Abstract
Pressing a blood vessel makes stopping natural flow of blood and brings into a change of color in surface of tissues from red to white. This phenomenon is called "ischemia". Such ischemia can be characterized by the time constant in the first order system. An issue in capturing the ischemia information is that the captured color includes two components, one comes from the blood itself and the other comes from the change of reflected condition due to the inclination of surface of tissue. This paper proposes an approach for evaluating the time constant due to the ischemia by considering the difference between the time constant by ischemia and the time constant by deformation. The proposed method is applied to our finger tip so that we can confirm its effectiveness.
