Performance Evaluation of IREDA Prototype System: An IR-Based

Portable Electronic Detection System for

Blood Alcohol Concentration

Panayiota Demosthenous

, Kleanthis Erotokritou

and Marios Sergides

Cy.R.I.C. Cyprus Research & Innovation Center Ltd, 28

October Avenue, 2414, Nicosia, Cyprus

Keywords: Ethanol Detection, Blood Alcohol Concentration (BAC), Breath Alcohol Concentration (BrAC), Transdermal

Alcohol Concentration (TrAC), Tissue Alcohol Concentration (TAC), Near Infrared (NIR), Diffused

Reflectance, Tissue Phantoms, Integrating Sphere, Touch-Based Detection, Gas-Based Detection.

Abstract: This paper demonstrates a prototype system called IREDA, which is an IR-based Portable Electronic

Detection System for Blood Alcohol Concentration. IREDA examines, a) the feasibility on detecting Ethanol

on human body via near-infrared diffused reflectance with a touch-based oriented detection, and b) the

feasibility on detecting Ethanol in human respiration via multiple light absorptions with gas-based detection.

IREDA has proved the feasibility on detecting ethanol vapour with limit of detection of about 12 mg/L, and

the feasibility on detecting Ethanol in solid gelatine samples. Even though, it is challenging to compare these

results with data alcohol consumption in humans, IREDA can be considered as a promising prototype towards

this direction.

1 INTRODUCTION

Driving under the influence (DUI) of alcohol is

responsible for the 25% of all road fatalities in the

European Union. According to the European

Commission Communication, efficient ways to

control alcohol intake and advice users on their ability

to drive are critical to prevent accidents. The need to

indirectly monitor blood alcohol levels for safety,

medical, legal or health reasons, as well as, for safe

recreational alcohol consumption, leaded to several

non-invasive solutions that use biofluid samples such

as lacrimal fluid, saliva, sweat. Alternative methods

consist of measuring breath alcohol concentration

(BrAC) or tissue alcohol concentration (TAC).

Breathalyzers are widely used for indirectly

determining BAC (Jurič, Fijačko, Bakulić, Orešić, &

Gmajnički, 2018), but their resulting measurements

usually suffer from inaccuracies due to interference

from external and internal factors such as humidity,

temperature, individuals’ traits, subject physiological

variations, contamination of mouth compounds and

https://orcid.org/0000-0001-5088-9029

https://orcid.org/0000-0002-7284-104X

https://orcid.org/0000-0002-4344-4416

environmental vapours. Two other methods, namely

an eyeglasses-based tear biosensing device

(Sempionatto, et al., 2019) and a saliva

electrochemical ring sensor (Mishra, et al., 2020), use

biofluid samples. However, the former involves tear

stimulation, and the latter is missing pH and

temperature sensors to compensate for temperature

changes or variations in saliva pH. Moreover, there

are several other transdermal alcohol sensing

methods (Fairbairn & Kang, 2019) that detect either

liquid or gas phases of alcohol just above the skin.

However, detection in sweat can only be achieved if

sweat is produced after a stimulation process, which

in general introduces limitations. Furthermore,

individual and environmental factors (e.g., skin

thickness, gender differences, humidity, temperature)

are introducing variations in transdermal alcohol

readings, which also present late response with a time

lag of a couple of hours. Finally, non-invasive optical

methods exist for blood alcohol concentration

measurements on tissue sample, among which,

infrared spectroscopy (IR) was found to be the most

Demosthenous, P., Erotokritou, K. and Sergides, M.

Performance Evaluation of IREDA Prototype System: An IR-Based Portable Electronic Detection System for Blood Alcohol Concentration.

DOI: 10.5220/0011666000003408

In Proceedings of the 11th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2023), pages 59-66

ISBN: 978-989-758-632-3; ISSN: 2184-4364

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

promising, employing either near-infrared (Ver Steeg,

et al., 2017) or mid-infrared spectrum (Guo, et al.,

2018). Specifically, wavelength-modulated differential

photothermal radiometry (WM-DPTR), has the

capability of measuring BAC with high resolution at

around 5 mg/dl and a low detection limit at around 10

mg/dl. However, this methodology is currently using

laboratory equipment, presenting limitations on further

miniaturization for personal use.

This work demonstrates a prototype system called

IREDA, which is an IR-based Portable Electronic

Detection System for Blood Alcohol Concentration.

