%0 Journal Article
	%A Fu-Hsuan Huang and  Po-Jung Yuan and  Kang-Ping Lin and  Hen-Hong Chang and  Cheng-Lun Tsai
	%D 2011
	%J International Journal of Biomedical and Biological Engineering
	%B World Academy of Science, Engineering and Technology
	%I Open Science Index 59, 2011
	%T Analysis of Reflectance Photoplethysmograph Sensors
	%U https://publications.waset.org/pdf/11506
	%V 59
	%X Photoplethysmography is a simple measurement of the
variation in blood volume in tissue. It detects the pulse signal of heart
beat as well as the low frequency signal of vasoconstriction and
vasodilation. The transmission type measurement is limited to only a
few specific positions for example the index finger that have a short
path length for light. The reflectance type measurement can be
conveniently applied on most parts of the body surface. This study
analyzed the factors that determine the quality of reflectance
photoplethysmograph signal including the emitter-detector distance,
wavelength, light intensity, and optical properties of skin tissue.
Light emitting diodes (LEDs) with four different visible
wavelengths were used as the light emitters. A phototransistor was
used as the light detector. A micro translation stage adjusts the
emitter-detector distance from 2 mm to 15 mm.
The reflective photoplethysmograph signals were measured on
different sites. The optimal emitter-detector distance was chosen to
have a large dynamic range for low frequency drifting without signal
saturation and a high perfusion index. Among these four wavelengths,
a yellowish green (571nm) light with a proper emitter-detection
distance of 2mm is the most suitable for obtaining a steady and reliable
reflectance photoplethysmograph signal
	%P 622 - 625