Method and system for preventing tampering with breath sample measurements - Patents.com

Abstract

The present invention relates to a breath analysis system and method, in particular to a breath analysis system and method for determining the validity of the measurement of the concentration of an intoxicating substance in a user's breath, thereby reducing the risk of falsifying the results, without increasing the analysis time or inconvenience to the user. A gaze detector is provided, the output signal of which is compared to a tracer substance signal to determine whether the signals have respective expected behaviors and relationships.

Description

[Technical Field]

[0001] The present invention relates to a breath analysis device and method, and more particularly to a breath analysis device and method that reduces the likelihood of falsifying results without increasing analysis time or inconvenience to the user. [Background technology]

[0002] Breath analysis devices are becoming increasingly common, especially in vehicles, as a means of detecting and preventing driving under the influence of intoxicating substances, particularly ethyl alcohol (ethanol). Breath analysis devices can be standalone units that provide a measurement of the substance content in the driver's breath, or they can even be handheld units. Alternatively, breath analysis devices can be part of a system that also includes equipment for identifying the driver and / or locking the vehicle. Such breath analysis devices are typically permanently mounted on the vehicle and can be, for example, an integrated part of the dashboard. Breath analysis devices can also be stationary systems used to restrict access to work areas, vehicle fleet depots, etc.

[0003] Providing a breath analyzer that has adequate sensitivity, is reliable, and provides a sufficiently fast analysis is not an easy task. This is particularly difficult when the breath analysis device should be able to detect multiple substances and should not be hindered by variations in moisture, CO2 content, etc. Breath analysis devices that meet these requirements are described, for example, in US 7,919,754 and US 9,746,454, which are incorporated herein by reference.

[0004] The breath analysis device may be part of a system that also includes a device for identifying the driver and / or locking the vehicle, a so-called "alcohol interlock device." Such breath analysis devices are typically permanently installed in the vehicle and may be an integrated part of the dashboard, for example, and may be further connected to the vehicle's control system. Alcohol interlock devices are widely used in offender programs as a mandatory accessory for the rehabilitation of car owners who have been convicted of drunk driving. In addition, similar systems and devices are used in commercial vehicles such as buses, taxis, and trains. However, it is believed that these systems will soon become commonplace in private vehicles as well, and in some cases even mandatory in at least some countries and regions.

[0005] The most common approach for both traditional in-vehicle breath testing devices and fixed testing laboratories is to use a mouthpiece that allows the user to clear their airway after taking a deep breath. This approach is called active detection. To ensure an accurate result, the user must provide a forced exhalation with nearly full lung capacity. This requires significant time and effort, especially for people with limited lung capacity. In addition, the mouthpiece, or parts of the mouthpiece, are often made of disposable plastic for hygienic reasons. This results in cumbersome handling and the use of a large amount of disposable plastic, which are questionable from an environmental perspective.

[0006] Non-contact detection is an alternative approach in which a mouthpiece is not utilized; the breath testing device typically receives a mixture of exhaled breath and ambient air, and the detection of intoxicants is determined from a breath sample acquired during normal breathing. This detection can be completely passive, requiring no user action, for example, while the user is performing routine, everyday vehicle startup. Alternatively, the user can be instructed to perform a specific action designed to facilitate the detection process, such as breathing toward an air intake. One problem with non-contact detection is the low concentration of the substance being detected and analyzed, even when the user is instructed to breathe in a specific direction. Established methods utilize a tracer gas, typically carbon dioxide or water vapor, always present in exhaled breath in very predictable amounts, both to trigger the analysis of the target substance and to facilitate the determination of the target substance's concentration value. However, making non-contact detection work satisfactorily in real-world scenarios has proven difficult. Accurately analyzing the concentration of an intoxicant can take a significant amount of time. This required time may be perceived as unacceptably long, for example, when starting a vehicle or when an employer attempts to enter a gated work site.

[0007] A further challenge with using non-contact breath analyzer systems is that such systems can be particularly susceptible to tampering. Tampering can include, for example, cooling the breath sample with a refrigerated tube or filtering the breath sample with charcoal. Tampering is a recognized problem and has been addressed in various ways. However, known approaches typically add significant complexity to the breath analyzer system, making it more cumbersome to use, or increasing the time required to provide results to the user.

[0008] EP3106872 discloses a system and method in which a breath analyzer system is provided with a camera and the images produced are analysed with advanced image analysis methods to detect and warn of tampering attempts. Summary of the Invention [Problem to be solved by the invention]

[0009] It is an object of the present invention to provide a breath analysis system and method of operation that overcomes the shortcomings of prior art non-contact detection systems. [Means for solving the problem]

[0010] This is achieved by a method as defined in claim 1 and a breath analysis device as defined in claim 10.

[0011] According to one aspect of the present invention, there is provided a method for determining the validity of a measurement of a concentration of an intoxicating substance in a user's breath, the method comprising: a measurement cell configured to sample a sensor signal representative of a concentration of the intoxicating substance and a sensor signal representative of a concentration of the tracer substance; and a line of sight detector having a predetermined field of view and configured to measure coverage of the field of view by an object and output a signal representative of the coverage. The above method is - monitoring an output signal of the gaze detector, and if the output signal deviates from a set background value, recording the gaze detector output signal as a function of time, the output signal change being a recorded gaze signal signature; - monitoring the tracer substance sensor signal and, if a peak in the tracer substance is detected, the peak indicates a possible exhalation phase of the user's breathing cycle, and deriving an exhaled breath concentration value of the intoxicant based on the intoxicant sensor signal and the tracer substance sensor signal; - comparing a recorded gaze signal signature derived from the gaze detector with at least one stored reference signal signature; - comparing the relationship between the line of sight detector output signal and the tracer substance signal to stored signal relationship criteria; If the recorded gaze signal signature matches the stored reference signal signature, and if the recorded gaze output signal and tracer substance signal satisfy the stored signal relationship criteria, the measurement of the breath concentration value is confirmed valid.

