Blood component assay device

Abstract

An apparatus for assaying blood alcohol concentration (BAC), comprising: a housing for receiving a person's finger; at least one light source that emits light of at least one assay wavelength in each direction, wherein the light emitted from all of these light sources converges to overlap within the same convergent region that illuminates the assay region of the finger received by the housing; a photosensor positioned to receive assay light reflected by tissue within the assay region and generate an assay signal in response thereto; and a photoshield that allows assay light from the convergent region to reach the photosensor and shields the photosensor from stray light from assay light originating from at least one light source that is not reflected by tissue within the assay region.

Description

[Technical Field]

[0001] <Related applications> This application claims the benefit pursuant to 35 U.S. SC 119(e) of U.S. Provisional Application No. 63 / 466,288, filed on 14 May 2023, the disclosure thereof, is incorporated herein by reference in its entirety.

[0002] <Field> Embodiments of this disclosure relate to methods and systems for assaying (or analyzing, measuring / assaying) human blood components. [Background technology]

[0003] <Background> Substance abuse is a major cause of road accidents. Alcohol abuse, in particular, contributes significantly to traffic accidents due to its easy availability, widespread acceptance, and frequent consumption by most segments of the population, accounting for nearly one-third of all traffic fatalities in the United States. For example, in 2020, 11,654 people died in drunk driving collisions in the U.S., roughly one death every 45 minutes. While it is generally assumed that relatively low blood alcohol concentration (BAC), which may result from social drinking, does not significantly impair a driver's ability to drive, even low levels of BAC have been found to reduce driving ability. BAC levels ranging from approximately 0.01 to 0.07 grams / deciliter (g / dl) were identified as contributing factors to over 2,000 traffic fatalities in the U.S. in 2020.

[0004] Accurate and easy-to-use methods and apparatus for measuring a person's blood components that may affect their ability to perform a task are advantageous. Technologies for rapidly and accurately determining a person's blood alcohol content (BAC) before allowing them to drive a vehicle (or take the driving wheel of a vehicle) appear particularly advantageous in controlling substance abuse-related traffic accidents. [Disclosure of the Invention] [Problems that the invention aims to solve]

[0005] <Overview> One embodiment of the present disclosure relates to a method and system for assaying a person's BAC relatively quickly and relatively accurately by measuring the reflectance of light from a person's finger at several different wavelengths (hereinafter referred to as assay wavelengths). The light at the assay wavelengths may also be called assay light. [Means for solving the problem]

[0006] The assay is performed by a relatively rapid and accurate assay apparatus (RACAS, or RACAS assay apparatus), which optionally includes a contact substrate transparent to light of the assay wavelength, on which the person being assayed for BAC presses their finger to establish a contact interface between the surface of the substrate and the skin of the finger. The RACAS comprises at least one light source that can be controlled to deliver light of each assay wavelength to the contact plate so that the delivered assay light is incident on the contact interface and reflected from the contact interface. For each assay wavelength, the RACAS includes at least one photosensor optionally coupled to the contact substrate to receive light reflected from the assay light delivered into the substrate by at least one light source from an area of ​​tissue of the finger near the contact interface, optionally referred to as assay tissue. The at least one sensor generates a signal, also hereafter referred to as the assay signal, in response to the intensity of the reflected assay light received by the at least one sensor.

[0007] The intensity of reflected assay light received by at least one sensor for each assay wavelength, and the associated assay signal, is a function of the respective intensity and angle of incidence of the assay light incident at the contact interface, minus the portion of the incident assay light that is delivered to and absorbed by the assay tissue of the finger at the contact interface. Absorption is a function of molecular components of the finger tissue, such as water and hemoglobin, and alcohol present in the assay tissue that absorbs and / or scatters light. RACAS processes the assay signal generated by at least one sensor to determine the concentrations of alcohol and other components (collectively, assay components) in the finger assay tissue that may have absorbed the assay light incident at the contact interface and influenced the assay signal. The determined alcohol concentrations are used to provide a human BAC measurement.

[0008] In one embodiment, processing the assay signal to determine the concentration of an assay component involves determining the concentrations of alcohol and at least one other assay component that maximize a probability function that provides the probability that a given set of assay signals is generated by a particular set of assay component concentrations.

