Abstract:
A system and method for nondestructive detection of gas in a sealed container. The system includes a light source housed in a light source housing and configured to emit a light beam for absorption in a substance to be measured, a detector housed in a detector housing and configured to detect the emitted light beam, a zone that accepts one or more of the sealed containers, each container being substantially optically transparent and containing the substance to be measured, the zone located between the detector and the light source, the light source configured to transmit the light beam through the zone, and a light source purging system comprising a light source channel surrounding the light source and positioned between the light source and the housing, the light source channel configured to expel purge gas from a purge gas source into the zone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The instant application claims the benefit of priority of U.S. provisional application No. 61/642,213, filed May 3, 2012, the disclosure of which is herein expressly incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to the field of optical absorption laser spectroscopy. More particularly, the present disclosure relates to a method and apparatus for increased purge efficacy in optical absorption spectroscopic measurements of gases in sealed containers. 
     2. Background Information 
     There presently exist systems in which gases in volume product containers are detected, analyzed and/or measured during pharmaceutical, food and beverage, consumer electronic production and the like. Optical absorption laser spectroscopy can quantify the amount of matter in a sample by directing laser energy at a sample of matter and measuring how much laser intensity is absorbed. Such systems can measure trace quantities and can nondestructively analyze gas contents within sealed containers, in order to determine, e.g., the amount of contaminants/species present in a sealed container. 
       FIG. 1  shows a related art optical absorption laser spectroscopy system  10  found in, e.g., U.S. Pat. No. 7,067,323, the contents of which are expressly incorporated herein in their entirety. Such a system  10  generally contains a light source  42 , a container  14 , a light collection element  44 , and a light detector  48 , and can be an enclosed design. 
     The region between the light source  42  and the light detector  48  is typically referred to as a sample region or detection zone  26 . In other words, in the detection zone  26 , the light emitted from the light source  42  passes through the detection zone along the optical axis of the light source and onto the detector. The light is of a special variety that is absorbed by a spectroscopic species of interest in a way that is detectable, which is considered the signal to be detected. The light collection is usually done with an optical lens  44 . The optical path B includes the light rays that are emitted by the laser light source  42  and also sensed by the detector  48 . Absorbers that are outside of the container  14  yet within the optical path B can adversely affect the signal picked up by the detector  48  as well as absorbers that are inside. To reduce or eliminate the effect of these external absorbers, some other inert gas (that does not contain absorbers, such as nitrogen) can be pumped into the optical path B from a gas source by a purging system  54  to displace or remove the ambient gas from the top of the detection zone  26 , which is referred to as a purge. By purging the unwanted gas or air through passages  56 , the system  10  can better determine solely the concentration of absorbers within a container, and to a high degree of accuracy. 
     For example, when detecting oxygen in a sealed pharmaceutical sample container, the oxygen in the atmosphere outside the container but along the laser path must be removed. Purging this gas away from the sample container is often the quickest and most efficient method for removing interfering gas species from the measurement region. 
     Optical absorption laser spectroscopy using sealed containers  14  that move quickly through the detection zone  26  can be a challenge due to the entrained flow of such as ambient air. A closed system where a purge gas can reliably displace all ambient gas and where the container to be measured is inserted into the apparatus can be forgiving with respect to the particular flow of the purge, so long as it is good enough to remove most of the ambient gas eventually, as the physical limitations of it are such that measurements take tens of seconds to minutes. 
       FIG. 2  shows a laser module of a related art optical absorption laser spectroscopy system. In this example, the laser source  42  is present in laser source housing  58   a , and includes a pair of passages  56  in the form of purge holes on opposite sides of the laser source. The flow of purge gas must be high in order to discharge and fill up the detection zone  26  with purge gas in a timely manner. Other related art laser modules have a plurality of purge holes that encircle the laser source  42 . The purge hole pattern determines the fluid flow dynamics when the purge gas flows out of the detector housing  58   b  and into the detection zone  26 . Generally the purge hole pattern encircling the laser source  42  requires a large volume of purge gas, and does not rapidly fill the volume outside the detector (i.e., the detection zone  26 ) with the purge gas, thereby slowing down the detection process. 
     In view of the above, a need has arisen to economically and rapidly purge gas from a detection zone during optical absorption spectroscopic measurement of gases in sealed containers. 
     SUMMARY OF THE DISCLOSURE 
     In order to accomplish gas detection a span of time shorter than using the aforementioned purge holes requires a more open apparatus that allows containers to enter and exit quickly. Additionally, ambient gas that is entrained with the parade of containers to be measured (not unlike a fan) can also be displaced by purge gas commensurately. A non-limiting feature of the disclosure rapidly and efficiently removes interfering gas species from a sample region. Another non-limiting feature of the disclosure improves the purge by introducing a more uniform flow of purge gas into the laser and detector path (i.e., the detection zone) via an annular ring or channel instead of the aforementioned discrete holes. The annular ring may be open all around the laser assembly and/or detector assembly, thereby providing a more uniform purge of the region of interest (such as a detection zone). 