[0012] According to one embodiment of the present invention, in the monitoring step, a background value of the gaze detector output signal is derived and the step of comparing the recorded gaze signal signature with a stored reference signal signature includes comparing at least one of the following parameters or a selection from said parameters: signal slope after initial rise, duration of the time period during which the signal is raised, signal value associated with the upper limit value, duration of the signal above a predefined level associated with the upper limit level, signal slope after peak or plateau.

[0013] According to one embodiment of the present invention, the stored signal relationship criterion includes a time relationship between the gaze detector output signal and the tracer substance signal. This time relationship criterion may require that an increase in the recorded gaze detector output signal, indicating an object is approaching the breath analysis device, occurs before the onset of a peak in the tracer substance signal. The time relationship criterion may further require that a peak in the recorded gaze detector output signal coincides with a peak in the tracer substance signal within a predetermined time interval. Furthermore, comparing the relationship between the gaze detector output signal and the tracer substance signal with the stored signal relationship criterion may include modifying the time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for the breath sample to reach the breath analysis device. Alternatively, the time relationship between the gaze detector output signal and the tracer substance signal may include an expected time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for the breath sample to reach the breath analysis device.

[0014] According to one embodiment of the present invention, the gaze detector is configured to measure thermal radiation. The breath analysis device may further comprise means for measuring ambient temperature, and the output signal from the gaze detector is compensated for the ambient temperature.

[0015] According to one aspect of the present invention, there is provided a breath analysis device, comprising: - a measurement cell configured to sample a sensor signal representative of the concentration of the intoxicating substance and a sensor signal representative of the concentration of the tracer substance; - a line of sight detector having a predetermined field of view and configured to measure coverage of the field of view by an object and to output a signal representative of the coverage; - a control and signal processing unit connected to the measuring cell and the line of sight detector, - monitoring an output signal of the gaze detector, and if the output signal deviates from a set background value, recording the gaze detector output signal as a function of time, the output signal change being a recorded gaze signal signature; - monitoring the tracer substance sensor signal and, if a peak in the tracer substance is detected, the peak indicating a possible exhalation phase of the user's breathing cycle, deriving an exhaled breath concentration value of the intoxicant based on the intoxicant sensor signal and the tracer substance sensor signal; - comparing a recorded gaze signal signature derived from said gaze detector with at least one stored reference signal signature; - comparing the relationship between the line of sight detector output signal and the tracer substance signal to stored signal relationship criteria; If the recorded gaze signal signature matches the stored reference signal signature, and if the recorded gaze output signal and tracer substance signal satisfy the stored signal relationship criteria, the measurement of the breath concentration value is confirmed valid.

[0016] According to one embodiment of the present invention, the gaze detector is configured to detect electromagnetic radiation and includes an aperture that determines the effective field of view of the gaze detector. The gaze detector may comprise a sensor that utilizes infrared detection and is configured to measure thermal radiation.

[0017] According to one embodiment of the present invention, the sensor of the line of sight detector (108) is an active sensor configured to utilize near-infrared reflectance measurements.

[0018] According to one embodiment of the present invention, the gaze detector is configured to have a field of view corresponding to a predefined area at a predefined distance from the breath analysis device, the predefined area being an area of ​​a typical human face of a person using the breath analysis device at the predefined distance, the predefined distance being associated with proper use of the breath analysis device and being between 100 and 300 mm.

[0019] According to one embodiment of the present invention, the breath analysis device further comprises means for measuring the ambient temperature, and the signal from the gaze detector is compensated for the ambient temperature.

[0020] According to one embodiment of the present invention, the gaze detector comprises a plurality of sensors configured to provide a corresponding plurality of output signals that provide a spatial resolution of the field of view that can form a low-resolution image of objects within the field of view. The gaze detector may comprise an 8x8 matrix of IR photodetectors.

[0021] According to one embodiment of the present invention, the breath analysis device is further configured to, in the monitoring step, derive a background value of the gaze detector output signal, and in the step of comparing the recorded gaze signal signature with the stored reference signal signature, compare one or a selection of the following parameters: signal slope after initial rise, duration of the time segment during which the signal is raised, signal value associated with the upper limit value, duration of the signal above a predefined level associated with the upper limit level, signal slope after peak or plateau.

[0022] According to one embodiment of the present invention, the breath analysis device is further configured to store a signal relationship criterion including a time relationship between the gaze detector output signal and the tracer substance signal. This time relationship criterion may require that an increase in the recorded gaze detector output signal, indicating that an object is approaching the breath analysis device, occurs before the onset of a peak in the tracer substance signal. The time relationship criterion may further require that a peak in the recorded gaze detector output signal coincides with a peak in the tracer substance signal within a predetermined time interval. Furthermore, comparing the relationship between the gaze detector output signal and the tracer substance signal with the stored signal relationship criterion may include modifying the time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for the breath sample to reach the breath analysis device. Alternatively, the time relationship between the gaze detector output signal and the tracer substance signal may include an expected time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for the breath sample to reach the breath analysis device.

[0023] The present invention can provide a breath analysis method and a breath analysis device that can verify the measurement of the concentration of an intoxicating substance in a user's breath.

[0024] One advantage provided by the present invention is that validation can be performed in a stand-alone unit without reliance on external databases or complex image analysis systems.

[0025] A further advantage is that the validation is fast and reliable, which is very important for the acceptance of implementing breath analysis systems and routines, for example in the workplace.

[0026] A further advantage of the breath analysis method and breath analysis device according to the present invention is that the method and device can be implemented in a variety of ways, including, but not limited to, handheld devices, fixed devices installed at the entrance to a work area, and in-vehicle devices. The breath analysis device can be easily integrated into the dashboard of a vehicle, utilizing existing functions and facilities provided in, for example, an automobile infotainment system. The breath analysis device can also be connected to a vehicle lock system, such as a so-called alcohol interlock device.