[0009] In one embodiment, the contact substrate comprises a flat plate against which a finger is pressed. Optionally, the contact substrate includes a curved surface, which may be part of a spherical surface against which the finger is pressed. Since the pressure applied by the finger to the contact substrate can affect the contact interface, the RACAS includes a pressure sensor that determines the “finger pressure”. The RACAS activates the transmission and reception of assay light to measure a person’s BAC when the pressure sensor indicates that the finger pressure is favorable for performing the measurement. Optionally, the RACAS includes an indicator light that responds to the measurement provided by the pressure sensor and indicates to the person when they are applying pressure to the contact substrate that is favorable for performing the BAC measurement.

[0010] In one embodiment, the RACAS includes a light shield (or light blocker) that protects at least one optical sensor from receiving light, also called stray light, that is not reflected by the assay tissue from assay light derived from at least one light source. Optionally, the light shield includes a shield housing having an optical entry port that optionally collimates and faces an area on or within the RACAS where assay tissue of a human finger is placed during the BAC assay. The assay light incident on the light shield through the optical entry port is directed towards the optical sensor by the collimating action of the light shield and / or by optical elements housed within the light shield.

[0011] Optionally, the RACAS may have no contact substrate and no material through which assay light propagates to reach the opening of at least one optical sensor from the assay tissue. Optionally, the RACAS includes a relatively thin protective panel disposed between the opening of at least one optical sensor and the assay tissue. In one embodiment, the protective panel can function as a contact panel on which a person whose BAC is assayed by the RACAS places a finger and provides the RACAS with assay tissue for illumination using the assay light.

[0012] This <Summary> is provided to introduce, in a simplified form, a selection of concepts that are further described in the <Detailed Description> below. This <Summary> is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Brief Description of the Drawings

[0013] Non-limiting examples of embodiments of the present disclosure are described below with reference to the figures accompanying this specification, which are listed after this paragraph. Identical features appearing in two or more figures are generally labeled with the same label in all figures in which they appear. Labels used to label icons representing a given feature in the figures of embodiments of the present disclosure may be used to refer to the given feature. Dimensions of features shown in the figures are selected for convenience and clarity of presentation and are not necessarily shown to a constant scale.

[0014]

FIG. 1A-1B

[0015]

FIG. 1C

[0016]

FIG. 2A-2B

[0017]

FIG. 3

[0018]

FIG. 4A-4B

[0019]

FIG. 5A-5B

[0020]

FIG. 6

[0021]

FIG. 7A-7B

[0022]

FIG. 8

[0023]

FIG. 9

[0024] <Detailed explanation> In the discussion, unless otherwise specified, adjectives such as “substantially” and “about” modifying the conditional or relational characteristics of the embodiments of the disclosure are understood to mean that the conditional or characteristic is defined within the permissible limits of the operation of the embodiments in the intended use. Whenever general terms in the disclosure are indicated by reference to examples or lists of examples, the examples referred to are provided as non-restrictive examples of the general terms, and the general terms are not intended to be limited to the specific examples referred to. The phrase “in embodiments” is used to introduce, whether related to permissibility or not, exemplary, and not necessarily required configurations of possible embodiments of the disclosure, such as “possible,” “optionally,” or “as examples.” The verbs “comprise,” “include,” and “have,” each of them, and their conjugations are used to indicate that the object of the verb is not necessarily a complete list of components, elements, or parts of the subject of the verb. Unless otherwise specified, the term "or" in the specification and claims is considered to be inclusive, not exclusive, and refers to at least one of the items to which "or" is attached, or a combination of two or more items to which "or" is attached.

[0025] Figures 1A and 1B show a top and bottom schematic perspective view, respectively, of a RACAS assay apparatus 20, which optionally includes a substantially hemispherical contact substrate 22 having a rotation axis 23, according to an embodiment of the present disclosure. The contact substrate 22 optionally includes a flat contact surface 24 and optionally a beveled edge surface 26 surrounding the flat bottom surface 27 of the contact substrate 22 perpendicular to the axis 23. The contact surface 24 is the area of ​​the contact substrate 22 to which a person whose BAC is being measured using the RACAS assay apparatus 20 presses their finger. The beveled edge surface 26 is the surface to which a plurality of light sources 30 and a plurality of photosensors 40 are optically coupled to the contact substrate 22. The light sources 30 are configured to emit assay light such that the emitted assay light is incident on the contact surface 24. The photosensors 40 are configured to sense the assay light reflected from the incident light by the contact interface and to generate assay signals in response thereto.

