SYSTEM AND METHOD FOR NON-INVASIVE SPECTROSCOPIC DETECTION FOR BLOOD ALCOHOL CONCENTRATION

Abstract

An apparatus and method for acquiring and analyzing a spectroscopic sample for a substance from a sampling region of the tissue of a person at an interstitial region between the fingers of the person, by way of a probe and a spectroscopic detector for radiating the interstitial region with electromagnetic radiation and analyzing a diffuse-reflectance signal obtained from the tissue at the sampling region. The apparatus preferably also incorporates a biometric sensor to perform a verification of the person.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and the benefit of U.S. Provisional Application No. 61/133,892, entitled “System for Non-Invasive Spectroscopic Detection for Blood Alcohol Concentration,” filed Jul. 3, 2008, the entire content of which is incorporated by reference herein. This application is a continuation-in-part of U.S. patent application Ser. No. 11/945,992, entitled “Apparatus for Non-Invasive Spectroscopic Measurement of Analytes, and Method of Using the Same,” filed Nov. 27, 2007, the entire content of which is incorporated by reference herein, which claims priority to and the benefit of U.S. Provisional Patent Applications No. 60/949,836, entitled “Apparatus and Method for Non-Invasive Spectroscopic Measurement of Blood Alcohol Concentration,” filed Jul. 13, 2007, and 60/966,028, entitled “Apparatus and Method for Non-Invasive Spectroscopic Measurement of Blood Alcohol Concentration,” filed Aug. 24, 2007, the entire contents of which are incorporated by reference herein. This application contains subject matter that is related to the subject matter contained in U.S. patent application Ser. No. 11/702,806, entitled “Method and System for Preventing Unauthorized Use of a Vehicle by an Operator of the Vehicle,” filed Feb. 5, 2007, the entire content of which in incorporated by reference herein. This application contains subject matter that is related to the subject matter contained in U.S. Provisional Patent Application No. 61/178,002, entitled “Dynamic Calibration of an Optical Spectrometer,” filed May 13, 2009, the entire content of which in incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an apparatus and method for the non-invasive detection of one or more substances in human blood. More particularly, the present invention relates to the non-invasive detection of the concentration of alcohol in human blood using optical spectroscopy. Specifically, various embodiments of the present invention provide an apparatus and method for spectroscopic non-invasive detection of the blood alcohol concentration in a person. Some of these embodiments preferably also employ a biometric verification to provide both a detected blood alcohol concentration and a biometric identification to assure that the detected blood alcohol concentration is obtained from an identified person.

2. Description of the Prior Art

One problem long extant in the prior art is to provide a reliable device for non-invasive detection of the blood alcohol concentration in a person. Another problem is to provide for the non-invasive detection of the blood alcohol concentration in the person in a fast and repeatable manner. A further problem is to provide verification of the person subjected to the blood alcohol concentration analysis. Various embodiments of the present invention provide a solution for the reliable, fast, repeatable, and verifiable detection of the blood alcohol (or other substance) concentration in an identified individual.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus are provided for precise spectroscopic detection of a substance present in the blood of a person, such as alcohol or its metabolic byproducts, preferably in conjunction with a biometric verification of that person. In accordance with one aspect of the present invention, the spectroscopic detection may be accomplished by impinging electromagnetic radiation on the tissue of a person and acquiring and analyzing electromagnetic radiation resulting from the interaction with the tissue of the person. The spectroscopic detection may be accomplished by way of an articulated probe head that applies a consistent pressure and angle to an interstitial region between the index and middle fingers of a person whose blood alcohol concentration is being detected coupled to an optical spectrometer. The probe head incorporates a fiber optic bundle that transmits and receives electromagnetic radiation impinged on the interstitial region to perform spectroscopic detection by the optical spectrometer.

In accordance with another aspect of the present invention, the spectroscopic detection of the blood alcohol concentration in a person is performed in conjunction with biometric verification of that person for authentication of the detection that is performed. The biometric verification may be accomplished by way of a fingerprint scan, for example.

The system of the present invention may be used to prevent operation of a vehicle, machinery, or heavy equipment, for example, if the presence of alcohol or its metabolic byproducts is detected as being present in a person above a predetermined concentration, which may be any concentration exceeding a zero concentration. In addition, the system may be used to prevent operation of the vehicle, machinery, or heavy equipment if the biometric authentication does not verify the person whose blood alcohol concentration is detected as a person authorized to operate the vehicle, machinery, or heavy equipment. This use also encompasses operators of public means of transportation, such as airplane pilots, train conductors, and bus drivers.

The system may also be used in law enforcement and probation applications, for example, to enforce restrictions on alcohol or other substance use for persons on probation. In addition, the system may be used in conjunction with a time clock so that an employer can monitor the employee for alcohol use on the job. The system may also be used in liquor establishments, such as restaurants and bars, to restrict serving alcohol to customers whose blood alcohol concentration exceeds a certain level. The system of the present invention may advantageously be a portable device, such as a hand-held device, which may be powered using a portable power supply, such as a battery.

