The cups of water .the water temperature
The human growth and the physical change of the body happens changethe finger vein shape. So the finger vein shape of an adult person is not thesame of his finger vein shape in his childhood. Nevertheless from some studiesit is shown that after the age of 20 the finger vein shape appears to be stablebecause in the adult age the growth is almost not much. Also when the persongetting older his bones strength and muscles generally decreased, which canshrink the vascular system and introduce changes/modifications in the fingervein patterns.
In addition when capturing the image of finger vein we use nearinfrared, so the width and disparity of finger vein temporal changes asconsequences of fluctuations in the amount of blood in veins. Such temporalchanges could be the result of intense physical activity, ambient temperatureor physiological changes. Furthermore disease also effects the patterns offinger vein such as diabetes, hypertension,and metabolic disorders, in addition to the natural physiological changes. Amount most of the studies and observations there are no known studies on thestability of finger vein patterns neither growth nor aging lifetime of aperson. Still, it is reasonable to consider that the finger veinidentification performance would be adversely effected by the aging and thephysiological changes in the body. In addition to the mentioned above the change of temperature also madetemporal physiological changes and effect the performance of the finger veinidentification. In order to observe the possible effect of temperature on the fingervein images, the article 3 shows that in their observation they took some images using imagingsetup from five subjects. Then at first they took each subject and put hisfingers in one of the five cups of water .
the water temperature of each cupdiffer from 3, 10, 15, 30, and 50 degrees. After that he moves his fingerimmediately within about a second for the imaging. In result two images of thesame finger were obtained at the same temperature. The obstained images alsosuggests the improvements in the clarity of finger vein patterns with theincrease in temperature from 3°C to 30°C or higher. Additionally if the ambienttemperature is low, the human blood viscosity increase, so finger vein becomesmaller in diameter because of this increasing. The result of this constrictingof finger veins cause decreasing in surface area than normal and thereforeforms the poor image patterns.
In the other hand if the ambient temperature is high,the human blood viscosity decrease, and the finger veins shows increasing inits diameter. The result of this dilating of finger veins cause increasing insurface area and blood volume, and therefore forms more useful and clear veinimage patterns. The patterns images of finger texture are however spotted to berelatively stable/similar and changes with temperature (if any) are difficultto ascertain just from the visualization of these images. Thus in the studymade by 3, they compute the genuine and imposter matching scores, using therespective best finger vein and finger texture matching method . As a resultthey showed that from a few dataset The distribution of genuine and impostermatching unlike high temperatures, low temperatures indicate better recognitionof finger texture images (likely because of better pattern formations from theskin contraction). However, the recognition index of the finger vein imagesdegrades at low temperature and this can be attributed to the poor clarity of veinimage patterns. Additionally, this experiment also indicates that for fingervein discrimination the shape and structure information is very important aslong as the width of the vessels shows change over different temperature and conditions,yet the shape and structure remains similar.