[0026] At least one optionally piezoelectric pressure sensor 50 is mounted on surface 27, optionally at the center of the surface directly opposite (or immediately opposite) the contact surface 24. The pressure sensor 50 generates a pressure signal in response to the pressure between the contact substrate 22 and the housing (not shown) that houses the substrate, which is generated by the force with which a person presses their finger against the contact surface 24.

[0027] In one embodiment, the number of light sources 30 is equal to the number of photosensors. Optionally, each light source 30 emits assay light at a different assay wavelength and is paired with a different photosensor 40 that receives the assay light emitted by the light source and is highly sensitive to it. The paired light sources 30 and sensors 40 are mounted on inclined surfaces 26 that are directly opposite each other at their respective ends of the diameter of the base surface 27, such that the central ray of the assay light emitted by the light source 30, incident on the center 25 of the contact surface 24 and reflected therefrom, is incident on the substantially center (not shown) of the aperture of the sensor 40 paired with the light source.

[0028] Figure 1C shows a schematic cross-sectional view of the RACAS20, which displays a light source 30 that sends a beam of assay light 33 that is incident on the center 25 of the contact surface 24 and reflected therefrom as a reflected beam 44. The reflected beam 44 is incident on a sensor 40 paired with the light source 30.

[0029] Figures 2A and 2B show a cross-sectional and perspective view, respectively, of a person (not shown) providing their BAC value using RACAS 20 according to an embodiment of the present disclosure. These figures schematically illustrate the assay signal used to determine the BAC, which is generated by a sensor 40 in response to the reflected assay light, by pressing a finger 100 against the contact surface 24 of the substrate 22, thereby creating a contact interface between the contact surface 24 and the finger, which affects the reflection of assay light from the contact surface. Figure 2A schematically shows a light source 30 that sends assay light 33 to the contact surface 24, and a sensor 40 paired with the light source that receives assay light 44 reflected by the contact surface 24 from the sent light 33. The perspective view of Figure 2B schematically shows the assay light sent to the contact surface 24 by all the light sources 30 and received by the light sensors 40 paired with each light source.

[0030] Figure 2B appears to show all the light sources 30 operating simultaneously to deliver assay light, but it should be noted that the implementation of embodiments of the present invention is not limited to the simultaneous operation of all light sources. The light sources may be operated individually and sequentially in any order, for example, or different groups of light sources may be operated sequentially.

[0031] Advantageously, the assay wavelengths to which the assay light is delivered by the light source 30 in RACAS 20 include wavelengths whose absorptive rates for components of interest in the tissue and blood within the finger 100 can be used to distinguish the concentrations of components within the finger. Generally, such wavelengths are those with substantially different absorptive rates. For example, the components of particular interest when performing BAC measurements according to embodiments of the present disclosure are, of course, alcohol and water. Figure 3 shows the absorption spectra of alcohol and water at 1 mg (milligram) / dL (deciliter) / mm (per mg (milligram) per dL (deciliter) per mm). From the absorption spectra, advantageous assay wavelengths appear to be wavelengths in the wavelength band including wavelengths 1.3 μm, 1.45 μm, and 2.3 μm.

[0032] In one embodiment, processing the assay signal generated by, for example, sensor 40 of FIG. 2B to determine the concentration of assay components and BAC involves determining the concentrations of alcohol and at least one other assay component that maximizes a probability function that provides the probability that a given set of assay signals results from a particular set of concentrations of assay components.

[0033] As an example, RACAS according to an embodiment of the present disclosure similar to RACAS20 includes a plurality of J assay light sources 30 each paired with a respective one of J assay light sensors 40, each light source sending assay light at a different assay wavelength λ j (1 ≦ j ≦ J). Further, assume that there are N components of interest (one of which is alcohol) having unknown concentrations ρ n (1 ≦ n ≦ N) in finger 100, which may affect the assay signal generated by the j-th (1 ≦ j ≦ J) light sensor in response to the reflected assay light of wavelength λj incident on the sensor. For a given skin color c, r(c, λ j ) n is assumed to represent the reflectance of the light at assay wavelength λ j for the n-th assay component of interest within finger 100. If the assay signal generated by the j-th light sensor 40 in response to the incident assay light of wavelength λ j reflected by contact surface 24 to the sensor is represented by R(λ j , c, ρ ) j , then R(λ j , c, ρ ) j is It can be written as TIFF2026517201000002.tif10169.