The system can be used for more than the detection of alcohol. For example, the system can be used to detect levels of glucose, lipids, triglycerides, cholesterol, creatinine, or other trace blood analytes found in the dermis of tissue.

The foregoing and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of various embodiments of the present invention, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments of the present invention will be described in conjunction with the accompanying drawings to facilitate an understanding of the present invention. In the drawings, like reference numerals refer to like elements.

FIG. 1 is a diagram of a housing that contains a probe head, probe base, and biometric sensor according to an exemplary embodiment of the present invention.

FIG. 2 is a front view of the probe head and probe base of FIG. 1.

FIG. 3 is a side view of the probe head and probe base of FIG. 1.

FIG. 4 is a side view of an alternative probe head and probe base configuration according to an exemplary embodiment of the present invention.

FIG. 5 is a depiction of the hand of a person showing interstitial regions between the fingers that constitute sampling regions at which spectroscopic detection may be performed in accordance with an exemplary embodiment of the present invention.

FIG. 6 shows multiple views of alternative embodiments of the present invention, in which the probe head has rotational freedom, and the probe base has translational freedom.

FIG. 7 depicts a cutaway view of one embodiment of the present invention in which two fingers of the person undergoing a detection procedure enter the housing.

FIG. 8 depicts a cutaway side view of one embodiment of the present invention in which the probe head rotation and the probe base translation are spring-biased by a single or multiple springs.

FIG. 9 depicts a cutaway top view of one embodiment of the present invention.

FIG. 10 is an illustration of a cutaway side view of one embodiment of the present invention in which the probe head rotation and probe base translation are biased by a single or multiple springs.

FIG. 11 depicts a cutaway view of one embodiment of the present invention.

FIG. 12 is an illustration of a top view of one embodiment of the present invention.

FIG. 13, comprising FIGS. 13A and 13B, depicts respective rear and front views of one embodiment of the present invention.

FIG. 14 is a depiction of an embodiment of the present invention in which one finger of the person undergoing a detection procedure enters the housing.

FIG. 15 is a schematic diagram of the optical portion of a spectroscopic detector in accordance with one embodiment of the present invention.

FIG. 16 is an architectural block diagram of the spectroscopic detector in accordance with one embodiment of the present invention.

FIG. 17 illustrates a spectrum resulting from spectroscopic analysis of the tissue of a person for the detection of the blood alcohol concentration, in particular the relationship between light wavelength and corresponding absorbance by water and ethanol (alcohol).

FIG. 18 illustrates the data from FIG. 17 in a different form, namely in terms of the transmission percentage rather than the absorbance.

FIG. 19 elaborates on FIG. 18 by adding the passband for an approximately 250 nanometer (nm) wide band-pass filter.

FIG. 20 illustrates stepping through the roughly 250 nm wide passband at regular discrete points using a Fabry-Perot etalon.

FIG. 21 depicts a microelectromechanical systems (MEMS) based Fabry-Perot etalon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagram of a housing 10 that contains a probe head 40, probe base 30, and biometric sensor 20 according to an exemplary embodiment of the present invention. The biometric sensor 20 is positioned to obtain unique information to identify a person in conjunction with detection of the blood alcohol concentration of the person. Verification of the person is preferably determined before or contemporaneously with the detection procedure that is performed at a predetermined sampling region of the person. The probe head 40 is configured within a housing 10 to assure that spectroscopic detection of the person is performed reliably.

The sampling region may be the interstitial region between fingers, and preferably is the interstitial region between the index and middle fingers of a hand of the person. Alternatively, the sampling region may be between the toes of the person. In addition, the region adjacent to a single finger or toe may serve as the sampling region. The size of the housing 10 may accommodate a single finger or toe, two fingers or toes, multiple fingers or toes, or the entire hand or foot of a person taking into account variations of physical size of extremities within the general population. The housing 10 is preferably sized to accommodate any two consecutive fingers of the hand of a person and, more particularly, the index and middle fingers of a person.

FIG. 2 is a front view of the probe head and probe base of FIG. 1. Included in the probe head 40 are the optical elements or other device for transmitting and receiving electromagnetic radiation used to perform spectroscopic detection. The probe base 30 may house the optics for the probe head 40 and provide support for the probe head 40.

FIG. 3 is a side view of the probe head and probe base of FIG. 1, illustrating a hinge mechanism connecting the probe head to the probe base. The hinge mechanism may also provide translational motion to the probe head from the same or different spring that provides rotational motion to the probe head. Alternatively, the translational motion of the probe head may result from translational motion of the probe base.

As shown in FIGS. 1-3, in accordance with one embodiment of the present invention, a probe head 40 of a spectroscopic apparatus is mounted to a probe base 30 by way of a spring-biased hinge 60, which enables rotation of the probe head in a vertical plane. Rotation of the probe head 40 assures that a fiber optic bundle 50 incorporated into the probe head seats flush against the tissue in an interstitial region 70, 80, 90, or 100 between the fingers of a person, as shown in FIG. 5, which may serve as sampling regions. The probe head 40 is mounted to the probe base 30 through a pressure transmitting mechanism, such as a spring, that causes the probe head to apply a consistent pressure against the tissue of the selected sampling region.