[0027] In the following, the invention will be described in more detail, by way of example only, with respect to non-limiting embodiments thereof and with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0028] [Figure 1] 1a and 1b are schematic diagrams of a breath analysis device according to the present invention, with FIG. 1a showing the breath analysis device and FIG. 1b showing the basic concepts of line of sight and field of view. [Figure 2a] 1 is a schematic graph showing the sensor signal of a breath analysis device according to the present invention, showing a graph of a typical sensor signal of a breath analysis device including a line of sight detector (upper graph) and a tracer, and a substance signal (lower graph). [Figure 2b] 1A and 1B are schematic graphs showing the sensor signal of a breath analysis device according to the present invention, and graphs and schematic diagrams showing the relationship between the variability of the signal and the field of view of the gaze detector; [Figure 2c] 1 is a schematic graph showing the sensor signal of a breath analysis device according to the present invention, illustrating a typical signal signature and quantification of an eye gaze detector; [Figure 3] 1 is a flow chart of a method according to the present invention; [Figure 4] 4a, 4b and 4c are schematic diagrams of different embodiments of gaze detector arrangements according to the present invention. [Figure 5] 1 is a graph of the spectral characteristics of one embodiment of an infrared thermometry based line of sight detector; [Figure 6] FIG. 1 illustrates an embodiment of a line of sight detector based on reflected near infrared radiation (NIR) including a graph of its field of view. [Figure 7] FIG. 1 illustrates the field of view provided by one embodiment of a line of sight detector that uses light emitting diodes and photodiodes to monitor light reflectance within a predefined field of view. [Figure 8] Figures 8a, 8b and 8c show schematic diagrams of different application examples of a breath analysis device according to the invention, including Figure 8a as a handheld device, Figure 8b as a wall mounted device and Figure 8c as an automobile integrated unit. DETAILED DESCRIPTION OF THE INVENTION

[0029] Terms such as "top," "bottom," "upper," "lower," "below," "above," and the like are used only to refer to the shape of embodiments of the invention as shown in the drawings and / or during normal operation of the device, and are not intended to limit the invention in any way.

[0030] Definition: The tracer is a physiological substance inherently associated with exhaled breath, such as carbon dioxide or water vapor.

[0031] Baseline refers to the signal level corresponding to the concentration of the intoxicant or tracer against which other instantaneous signal values ​​are referenced. Offset error is the deviation from the baseline.

[0032] The concentration peak is defined by the maximum of the measured concentration versus time, with an increase in concentration before the peak maximum and a subsequent decrease.

[0033] The breath analysis device and method of the present invention will be primarily described as a non-contact detection system mounted on a vehicle, which represents an important embodiment of the present invention. The breath analysis device can be fully integrated into the vehicle, for example, utilizing the existing vehicle infotainment system for communication with the user and / or the HVAC system for detecting the airflow to the breath analysis device. An integrated system breath analysis device is described in SE1950840-7, which is hereby incorporated by reference. The vehicle breath analysis device of the present invention can also be retrofitted into a vehicle, in which case the breath analysis device will typically be more independent from other components of the vehicle instrumentation. As will be recognized by those skilled in the art, the present teachings are equally suitable for stand-alone systems, such as systems at the entrances to work areas, fleet depots, etc. The breath analysis device and method of the present invention can also be a handheld system used in a vehicle or elsewhere.

[0034] The breath analysis devices and methods according to the present invention can be easily combined with recently developed systems and methods for improving the speed and performance of breath analysis devices, for example as described in SE1950840-7 and SE2050105-2, which are hereby incorporated by reference.

[0035] FIG. 1a is a schematic diagram of a breath analysis device 100 according to the present invention. The breath analysis device 100 comprises a housing 101, a metering cell 102, a gaze detector 108, one or more audiovisual communication units 113, and a control and signal processing unit 114. The breath analysis device 100 is adapted to analyze the breath of a user within a predefined maximum distance. By deriving the concentrations of both the intoxicant and the tracer gas at this distance, the breath concentration of the intoxicant can be derived. The tracer gas has a known breath concentration, and by measuring its concentration at the position of the metering cell 102, the amount of dilution of the breath can be derived. Typically, carbon dioxide (CO2) or water vapor (HO) is used as a tracer gas, exhibiting nominal concentrations of 4.2 and 5.6 percent by volume in human breath, respectively.

[0036] The measurement cell 102 is provided with an inlet 103 and an outlet 104 in the housing 101, and means for forcing air to flow from the inlet 103 to the outlet 104, such as a fan 105. During operation, the measurement cell 102 is continuously exposed to air drawn from the breath sampling inlet 103. The inlet 103 is located on the surface of the housing 101 that faces the user during operation of the breath analysis device 100.

[0037] In embodiments in which the breath analysis device 100 is provided in a vehicle, the breath analysis device 100 may be fully integrated, for example into the dashboard, in which case the housing 101 is not a separate component. Also, in the case of a fully integrated device, the breath analysis device 100 may not have a dedicated audiovisual communication unit 113 and a dedicated control and signal processing unit 114, but rather utilize such functionality provided in the vehicle. Therefore, these units should be considered as functional units in integrated embodiments.

[0038] The measuring cell 102 preferably operates on the principle of infrared (IR) spectroscopy. The IR emitter 106 emits a beam of IR radiation, which is absorbed by the IR detector 107 after reflection from the inner wall of the measuring cell 102. The surface of the inner wall is preferably coated with a highly reflective material, such as aluminum. The number of reflections and collimation of the IR beam can be adapted to the expected range of IR absorption coefficients and concentrations of the tracer and intoxicant. The emitter 106 is typically a blackbody film with a small mass and is therefore adapted to emit pulsating radiation in a broad wavelength range from 3 to 10 μm with a repetition rate of 5 Hz or higher. The IR detector 107 includes narrow-band filters tuned to the absorption peaks of one or several intoxicants, such as ethyl alcohol, which has an absorption peak at 9.5 μm, and one or several tracer gases, such as carbon dioxide and water vapor, which have absorption peaks at 4.3 and 6.0 μm, respectively. The presence of an intoxicant or tracer gas results in a reduction in IR intensity, which is converted into an electrical signal by a multi-channel IR detector 107 having an optical filter adapted to a specific absorption peak and operating synchronously with the repetition rate of the IR emitter 106. As will be appreciated by those skilled in the art, other types of measurement cells operating according to different principles may also be utilized. The choice of measurement cell or measurement principle may depend, for example, on the specific intoxicant being analyzed or on design constraints such as power consumption or cost. The present invention is not limited to a specific measurement cell or measurement principle for measuring the breath concentration of a specific intoxicant.

