4. Experimental procedure and the database

The Thermo Vision Micron A10 Model infrared camera was used to capture the thermal images from the face. This camera has an operating wavelength range from 7.5 to 13 μm, and a radiometric dynamic range which adjusts automatically to temperature range. This wavelength region corresponds to the maximum of the Wien curve for blackbody emission with temperature at 300K. This is exactly the behavior in emitting electromagnetic radiation from the human skin [22]. In our experiment, 41 persons participated among them 10 females. A quantity of half liter of wine which corresponds to 62.4 mL of alcohol was consumed by each subject, in an hour time duration. A first frame sequence of 50 frames was obtained for each person before alcohol consumption. Another sequence of the same number of frames was acquired half an hour after consuming the last glass of wine. The frame rate acquisition was set to 10 frames/sec.

xi ¼ ½181 169 203 166 217 175 171 189 169 206 152 144 243 165 225 147 247 149 247 127�

dimensional space.

transformation is:

simpler way (preferably in two dimensions).

same direction with alcohol consumption (Figure 2).

suitable directions for maximum separability, has to be found.

which corresponds to a point in the 20-dimensional space; since in each single acquisition, 50 images are grabbed and this information corresponds to a cluster of 50 points in the 20-

It is important to find out if the cluster which corresponds to the same person moves in the feature space as the person consumes alcohol [24]. Simultaneously, we have to examine if the cluster of each person moves toward the same direction with alcohol consumption. If the direction of movement due to alcohol consumption is different for different persons, then we would have many directions in the 20-dimensional space, toward which the clusters of the drunk persons are moving. In this case, it would be difficult to demonstrate the space in a

In this paragraph, it is analytically explained that the final problem is of two dimensions since only two of the eigenvalues obtained by means of the generalized eigenvalues problem are of significant value. In these two dimensions, it is evident that the clusters are moving toward the

In our case, the feature space dimensionality was examined by the statistics of the clusters of eight persons. Consequently, there exist eight clusters in the feature space for the sober persons and the corresponding eight clusters for the drunk persons projecting onto this 2-D space, the

This maximum separability in a reduced dimensionality space is achieved by a linear transformation W. The two most important directions wi of W are used for projection. This linear

yi <sup>¼</sup> wt

Figure 1. Twenty points were obtained on each face to monitor temperature changes with the consumption of alcohol.

xi (2)

<sup>t</sup> (1)

151

Intoxication Identification Using Thermal Imaging http://dx.doi.org/10.5772/intechopen.72128

The resolution of the infrared images is 128 160 pixels. The camera was quite close to the face of the person so that the thermal image contains the whole face. The experimental procedure requires the availability of the thermal images of an intoxicated person as well as the thermal images of the corresponding sober person so that comparisons can be carried out. The persons that participated in the experiment were alert about the strict requirements of the procedure. Researchers working close to our research group and being sensitized on the experimental requirements took part in the experiment. All of them were healthy and willing to release their personal data to the public (http://www.physics.upatras.gr/sober/). The created database contained all relevant information for the participants (age, weight, sex, etc.). We considered the person who consumed half a liter of wine as drunk or intoxicated. In the experimental procedure, no blood tests were contacted.

Three glasses of wine are enough to bring a person in the intoxication situation which corresponds in exceeding 0.2 mg/L of exhaled air [15]. However, with this quantity of wine, other participants were brought in the limit of intoxication while others were deeply intoxicated. Measurements carried out by the police showed off these differences in persons' intoxication (breathalyzer 0.22–0.9 mg/L). The maximum concentration of alcohol in the exhaled air was reached half an hour after the consumption of the last glass of wine. This concentration was found at 0.22 mg/L for the heavy persons that used to drink alcohol and raised to 0.9 mg/L for the light persons that used not to drunk alcohol. Gradually, breathalyzer indication decreases. Females were more sensitive to alcohol than the males.

Finally, it is worth mentioning that all participants were healthy and calm when the experiment started, and had not undergone any kind of body exercise. All participants were present at the room of experiment half an hour before its initiation. Actually, the purpose of the experiment was to reveal temperature changes caused only by alcohol consumption. No other abnormality is considered.
