Spectrometer for analysis of multiple samples

A spectrometer (100) includes a light source (102) providing output light (106) to the bundled input ends (108) of multiple light pipes (110). The light pipes (110) branch into sets (118) between their input ends (108) and output ends (114), with each set (118) illuminating a sample detector (126) (via a sample chamber (122)) for measuring light scattered or emitted by a sample, or a reference detector (128) for obtaining a reference/datum measurement of the supplied light, so that comparison of measurements from the sample detector (126) and the reference detector (128) allows compensation of the sample detector measurements for drift. Efficient and accurate measurement is further assured by arraying the multiple light pipes (110) in each set (118) about the input bundle (116) so that each set receives at least substantially the same amount of light from the light source (102).

FIELD OF THE INVENTION

This document concerns an invention relating generally to molecular spectrometry, and more specifically to sample processing arrangements in infrared, near infrared, Raman, and other spectrometers.

BACKGROUND OF THE INVENTION

Spectrometry is a well known technique used to identify the characteristics of gas, liquid, and solid samples, wherein light is directed at a sample and the light leaving the sample is then picked up by a photosensitive detector to be analyzed for changes in wavelength. These changes provide information regarding the composition of the sample, its chemical bonds, and other features.

It is often desirable to take measurements from multiple samples simultaneously (or nearly so) to increase analysis speed. This can be done by providing multiple sample chambers, and then providing a moving mirror which directs illumination from the light source to each chamber in turn (with the light then being received by one or more detectors). While this arrangement is beneficial, developers have sought to eliminate the moving mirror owing to the burdens of its maintenance, and the sequential illumination of the sample chambers also limits analysis speed since a user must await the results from the later chambers in the sequence.

In one known spectrometry arrangement which is believed to be exemplified by the FTPA2000 200 spectrometer (ABB Inc., Norwalk, Conn., US), multiple fiberoptic cables receive light from a lamp, and each cable illuminates a separate sample chamber containing a sample to be analyzed. Return fiberoptic cables then each receive the light from each sample and provide it to a detector (with one detector per each sample chamber and return cable) to provide analytical measurements. This arrangement can therefore provide truly simultaneous sample measurements while eliminating the moving mirror. However, an arrangement of this nature can suffer from drift in its components; for example, changes in ambient temperature can change factors such as detector sensitivity, the refractive index of the fiberoptic cables, etc., which can in turn affect measurement accuracy. Additionally, such an arrangement is also susceptible to measurement uncertainties owing to differences between the different “channels” used to obtain measurements from the different chambers. Different channels can experience different degrees of drift, and it is also difficult to obtain the “same light” (i.e., the same light flux/intensity) into each of multiple cables arrayed about the light source. Beamsplitters (e.g., dichroic mirrors, prisms, etc.) can be used to divide the light from a light source into a number of different beams of approximately equal intensity to supply the input cables, but here too drift, imperfections, etc. limit the ability to exactly match light input to the different input cables.

A similar arrangement, which is believed to be exemplified by the InfraSpec NR800 spectrometer (Yokogawa Electric Corporation, Tokyo, JP), has multiple fiberoptic input cables extending from a light source, with each illuminating a separate sample chamber. Each input cable is provided with a beamsplitter whereby its transmitted light is divided into two portions, one illuminating its sample chamber (and subsequently a sample detector) and one illuminating a reference detector. Comparison of the measurements from the sample and reference detectors beneficially allows the sample detector measurements to be at least partially compensated for drift. However, this arrangement still has the disadvantages that the beamsplitter still may not provide the same light to the sample and to the reference detector, and additionally the input cables may not each receive and provide the same light from the light source.

It would therefore be useful to have available additional spectrometer arrangements which allow simultaneous (or nearly so) measurements from multiple samples, while at the same time minimizing (or compensating for) drift within and between the channels used to measure each sample.