Alternatively, the probe base 30 may be spring-biased (see, for example, FIG. 10), enabling both the probe base and the probe head 40 to move translationally. This assures consistent pressure against the tissue of the person at the sampling region. In accordance with another embodiment of the present invention, the probe base 30 and the probe head 40 may both be spring-biased (see, for example, FIG. 8) to enable the translational motion needed to apply consistent pressure against the tissue of the sampling region. In yet another embodiment, a single spring may be employed to provide biasing for both the rotation as well as translational motion of the probe head 40 and probe base 30. Persons skilled in the art will understand that other means for producing consistent pressure and angle may be employed. Alternatives to a spring or springs include, but are not limited to, mounting the probe base 30 or the probe head 40 on ball bearings to harness gravity to supply consistent pressure or to employ a gas-filled piston.

The probe head 40 and probe base 30 combine to provide the probe head rotational and translational freedom while mounted in a housing 10. The rotational freedom of the probe head 40 enables the probe head to conform to the contour of the tissue of the person in the sampling region by varying the angle of the probe head 40 with respect to the tissue of the person. The translational freedom of the probe head 40 enables the probe head to impart a consistent pressure on the tissue of the person in the sampling region.

The probe head 40 acquires readings in the interstitial region between the fingers, where there is lower muscle density. In accordance with a preferred embodiment of the present invention, detection is performed between the palmar interossei and dorsal interossei muscles. Other portions of the finger that are low in muscle density may be appropriate as sampling regions as well. Detecting between the muscles provides results that are more representative of substances in the blood, with less interference from variations due to constituents in the muscle, such as lactic acid, that may produce less reliable results in the detection of the blood alcohol concentration. The interstitial region intermediate the fingers of a person is minimally affected by the presence of acid in muscle tissue.

FIG. 4 is a side view of an alternative probe head and probe base configuration according to an exemplary embodiment of the present invention, illustrating an alternative mechanism 60′ connecting the probe head 40 and probe base 30. FIG. 6 shows multiple views of alternative embodiments of the present invention, in which the probe head has rotational freedom, and the probe base has translational freedom. FIGS. 8-12 show some of these embodiments in more detail.

FIG. 8 depicts a cutaway side view of one embodiment of the present invention in which the probe head rotation and the probe base translation are spring-biased by a single or multiple springs. Probe head 1040 rotates on axis 1041 and is biased by spring 1045. Probe base 1030 is biased by spring 1035.

FIG. 9 depicts a cutaway top view of one embodiment of the present invention, with biometric sensor 1120, probe head 1140, and fiber optic bundle 1150.

FIG. 10 is an illustration of a cutaway side view of one embodiment of the present invention in which the probe head rotation and probe base translation are biased by a single or multiple springs. Here, housing 1210 holds rotating probe head 1240, which is attached to probe base 1230 that is biased by spring 1235.

FIG. 11 depicts a cutaway view of one embodiment of the present invention, with biometric sensor 1320, probe head 1340, and fiber optic bundle 1350.

FIG. 12 is an illustration of a perspective view of one embodiment of the present invention. Here, open end 1465 allows finger access to the biometric sensor 1420, probe head 1440, and fiber optic bundle 1450.

FIG. 13, comprising FIGS. 13A and 13B, depicts respective rear and front views of one embodiment of the present invention. In FIG. 13A, closed end 75 has an opening 76 for receiving, for example, a power cord, fiber optic bundles, etc. In FIG. 13B, open end 65 is shown for receiving a subject's fingers.

FIG. 5 is a depiction of the hand of a person showing interstitial regions between the fingers that constitute sampling regions at which spectroscopic detection may be performed in accordance with an exemplary embodiment of the present invention. Other sampling regions of the fingers may also be suitable for spectroscopic detection due to a low density of muscle tissue, or for other reasons.

Referring to FIG. 5, performing detection at a location 70, 80, 90, or 100 provides the advantage that the selected sampling region has a relatively low density of muscle tissue, particularly in the regions between the palmar interossei and dorsal interossei muscles. Muscle tissue may contain significant variations in the concentration of lactic acid, which may interfere with reliable detection of blood alcohol concentration. In accordance with a preferred embodiment of the present invention, the probe head 40 seats in the interstitial region 70 between the index and middle fingers of a person. Thus, the spectroscopic detection is performed on the interstitial tissue in the region 70 between the index and middle fingers of the person.

In accordance with a preferred embodiment of the present invention, a person inserts two fingers into the housing 10, which contains the probe head 40 and probe base 30, as shown in FIG. 7. The housing 10 is large enough to accommodate fingers of various sizes to account for variations within the general population, yet is small enough to prevent tampering with the probe head 40 or a biometric sensor 20. In accordance with a preferred embodiment of the present invention, the biometric sensor 20 is mounted near the aperture of the housing 10. In that way the biometric verification establishing the identity of the person can be accomplished before the spectroscopic detection is performed, and the spectroscopic detection cannot be performed without the biometric authentication of the same person whose blood alcohol concentration is detected.

FIG. 14 is a depiction of an alternative embodiment of the present invention in which one finger of the person undergoing a detection procedure enters the housing 2910. Also shown is a biometric sensor 2920.