[0039] The gaze detector 108 is arranged to provide information when an object is presented and correctly positioned relative to the inlet 103 so that the breath sample can be accurately analyzed. This is referred to as the gaze detector 108 being arranged to provide an object presence signal. The gaze detector 108 is further arranged to provide information, referred to as a signal signature, regarding the nature of the object, i.e., whether the object is a living human or not. The different measurement techniques implemented by the various gaze detectors are described further below.

[0040] As shown schematically in FIG. 1b, the gaze detector 108 has a defined effective field of view, denoted Ω. This field of view is typically provided as a solid angle quantified in steradians. Alternatively, this field of view can be given as an angle α in the horizontal or vertical direction, or as a combination of angles α and β in the horizontal and vertical directions, respectively. The gaze detector typically has an inherent field of view from the basic design. This inherent field of view can be modified, depending on how the gaze detector 108 is mounted within the housing 101, by providing further means such as one or more lenses and / or an aperture in front of the gaze detector 108 that provides the effective field of view Ω. Those skilled in the art of gaze detectors with inherent fields of view know how to provide means for changing the angle of view for a desired effective field of view. The field of view is typically fixed, although means for adjusting the field of view can be envisioned. The gaze detector 108, when mounted within the housing 101, further has a field of view direction, indicated by arrow A, that defines a possible centerline of the field of view in FIG. 1b. The field of view direction typically depends primarily on how the gaze detector 108 is mounted within the housing 101 and / or how the entire breath analysis device 100 is mounted, for example, on a dashboard. The gaze detector 108 and means for controlling the field of view, if necessary, are typically positioned within the housing so that the effective field of view and field of view direction correspond to the position and coverage of the user's face during normal operation of the breath analysis device 100. Typically, the user is instructed to exhale toward the inlet 103 within a predefined maximum distance between the subject's face and the inlet 103, typically 100-300 mm. A typical face with a height / width of 200 mm and 150 mm, respectively, may provide angles α and β in the range of 20-100°. As mentioned above, the field of view, and thus the field of view direction, may be adjustable, for example, by adjusting the shape of the detector or the optical configuration. In one embodiment, the field of view and / or field of view direction are parameters adjustable by the control and signal processing unit 114.

[0041] The gaze detector 108 is typically positioned laterally to the breath sampling inlet 3 of the measurement cell 102 on the outer surface 101a of the breath analysis device 101. The field of view α of the gaze detector 108 is adapted to be encompassed by the subject's face at a predefined maximum distance. The gaze detector 108 includes a sensor 111, typically a multilayer microstructure 111, which provides an electrical signal corresponding to the average temperature, reflectance, or other specific property of objects within its field of view. The active area of ​​the microstructure 111 is typically 0.3 x 0.3 mm.

[0042] The field of view is adapted to a predefined distance by an optical device 110, typically a refractive lens.

[0043] According to one embodiment, the breath analysis device 100 is provided with an auxiliary sensor 112 adapted to monitor the immediate environment, for example, the ambient temperature. This can be useful, for example, if the gaze detector 108 is an IR sensor and p may have some cross-sensitivity to the ambient temperature. By measuring the effects of both radiant and conductive heat and combining the signals, the influence from the ambient temperature can be minimized. The auxiliary sensor 112 can be arranged to measure other ambient variables as well, including humidity, barometric pressure, and illuminance.

[0044] The breath analysis device 100 may further include or be connected to a power source (not shown) and data communication means (not shown) for bidirectional transfer of information between the breath analysis device 101 and other electronic devices, such as means for controlling the maneuverability of the vehicle.

[0045] The functionality and method of the breath analysis device 100 according to the invention enabling the measurement of the concentration of an intoxicating substance in a user's breath will first be explained in a general case, with reference to the schematic graphs of Figures 2a to 2c and the flow chart of Figure 3, followed by a description of different embodiments utilizing different detector technologies relating to the gaze detector 108. Figure 2a shows the output signal from the gaze detector 108 and the output from the measurement cell 102, where the upper curve marked T relates to the tracer signal and the lower curve S relates to the substance signal.

[0046] The breath analysis device 100 described with reference to Figures 1a-1b is configured to carry out the steps of the method. In particular, the measurement cell 102 of the breath analysis device 100 is configured to sample a sensor signal representative of the concentration of an intoxicating substance and a sensor signal representative of the concentration of a tracer substance, preferably but not exclusively using the IR-based technology mentioned above. The functionality is controlled by a control and signal processing unit 114, and the sensor / detector signals are processed by the control and signal processing unit 114. The gaze detector 108 is configured with a predetermined field of view Ω and is configured to measure the coverage of the field of view by an object and to output a signal representative of the coverage.

[0047] The method according to the invention, which is carried out using the breath analysis device 100 and controlled by the control and signal processing unit 114, comprises: 305: - monitoring the output signal of the line of sight detector 108; 310: - If the output signal deviates from the set background value, 315: - recording an eye gaze detector output signal as a function of time, the output signal change being a recorded eye gaze signal signature; 320: - monitoring tracer substance sensor signals; 325: - if a peak in the tracer substance is detected, the peak indicates a possible expiratory phase of the user's breathing cycle; 330: - Deriving a breath concentration value of the intoxicant based on the intoxicant sensor signal and the tracer substance sensor signal. The effectiveness of measuring breath concentration values ​​is 335-340: - comparing the recorded gaze signal signature from the gaze detector 108 with at least one stored reference signal signature to determine whether the recorded gaze signal signature matches the stored reference signal signature, thereby indicating that a human is approaching the breath analysis device 100; 345-350: - comparing the relationship between the line of sight detector output signal and the tracer substance signal with stored signal relationship criteria to determine whether the recorded line of sight output signal has an expected relationship with the tracer substance signal. 355: - A derived breath concentration value of an intoxicating substance is determined to be a valid measurement in the sense that it has not been tampered with if both the recorded gaze signal signature matches a stored reference signal signature and the gaze detector output signal and the tracer substance signal satisfy stored signal relationship criteria.