SUMMARY OF THE INVENTION

The invention involves spectrometry devices and methods which are intended to at least partially solve the aforementioned problems. To give the reader a basic understanding of some of the advantageous features of the invention, following is a brief summary of preferred exemplary versions of the invention, with reference being made to the accompanyingFIGS. 1aand1bof the drawings (which are described in greater detail below). As this is merely a summary of the preferred versions, it should be understood that more details may be found in the Detailed Description set forth elsewhere in this document. The claims set forth at the end of this document then define the various versions of the invention in which exclusive rights are secured.

Referring to the exemplary version of the invention schematically depicted inFIGS. 1aand1b, a spectrometer100(e.g., a near infrared spectrometer) includes a light source102(in this case an incandescent filament104) which provides output light106to the input ends108of multiple light pipes110, with the output light106inFIG. 1afirst being passed to an interferometer112. The multiple light pipes110are preferably arranged in a manner exemplified byFIG. 1b, wherein the light pipes110each of which extends between its input end108and an opposing output end114have their input ends108arrayed into a closely spaced bundle116which receives the output light106from the light source102. The bundled light pipes110branch into sets118between their input ends108and output ends114, with four sets118A,118B,118C, and118D being depicted inFIG. 1b(and collectively being referred to as sets118). Preferably, at least some of the sets118include multiple light pipes110, with each set118defining an independent optical path whereby no set118receives light from any of the other sets118. At least some of the light pipes110within each set118preferably have their input ends108spaced from each other within the bundle116by the input ends108of light pipes110of other sets118, as depicted by the exemplary arrangement inFIG. 1bwherein each light pipe110in set118A is spaced from at least some of the other light pipes110in set118A (with these light pipes110also simply being labeled A at their bundled input ends108); each light pipe110in set118B is similarly spaced from at least some of the other light pipes110in set B (with these light pipes110also simply being labeled B at their bundled input ends108); etc. Overall, the desired objective is to have each set118of light pipes110receive approximately the same light from the light source102, and since the intensity, wavelength, and/or other qualities of the emitted light may vary about the image of the light source102(since it is in effect the projected image of the light source102which is received by the input ends108of the light pipes110), it is useful to have all sets118of light pipes110have an approximately equal distribution about the area of the light receiving bundle116.FIG. 1bshows such an arrangement, wherein each of the sets118A,118B,118C, and118D has at least substantially the same spatial distribution of light pipes110as any others of the sets118about the area of the input bundle116. Additionally, the input ends108are preferably maintained in the bundle116so that they are collectively surrounded by a circumferential boundary120which is shaped at least substantially complementary to the output light image106from the light source102. For example, inFIG. 1a, the projected light image from the filament104in the light source102is substantially polygonal (more precisely, substantially rectangular), and thus the bundled input ends108of the light pipes110inFIG. 1bare restrained to rest within a complementary polygonal boundary120, the boundary120being sized and shaped to closely conform to the projected image106. By shaping the boundary120of the bundle116to be complementary to the output light image106, the sets118are closely coupled to the light source102to transmit optimal (or nearly so) light therefrom. At the same time, the light pipes110of each set118are such that each set118receives approximately the same light from the output light image106and transmits it to the output ends114of its light pipes110.

At the output ends114, the sets118provide light to several sample chambers122(with a series of some number N of sample chambers122being shown inFIG. 1a), with each sample chamber122being appropriate for receiving samples to be spectrometrically analyzed. One of the sets118also preferably extends to a reference location124isolated from the sample chambers122. The light provided to the sample chambers122is in turn received by sample detectors126(with N sample detectors126being shown inFIG. 1a), and a reference detector128is also preferably provided to receive light at the reference location124directly from the output ends114of one of the sets118(i.e., without receiving the light from am intervening sample chamber122).