IREDA examines the feasibility of detecting blood

alcohol (ethanol) in a) human body via near-infrared

(NIR) diffused reflectance with a touch-based

oriented detection (P. Demosthenous, Near Infrared

Diffused Reflectance on Tissue Simulating Phantoms

for Optical Applications., 2022), and b) in human

respiration via multiple light reflection and

absorption with gas-based detection (P.

Demosthenous, Infrared Spectroscopic Application

using an Integrating Sphere for Measuring Vapor

Ethanol, 2022).

The main optical component of the system is an

integrating sphere for the efficient collection of the

diffused light from the sample. Integration spheres

are known to be beneficial in spectroscopic

applications (LM. Hanssen, 2022) and are used to

enhance the collection of backscattered light in non-

invasive sensing applications such as, finger photo

plethysmography for determining blood

concentration (T. Yamakoshi, 2015), and laser

spectroscopy for glucose sensing (A. Werth, 2018).

Likewise, integrating spheres are used in gas sensing

applications, as they easily increase the effective

optical path length from the light source to the

detector. Hence, the interaction length between light

and the gas sample becomes longer (S. Tranchart,

1996), increasing the sensitivity of the gas-based

detection system. To examine NIR diffused

reflectance on simulating tissues, the experiments use

low-cost optical tissue phantoms (L. Ntombela, 2020)

composed of water, gelatine, and titanium dioxide

(TiO

) powder. Such samples are commonly used in

optical applications to mimic human tissue.

The following sections present the system

implementation, as well as the experimental testing

and results for the performance evaluation of IREDA.

2 SYSTEM IMPLEMENTATION

This section describes: a) the hardware architecture of

the system, b) the optical setup and optoelectronics

that has been used, c) the system’s software with the

signal processing algorithm, and d) the overall system

integration.

2.1 System’s Hardware Architecture

There are several individual modules that are

included in the hardware development of IREDA.

These are a) the current driver, b) the temperature

controller of the light sources, c) the transimpedance

amplifier of the photodetector, and d) the main

control unit (MCU) of the system. Figure

shows the

architecture of the hardware electronic subsystem.

This design presents all the connections between the

specified peripherals and clarifies the communication

protocols and the digital and analogue signals

between them, as well as the power supply

requirements.

A laser diode driver has been chosen to drive the

NIR light sources at a constant current mode. This

module can drive two independent outputs up to

250mA, controlled by two separate modulation

signals. A temperature controller is used to set and

control the temperature of the light sources, ensuring

wavelength stability during optical measurements. A

transimpedance amplifier was chosen, for the

amplification of the photodetector signal. This

amplifier converts photodiode’s output current to

voltage with a switchable gain from 1, 10 and 100

MV/A. A controller from National Instruments has

been used as the MCU.

Figure 1: IREDA hardware architecture.

The MCU is responsible to control all the above

peripherals, the laser driver, the TECs and the

photodetector. Specifically, the MCU is used to set

the optical intensity and wavelength of the NIR light

sources, read the photodetector signal, and provide

PHOTOPTICS 2023 - 11th International Conference on Photonics, Optics and Laser Technology

the collected data to the ‘data analysis software’. The

optical intensity can be controlled via the laser driver

that applies a constant or pulsed current through the

lasers’ anode and cathode. The laser wavelength can

be controlled by changing the lasers’ temperature

using the temperature controller. While the light

sources illuminate the sample, the photodetector

collects the reflected radiation that gives information

on ethanol presence within the sample. The

photodetector signal is then digitized by an analogue-

to-digital converter (ADC) on the MCU. The raw data

are then provided to a custom-made LabVIEW data

analysis software for further processing.

2.2 Optics and Optoelectronics

The optical setup described in this section is designed

to accommodate two separate infrared light sources,

which can be detected by a single photodetector. The

schematic of the optical module used in IREDA, is

show in Fig. 2.

Figure 2: Schematic of IREDA optical apparatus.

This optical setup consists of two NIR sources at

1.6 μm and 2.3 μm. The former is a light emitting

diode (LED) and it is connected to a temperature-

controlled mount. The 2.3 μm source is a distributed

feedback laser diode. Directly after the 1.6 μm LED

source, a collimator lens is used. Subsequently, the

collimated beam passes through an inversed telescope

system (-20x) formed by two additional lenses to

reduce the beam diameter down to slightly less than 8

mm which is the port opening of the integrating

sphere. In the path of the 2.3 μm source merely a

telescope system is advised, consisting of 15 mm and

35 mm focal length lenses to increase the beam

diameter. The two beams then arrive at a short pass

dichroic mirror with cut-off wavelength at 1800 nm

allowing for wavelengths shorter than 1800 nm to be

transmitted and longer wavelengths to be reflected.

