said sensor probe, and wherein said exit face of said sensor is comprised of a second portion of said front surface of said sensor probe. 5. The critical wavelength refractometer of claim 1, wherein said detector is a spectrograph. 6. The critical wavelength refractometer of claim 1, further comprising an optical collimator interposed between said broadband light source and said sensor. 7. The critical wavelength refractometer of claim 1, further comprising a first optical fiber interposed between said broadband light source and said sensor and a second optical fiber interposed between said sensor and said detector. 8. The critical wavelength refractometer of claim 1, wherein said sensor is fabricated from a material selected from the group consisting of silica, crown glass, flint glass and germanium doped silica. 9. The critical wavelength refractometer of claim 1, further comprising: a beam splitter interposed between said broadband light source and said sensor, wherein said beam splitter divides said light from said broadband light source into a reference beam and a sensing beam, wherein said sensing beam is optically coupled to said sensor; and a second detector, wherein said reference beam is optically coupled to said second detector, said second detector measuring spectral intensity for said reference beam, and wherein said microprocessor is coupled to said second detector. 10. The critical wavelength refractometer of claim 9, wherein said beam splitter is a polarizing beam splitter. 11. The critical wavelength refractometer of claim 1, further comprising: a beam splitter interposed between said broadband light source and said sensor, wherein said beam splitter divides said light from said broadband light source into a reference beam and a sensing beam, wherein said sensing beam is optically coupled to said sensor, and wherein said reference beam is optically coupled to said detector; a first shutter interposed between said beam splitter and said detector, wherein said first shutter controls entry of said sensing beam to said detector; and a second shutter interposed between said beam splitter and said detector, wherein said second shutter controls entry of said reference beam to said detector. 12. The critical wavelength refractometer of claim 11, wherein said beam splitter is a polarizing beam splitter. 13. The critical wavelength refractometer of claim 11, wherein said first shutter is interposed between said sensor and said detector. 14. The critical wavelength refractometer of claim 11, further comprising optical means for coupling said reference beam to said detector, said optical means comprising at least one mirror and at least one beam combiner. 15. The critical wavelength refractometer of claim 1, said sensor further comprising a sensor window, wherein said at least one sensing surface comprises a first portion of a lower surface of said sensor window, and wherein a second portion of said lower surface of said sensor window is mirrored, wherein said critical wavelength refractometer further comprises: a beam splitter interposed between said broadband light source and said sensor, wherein said beam splitter divides said light from said broadband light source into a reference beam and a sensing beam, wherein said sensing beam is optically coupled to said first portion of said lower surface of said sensor window, and wherein said reference beam is optically coupled to said second portion of said lower surface of said sensor window; and a second detector, wherein said reference beam is optically coupled to said second detector, said second detector measuring spectral intensity for said reference beam, and wherein said microprocessor is coupled to said second detector. 16. The critical wavelength refractometer of claim 15, wherein said beam splitter is a polarizing beam splitter. 17. The critical wavelength refractometer of claim 1, said sensor further comprising a sensor window, wherein said at least one sensing surface comprises a first portion of a lower surface of said sensor window, and wherein a second portion of said lower surface of said sensor window is mirrored, wherein said critical wavelength refractometer further comprises: a beam splitter interposed between said broadband light source and said sensor, wherein said beam splitter divides said light from said broadband light source into a reference beam and a sensing beam, wherein said sensing beam is optically coupled to said first portion of said lower surface of said sensor window, and wherein said reference beam is optically coupled to said second portion of said lower surface of said sensor window, and wherein said reference beam is optically coupled to said detector; a first shutter interposed between said first portion of said lower surface of said sensor window and said detector, wherein said first shutter controls entry of said sensing beam to said detector; and a second shutter interposed between said second portion of said lower surface of said sensor window and said detector, wherein said second shutter controls entry of said reference beam to said detector. 18. The critical wavelength refractometer of claim 17, wherein said beam splitter is a polarizing beam splitter. 19. A method of determining an index of refraction of a material in contact with a sensing surface of a sensor, the method comprising the steps of: transmitting a light beam from a broadband light source into said sensor, said sensor having a second index of refraction; fixing an angle of incidence of said light beam relative to said sensor, wherein said light beam undergoes multiple internal reflections against said sensing surface of said sensor, wherein each of said multiple internal reflections against said sensing surface provides a separate sensing location, wherein said material is in contact with said sensing surface of said sensor; transmitting said light beam exiting from said sensor to a spectrographic detector, said spectrographic detector measuring light intensity as a function of wavelength for said light beam exiting said sensor; monitoring the light intensity as a function of wavelength for said light beam exiting from said sensor with said spectrographic detector; determining a critical wavelength corresponding to said light beam exiting from said sensor; and determining the index of refraction of said material from said critical wavelength, said angle of incidence, and said second index of refraction corresponding to said sensor.