Non-contact blood flow determination using a laser speckle method

An electro-optical device is described which allows the non-contact determination of the skin blood flow and its temporal course. As the laser light penetrates the skin, it is not only scattered from the epidermis but also from the moving red blood cells in the capillaries. The scattered light is time dependent and can be described in terms of the dynamic laser speckle effect. Measurements at the skin demonstrate that there is a so-called ‘involuntary body movement’ which must be taken into account when the measurement of the blood flow is determined. Theoretical considerations show a way to reduce the influence of this movement. Some measurements demonstrate the response of the device to blood flow variations.