The combined beams then enter the integrating sphere

and illuminate the sample mounted at the opposite

port, the ‘sample port’. The integrated sphere is

chosen here to collect the light that is diffusely

reflected by the sample at all angles, thus maximizing

the detector’s signal and increasing signal stability.

As mentioned previously, the beam diameter from

both light sources is reduced to be slightly smaller

than the port diameter of the integrating sphere. This

is done to allow the light to interact with a maximum

area of the sample without being directly reflected by

the inner walls of the sphere. An NIR detector is

connected to the side port to measure light intensity

as reflected by the sample. The fine adjustment of the

two lens systems was achieved by leaving the top port

open but in the absence of sample. Since both beams

are collimated and with diameters slightly less than

port size, the detected signal was almost null. The

maximum device signal was detected when the top

port was sealed with a reflective-coated plug.

A real image of the optical module is shown in

Fig. 3. This optical setup, as described above, was

designed as a touch-based detection system for

ethanol detection in ‘tissue’ samples. At the same

time, this setup can be used as a gas-based detection

system for vapor ethanol detection, where multiple

light reflections within the integrating sphere offer

multiple absorption paths into the gas that fills the

sphere. The difference in this case is that the top port

of the sphere is kept closed with its reflective-coated

plug, while the side port of the sphere now serves as

the gas/vapor inlet port.

Figure 3: The optical setup of IREDA.

Performance Evaluation of IREDA Prototype System: An IR-Based Portable Electronic Detection System for Blood Alcohol Concentration

2.3 System Software-Signal Processing

During an optical measurement, both light sources are

operated simultaneously and are modulated by a

square waveform. To differentiate the signal

originated by the two different light sources, one is

modulated at 100 Hz and the other at double this

value. The synchronous detection of the

photodetector (PD) signal is done digitally by

sampling the measured and modulation signals and

processing them via the IREDA data analysis

software.

Figure 4

shows an example of the two

modulated signals and the total PD signal which is a

summation of the two. Furthermore, a digitally lock-

in signal processing algorithm is implemented (M.

Baer, 2021). Via this algorithm we managed

simultaneous signal acquisition from two light

sources, by synchronous detection of their

modulation signals of orthogonal frequencies.

Figure 4: Example of the modulation and photodiode

signals as measured via the oscilloscope signal.

The IREDA software is used to visualize the

analyzed data in real time. The temperature control,

current control and modulation of the light sources

(LS) can be also accessed and modified by the

software. The modulation of the two LSs can be

visualized and verified by the real-time PD signal.

Additionally, the signal corresponding to each

individual LS as well as their ratio is displayed. When

light is lost due to absorption or for example due an

integrating sphere open port, there is a decrease

observed in the individual LS signals.

2.4 System Assembly

The optical setup, the electronic hardware, and the

data analysis software were integrated together within

an acrylic enclosure to construct IREDA system.

Figure 5 presents the final integrated prototype

system, indicating the main modules and optical

components.

Figure 5: The integrated IREDA prototype.

3 EXPERIMENTAL TESTING

AND RESULTS

This section describes the experimental validation of

IREDA’s performance, both as a) a touch-based and

b) gas-based ethanol-detection system. Both cases

used the same configuration parameters. The applied

voltage to the 1.6 μm LED ( LS1 ) source was set at

1 V, and 1.5 V for the 2.3 μm laser source ( LS2 ),

while the two sources were modulated at 0.1 kHz and

0.2 kHz respectively. The amplifier connected to

photodiode detector was set to an amplification value

of 10 MV/A.

3.1 Validation of the Gas-Based

Detection System

3.1.1 Experimental Configuration Using

Latex Balloon as the Vapour Provider

A latex balloon was used to provide the integrating

sphere with a constant volume of ethanol vapour. A

specific amount of liquid solution was added to the

balloon prior inflation. The balloon was inflated to a

diameter of approximately 20±1 cm and sealed

allowing the solution to evaporate for several

seconds. Subsequently, it was connected to the

“sample port” via a tube (Fig. 8) and the air-vapour

mixture was released into the sphere. Due to the

constant volume of air used in this method, an actual

2345

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(

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2.3 μm modulation

PHOTOPTICS 2023 - 11th International Conference on Photonics, Optics and Laser Technology

sample concentration can be calculated by

approximating the balloon volume to that of a sphere.