[0034] In Equation (1), ρ represents the set of concentrations {ρ n |(1 ≦ n ≦ N)}, DS(λ j ) j is a proportionality constant, and among other things, the intensity of the light sent by the j-th light source, wavelength λ jIt is a function of the sensitivity of the j-th sensor to light and related geometric parameters such as the reflection angle of the reflected assay light.

[0035] c and ρ Each known value c * and ρ * Regarding the given expected assay signal R(λ), j ,c, ρ ) j The probability density function for the j-th light sensor 40 that provides the following is given: TIFF2026517201000003.tif8169 in formula, R * (λ j ,c * , ρ * ) j is, c * and ρ * This is the expected assay signal for [the substance].

[0036] For the sake of presentation, unknown concentration ρ And the actual assay signal provided by the j-th sensor 40 for skin color c is "abbreviated", R j Represented by c and ρ The set of actual assay signals provided by all J sensors 40 for the unknown value of is given by the vector [R] = {R j Let it be expressed as |(1≦j≦J)}. In one embodiment, c * and ρ * The probability density function for J sensors 40 that provide a given set of actual assay signals [R] is a multivariate Gaussian density function. TIFF2026517201000004.tif7169(in the formula, λ The set of assay wavelengths {λ j It is assumed that |(1≦j≦J)} represents this. In this case, TIFF2026517201000005.tif7169 is, It can also be written as TIFF2026517201000006.tif22169, and here, R * For the sake of presentation, it is assumed that the covariance matrix is ​​diagonal. In equation (2), skin color c * and the concentration of assay components ρ * Expected assay signal R * is an unknown that needs to be solved, R j Please note that this is a known actual assay signal. * , ρ * What is the value of c? * , ρ * P([R]( λ ,c, ρ This can be determined by deciding which value to maximize. Determining the value to maximize can be achieved using any suitable procedure known in the art. For example, α * , ρ * This can be determined using the least squares method, the continuous optimization technique, or optionally, the gradient descent method.

[0037] In one embodiment, the set of concentration ρ * ={ρ n The concentration ρ of |(1≦n≦N)} * Assuming that 1 is the concentration of alcohol, ρ * Use 1 to determine the BAC.

[0038] In one embodiment, the actual assay signal vector [R] may be processed by any of the various types of artificial intelligence (Al), such as machine learning algorithms, decision trees, regression algorithms, and various types of neural networks. For example, the actual assay signal vector [R] may be processed by a convolutional neural network (CNN) or a deep neural network (DNN), which provides probabilities for each of a given number of BAC ranges in which the actual assay signal vector falls.

[0039] In the example above, RACAS20 comprises a substantially hemispherical contact substrate, but the implementation of embodiments of the present disclosure is not limited to hemispherical or spherical. For example, Figures 4A and 4B show schematic views of RACAS120 from above and below, respectively, according to an embodiment of the present disclosure. In one embodiment of the present disclosure, RACAS120 comprises a rectangular parallelepiped contact substrate 122 having a flat contact surface 124, to which a person presses their finger 100 to provide a contact interface with the contact substrate and to determine the person's BAC. RACAS120 optionally comprises a plurality of, optionally four, light sources 130, each sending light of at least one different assay wavelength to the substrate 122, and a single photosensor 140 that generates an assay signal in response to the incident assay light sent by each of the light sources 130. The photosensor 140 may comprise a plurality of photosensitive pixels (not shown), each of which generates an assay signal in response to the incident assay light sent by the light sources 130.

[0040] Figures 5A and 5B show schematic diagrams from above and below views of a RACAS220, similar to the RACA120 and comprising a plurality of optionally four light sources 130 and a single light sensor 140, according to one embodiment of the present disclosure. However, unlike the RACAS120, the RACAS220, according to one embodiment of the present disclosure, comprises a prism-shaped contact substrate 222 having a curved contact surface 224 instead of the flat contact surface 124 of the RACAS120, to which a person presses their finger 100 to determine their BAC. Contract surface (or contact surface)124 has a radius of curvature that is advantageous for fitting a human finger 100 in order to facilitate the provision of a relatively large contact interface between the contact substrate 222 and the finger.

[0041] Figure 6 schematically shows a RACAS300 equipped with an optical shield to protect the optical sensor from stray light, according to an embodiment of the present disclosure.