FIG. 15 is a schematic diagram of a spectroscopic detector 110 in accordance with one embodiment of the present invention. The spectroscopic detector 110 comprises a lamp 112 that provides a source of light. The light produced by the lamp 112 is then collimated by collimation lenses 114, which may be constructed from calcium fluoride. The light passing through the collimation lenses 114 is radiated through an aperture 115 to prevent light that is not collimated from being transmitted.

The spectroscopic detector 110 also comprises a chopper device 116 on which collimated light impinges. The chopper device 116 comprises a chopper wheel 118 driven by a chopper motor 120. The chopper wheel 118 has an arcuate slot 118A, which transmits light, and an opaque portion 118B, which masks light, so collimated light is either on or off depending upon the rotation of the chopper wheel 118. In one preferred embodiment, the chopper motor 120 rotates the chopper wheel 118 at 10,000 rpm. The principle of operation of the chopper device 116 is well understood by persons skilled in the art.

Alternatively, an LED may be employed as the light source. The advantage of an LED is that the LED may be configured as a pulsed light source, which eliminates the need for a chopper having the spinning chopper wheel 118 to reduce the number of moving parts. As will be described in more detail below, the light from the light source is pulsed by the chopper device 116, or alternatively by a pulsed LED.

During the period that the light is off, dark current is integrated. During the period that the light is on, the amplitude of light received by a detector is detected by integrating the dark current signal produced by the detector and comparing the signal produced when light is received by an alcohol signal detector.

The chopper device 116 not only feeds light from the light source, but also provides a feedback timing signal to the optical spectrometer. That is, the chopper device 116 both supplies pulsed light, as well as provides a timing signal that the spectrometer uses to be sure it is integrating the dark current at the correct point in the chopper wheel's rotation. The chopper device 116 is employed because the dark current is relatively high compared to the light sensed by the alcohol signal detector.

One embodiment in accordance with the present invention is shown to assure that a sufficient number of photons is impinged on the tissue of the person whose blood alcohol concentration is being detected. Accordingly, FIG. 15 shows a sampling region illuminating arm 122 and a wavelength calibration arm 124.

As shown in FIG. 15, the light passing through the chopper device 116 is impinged on light band-pass filters 126 and 128. The reason for two band-pass filters is that the lamp 112 is employed instead of an LED, so there is a great deal more light in the visible portion of the spectrum. Because the band-pass filter 126, for example, has to be narrow and have an optimum pass characteristic over the operating region of the spectrum, there is a tendency that the band-pass filter 126 may transmit light in shorter wavelength regions. Consequently, a second band-pass filter 128 may be provided that is a broader one that cuts off light in the shorter wavelength regions.

A photodiode 129, which may be a silicon diode, is preferably incorporated to sense visible light produced by the lamp 112. The photodiode 129 is positioned between the lamp 112 and the band-pass filters 126 and 128, which is prior to the extraction of infrared (IR) resulting from transmission through the band-pass filters. The photodiode 129 monitors the chopper frequency. This is to assure that the timing is known for integration of the dark current.

Referring now to the sampling arm 122 shown in FIG. 15, the light passed by the band-pass filters 126, 128 is input to a piezo-electrically actuated scanning Fabry-Perot etalon 130, which transmits only a portion of the incident light that is within a narrow wavelength range about a desired center wavelength. The width of the wavelength passband of the piezo etalon 130 is determined by the reflectivity of the optical coatings on the etalon, while the center wavelength is determined by the thickness of the etalon air gap. The center wavelength can be tuned by changing the voltage applied to the piezoelectric spacer element. The transmitted light is directed through a beam splitter 132 and focusing lenses 134 to the input of a source optical fiber 136 that comprises part of the fiber bundle 50. The source optical fiber 136 in turn routes the light to the sampling region, for example, the interstitial region between the index and middle fingers 70.

As shown in FIG. 15, the beam splitter 132 also redirects a small portion of the light output by the piezo etalon 130 to the wavelength calibration arm 124. The beam splitter 132 may be constructed from calcium fluoride and may redirect approximately three percent of the light to the wavelength calibration arm 124. The wavelength calibration arm 124 comprises a Fabry-Perot fixed etalon 138 and a focusing lens 140. The focusing lens 140 focuses the output of the fixed etalon 138 on a wavelength calibration detector 142, which may be an InGaAs detector to detect amplitude, and which is preferably temperature-controlled by a thermoelectric (Peltier) cooler (TEC) to reduce dark current.

The light emitted from the source optical fiber 136 and impinged on the sampling region 70 is diffuse-reflected by the tissue of the person whose blood alcohol concentration is being detected to collection fibers 144. The collection fibers 144 route the received light through focusing lenses 146 to an alcohol signal detector 148, which may be an InGaAs detector, and which is preferably temperature-controlled by a TEC to reduce dark current. Thus, there are two detectors, the wavelength calibration detector 142 and the alcohol signal detector 148.