By use of the foregoing arrangement, one can spectrometrically examine some number N of samples (seeFIG. 1a) while simultaneously obtaining a reference reading, so that the readings from the sample detectors126can be compared to a simultaneously obtained “datum” measurement from the reference detector128for purposes of calibration/validation. This arrangement can take a number of forms, e.g., that ofFIG. 1a, in each sample chamber122has its own detector126and the reference detector128takes measurements simultaneously with those taken from the sample detectors126. An alternative arrangement is depicted inFIG. 2, wherein there are fewer sample detectors226than sample chambers222, and the sample detector226sequentially moves between the chambers222to be analyzed, with the reference detector228also taking measurements simultaneously with those taken from the sample detector226. As an alternative arrangement the readings from the sample detectors can be compared to measurements which are not simultaneously captured from the reference detector. As an example, in the arrangement ofFIG. 3, the sample detectors326are used to simultaneously collect readings from all of the sample chambers322, and then the sample detectors326are moved in sequence to the reference location324so that reference measurements may be captured from each. Thus, each detector326captures both sample and reference measurements in sequence.

Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings.

DETAILED DESCRIPTION OF PREFERRED VERSIONS OF THE INVENTION

To expand on the discussion given in the foregoing Summary of the Invention of this document, referring toFIG. 1b, the light pipes110preferably take the form of identical fiberoptic cables which extend from their bundled input ends108to divide into sets118, with the same number of light pipes110per set118, and with each set118having at least substantially the same amount of input area per unit area across the input bundle116. InFIG. 1b, this is provided by situating the input ends108of the light pipes110from each set118in a regular array, i.e., in a predictable A, B, C, D arrangement. However, it should be understood that the light pipes from each set118could be essentially randomly arrayed at the input bundle116so long as each set118receives approximately the same light per unit area across the input bundle116.

FIG. 1balso depicts a preferred bundling arrangement, wherein the input ends108of the light pipes110are constrained to fit within a boundary120which is complimentary to the output light image106from the interferometer112by fitting the input ends108within a windowed cap130(the window being defined by the boundary120). The light pipes110are thus held in a fixed array throughout the length of the cap130(i.e., descending intoFIG. 1b), after which light pipes110spaced across the input bundle116may be collected into the sets118A,118B,118C, and118D. The light pipes110within these sets118A,118B,118C, and118D are shown bound within protective covering sheaths132inFIG. 1b(and with each of the sets118further being shown bound within an overall bundle sheath134extending from the cap130).

It should be understood that the four sets118depicted inFIG. 1bare only exemplary, and fewer or greater numbers of sets may be included depending on how many sample chambers122, sample detectors126, and reference detectors128are to be supplied with light. Similarly, the number of light pipes within each set118may vary, as well as the manner in which they are arrayed at the input bundle116(as noted previously). In some cases, it may be desirable to have different sets118receive different types or amounts of light at their input ends108. To illustrate, it might be desirable to have different ones of the sample chambers122receive light of different intensities where different chambers122are to receive different components of a multiphase mixture, e.g., one chamber122receiving a denser or solid (and thus usually more opaque) fraction, another chamber122receiving a more translucent liquid fraction, another chamber122receiving a highly transparent gas fraction, etc. In this case, selected sets118might include more light pipes110, or light pipes110having greater diameter, so that this set(s)118might transmit more light than other sets118(which can be useful for obtaining more accurate measurements from more opaque samples). Additionally or alternatively, it might be desirable to have certain sets118(and thus their sample chambers122) receive different wavelength ranges appropriate for different types of samples. In this case, different sets118might be formed of light pipes110which selectively pass desired wavelength ranges and block others.

Further, it should be understood that the arrangements ofFIGS. 1A,2, and3are merely exemplary, and many possible arrangements exist beyond those depicted. For example, each of the sample chambers222inFIG. 2could be replaced with a row or other set of sample chambers (descending into the view ofFIG. 2, i.e., with other chambers222being behind those shown), and the detectors226and228could likewise be replaced with a row or other set of detectors226and228. During analysis, the row of sample detectors226could then move from row to row of sample chambers222while the row of reference detectors228would take reference measurements simultaneously. Such an arrangement would effectively resemble a combination of arrangements ofFIG. 1bandFIG. 2, wherein a two dimensional array of chambers222and detectors226/228is provided, and whereinFIGS. 1B and 2each depict one dimension of this array. Such an arrangement might also only use one reference detector228rather than several, though multiple detectors228(e.g., having different sensitivities over different wavelength ranges) may be more useful where qualitatively (and/or quantitatively) different light is passed by different sets218.