     Another non-limiting feature of the disclosure requires less purge flow for the purposes of optical absorption spectroscopy than prior art designs, and displaces ambient gas in the inspection region more quickly. As a result of this improved purge, spurious signal from ambient gas can be eliminated and the measurement of the species of interest can be better qualified as being only from within a sealed container. 
     A feature of the disclosure provides a system for nondestructive detection of gas in a sealed container, the system having a light source housed in a light source housing and configured to emit a light beam for absorption in a substance to be measured, a detector housed in a detector housing and configured to detect the emitted light beam, a zone that accepts one or more of the sealed containers, each container being substantially optically transparent and containing the substance to be measured, the zone located between the detector and the light source, the light source configured to transmit the light beam through the zone, and a light source purging system having a light source channel surrounding the light source and positioned between the light source and the light source housing, the light source channel configured to expel purge gas from a purge gas source into the zone. 
     The light source channel may further be configured to expel the purge gas toward an optical axis of the light source. Additionally, the light source channel may completely and uninterruptingly surround the light source. 
     Also provided may be a lens housed in the detector housing and configured to focus the light beam onto the detector, the lens located between the zone and the detector, and a detector purging system having a detector channel surrounding the lens and positioned between the lens and the detector housing, the detector channel configured to expel purge gas into the zone the channel configured to expel purge gas into the zone. 
     The system may further include a lens frame configured to hold the lens, a plurality of lens frame channels positioned between the lens frame and the lens, each lens frame channel of the plurality of lens frame channels extending in the optical axis direction of the light source and configured to pass the purge gas from the purge gas source to the detector channel. Also, the thickness of the detector channel may be one millimeter or less in the optical axis direction of the light source. 
     Also, the detector channel may be further configured to expel the purge gas toward the optical axis of the light source. Further, the detector channel may completely and uninterruptingly surrounds the light source. 
     In another aspect, also provided may be a pre-purge system having at least one pre-purge aperture located in the light source housing on a side of the light source corresponding to an insertion direction of the container into the zone, the at least one purge aperture configured to pass the purge gas from the purge gas source into a region upstream of the zone. Additionally provided may be a pre-purge system having at least one pre-purge aperture located in the detector housing on a side of the detector corresponding to an insertion direction of the container into the zone, the at least one purge aperture configured to pass the purge gas from the purge gas source into a region upstream of the zone. 
     In another aspect, a system for detection of gas in a sealed container may be provided, the system having a light source housed in a light source housing and configured to emit a light beam for absorption in a substance to be measured, a detector housed in a detector housing and configured to detect the emitted light beam, a zone that accepts one or more of the sealed containers, each container being substantially optically transparent and containing the substance to be measured, the zone located between the detector and the light source, the light source configured to transmit the light beam through the zone, a lens housed in the detector housing and configured to focus the light beam onto the detector, the lens located between the zone and the detector, and a detector purging system having a detector channel surrounding the lens and positioned between the lens and the detector housing, the detector channel configured to expel purge gas into the zone the channel configured to expel purge gas from a purge gas source into the zone. 
     In a further aspect, a method for detection of gas in a sealed container may be provided, the method having providing a detection zone located between having a light source housed in a light source housing and configured to emit a light beam for absorption in a substance to be measured, and a detector housed in a detector housing and configured to detect the emitted light beam, the detection zone configured to accept one or more of the sealed containers, each container being substantially optically transparent and containing the substance to be measured, the light source configured to transmit the light beam through the zone onto the detector, expelling purge gas from a purge gas source into the detection zone via a light source channel surrounding the light source and positioned between the light source and the light source housing. 
     Also, the expelling may include expelling the purge gas toward an optical axis of the light source. Further, the light source channel may completely and uninterruptingly surrounds the light source. 
     Further, the expelling may include expelling the purge gas into the detection zone from the purge gas source via a detector channel surrounding a detector lens configured to focus the light beam onto the detector, the lens may be located between the detection zone and the detector, and the detector channel may be positioned between the detector lens and the detector housing. 
     Also, the expelling may further include passing the purge gas from the purge gas source to the detector channel through a plurality of lens frame channels positioned between a lens frame and the lens held by the lens frame, each lens frame channel of the plurality of lens frame channels extending in the optical axis direction of the light source. 
     In addition, the expelling may further include expelling the purge gas toward the optical axis of the light source. Also, in the method, the detector channel may completely and uninterruptingly surround the light source. 
