Optics: measuring and testing – By dispersed light spectroscopy – With raman type light scattering
Reexamination Certificate
2000-06-26
2002-03-05
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
With raman type light scattering
Reexamination Certificate
active
06353476
ABSTRACT:
FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not Applicable.
FIELD OF THE INVENTION
The present invention pertains generally to the field of spectroscopy. More particularly, the present invention pertains to an apparatus that permits substantially simultaneous collection, and subsequent comparison, of one or more emissions from a plurality of radiation beams. The present invention is particularly, but not exclusively, useful for comparing spectral measurements from scattered emission beams from one or more known qualified substances and one or more unknown but qualified substances, having substantially similar characterizations.
BACKGROUND OF THE INVENTION
Spectroscopy is a general term for the process of measuring energy or intensity as a function of wavelength in a beam of light or radiation using an instrument generally referred to as a spectroscope. Many conventional spectroscopes, and components comprising a spectroscope system, also referred to as an instrument, may include features and components such as a slit through which radiation may pass, a collimator for producing a parallel beam of radiation, one or more prisms or gratings for dispersing radiation through differing angles of deviation based on wavelength, and components for viewing dispersed radiation. Spectroscopy uses absorption, emission, or scattering of electromagnetic radiation by atoms, molecules or ions to qualitatively and quantitatively study physical properties and processes of substances.
Light or radiation that during operation of a spectroscope system is to be directed at one or more substances may be referred to as excitation radiation. A beam of excitation radiation from a source of excitation radiation may be referred to as an excitation beam. As indicated, a spectroscopy instrument may include a number of components for directing, redirecting, dispersing, and modifying an excitation beam, including, without limitation, mirrors, gratings, wave guides, filters, lenses and similar components. An excitation beam may be directed at and through one or more of such components before being directed at selected substances.
Redirection of a radiation beam following contact with a substance commonly is referred to as scattering of radiation. To the extent that atoms or molecules in a substance absorb all or a portion of a beam of radiation, rather than reflect the radiation of an excitation beam, a substance may become excited, and the energy level of the substance may be increased to a higher energy level. Radiation that passes through a substance may produce a small portion of light that is scattered in a variety of directions. Radiation that is scattered but continues to have the same wavelength as the excitation radiation that contacted the substance may have the same energy, a condition often referred to as Rayleigh or elastically scattered light. Alternatively, radiation that is scattered during a change of vibrational state in molecules may be scattered with a different energy, and such scattered light is called Raman scattered light.
As regards Raman scattered light, a wave associated with electromagnetic radiation may be described by (i) wavelength, the physical length of one complete oscillation, and by (ii) frequency of the wave, the number of oscillations per second that pass a point. If radiation is directed at a substance, the wavelength of the radiation may remain substantially unchanged in scattered radiation. Alternatively, if radiation is directed at a substance, the wavelength in the scattered radiation may acquire one or more different wavelengths. The energy differential between the original radiation, and the scattered radiation, may be referred to as a Raman shift. The Raman shift is significant because spectroscopic measurement of Raman scattered light seeks to measure the resulting wavelength of such scattered light.
Raman phenomena are used in conjunction with spectroscopy to qualitatively and quantitatively study physical properties and processes of a substance, including without limitation, identification of chemical characterizations including, but not limited to, properties, compositions, and structures. The phenomenon of Raman scattered light, therefore, is useful in spectroscopy applications for studying qualities and quantities of physical properties and processes of substances, including identification of chemical properties, compositions, and structure of a substance. Raman shift spectroscopic analytical techniques are, therefore, applied to qualitative and quantitative studies of matter. If radiation is used to scatter light from a substance, and scattered radiation data is measured, the scattered radiation may provide one or more spectral data, including but not limited to frequencies associated with the substance, as well as the intensities of those shifted frequencies. The frequencies may be used to identify, without limitation, the chemical composition of the substance.
Merely identifying the chemical properties, composition, structure and other characterizations of a substance, however, is only one objective of use of Raman technology. Another objective of using the Raman phenomena in connection with spectroscopy is to rapidly obtain a high quality characterization of molecular matter. Raman spectroscopy frequently is used because Raman technology has the advantage of being nondestructive of physical matter being characterized. In addition, Raman technology requires minimal sample preparation, and often may provide information about an analyte although the analyte may be but a minor ingredient in a complex mixture or admixture of physical matter.
Although the qualitative capabilities of Raman technology have been recognized, providing and enhancing quantitative capabilities have remained challenging. A number of factors contribute to the lack of quantitative capabilities of Raman technology. For example, a single beam of radiation generally is used to implement Raman technology in connection with substance analyses. Conventional Raman experimentation often uses a source of incident radiation substantially monochromatic, preferably providing a single frequency or wavelength. Acceptance by those skilled in the art that the source of the excitation beam should be substantially monochromatic and provide a single frequency or wavelength has led to use of a variety of laser light sources as a source of excitation radiation. However, if an excitation beam changes frequency, the Raman shift calibration may be disturbed; if an excitation beam changes intensity, the Raman magnitude may change. Quantitative analysis also is complicated because, without the existence of a reference beam of radiation for comparison, instrumentation variabilities may affect the spectral shape of a Raman spectral measurement. A number of components of an instrument may contribute individually and collectively to undesirable instrumentation variabilities that affect spectral data measured by the instrument. Spectroscopic measurements of Raman scattered light, therefore, seeking to measure wavelength or intensities, or both, of scattered light, may be affected by the instrument, or spectroscopic system, itself.
While efforts have been introduced to compensate for these problems associated with quantitative Raman measurements, what still is needed is an apparatus that is independent of instrumentation variabilities, and has the capability of directly comparing one or more known qualified substances or materials with one or more known unqualified substances or materials whose spectral data have been collected simultaneously or substantially simultaneously.
Use of Raman technology would be enhanced if those and related problems were solved. At least one advantage of the novel present invention is that it provides an apparatus for substantially simultaneous collection of one or more emissions from a plurality of radiation beams. Another advantage of the present invention is the capability of the apparatus and method of the invention to compare spectral data and measurements from different beams from n
Allen Fritz Schreyer
Butterfield Danny S.
Evans F. L.
Law Office of Ray R. Regan
New Chromex, Inc.
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