[0048] Step 305 of monitoring the output signal of the gaze detector 108 and steps 310-315 of recording the gaze signal signature may typically involve establishing a background or baseline value. This may be an output signal value sampled and averaged over one or several seconds. Deviations from the background level, indicative of an object within the field of view of the gaze detector 108, are detected to trigger recording of the gaze signal signature. How this detection is performed is further described below. The level 20 shown in FIG. 2a is representative of a typical background signal, while the upper level 21 is representative of the signal contributed by an object within the field of view. Depending on the time the object or person remains within the field of view of the gaze detector 108, the upper level 21 may have the form of a plateau, a broad peak, or a narrow peak. The narrow peak corresponds to the person leaning toward the breath analysis device 100 and moving back slightly or continuously.

[0049] According to one embodiment, the gaze signal signature comprises, for example, a time change in the signal above the upper level 21 shown in Figure 2b, which may be considered to indicate that an object is moving or to detect an action of the object, such as exhaling. For example, a thermal change caused by exhaling may be detected by the gaze detector 108 in the form of an IR sensor.

[0050] According to an embodiment of the present invention, in steps 345-350 comparing the relationship between the gaze detector 108 output signal and the tracer substance signal, the stored signal relationship criterion includes an expected time relationship between the gaze detector output signal and the tracer substance signal. This time relationship criterion may require that a rise in the recorded gaze detector output signal, indicating an object approaching the breath analysis device 100, occurs before the onset of the peak 44 in the tracer substance signal. The time relationship criterion may also require that a peak in the recorded gaze detector output signal matches a peak in the tracer substance signal within a predetermined time interval. This comparison may include modifying the time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined factor related to an expected time delay related to the time required for the breath sample to reach the breath analysis device. Alternatively, the time delay between the peak in the gaze detector output signal and the peak in the tracer substance signal may be an inherent relationship criterion in that a predictable time delay may be associated with the correct and normal behavior of a user using the breath analysis device 100. On the other hand, if a user attempts to tamper with the measurement by using, for example, CO2 supplied from a tube closer to the inlet 103, this will result in a different time delay than expected.

[0051] According to an embodiment of the present invention, steps 335-340 of comparing the recorded signature signal with a stored reference signal signature include comparing at least one or a selection of the following parameters: signal slope after the initial rise, duration of the time segment during which the signal rises, signal value associated with the upper limit 21 (plateau value), duration of the signal above a predefined level associated with the upper limit 21, and signal slope after the peak or plateau. Suitable parameters and how they may be utilized are schematically illustrated in Figures 2b-2c. Figure 2b provides an illustration of the gaze LoS signal, the synchronized Tracer T signal, and the presence of a human face appearing within the field of view of the gaze detector. Initially, the field of view represents a background that may be unstructured, as shown, or structured but with a fixed surface. When a human face appears within the field of view, the gaze signal changes from a steady-state background level and reaches an upper limit level, typically in the form of a plateau or broad peak, when most of the field of view is covered. Some signal changes can be observed at this upper level corresponding to small movements of the human face, as well as changes in the shape of the mouth opening and exhalation, for example. The tracer signal T typically exhibits a distinct peak coincident with the human exhaling. As the human face leaves the field of view, the gaze signal plateaus and returns to the background level.

[0052] Figure 2c) illustrates in somewhat more detail the gaze signal from the gaze detector as a function of time. This signal can be divided into time segments, each characterized by the signal slope characteristic of that segment. The transitions between segments are determined by the segment and the coordinate L in this example. i ;t i , i=1,2,...8. The coordinates L in this example are i ;t idefines the signal signature. In particular, the nearly flat time segment 0-t1 represents the background signal, t1-t2 represents a sharp rise coinciding with the entry of an object, usually the human face being inspected, into the field of view, t5-t6 represents a plateau as the object fills the field of view, and t6-t7 represents the start of a decline as the object moves out of the field of view. Additional time segments t2-t3, t3-t4, t4-t5, and t7-t8 are intermediate states that may or may not be significant for interpreting the signal signature.

[0053] L i ;t i The identification of the coordinates is performed by a simple algorithm that uses the derivative of successive time samples to provide the current slope value and compare it with the previous time sample.

[0054] In the example described above and shown in FIG. 2c), the stored reference signal signature is L i ;t i The parameter set of coordinates, i = l, 2,..., N, has the characteristics of (i) the background stationary phase, (ii) the rising phase, (iii) the leveling off, and (iv) the beginning of the falling phase. i ;t i The set of coordinates typically includes a tolerance for normal variability based on empirical data obtained from actual implementations of gaze detectors.

[0055] When one gaze signal is compared to another with a slightly different field of view, the two signals will clearly appear nearly identical, except for a slight time delay due to the translational movement of objects entering or leaving the field of view. Thus, the coordinate L i ;t i will differ slightly in time between the two signals in such cases. In contrast, the time change of the shape of the object, e.g., opening the mouth, will be i ;t i It does not provide a similar time difference of coordinates. When several objects move independently of each other, L i ;t i The time difference between the two trials does not show a very orderly change over time, which is the case for operational trials.

[0056] According to one embodiment, the gaze signal signature relates to the gaze detector 108 with additional spatial resolution, whereby signal changes over time can also be attributed to specific regions. For example, a simple array of IR sensors resolves time-dependent thermal changes localized to a portion of an object into an "image" that might occur if the object were a human face exhaling warm breath. By using a composite signal from two or several regions, it is possible to distinguish between translational movement of an object and changes in the object's shape. Translational movement manifests itself in the time difference between signal signatures representing nearby but different fields of view. On the other hand, signal signatures resulting from shape changes occur simultaneously in two nearby fields of view.