Data collection initiated prior connecting the

balloon to the sample port to ensure zero absorption

i.e., maximum PD signal. The balloon was then

allowed to deflate resulting to PD signal drop due to

absorption. Afterwards, the balloon was

disconnected and allowed the system to “empty”.

After observing maximum PD signal denoting

“empty” sphere, an additional balloon with different

ethanol concentration was connected. Figure 6

shows an example of a raw data sequence recorded

in this set of experiments. Different regions

represent time periods where the sphere contained

no ethanol vapour (empty), was filled with vapour

(filling) and finally exhausting the vapour again

(emptying).

Figure 6: Example of photodiode signal. The different

coloured time regions represent the process of ethanol

vapour entering and exiting the integrating sphere.

Different concentrations of ethanol were

investigated with this configuration, ranging from 15

– 240 mg/L. Figure 7 presents the normalised

transient PD signal for both light sources. It was

observed that increasing ethanol concentration

resulted to a greater drop in PD signal for LS2, with a

maximum decrease of 10% recorded for the highest

concentration. In the case of LS1 the change in

absorption was less significant.

The collected data confirmed the capability of the

setup detecting alcohol vapour, while making it was

possible to differentiate between different

concentrations. Furthermore, lower concentrations of

alcohol vapor needed to be evaluated to assess the

limit of detection and to also compare to the

functionality commercial devices.

Figure 7: Normalised photodiode signal for (top) 1.6 μm

and (bottom) 2.3 μm light sources, for different

concentrations of ethanol vapour. Data presented here are

up to the time where minimum PD signal was observed i.e.,

maximum absorption.

3.1.2 Experimental Configuration Using a

Commercial Breathalyser

In order to compare the detection of gas ethanol in

IREDA to a commercial device, a breathalyser was

incorporated to the experimental setup. Additionally,

the concentration calculation method was verified by

this process. A split Y-tube was connected to the

sample port so that the vapour from the latex balloon

entered the breathalyser and the integrating sphere at

the same time. An image of the modified

experimental setup is shown in

Figure 6

Figure 6: (left) Air-filled balloon connected to the setup,

(right) modified experimental setup with a breathalyser.

024681012

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2.3 μm

Performance Evaluation of IREDA Prototype System: An IR-Based Portable Electronic Detection System for Blood Alcohol Concentration

The balloon sample was prepared in an identical

manner to the previous experiments and connected to

the Y-tube. Upon deflation the readings of the

breathalyser and PD signal were recorded. It was

noted that the breathalyser was saturated at about 14

μL of added liquid ethanol. A linear relation between

the amount of ethanol added and the breathalyser

reading was observed as shown in Figure 7. By fitting

the data, a conversion factor from μL to mg/L of

0.172 mg/L/μL was obtained, which agreed with the

one derived by the concentration calculations for a 21

cm diameter sphere and 90% ethanol (0.171

mg/L/μL). It is noteworthy that the PD signal was

indistinguishable for these lower concentration

values (

Figure 8

Figure 7: Breathalyser reading versus volume of ethanol

added to the latex balloon. The breathalyser saturated for

values over 14 μL (dashed red circle). The red solid line

represents the linear fit of the data giving a conversion

factor of 0.172 mg/L/μL.

Figure 8: Normalised PD signal of the 2.3 μm laser source

for lower ethanol concentrations between 0 and 12 mg/L.

No notable change in signal was observed for

concentrations below 12 mg/L.

The minimum concentration that the apparatus

was able to detect was 12 mg/L of ethanol vapour.

Furthermore, the signal for LS1 presented relatively

minor changes for different concentrations and for

this reason the data is omitted here. It can be

concluded that the IREDA setup in its present form

has an alcohol vapour detection limit of about 12

mg/L which is in the range of the upper limit of some

commercial breathalysers.

3.1.3 Experimental Configuration Using an

Air-Pressure Regulator Valve

To further optimize the setup, a pressure regulator

was added between the balloon and the integrating

sphere. This offered a controlled flow of gas mixture

and granted monitoring light absorption as the

integrating sphere was slowly filled. The regulator

was set at a constant pressure of 0.2 bar. This

eliminated the problem of the ethanol vapour mixture

entering and exiting the sphere in an uncontrolled

fashion thus creating inconsistencies between

measurements. As the sample vapour was flowing

into the sphere, the photodiode signal was decreased,

eventually reaching a minimum value. As the sphere

was filled with ambient air, absorption decreased,

resulting to an increased photodiode signal.

