Integrated laser Doppler blood flowing combining optical contact force

Abstract

Laser Doppler blood flowmeter (LDF) is a non-invasive method for measuring micro circulation, and has been developed since 1977. It is necessary to control contact force between a LDF and measurement part (skin surface), in order to obtain accurate blood flow. We suggest new multifunctional sensor modules which can measure both blood flow and contact force. A sensor module has a multi-layer ceramic chip with vertical cavity surface emitting laser (VCSEL), photo diodes, and op-amp circuits, and a hollow shell with a mirror and a lug. Some of incident light penetrates into a finger, and the scattering light, which have biological signal (blood flow) are detected by one photodiode. On the other hand, a photodiode can detect reflecting light from a mirror, which is displaced by a contact force. In this paper, we fabricate multifunctional sensor module and attempt to simultaneously measure the blood flow and contact force.