     The method may further include pre-purgingly expelling the purge gas from the purge gas source into a region upstream of the detection zone prior to the expelling purge gas, via at least one purge aperture located in the light source housing on a side of the light source corresponding to an insertion direction of the container into the zone. 
     The method may additionally include pre-purgingly expelling the purge gas from the purge gas source into a region upstream of the detection zone prior to the expelling purge gas, via at least one purge aperture located in the detector housing on a side of the detector corresponding to an insertion direction of the container into the zone. 
     In a further aspect, a method for detection of gas in a sealed container may be provided, the method having providing a detection zone located between having a light source housed in a light source housing and configured to emit a light beam for absorption in a substance to be measured, and a detector housed in a detector housing and configured to detect the emitted light beam, the detection zone configured to accept one or more of the sealed containers, each container being substantially optically transparent and containing the substance to be measured, the light source configured to transmit the light beam through the zone onto the detector, expelling purge gas from a purge gas source into the detection zone via a detector channel surrounding the lens and positioned between the lens and the detector housing. 
     Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings, and the above description should not be considered to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings, by way of non-limiting examples of preferred embodiments of the present invention, in which like characters represent like elements throughout the several views of the drawings, and wherein: 
         FIG. 1  shows a schematic side sectional view of a related art optical absorption laser spectroscopy system; 
         FIG. 2  shows a schematic perspective view of a related art laser source; 
         FIG. 3  shows a perspective view of the related art optical absorption laser spectroscopy system; 
         FIG. 4  shows a perspective view of a light source of the optical absorption laser spectroscopy system according to a non-limiting aspect of the present disclosure; 
         FIG. 5  shows a schematic side sectional optical absorption laser spectroscopy system according to a non-limiting aspect of the present disclosure 
         FIG. 6  shows a perspective view of a detector of the optical absorption laser spectroscopy system according to a non-limiting aspect of the present disclosure; 
         FIG. 7  shows an exploded view of the detector of the optical absorption laser spectroscopy system according to a non-limiting aspect of the present disclosure; and 
         FIG. 8  shows a perspective view of a pre-purge system of the optical absorption laser spectroscopy system according to a non-limiting aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In view of the foregoing, the present disclosure, through one or more of its various aspects, embodiments and/or specific features or sub-components, is thus intended to bring out one or more of the advantages as specifically noted below. 
     The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice. 
     Referring now to the drawings wherein like characters represent like elements,  FIGS. 4-7  show an optical absorption spectroscopy system  100  in accordance with a non-limiting aspect of the disclosure. The system  100  includes a light source  142  housed in a light source housing  158   a , a light collection element  144  such as a lens, and a light detector  148 . The light source  142  emits a light beam (e.g., a laser beam) through a substance to be measured in a sample container, the light collection element  144  and onto the light detector. The sample container is present in a detection zone  126  through which substantially transparent sample containers pass. 
     The light collection element  148  and light detector  148  are housed in a detector housing  158   b . In alternative aspects, it is appreciated by those skilled in the art that the light detector  148  may include all elements needed to detect light emitted by the light source  148 . It is also appreciated by those skilled in the art that while a laser light is described herein as the light source, the light source can be any suitable source of radiant energy. It is further noted that while a single light collection element  144  is shown on the side of the light detector, it is appreciated by those skilled in the art that a light collection element may be provided on the side of the light source alternatively or additionally to the light collection element on the side of the light detector, that that more than one light collection element may be implemented on either or both of the light detector side and the light source side. 
     As shown in  FIGS. 4-5 , a light source purging system includes an annular light source channel  152   a  circumferentially surrounding the light source  142 , which is in communication with a purge gas source via a supply pipe  146   a . The annular channel  152   a  is located between the outside of the light source housing  158   a  facing the detection zone  126  and the light source  142 . Rather than (or in addition to) providing discrete holes in the light source housing  158   a , the annular channel  152   a  discharges purge gas such as nitrogen (or other inert gas that does not contain absorbers) toward an (optical) axis of light radiated from the light source  142  and then into the detection zone  126 . The annular channel  152   a  improves the purge of the detection zone  126  by introducing a more uniform flow of purge gas into the detection zone, thereby providing a more uniform purge of the detection zone. Such a configuration allows purge gas to flow all around the light source and out into the detection zone  126 . 
     Although the annular channel  152   a  is shown as being open around the entirety of the light source  142  (i.e., it is uninterrupted) it is appreciated by those skilled in the art that in alternative aspects, the annular channel may interrupted (i.e., the annular channel may include a plurality of arcuate channel segments arranged about the light source so that the light source is either completely or partially surrounded by the channels in a circumferential direction, each arcuate channel segment extending in an arc in the circumferential direction). In one aspect, the thickness of the annular channel  152   a  is one millimeter or less in the optical axis direction of the lens. 