As described above, light is delivered onto the tissue by the fiber bundle 50, which is preferably a bifurcated bundle. In one preferred embodiment, the source light is radiated by one fiber 136 having a diameter of 600 microns and is contained in a barrel having a given wall thickness of approximately two hundred microns. Then, the detected light is received through a bundle of other fibers 144 and fed to the alcohol detector 148. There is a small separation between the source fiber 136 and the collection fibers 144. Consequently, only light that penetrates into the tissue to some depth is collected.

The fixed etalon 138 has transmission peaks separated by the desired wavelength sampling interval. The light level at the detector behind the fixed etalon 138 is monitored, and the voltage on the piezoelectric actuator of the piezo etalon 130 is adjusted in order to maximize the light signal. Data is taken at the voltages that correspond to each of the transmission peaks within the desired measurement range. By using the fixed etalon 138 as a reference, data can be taken at a repeatable set of center wavelengths despite hysteresis or other variabilities in the piezoelectric element. Accordingly, the signal from the wavelength calibration detector 142 determines defined sampling points. It also enables internal calibration, because the wavelength calibration detector 142 enables intensity fluctuations in the light source to be monitored.

The disadvantage to the configuration shown in FIG. 15 is that there are two detectors, which increases cost. Alternatively, in accordance with another embodiment of the present invention, the piezo etalon 130 and fixed etalon 138 may be configured in series. However, a disadvantage to such a series configuration is that there is a reduction of light that contacts the tissue by almost an order of magnitude. This is because the linewidth decreases from approximately 8 nanometers (nm) wide to approximately 1 nm wide. Thus, a significant amount of light is lost. In yet another embodiment of the present invention, the fixed etalon 138 may be eliminated. The disadvantage is that the sampling points may not be set as accurately.

In accordance with other embodiments of the present invention, the piezo etalon 130 can be replaced with another type of scanning filter, for example:

• • Liquid crystal (LC) tunable filter (See the CRI product literature, for example). The disadvantage is that LC filters tend to be more expensive than piezo etalons.
  • Thermo-optically tuned filter (See the Aegis Lightwave product literature, for example).
  • Microelectromechanical systems (MEMS) based Fabry-Perot etalon. In this case, the air gap of the etalon is tuned by electrostatically or electromagnetically actuating a micro-machined element. The advantages of MEMS-based filters include low cost and small size (see, for example, FIG. 21, illustrating a MEMS-based Fabry-Perot etalon).

FIG. 16 is an architectural block diagram of the spectroscopic detector 110 in accordance with a preferred embodiment of the present invention. The optical portion of the spectroscopic detector 110 described above is contained in a housing or box 200. The housing 200 is dust-tight, because a fan (not shown) may be incorporated to cool various elements. Consequently, dust is prevented from blowing into the optics. On the other hand, only a portion 201 of the housing 200 containing the focusing lenses 146 and the alcohol signal detector 148 is lighttight so that no light except light collected from the tissue at the sampling region 70 is detected.

Additionally, the spectroscopic detector 110 comprises detector boards 202 and 204 connected to the wavelength calibration detector 142 and the alcohol signal detector 148, respectively, to provide pre-amplification; a driver board 206; and a power supply 208. The driver board 206 comprises a serial port 209 for connection to an analysis system 210 for analyzing the alcohol detection signal. The detector boards 202 and 204 and driver board 206 are preferably configured on a PC board that is the same size as the housing 200, so that the PC board forms a lid to the box. A rubber ring may be incorporated around the edge of the PC board. All cabling is preferably on one side of the PC board, so that the PC board may lift up like a hinge to access the underside of the PC board, as well as the optics. The power supply 208 is preferably housed underneath a thick plate to avoid heat transfer and electrical noise.

As shown in FIG. 16, the driver board 206 comprises a lamp driver 212 for the lamp 112, a piezo driver 214 for the piezo etalon 130, and a chopper driver 216 for the chopper motor 120. The photodiode 129 may be combined with a photodiode driver 218 and mounted on the driver board 206. The driver board 206 also comprises temperature controllers 220 and 222 for cooling the image detectors 142 and 148, respectively, and a processor 224 and a driver 226 for the serial port 209 coupled to a computer 228 for analysis.

Additionally, as shown in FIG. 16, the spectroscopic detector 110 in accordance with one embodiment of the present invention comprises a contact switch and indicator LED 230 to assure that there has been contact made with the tissue at the sampling region 70, because the fiber bundle 50 may not be completely covered by the tissue. The contact switch 230 is preferably positioned directly above the fiber bundle 50 so that only when there is complete contact with the tissue is the electrical signal sent that indicates data may be acquired. The driver board 206 comprises a driver 232 for the contact switch and indicator LED 230.

In addition, as shown in FIG. 16, a diffuse reflectance surface, such as a Spectralon disc 234, is preferably provided that is employed for white light calibration, for example, a few times a day. Consequently, while the fixed sampling positions are determined by the fixed etalon 138 depending on the wavelength, there is also a need to provide a calibration for the signal obtained from the tissue, which is a diffuse reflectance signal. The calibration accounts for the shape to the light that finally reaches the tissue due to the band-pass filters 126, 128 and piezo etalon 130 and other optics. Therefore, instead of having a flat source of light impinging on the tissue, there is a shape to the source light that is determined using a diffuse reflectance surface such as the Spectralon disc 234.