The experiments were again divided into two

concentration groups, low and high. The first one

ranged from 0 – 7.5 mg/L with an additional high

concentration of 30 mg/L for testing purposes, while

the second group consisted of higher concentrations

ranging from 0 – 120 mg/L.

Figure 9

presents the

normalised signal at 2.3 μm for both groups. Data

presented here are up to 45 s; after this time frame the

photodiode signal started increasing. Similar to the

previous measurements, a noticeable drop in PD

signal for high concentrations was observed but not

in the case of the lower values. Nevertheless, the

incorporation of the regulator to the setup allowed for

the collection of a greater number of data points

during each run which also revealed fluctuations in

the signal over time.

Afterwards, the repeatability of data collection

was assessed for a longer period. For these

measurements, a latex balloon was filled with a

certain amount of ethanol and deflated through the

regulator. The integrating sphere was then flashed

with ambient air and then filled again with the same

concentration of ethanol vapour. This was repeated

three times for each concentration, and it was found

that repeated measurements were consistent. The

average minimum signal value for each concentration

was then derived. The same procedure was carried for

-2 0 2 4 6 8 101214161820

0.0

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1.0

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2.0

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3.0

Breathalyser Reading (mg/L)

Ethanol added

(µ

)

Linear Fit

Slope

0.17219 ± 0.0024

PHOTOPTICS 2023 - 11th International Conference on Photonics, Optics and Laser Technology

the zero concentration data points. A plot of the

average signal versus concentration revealed a linear

relationship (Figure 10), which in turn gave the rate

of signal decrease with concentration, and it was

found to be -0.0013 (mg/L)

-1

which can be considered

as the sensitivity of the device.

Figure 9: Normalised PD signal of the 2.3 μm laser source

for (top) lower and higher (bottom) ethanol concentrations

while the ethanol vapour flow was controlled by a pressure

regulator set at 0.2 bar.

Figure 10: Average of the minimum signal versus ethanol

concentration. The dashed red line is the linear fit of data.

3.2 Touch-Based Detection System

Validation with Gelatine Samples

Subsequently, alcohol vapour was replaced by a

gelatine mixture to test the device operation with solid

samples resembling human tissue. Gelatine was the

best candidate since it possesses similar properties

with human tissue, it is easily accessible and low-cost.

A generic gelatine powder used for cooking purposes

was used in the following experiments. The samples

were prepared by mixing gelatine powder with water

and TiO2. The mixture was shaken for 5 minutes,

microwaved for 20 seconds, and rotated on a carousel

for 20 minutes. Afterwards, the mixture was poured in

shallow round plastic containers (volume = 2.5 ml)

and allowed to thicken and cool to room temperature

(25℃). The sample was placed at the top port so the

incoming light from the sources was directly incident

on the gelatine while a known amount of ethanol was

injected to gelatine via syringe. Data was collected on

individual samples by increasing the injected ethanol

after a period. At some point, the sample was allowed

to relax so the ethanol was completely evaporated as

shown in Figure 11. This was done to test that the

signal returns to maximum (no absorption) while

using the same sample in the absence of ethanol. The

results revealed that by increasing the injected amount

of ethanol in gelatine the LS2 signal further decreased.

Even though a thorough comparison between these

results and data involving real human tissue and

alcohol consumption cannot be claimed, it is evident

that the IREDA setup can detect changes in ethanol

concentration present in solid samples.

Figure 11 : Normalised PD signal of the 2.3 μm laser source

for added injected ethanol volume in gelatine samples.

Dashed red lines represent the average values.

4 CONCLUSIONS

IREDA has proved the ability to detect ethanol

vapour that simulate human respiration, via multiple

0 5 10 15 20 25 30 35 40 45

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wait

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(

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no ethanol

Performance Evaluation of IREDA Prototype System: An IR-Based Portable Electronic Detection System for Blood Alcohol Concentration

light absorptions within an integrating sphere, leading

to a gas-based detection setup with limit of detection

of about 12 mg/L. Moreover, the feasibility on

detecting ethanol in solid gelatine samples that

simulate ‘tissue’ samples, via touch-based oriented

detection and NIR diffused reflectance has been

demonstrated. Even though, it is challenging to

compare these results with data alcohol consumption

in humans, IREDA can be considered as a promising

prototype towards this direction.

ACKNOWLEDGEMENTS

The work was supported by the Project POST-

DOC/0718/0186 which is co-financed by the

European Regional Development Fund and the

Republic of Cyprus through the Research and

Innovation Foundation

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