[0057] According to one embodiment in which the gaze detector 108 is a passive IR sensor operating in the wavelength range 5-8 μm, and whose output signal corresponds to the average temperature of objects within its field of view, the following signal characteristics are valid: The difference between the plateau level 21 and the background level 20 corresponds to the difference between the skin temperature of a person's face and the average temperature of the background when a person's face is not within the field of view of the gaze detector 108.

[0058] According to one embodiment in which the line-of-sight detector 108 comprises a light-emitting diode (LED) illuminating a predefined field of view and a photodiode configured to detect reflected light from essentially the same field of view, the background level 20 and upper limit level 21 each correspond to the average reflectance of objects within that field of view. Disturbances from external light sources can be minimized by synchronous operation between the LED and the photodiode, and by selecting an operating wavelength range of 0.8-1.0 μm, slightly above the visible range.

[0059] A common feature of each embodiment of the line of sight detector 108 is that electromagnetic radiation is used in either a passive or active mode of operation. The line of sight detector 108 of the embodiment includes an aperture that directly or indirectly determines the actual field of view. To avoid undesirable effects of wave diffraction, this aperture is preferably much larger than the operating wavelength range. Figures 4a-4c show the line of sight detector 108 in three alternative embodiments, each including an optical device 110 that defines the field of view 109 and a sensor 111 in the form of a multilayer microstructure 111.

[0060] It should be understood that several passive and active sensor principles can be used for the sensor 111. Infrared thermometry is an example of a passive sensor, where the narrow skin temperature range of a human face provides useful contrast against the background. The use of near-infrared (NIR) reflectance measurement is an example of an active sensor. The field of view in this case is defined by a distinct diverging beam of NIR radiation. The presence of a diffusely reflecting object within the field of view provides a reflectance signal that can be detected by a photodiode in close proximity to the NIR emitter.

[0061] The line-of-sight detector device 408a of FIG. 4a) is based on the line-of-sight principle, comprising an aperture 410a having a width w that defines a field of view 405a.

[0062] Width F a a predefined distance D between the face of the person under test and the opening 410a, a is the angle q a defines the field of view 405a by, where tan q a / 2=F a / 2D a Furthermore, the width w of the opening 410a, the size s of the microstructure 411a, and the distance d between the outer surface of the breath analysis device 100 and the surface of the microstructure 411a are a is given by equation (1).

[0063]

number

[0064] By using equation (1), F a , D a , d a , and s are known, w can be determined. a = 150 mm, D a = 100 mm, s = 0.3 mm, and d a When using = 0.5 mm, an aperture width w = 0.45 mm is appropriate. Therefore, the configuration shown in Figure 3a) is suitable for a relatively short distance D a The human adult face typically has an oval shape with approximate widths of 150 mm and 200 mm in the horizontal and vertical directions, respectively. The shape of the opening 410a may optionally be correspondingly oval or elliptical.

[0065] An embodiment of the gaze detector device 408b is shown diagrammatically in Fig. 3b) and comprises an optical device 410b suitable for a longer distance between the person's face and the outer surface of the housing 101 of the breath analysis device 100. The optical device 410b directs the thermal radiation towards the person's face F b The distance D is provided to focus the light from the object to the sensor 411b. b and d b is defined as shown in Figure 3b). The focal length of the lens, f, can be calculated from equation (2).

[0066]

number

[0067] The relationship between the size s of the microstructures 11b is given by equation (3).

[0068]

number

[0069] The following number D b = 300 mm, d b = 0.6 mm, and s = 0.3 mm, resulting in f = 0.6 mm and Fb = 150 mm. Therefore, the optical device 110b has a width F b = 150 mm, the distance D between the person's face and the outer surface of the breath analysis device 101 b = Provides a sufficient field of view for 300mm.

[0070] The material of lens 410b should preferably have a refractive index of 1.5-1.7 and low absorption in the wavelength range of 5-8 μm for passive IR temperature measurement sensors and 0.8-1.0 μm for NIR reflectance sensors. Polyethylene and polyester (Mylar™) are examples of polymers with sufficient infrared transmission properties. Suitable spherical or parabolic lens shapes can be obtained by injection molding or die casting of polymer materials.

[0071] One embodiment of the line-of-sight detector device 408c is shown schematically in FIG. 4c and includes an optical device 410c with multiple lenses 410d, 410e, and 410f, each with different fields of view and focal lengths that allow for the separation of radiant heat detection into separate regions, and multiple, preferably microstructured, sensors 411c, 411d, and 411e positioned in one or several image planes to allow for different apertures and angular fields of view. As will be appreciated by those skilled in the art, the illustrated device with three lenses and three sensors is a non-limiting example. More lenses / sensors may be provided, for example, in a 2D array. By adding information about the angular heat distribution, a more accurate analysis of the combined signal from sensors 411c, 411d, and 411e may be achieved.

[0072] Figure 5 shows a graph of the infrared spectral distribution of thermal radiation from a black body BB at a temperature of 35°C within the wavelength range l = 2 to 10 μm according to Planck's equation for blackbody radiation. Human skin exhibits an emissivity coefficient of approximately 0.95 regardless of skin color, and therefore the calculated thermal radiation from a black body is an accurate approximation of the thermal radiation from human skin. As the temperature increases from 35°C, the graph shown for BB shifts toward shorter wavelengths and also increases in magnitude, as is evident from Planck's equation. Therefore, measuring the radiant power in one or several wavelength intervals is an indirect measure of surface temperature.

[0073] The graph in Figure 5 also shows the spectral response of a photovoltaic multilayer microstructure based on the III-V semiconductor indium arsenic antimonide compound InAsSb, which can be advantageously used as the sensor 111. This multilayer microstructure includes at least one layer exhibiting a depletion of charge carriers, electrons, or holes. The depletion layer can be created by a p-n junction between p-dopant or n-dopant materials or by a Schottky barrier. When a photon with the appropriate energy is absorbed in this layer, a charge and voltage are generated. The detailed response characteristics of the curve labeled "InAsSb" in Figure 5 are determined by the energy band gap of the semiconductor material, which can be modified by substitution between the elements arsenic (As) and antimony (Sb). Such compositional variations can shift the dip occurring at longer wavelengths to shorter wavelengths by as much as 1.5 μm.