The calibration employing the Spectralon disc 234 may actually be employed for two purposes. First, the calibration may be performed while slowly scanning through the operating spectrum to locate the voltage values for the piezo etalon 130 that correspond to the desired sampling positions. Second, the Spectralon calibration is performed a few times a day, for example, to obtain a blank measurement to the background, that is, what light is detected by radiating the Spectralon disc 234. Then, when actual tissue is sampled, the resulting data is divided by the calibration data to yield the alcohol concentration data.

In operation, the coatings for the band-pass filters 126, 128 are intended to pass a particular wavelength range associated with detection of blood alcohol concentration, for example. This particular wavelength range is in the 2.1-2.5 micron range, as shown in FIG. 17 (shaded portion). FIG. 17 compares the light absorbance of water and ethanol (alcohol) across different wavenumbers from 7000 to 4000 inverse centimeters (cm⁻¹), which corresponds to wavelengths from 1430 to 2500 nm, roughly 1.4 to 2.5 microns. Though the correspondence is not linear, a linear wavelength scale corresponding to the wavenumber range is provided directly below the wavenumber scale. In addition, dashed lines approximating the correspondence are drawn between the two scales at selected wavenumbers of interest.

The particular wavelength range of interest is one in which water is generally very highly absorptive, as indicated by the absorption curve 300. However, within the range of interest, a dip 302 occurs in the water absorption spectrum, and coincident with the dip 302, there are several peaks 304 associated with alcohol that have a higher absorption than water in that narrow region. This region is selected for analysis, because a contribution due to the presence of alcohol can be detected. This region is in the approximate wavelength region of approximately 2.1 to 2.5 microns, and, more particularly, can be in the range of approximately 2150 to 2400 nm. This is the shaded portion of FIG. 17, and corresponds to a wavenumber range of approximately 4650 to 4170 cm⁻¹. It is the actual wavelength scan region for light supplied by the piezo etalon 130 in an exemplary embodiment of the present invention.

The alcohol concentration sampling window region corresponding to the dip 302 only occupies approximately 250 nm of the 2.1-2.5 micron range (which is in the high near-infrared spectral region), as shown in FIG. 17. 250 nm is a relatively small wavelength region, especially when considering the wavelength range over which large spectrometers such as a Fourier Transform InfraRed (FTIR) based on a Michelson Interferometer or a standard dispersive spectrometer employing a grating operate. However, Michelson Interferometers are expensive and bulky while a dispersive spectrometer that uses a diffraction grating to disperse the light across an InGaAs array detector is also expensive due to the cost of the array detector. In contrast, as described above, one embodiment of the spectroscopic detector 110 shown in FIG. 15 comprises two detectors 142, 148, or in an alternative embodiment requires only one detector.

FIG. 18 illustrates the data from FIG. 17 in a different form, namely in terms of the light transmission percentage rather than the absorbance. Note in particular the data around 4400 cm⁻¹, where the transmission percentage of alcohol falls considerably below that of water. FIG. 19 adds an exemplary passband to FIG. 18 that can be obtained, for instance, by passing white light through an appropriate band-pass filter to limit the actual light used by the spectroscopic detector 110 to roughly a 250 nm wide range of interest. FIG. 20 illustrates stepping through the roughly 250 nm wide passband at regular discrete points using a Fabry-Perot piezoelectric etalon.

Accordingly, as shown in FIG. 19, an approximately 250 nm window in the 2.1-2.5 micron range region is scanned. Specifically, as shown in FIG. 20, by applying different voltages across a piezo comprising the piezo etalon 130, the light incident on the piezo etalon is stepped through the wavelengths of light within the window. In accordance with a preferred embodiment of the present invention, the piezo etalon 130 is actually stepped with 7 to 8 nm resolution. Additionally, the fixed etalon 138 has a resolution of one nm spaced every 7 to 8 nm. Consequently, the piezo etalon 130 in combination with the fixed etalon 138 produce approximately 28 data points across a 212 nm region corresponding to the sampling window, and having a linewidth of one nm with one nm wavelength accuracy. The data points are at known wavelengths.

The spectroscopic detector 110 actually collects diffuse reflectance, so when light impinges on tissue, the tissue is very highly scattering. The light undergoes multiple scattering absorption steps, such that the optical properties of the tissue are sampled, and the diffuse reflectance received from the issue is then collected by the collection fibers 144. The alcohol contribution is approximately 0.3 percent of the tissue diffuse reflectance. Consequently, a signal-to-noise of approximately 100 is needed in order to discern the alcohol concentration signal.

Preferably, a voltage is applied to the piezo etalon 130 by the piezo-electric driver 214 that includes any needed correction for the creep and hysteresis of the piezo. If a voltage is applied to scan very slowly across the alcohol concentration scanning window region, the scan time is relatively long. Preferably, the scan is performed in approximately five seconds or less to obtain the data points for analysis of the blood alcohol concentration. Accordingly, one embodiment of the present invention determines the voltage values that correspond to each one of the wavelengths employed for alcohol concentration analysis, which requires calibration since the operation of the piezo comprising the piezo etalon 130 is subject to variation for reasons such as thermal drift.