Similarly, the arrangement ofFIG. 3might be combined with the arrangement ofFIG. 1b, wherein theFIG. 3arrangement has each of its sample chambers322and detectors326replaced with rows of chambers322and detectors326, with each chamber322being illuminated by its own light pipe set318. In this case, the light pipe set318illuminating the reference location324inFIG. 3might also be replaced by multiple light pipe sets318illuminating multiple reference locations324, each of which later receives corresponding detectors226in sequence.

Additionally, in the arrangements ofFIGS. 2 and 3, it should be understood that it is not necessary that the detectors226/326move relative to fixed light pipe sets218/318, and it is possible that the light pipe sets218/318(and chambers222/322) might move with respect to the detectors226/326. For example, in the arrangement ofFIG. 3, the light pipe set318illustrated as illuminating the reference location324might have its output ends314moved to illuminate each of the sample detectors326in turn (assuming no interference from the sample chambers322or other components).

The light source102need not take the form of an incandescent filament104, and could instead take the form of a light emitting diode, laser, or other source of light (whether multichromatic or monochromatic), with different types of light sources being more suitable for different types of spectrometry applications. Since the projected image106of the light source102may vary in accordance with the type of light source102being used, it should be understood that the shape and size of the boundary120of the light pipe bundle116may vary with the light source102used so that the light pipes110may complementarily receive the light source image106at their input ends108.

The light pipes110preferably (but need not) take the form of fiberoptic cables, and they could instead take the form of other light transmitting media, e.g., gel tubes, hollow tubes with internally reflecting surfaces, translucent films or other translucent members, or other matter which directs light along the desired path (preferably with high internal reflection such that minimal light loss occurs). Fiberoptic cables, being readily available and relatively inexpensive, are merely the presently preferred form of the light pipes110. Further, the light pipes110need not be continuous between their input and output ends108and114and may include different media along their lengths, e.g., a portion of a length of a light pipe110could transmit light into an air gap for receipt into the remaining length of the light pipe110.

The sample chambers122may also be provided in a variety of forms, e.g., fully or partially enclosed cells, wells, or other volumes, flow through channels, etc. The invention may be implemented with either static samples or those that are time resolved, e.g., samples whose composition changes over time owing to chemical reactions or other events. Additionally, it should be understood that while simultaneous or sequential analysis of multiple samples is discussed above, this can take the form of simultaneous or sequential analysis of multiple regions on the same sample. In this case, the sample might be divided into separate sample chambers, or it might remain as a unitary volume of material in a single chamber, wherein the single chamber is subdivided into a number of effective smaller chambers (e.g., the chamber receives light from the output ends114of several light pipes110spaced about the chamber, preferably in such a manner that there is no crosstalk between the light pipes110and their detectors126). In this case, the multiregion analysis of the unitary sample is effectively equivalent to the analysis of several samples.

The detectors126/128may be any photosensitive element suitable for use as a detector, with a variety of germanium (Ge), silicon (Si), indium gallium arsenide (InGaAs), and other detectors being readily available from suppliers. It should be understood that the detectors126need not receive light directly from sample chambers122, and instead the light from the sample chambers122may be transmitted to detectors126via further light pipes or other means of light transmission. Such an arrangement can be useful since all detectors126might then be more conveniently located in a climate controlled location so that they experience the same temperatures and other ambient conditions, thereby reducing their relative drift.

The invention may be implemented in any suitable molecular spectrometer, including infrared (IR), near infrared (NIR), ultraviolet (UV Vis), Raman, and other spectrometers using Fourier Transform (FT) or other analysis techniques. Exemplary spectrometers which might implement the invention include the NICOLET and ANTARIS FT IR and FT NIR spectrometers provided by Thermo Electron LLC (Madison, Wis., USA).

Since the foregoing discussion is intended to merely present preferred versions of the invention, it should be understood that the invention is not intended to be limited to these preferred versions, but rather is intended to be limited only by the claims set out below. Thus, the invention encompasses all different versions that fall literally or equivalently within the scope of these claims.