METHODS AND SYSTEMS FOR CHEMICAL COMPOSITION MEASUREMENT AND MONITORING USING A ROTATING FILTER SPECTROMETER

• US 20130293893A1
• Filed: 07/01/2013
• Published: 11/07/2013
• Est. Priority Date: 07/30/2008
• Status: Active Grant

• Current Assignee: Pason Systems USA Corporation
• Original Assignee: Pason Systems USA Corporation
• Inventors: Bonyuet, David, Saptari, Vidi A.
• Granted Patent: US 9,250,132 B2
• Time in Patent Office: Days
• US Class Current: 356/418
• CPC Class Codes: G01J 2003/1247 Tuning
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0235 using means for replacing an element by another, for replacing a filter or a grating
• CPC Class Codes: G01J 3/06 Scanning arrangements arrangements for order-selection
• CPC Class Codes: G01J 3/32 Investigating bands of a spectrum in sequence by a single detector
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/3174 Filter wheel
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/129 Using chemometrical methods

Abstract

The invention relates to methods and systems for measuring and/or monitoring the chemical composition of a sample (e.g., a process stream), and/or detecting specific substances or compounds in a sample, using light spectroscopy such as absorption, emission and fluorescence spectroscopy. In certain embodiments, the invention relates to spectrometers with rotating narrow-band interference optical filter(s) to measure light intensity as a function of wavelength. More specifically, in certain embodiments, the invention relates to a spectrometer system with a rotatable filter assembly with a position detector rigidly attached thereto, and, in certain embodiments, the further use of various oversampling methods and techniques described herein, made particularly useful in conjunction with the rotatable filter assembly. In preferred embodiments, the rotatable filter is tilted with respect to the rotation axis, thereby providing surprisingly improved measurement stability and significantly improved control of the wavelength coverage of the filter spectrometer.

Claims

1-48. -48. (canceled)

49. A spectroscopic system for detecting electromagnetic radiation that has passed through or is reflected from a sample, the system comprising:

an electromagnetic radiation source having a variable intensity;

a filter assembly configured to filter a beam of electromagnetic radiation produced by the electromagnetic radiation source;

a position detector configured to detect a position of the filter assembly;

a controller configured to adjust the intensity of the electromagnetic radiation source; and

an electromagnetic radiation detector configured to detect electromagnetic radiation that has passed through or is reflected from a sample.

50. The spectroscopic system of claim 49, wherein the filter assembly is rotatable and wherein the position detector is configured to detect an angular position of the filter assembly.

51. The spectroscopic system of claim 49, wherein the controller is in communication with the position detector and is configured to adjust the intensity of the electromagnetic radiation source based on a detected position of the filter assembly.

52. The spectroscopic system of claim 51, wherein the filter assembly comprises a filter having an active portion and an inactive portion and wherein the controller is configured to decrease the intensity of the electromagnetic radiation source when a beam of electromagnetic radiation from the electromagnetic radiation source is incident on an inactive portion of the filter.

53. The spectroscopic system of claim 49, wherein the controller comprises a voltage regulator for controlling a voltage supplied to the electromagnetic radiation source.

54. The spectroscopic system of claim 49, comprising a plurality of electromagnetic radiation sources.

55. The spectroscopic system of claim 54, comprising a plurality of electromagnetic radiation detectors.

56. The spectroscopic system of claim 49, comprising a variable gain amplifier configured to convert a light signal from the electromagnetic radiation detector into an electrical signal.

57. The spectroscopic system of claim 56, wherein the amplifier is in communication with the position detector and is configured to automatically adjust a gain profile of the electrical signal based on a detected position of the filter assembly.

58. The spectroscopic system of claim 49, wherein the filter assembly is configured for rotation about an axis substantially perpendicular to a path of a beam of electromagnetic radiation produced by the electromagnetic radiation source.

59-63. -63. (canceled)

64. A spectroscopic method for detecting electromagnetic radiation that has passed through or is reflected from a sample, comprising:

filtering a beam from an electromagnetic radiation source with a rotating filter assembly;

detecting an angular position of the rotating filter assembly with a position detector having at least one component rigidly coupled to the rotating filter assembly;

intercepting the beam with a sample;

detecting the beam with an electromagnetic radiation detector; and

processing a spectral data signal from the electromagnetic radiation detector to produce 10 chemical information about the sample.

65. The spectroscopic method of claim 64, wherein the rotating filter assembly is configured to rotate about an axis substantially perpendicular to a path of a beam of electromagnetic radiation produced by the electromagnetic radiation source.

66. The spectroscopic method of claim 64, wherein the rotating filter assembly comprises a narrow-band interference filter.

67. The spectroscopic method of claim 64, wherein the rotating filter assembly comprises at least three filters.

68. The spectroscopic method of claim 64, wherein the position detector comprises an encoder configured to produce at least a first signal comprising a series of digital pulses at a first frequency, each digital pulse corresponding to an angular position of the rotating filter assembly.

69. The spectroscopic method of claim 64, comprising digitizing an analog spectral signal from the electromagnetic radiation detector.

70. The spectroscopic method of claim 69, wherein digitizing is performed at a frequency significantly greater than necessary to accurately reproduce the analog spectral signal.

71. The spectroscopic method of claim 70, wherein digitizing is performed at a frequency greater than a Nyquist criterion corresponding to the analog spectral signal.

72. The spectroscopic method of claim 71, wherein digitizing is performed at a frequency greater than at least ten times the Nyquist criterion.

73. The spectroscopic method of claim 64, comprising applying a convolution function to a spectral signal from the electromagnetic radiation detector to enhance wavelength stability and/or repeatability, and/or thereby improving signal-to-noise ratio.

74-91. -91. (canceled)