     As shown in  FIGS. 5-7 , a detector purging system includes an annular detector channel  152   b  circumferentially surrounding the lens  144 , which is in communication with a purge gas source via a supply pipe  146   b . The annular channel  152   b  is located between the outside of the detector housing  158   b  facing detection zone  126  and the lens  144 . Rather than (or in addition to) providing discrete holes in the detector housing  158   b , the annular channel  152   b  discharges the purge gas toward the optical axis of lens  144  and then into the detection zone  126 . As with the light source channel  152   a , the detector channel  152   b  improves the purge of the detection zone  126  by introducing a more uniform flow of purge gas into the detection zone, thereby providing a more uniform purge of the detection zone. Thus configuration allows purge gas to flow all around the lens  144  and out into the detection zone  126 . 
     Although the annular channel  152   b  is shown as being open around the entirety of the lens  144  (i.e., it is uninterrupted) it is appreciated by those skilled in the art that in alternative aspects, the annular channel may interrupted (i.e., the annular channel may include a plurality of arcuate channel segments arranged about the lens so that the lens is either completely or partially surrounded by the channels in a circumferential direction, each arcuate channel segment extending in an arc in the circumferential direction). 
     As shown in  FIG. 7 , the detector purging system also includes a lens frame  162  which holds the lens  144 . The lens frame includes one or more axial lens frame channels  164 , each lens frame channel generally extending in a direction N of purge gas flow from the supply pipe  146   b  (which is also a direction generally parallel to the optical axis of the lens  144 , and which is further a direction orthogonal to a plane passing through the entire annular channel  152   b ). Further, each lens frame is in open communication on one end thereof with the supply pipe  146   b  and on the other end thereof with the annular channel  152   b , so that purge gas passes from the supply pipe  146   b , through the axial frame channels  164 , into the annular channel(s)  152   b  and then into the detection zone  126 . In one aspect, the annular channel  152   b  is defined in the optical axis direction by the lens  144  on one side, and the inside of the detector housing  158   b  on the other side and the thickness of the annular channel  152   b  may be one millimeter or less in the optical axis direction of the lens. 
     Although the figures show eight axial frame channels  164  equally spaced about the lens  144 , those skilled in the art would appreciate that more or less than eight axial frame channels may be employed, and that the spacing between the axial frame channels need not be equally spaced. It is noted that the light source purging system and detector purging system are collectively referred to as the spectroscopy system purging system, and that while the optical absorption spectroscopy system  100  includes both the light source purging system and detector purging system each of which expels purging gas on an opposite side of the detection zone  126 , in alternative aspects, only a light source purging system or only a detector purging system may be provided. 
       FIG. 8  shows a further feature of the optical absorption spectroscopy system  100  which includes a pre-purging system  165  configured to expel purge gas from a plurality of pre-purge apertures  168 . Specifically, the purge gas may be supplied from gas purge line  170  into a pre-purge cap  166  installed over the detector housing  158   b  surrounding the lens  144  (so as not to interfere with the purge gas being expelled from the annular channel  152   b ). The pre-purge apertures  168  are configured to expel purge gas into a region upstream  126   u  (in relation to a direction of flow D of sample container) of the detection zone  126 . In the case of rapid movement of the sample containers into the detection zone  126 , the pre-purging system  165  expands the area to be purged beyond the detection zone  126 , i.e., to the area  126   u  before the sample container enters the detection zone, which reduces the amount of ambient air that the light source purging system and/or detector purging system has to displace. Thus, depending on the specific configuration of the sample containers and the means by which the sample containers are passed through the detection zone  126 , the purge gas exiting from the system  100  may be directed wholly or partially in the direction of the sample containers incoming to the detection zone in order to counteract the effects of the ambient gas entrainment. Although  FIG. 8  shows the pre-purging system  168  used in conjunction with the detector side of the system  100 , it is appreciated by those of skill in the art that the pre-purging system may additionally or alternatively used in conjunction with the light source side of the system. 
     The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive. 
     One or more embodiments of the disclosure may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. All publications, patent applications, patents, and other references mentioned herein are expressly incorporated by reference in their entirety. 
     Unless otherwise indicated, all numbers expressing quantities of ingredients and the like used in the specification and claims are to be understood as being modified in all instances by the term “about.” The terms “generally” and “approximately” as used herein are to be understood as an approximation allowing for variations while still maintaining the efficacy of the invention. Accordingly, unless indicated to the contrary, the numerical and geometric parameters and relationships set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical and geometric parameters and relationship should be construed in light of the number of significant digits and ordinary rounding approaches. 
     The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter. 
     The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.