[0042] In one embodiment, the RACAS 300 comprises at least one, and optionally three or more, light sources 302 for illuminating assay tissue of a human finger with assay light, as schematically shown in Figure 6, and a photosensor 306 for sensing assay light reflected from the assay light illuminating the assay tissue. The photosensor 306 is seated inside an optionally cylindrical photoshield 312 formed from a material opaque to assay light, the photoshield 312 having an inlet port 313 through which light can enter the photoshield and reach the sensor 306. The light entering the photoshield 312 through the inlet port 313 is optionally collected and directed to the photosensor by a focusing lens 314. The light sources, photosensor, and photoshield are housed in a housing 320, the housing 320 having an access opening 322 on the upper wall 324 of the housing. The photoshield 312 is mounted in the housing 320 such that the inlet port 313 of the shield is optionally substantially within the access opening and coplanar with the access opening.

[0043] The person being assayed for BAC by RACAS300 positions their finger so as to overlap the access opening 322 and cover the inlet port 313, illuminating the area of ​​the finger and providing reflected assay light that enters the photosensor 306, as described later. Optionally, the access opening is covered with a protective cover (not shown), on which the person places their finger to assay their BAC. Figure 6 schematically shows the finger 100 of a person being assayed for BAC by RACAS300 positioned over the inlet port 313.

[0044] Optionally, each light source 302 comprises at least one light-emitting element 303 that emits assay light, and an optical collimator lens 304 that receives light 350 from the light-emitting element and collimates the light into a beam of assay light 351. In one embodiment, all light sources 302 are mounted within a housing 320, so that the beam 351 of assay light 350 from all light sources propagates through an access opening 322, converges to substantially overlap with the same assay region 102 in finger 100, and illuminates it. Optionally, each light source comprises a focusing lens that focuses the beam 351 into the assay region. Reflected assay light 352 reflected from the beam 351 by the assay tissue in the assay region 102 enters the light shield 312 through an inlet port 313 and is directed to a photosensor 306 by a focusing lens 314.

[0045] In one embodiment, at least one light-emitting element 303 of the light source 302 includes a plurality of light-emitting elements (not shown in Figure 6). The plurality of light-emitting elements may include LEDs and / or laser diodes, and may provide assay light at a plurality of different assay wavelengths. Optionally, each light source 302 provides assay light at wavelengths of 1300 nm, 1460 nm, and 2300 nm.

[0046] Figures 7A and 7B schematically show a cross-sectional view and a perspective view of the RACAS400 according to an embodiment of the present disclosure. The cross-section lies in the plane shown as plane BB in both Figures 7A and 7B.

[0047] RACAS400 comprises a finger cradle 402 for receiving a human finger 100 to be assayed by RACAS according to embodiments of the present disclosure. In one embodiment, RACAS400 comprises at least one light source similar to the light source 302 shown in Figure 6, and two as schematically shown in Figures 7A and 7B. The light sources are mounted on the cradle 402 such that a light beam 351 from the light source passes through an access opening 404 formed in the cradle and focuses to illuminate the same assay area 102 within the finger 100. Optionally, a light sensor shielded by a light shield similar to the light sensor 306 and shield 312 shown in Figure 6, respectively, is mounted below the cradle 402 so that the cradle 402 receives the finger 100 to receive assay light reflected from assay tissue within the assay area 102. Optionally, the access opening 404 and inlet port 313 are covered with protective covers (not shown), a person places their finger over them, and the person's BAC is assayed by RACAS400.

[0048] Figure 8 schematically shows yet another RACAS500 equipped with a light-shielded light sensor according to an embodiment of the present disclosure.

[0049] The RACAS500 optionally comprises a finger cradle 502, an optical sensor shielded by an optical shield, which may be similar to the optical sensor 306 and shield 312 shown in Figure 6, respectively, and optionally a plurality of four light sources 302. The shield 312 has an inlet port 313 optionally located on the bottom region 503 of the surface 504 of the cradle. The light sources 302 are positioned and configured such that assay light from the light sources passes through their respective exit windows 506 on the surface 504 to illuminate the same area of ​​the finger placed in the cradle in contact with the inlet port 313 and exit windows 506, or a protective cover above the inlet port and exit windows.

[0050] Figure 9 shows a schematic diagram of a light source 302 comprising a plurality of light-emitting elements 303 that emit assay light, according to an embodiment of the present disclosure.