In order to perform the calibration, a diffuse reflectance surface, such as the Spectralon disc 234, is employed. For example, the Spectralon disc 234 may be white Spectralon, which is approximately 99.8 percent diffuse-reflective and has an essentially flat response. The light impinged on the Spectralon disc 234 during calibration produces a sufficient diffuse reflectance signal for calibration.

Accordingly, the piezo etalon 130 is scanned slowly across the alcohol concentration scanning window employing the Spectralon disc 234 for calibration, and the voltages applied to the piezo are acquired at which peak diffuse reflectance from the Spectralon disc are detected corresponding to the sampling points. The values of the voltages are stored in a lookup table by the processor 208. The voltages stored in the lookup table are then applied to the piezo etalon 130 to produce the wavelengths corresponding to the sampling points in the alcohol concentration scanning window region, so that when a person inserts his or her hand, the piezo etalon can quickly jump to each one of the wavelength sampling positions. The scan speed is fast, because the voltages for the piezo comprising the piezo etalon 130 may be applied to jump from one sampling wavelength to the next. Alternatively, they may be reset to zero before the voltage is applied so that the piezo etalon jumps to the next sampling wavelength if needed to correct for creep and hysteresis.

While diffuse reflectance occurs relatively quickly, there is a finite amount of time required for the piezo etalon 130 to jump to a wavelength sampling position and then settle. The settling time is relatively short, about a millisecond or less. However, in accordance with one embodiment of the present invention, each integration involves both a signal integration and a dark current integration. For this embodiment, an additional period of approximately 30 milliseconds is also provided between each wavelength sampling point while scanning to provide sufficient time during which there is no signal on the alcohol detector 148 to enable integration of the dark current to be performed.

In accordance with another embodiment of the present invention, multiple scans are preferably preformed. That is, one scan across the alcohol concentration sampling window region is performed, then one or more additional scans are performed. Each one of these spectra may be used to obtain an average for multivariate calibration analysis while maintaining information respecting the third and fourth moments to aid the analysis.

The data for the resulting spectra may be converted to information regarding a chemical substance present in the blood by way of multivariate calibration techniques (e.g., principal component regression (PLS), classical least squares (CLS), and partial least squares (PCR) regression models). Multivariate calibration is employed, because the alcohol concentration detection signal is about 0.3 percent within the spectrum that results by scanning across the alcohol concentration scanning window region, which is too small to perform peak analysis. Consequently, multiple different spectra are acquired for which the alcohol concentrations are known, for example, by employing a blood draw or, alternatively, by employing an evidentiary breathalyzer device to provide reference values. These multiple different spectra are obtained from different people, or, alternatively, from the same person at multiple alcohol concentration levels, for many people/persons. As a result, reference spectra are stored, for which the corresponding alcohol concentrations are known.

Then, to determine the blood alcohol concentration, the reference spectra are employed to generate a regression vector or B vector. The concentration of interest is the spectrum, or average of the detected spectra, obtained by scanning across the alcohol concentration scanning window dotted (i.e., multiplied) with the B vector. To determine the unknown blood alcohol concentration, the B vector is multiplied by the spectrum or average of spectra that has been detected, to yield a blood alcohol concentration. From this perspective, the multivariate calibration step can be regarded as the calculation of a regression vector, whose length is the amount of net signal when the value of the property of interest (e.g., blood alcohol concentration) is equal to a known blood alcohol concentration. The determination step can be interpreted as projecting the detected spectrum onto the direction of the net regression vector. The length of the detected spectrum divided by the length of the net regression vector is the value of the property of interest, namely, the detected blood alcohol concentration.

The multivariate calibration technique may be employed to perform quantitative analysis respecting the alcohol spectrum detected by scanning across the alcohol concentration scanning window to yield a blood alcohol concentration measurement, for example, 0.06 blood alcohol concentration. Alternatively, rather than performing a quantitative measurement, a classification may be provided, for example, zero blood alcohol concentration, less than 0.07, or greater than 0.07.

An embodiment of the present invention acquires both spectral information indicative of blood alcohol concentration, as well as a biometric verification. The biometric verification is employed to confirm the identity of the person whose blood alcohol concentration is detected.

An alternative embodiment of the present invention acquires both spectroscopic information related to blood alcohol concentration and information related to other physiological parameters such as tissue oxygenation or lactic acid concentration. The measurement of these alternative physiological parameters is used to confirm that a valid biological sample is presented to the instrument for measurement. In addition, the measurement of these additional parameters can be used to correct for variability in the optical transmission of tissue and, hence, can improve the accuracy and/or precision of the blood alcohol measurement.

Besides alcohol, the above technique can be used to detect other substances that appear in tissue. For example, glucose can be detected using embodiments of the present invention in approximately the 2000 to 2225 nm wavelength region. In addition, cholesterol can be detected using wavenumber ranges of approximately 4500 to 4000 cm¹, which corresponds to an approximate wavelength region of 2225 to 2500 nm. Triglycerides can be detected using a wavelength region of approximately 3125-3570 nm.