[0074] By combining several microstructures with different spectral distributions compared to the curve InAsSb, the accuracy of skin temperature measurement can be significantly improved. Photovoltaic microstructures with sufficient properties are commercially available from Asahi Kasei Electronics, Tokyo, Japan, under the product lines AK9752, AK9754, and AK9756.

[0075] Photovoltaic microstructures may include sensor elements that respond to thermal conduction in addition to photovoltaic elements that respond to thermal radiation, and may also advantageously include Peltier elements that allow the microstructure to be heated or cooled to pre-set and controlled temperatures.

[0076] The spectral transmission curve of the long-pass filter LP is also included in the graph of FIG. 5. The long-pass filter LP can be inserted into the optical path of the sensor 111 to minimize cross-sensitivity to interference from light sources emitting at shorter wavelengths. Long-pass or band-pass transmission characteristics can be achieved using a variety of inorganic and polymeric materials (S. Musikant, Optical Materials, 1985, pp. 176-199). The spectral distributions in FIG. 5 are normalized to the maxima of emission (E), response (R), and transmission (T) of the blackbody radiator, photovoltaic microstructure, and long-pass filter, respectively.

[0077] Sensors 111 in the form of photovoltaic microstructures have a distinct advantage over thermopiles, which operate on the thermoelectric principle, for example, in providing a true DC response. Thermoelectric devices require a temperature difference between two or more locations, setting a low frequency limit for operability. Therefore, limitations due to heat conduction and compact design reduce the attractiveness of thermoelectric devices compared to photovoltaic structures. An additional advantage of photovoltaic microstructures is their superior resolution, resulting in a higher signal-to-noise ratio.

[0078] 6 and 7 show representations of the fields of view obtained with two types of device as examples of physical implementations of the invention.

[0079] The graph in Figure 6 shows the horizontal and vertical angular distribution of the field of view obtained with a commercially available 8x8 matrix IR photodetector (Panasonic AMG88). The gaze detector according to this embodiment can divide the field of view into a low-resolution image. The full field of view of ±30 degrees in each of the horizontal and vertical directions can be divided into 8x8 = 64 separate elements, and the gaze signal can be composed of a composite of several signals from each of the 64 elements.

[0080] The graph in Figure 7 represents an example of the field of view provided by a line-of-sight detector that includes a commercially available light-emitting diode and photodiode (VCNL3040, Vishay Semiconductors, Inc.) that monitors the reflectance of nearby objects. As shown in the graph, the field of view is represented by an annular reflectance distribution with a 50% falloff at ±15 degrees.

[0081] Figure 8 shows a typical operation of a breath analysis device according to the present invention, which may be incorporated into a handheld device 81a as shown in Figure 8a, a freestanding wall-mounted instrument 51b as shown in Figure 8b, or a unit 51c integrated into, for example, the steering wheel (as shown) or dashboard of a vehicle, as shown in Figure 8c.

[0082] As shown in FIG. 8a, in the case of a handheld device 51a, the user is instructed via the communication unit 113 to hold the device 51a in their hand, bring it within a predefined distance, and then exhale towards it.

[0083] As shown in Figure 8b, in the case of a freestanding wall-mounted appliance 51b, the user is instructed via the communication unit 113 to approach the appliance 51b until they reach a predefined distance and then exhale towards it.

[0084] As shown in Figure 8c, in the case of a unit 51c integrated into the steering wheel of a vehicle or the like, the person being tested is instructed via the communication unit 113 to bend towards the unit 51c, thereby bringing it within a predefined distance, and then exhale towards it.

[0085] A change in the relative distance between the user and the breath analysis device 100, either as a result of the user moving closer to the device or leaning towards the device, will result in an gaze detector signal according to the graphs of Figures 2a-2c. The details of the gaze detector signal signature will vary depending on the intended implementation, and will be taken into account when setting the reference signal signature, which stores the reference signal utilized in the method described with reference to Figure 3. Those skilled in the art will readily arrive at a suitable reference signal signature relevant to a particular implementation based on a limited set of experiments where a typical and preferably user tests the equipment.

[0086] The above-described embodiments should be understood as illustrative examples of the system and method of the present invention. Those skilled in the art will understand that various modifications, combinations, and variations can be made to the above-described embodiments. In particular, different part solutions in different embodiments can be combined in other configurations where technically possible.

Claims

1. A method for determining the validity of a measurement of a concentration of an intoxicating substance in a user's breath using a breath analysis device (100), comprising: The breath analysis device (100) a measuring cell adapted to sample a sensor signal representative of the concentration of the intoxicating substance and a sensor signal representative of the concentration of a tracer substance; a line of sight detector having a given field of view and adapted to measure the coverage of said field of view by objects and to output a signal representative of the coverage, The method comprises: (305) monitoring the output signal of the gaze detector (108) and (310) if the output signal deviates from a set background value, (315) recording the gaze detector output signal as a function of time, the output signal change being a recorded gaze signal signature; (320) monitoring the tracer substance sensor signal, (325) determining if a peak in the tracer substance is detected, said peak indicating a possible exhalation phase of the user's breathing cycle, and (330) deriving a value of the exhaled breath concentration of the intoxicant based on the intoxicant sensor signal and the tracer substance sensor signal; (335) comparing said recorded gaze signal signature originating from said gaze detector (108) with at least one stored reference signal signature; (345) comparing the relationship between said line of sight detector output signal and said tracer substance signal with stored signal relationship criteria; (340, 350, 355) if the recorded gaze signal signature matches the stored reference signal signature and if the recorded gaze output signal and the tracer substance signal satisfy the stored signal relationship criteria, the validity of the measurement of the breath concentration value is confirmed.