[0051] Therefore, according to one embodiment, an apparatus for assaying blood alcohol concentration (BAC) is provided, the apparatus comprising a housing for receiving a human finger; at least one light source, each sending light of at least one assay wavelength in each direction, wherein the light from all of the at least one light source converges to overlap within the same convergence region that illuminates the assay region of the finger received by the housing; a photosensor arranged to receive assay light reflected by tissue within the assay region and generate an assay signal in response thereto; and a photoshield that allows assay light from the convergence region to reach the photosensor and shields stray light not reflected by tissue within the assay region from assay light originating from at least one light source. Optionally, the photoshield comprises a tubular surface defining a lumen and an inlet port facing a convergence region through which light can pass to enter the lumen. Optionally, the photoshield houses a focusing lens that receives light entering the lumen through the inlet port and directs this light towards a sensor. Optionally, the photosensor is located within the lumen.

[0052] In one embodiment, light from each of at least one light source passes through the entrance port of the light shield as it propagates into the focusing region. In one embodiment, the at least one light source includes a plurality of light sources, all of which are located on the same side of the focusing region. In one embodiment, the at least one light source includes a plurality of light sources, at least two of which are located on opposite sides of the focusing region.

[0053] In one embodiment, the housing comprises a cradle having a surface for receiving fingers. Optionally, each of at least one light sources delivers assay light through an exit window located on the surface of the cradle. Optionally, each of the exit windows of at least one light source is covered by a protective cover transparent to the assay light. In one embodiment, a light-shielding inlet port is located on the surface of the cradle. Optionally, the inlet port is covered by a protective cover transparent to the assay light.

[0054] In one embodiment, the device includes a controller that processes assay signals from a light source in order to determine the BAC value.

[0055] The descriptions of embodiments of the present invention in this application are provided as examples and are not intended to limit the scope of the invention. The described embodiments include different features, but not all of them are required in all embodiments of the invention. Some embodiments utilize only some of the features, or possible combinations of features. Modifications of the described embodiments of the invention, and embodiments of the invention including different combinations of features of the described embodiments, will be conceivable to those skilled in the art. The scope of the invention is limited only by the claims.

[0056] the above" ρ " is the bolded "ρ", λ " represents the bold letter "λ", and [R] is This represents JPEG2026517201000007.jpg7169.

Claims

1. An apparatus for assaying blood alcohol concentration (BAC), wherein the apparatus is A housing for receiving a human finger, At least one light source that emits light at at least one assay wavelength in each direction, wherein the light emitted from all of the at least one light source converges to overlap in the same convergence region that illuminates the assay area of ​​the finger received by the housing, A photosensor is positioned to receive assay light reflected by tissue within the assay region and generate an assay signal in response thereto. A light shield that enables assay light from the convergence region to reach the photosensor and shields the photosensor from stray light that is not reflected by the tissue in the assay region from assay light generated from at least one of the light sources, A device that includes this.

2. The apparatus according to claim 1, wherein the light shield comprises a tube surface defining a lumen and an inlet port facing the convergence region through which light can pass to enter the lumen.

3. The apparatus according to claim 2, wherein the light shield houses a focusing lens that receives light entering the lumen through the inlet port and directs the light toward the sensor.

4. The apparatus according to claim 3, wherein the light sensor is disposed within the lumen.

5. The apparatus according to claim 2, wherein light from each of the at least one light sources passes through the inlet port of the light shield when it propagates to the convergence region.

6. The apparatus according to claim 1, wherein the at least one light source includes a plurality of light sources, all of which are located on the same side of the convergence region.

7. The apparatus according to claim 1, wherein the at least one light source includes a plurality of light sources, at least two of which are arranged on both sides of the convergence region.

8. The apparatus according to claim 1, wherein the housing comprises a cradle having a surface for receiving the fingers.

9. The apparatus according to claim 8, wherein each of the at least one light source delivers assay light through an exit window located on the surface of the cradle.

10. The apparatus according to claim 9, wherein each of the outlet windows of the at least one light source is covered with a protective cover that is transparent to assay light.

11. The apparatus according to claim 8, wherein the optical shield inlet port is located on the surface of the cradle.

12. The apparatus according to claim 11, wherein the inlet port is covered by a protective cover that is transparent to assay light.

13. The apparatus according to claim 1, further comprising a controller that processes the assay signal from the light source in order to determine the value of the BAC.

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