Different substances may also have multiple wavelength regions where their concentrations can be detected. For instance, low density lipoprotein (LDL) cholesterol can be detected using approximate wavelength regions of 1700-1800 nm, 3330-3570 nm, and 5550-5880 nm; total cholesterol can be detected using approximate wavelength regions of 3330-3570 nm and 5550-5880 nm; and high density lipoprotein (HDL) cholesterol can be detected using approximate wavelength regions of 2860-3570 nm, 5550-5880 nm, and 6670-11,100 nm.

While the foregoing description has been with reference to particular embodiments and contemplated alternative embodiments of the present invention, it will be appreciated by those skilled in the art that changes in these embodiments may be made without departing from the principles and spirit of the invention. Accordingly, the scope of the present invention can only be ascertained with reference to the appended claims.

Claims

1. An apparatus for acquiring and analyzing a spectroscopic sample for a substance from a sampling region of the tissue of a person, the apparatus comprising:

a source of electromagnetic radiation;

a probe for delivering the electromagnetic radiation to the tissue at the sampling region and obtaining a diffuse-reflectance signal from the tissue at the sampling region; and

a spectroscopic detector for analyzing the diffuse-reflectance signal for presence of the substance.

2. The apparatus of claim 1, further comprising a biometric sensor to perform a verification of the person.

3. The apparatus of claim 2, wherein the biometric sensor is a fingerprint scanner.

4. The apparatus of claim 2, wherein the apparatus controls access to a vehicle, machinery, or heavy equipment, and denies access if the biometric verification fails to verify the person as someone authorized to operate the vehicle, machinery, or heavy equipment.

5. The apparatus of claim 1, wherein the substance is alcohol.

6. The apparatus of claim 5, wherein the analysis comprises determining a blood alcohol concentration of the person.

7. The apparatus of claim 6, wherein the electromagnetic radiation being analyzed is in the wavelength range of about 2.1 microns to about 2.5 microns.

8. The apparatus of claim 1, wherein the substance is glucose.

9. The apparatus of claim 1, wherein the electromagnetic radiation being analyzed is in the wavelength range of about 2000 nanometers (nm) to about 2225 nm.

10. The apparatus of claim 1, wherein the substance is cholesterol.

11. The apparatus of claim 1, wherein the electromagnetic radiation being analyzed is in the wavelength range of about 2225 nm to about 2500 nm.

12. The apparatus of claim 1, wherein the sampling region comprises the interstitial region between two adjacent fingers of the person.

13. The apparatus of claim 12, wherein the sampling region comprises the interstitial region between an index finger and a corresponding middle finger of the person.

14. The apparatus of claim 1, further comprising two spectroscopic detectors: a substance detector for detecting the substance and a wavelength calibration detector for calibrating the substance detector.

15. The apparatus of claim 1, wherein the probe comprises a fiber optic bundle.

16. The apparatus of claim 15, wherein the fiber optic bundle is bifurcated, with one portion for delivering a source radiation to the sampling region and another portion for returning a detected radiation to the spectroscopic detector.

17. The apparatus of claim 1, wherein the spectroscopic detector comprises a tunable Fabry-Perot etalon.

18. The apparatus of claim 17, wherein the tunable Fabry-Perot etalon is tuned by using a piezoelectric element.

19. The apparatus of claim 17, wherein the tunable Fabry-Perot etalon is tuned by using a microelectromechanical systems (MEMS) device.

20. The apparatus of claim 17, further comprising a fixed Fabry-Perot etalon configured to calibrate the tunable Fabry-Perot etalon.

21. The apparatus of claim 1, further comprising a diffuse reflectance surface to calibrate the spectroscopic detector.

22. A method of using the apparatus of claim 1 as a screening device, the method comprising controlling access based on the analysis of the substance being above a predetermined concentration.

23. The method of claim 22, wherein the substance is alcohol.

24. The method of claim 23, wherein the controlling access is for controlling patron access to alcohol in public establishments.

25. The method of claim 22, wherein the controlling access is for controlling driver access to an automobile.

26. The method of claim 22, wherein the controlling access is for controlling operator access to heavy machinery or equipment.

27. The method of claim 22, wherein the controlling access is for controlling operator access to means of public transportation.

28. The method of claim 22, wherein the person is on probation.

29. The method of claim 22, wherein the person is an employee and the controlling access is for controlling access by the employee to his or her job.

30. A method of non-invasive spectroscopic detection of a substance from the tissue of a person, the method comprising:

impinging electromagnetic radiation on a sampling region of the tissue of the person;

obtaining a diffuse reflectance signal from the tissue at the sampling region; and

spectroscopically analyzing the diffuse-reflectance signal for presence of the substance.

31. The method of claim 30, further comprising verifying the person's identity through a biometric sensor.

32. The method of claim 30, wherein the substance is alcohol and the method further comprises determining the blood alcohol concentration of the person.

33. The method of claim 30, wherein the electromagnetic radiation analyzed is in the wavelength range of about 2.1 microns to about 2.5 microns.

34. The method of claim 30, wherein the sampling region comprises the interstitial region between two adjacent fingers of the person.