2. 2. The method of claim 1, wherein in the monitoring step (305), a background value of the gaze detector output signal is derived and the step of comparing (335) the recorded gaze signal signature with the stored reference signal signature comprises comparing at least one of the following parameters, or a selection from said parameters: signal slope after an initial rise, duration of a time segment during which the signal rises, a signal value associated with an upper limit value (21), duration of a signal above a predefined level associated with the upper level (21), signal slope after a peak or plateau.

3. The method of claim 1 or 2, wherein the stored signal relationship criteria includes a time relationship between the line of sight detector output signal and the tracer substance signal.

4. 4. The method of claim 3, wherein the time relationship criterion is that an increase in the recorded gaze detector output signal, indicating that an object is approaching the breath analysis device (100), occurs before the onset of the peak in the tracer substance signal.

5. 5. The method of claim 4, wherein the time relationship criterion requires that a peak in the recorded line of sight detector output signal coincides with the peak in the tracer substance signal within a predetermined time interval.

6. 6. The method of claim 5, wherein the step (345) of comparing the relationship between the gaze detector output signal and the tracer substance signal with stored signal relationship criteria includes modifying the time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for a breath sample to reach the breath analysis device (100).

7. The method of claim 3, wherein the time relationship between the gaze detector output signal and the tracer substance signal comprises an expected time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for a breath sample to reach the breath analysis device (100).

8. The method of claim 1 or 2, wherein the line of sight detector (108) is configured to measure thermal radiation.

9. 3. The method according to claim 1 or 2, wherein the breath analysis device (100) further comprises means for measuring an ambient temperature, and the output signal from the gaze detector (108) is compensated for the ambient temperature.

10. A breath analysis device (100) configured to perform a measurement of a concentration of an intoxicating substance in a user's breath and to verify said measurement, comprising: The breath analysis device (100) a measuring cell (102) adapted to sample a sensor signal representative of the concentration of said intoxicating substance and a sensor signal representative of the concentration of a tracer substance; a line of sight detector (108) having a given field of view and adapted to measure the coverage of said field of view by an object and to output a signal representative of the coverage; a control and signal processing unit (114) connected to said measuring cell (102) and to said line of sight detector (108), said breath analysis device (100) comprising: (305) monitoring the output signal of the gaze detector (108) and (310) if the output signal deviates from a set background value, (315) recording the gaze detector output signal as a function of time, the output signal change being a recorded gaze signal signature; (320) monitoring the tracer substance sensor signal, (325) determining if a peak in the tracer substance is detected, said peak indicating a possible exhalation phase of the breathing cycle of the user, and (330) deriving an exhaled breath concentration value of the intoxicant based on the intoxicant sensor signal and the tracer substance sensor signal; (335) comparing said recorded gaze signal signature originating from said gaze detector (108) with at least one stored reference signal signature; (345) comparing the relationship between the line of sight detector output signal and the tracer substance signal with stored signal relationship criteria; - (340, 350, 355) if the recorded gaze signal signature matches the stored reference signal signature and if the recorded gaze output signal and the tracer substance signal satisfy the stored signal relationship criteria, the validity of the measurement of the breath concentration value is confirmed, the breath analysis device (100).

11. 11. The breath analysis device (100) of claim 10, wherein the gaze detector (108) is configured to detect electromagnetic radiation and includes an aperture that determines an effective field of view of the gaze detector (108).

12. 12. The breath analysis device (100) according to claim 10 or 11, wherein the line of sight detector (108) comprises a sensor (111) using infrared detection and configured to measure thermal radiation.

13. The breath analysis device (100) of claim 12, wherein the sensor (111) of the line of sight detector (108) is an active sensor configured to utilize near-infrared reflectance measurements.

14. The breath analysis device (100) of claim 10 or 11, wherein the gaze detector (108) is configured to have a field of view corresponding to a predefined area at a predefined distance from the breath analysis device, the predefined area being an area of ​​a typical human face of a person using the breath analysis device (100) at the predefined distance, the predefined distance being associated with a proper use of the breath analysis device (100) and being between 100 and 300 mm.

15. The breath analysis device (100) according to claim 10 or 11, further comprising means for measuring an ambient temperature, and the signal from the gaze detector (108) is compensated for by the ambient temperature.

16. The breath analysis device (100) of claim 10 or 11, wherein the gaze detector (108) comprises a plurality of sensors (411c, 411d, 411e) configured to provide a corresponding plurality of output signals providing a spatial resolution of the field of view.

17. The breath analysis device (100) according to claim 10 or 11, wherein the line of sight detector (108) comprises an 8x8 matrix of IR photodetectors.

18. 12. The breath analysis device (100) of claim 10 or 11, wherein in the monitoring step (305), a background value of the gaze detector output signal is derived and the step (335) of comparing the recorded gaze signal signature with the stored reference signal signature comprises comparing at least one of the following parameters or a selection from said parameters: signal slope after an initial rise, duration of a time segment during which the signal rises, a signal value associated with an upper limit value (21), duration of a signal above a predefined level associated with said upper level (21), signal slope after a peak or plateau.

19. 12. The breath analysis device (100) of claim 10 or 11, wherein the stored signal relationship criteria comprises a time relationship between the line of sight detector output signal and the tracer substance signal.

20. The breath analysis device (100) of claim 19, wherein the time relationship criterion is such that an increase in the recorded gaze detector output signal, indicating that an object is approaching the breath analysis device (100), occurs before the start of the peak in the tracer substance signal.

21. 21. The breath analysis device (100) of claim 20, wherein the time relationship criterion is such that a peak in the recorded gaze detector output signal coincides with the peak in the tracer substance signal within a predetermined time interval.

22. The breath analysis device (100) of claim 21, wherein the step (345) of comparing the relationship between the gaze detector output signal and the tracer substance signal with stored signal relationship criteria includes modifying the time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for a breath sample to reach the breath analysis device (100).

23. The breath analysis device (100) of claim 19, wherein the time relationship between the gaze detector output signal and the tracer substance signal includes an expected time difference between the peak in the gaze detector output signal and the peak in the tracer substance by a predetermined coefficient related to an expected time delay related to the time required for a breath sample to reach the breath analysis device (100).

Images