Rajashree Doshi, Anagha Panditrao / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 2, March -April 2013, pp.559-562 559 | P a g e Non-Invasive Optical Sensor for Hemoglobin Determination Rajashree Doshi *, Anagha Panditrao ** *(Department of Instrumentation and Control, Pune University, India) ** (Department of Instrumentation and Control, Pune University, India) Abstract Hemoglobin (Hb) is an important component of red blood cells. This paper presents an optical non-contact technique that provides Hb concentration measurement. The absorption coefficient of blood differs at different wavelength this fact is used to calculate the optical characteristics of blood. In this newly developed system, absorption of light by oxygenated and deoxygenated hemoglobin is measured at two wavelength 660nm and 940nm. The particular wavelength of light is obtained from red and IR LED. Constant current circuit is designed to drive the LEDs. Transmitted light through an area of skin on finger was detected by a photodiode. Ratio of red to IR signal after normalization is calculated for determination of Hb. Signal acquisition by this method is totally noninvasive. The sensors assembled in this investigation are fully integrated into wearable finger clips. Keywords-blood, hemoglobin, infrared, LED, noninvasive, optical method 1. Introduction Hemoglobin (Hb) is the most vital component in human blood, and is responsible for transporting oxygen from the lungs to the rest of our body. It is composed of a protein, called globin, and an iron containing compound called heme. Hemoglobin level is an important clinical parameter for assessing anemia in both chronic and acute conditions, and is among the most commonly performed blood tests. If Hb concentration falls below normal, this is called anemia. Anemia is a condition in which the Hb concentration in the blood drops below a defined level, resulting in a reduced oxygen-carrying capacity of red blood cells. In its severe form, anemia is associated with fatigue, weakness, dizziness and drowsiness, and may lead to death [1]. Currently, invasive methods are used to measure the Hb concentration, whereby blood is ejected from the patient and subsequently analyzed. Apart from the discomfort of ejecting blood samples, an added disadvantage of this method is the delay between the blood collection and its analysis, which does not allow real time patient monitoring in critical situations. A noninvasive method allows pain free continuous on-line patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data. Since the near infrared light was found to penetrate a great depth into biological tissues, near-infrared spectroscopy has been developed into a noninvasive method for biomedical sensing and clinical diagnosis. Oximetry, is well known as typical example of a near-infrared application in clinic, and can be used to noninvasive measure the oxygen saturation of human blood in- vivo [2]. The absorption of whole blood in the visible and near infrared range is dominated by the different hemoglobin derivatives and the blood plasma that consists mainly of water. It is well known that pulsatile changes of blood volume in tissue can be observed by measuring the transmission or reflection of light through the blood volume. This diagnostic method is known as photoplethysmography (PPG) [3]. Aldrich et al. have reported on the ability to use NIR transmission through the fingertip at a single pseudoisosbestic wavelength (905 nm) coupled with a sonomicrometer to monitor pulsatile changes in the optical path length through the finger as well as correct for interpatient variation in finger diameter [4]. A wholly optical method for direct measurement of Hb noninvasively was reported by Jeon et al., who used a 5-wavelength diode-emitting array, but this method requires more robust detection mechanisms [5]. This newly developed optical sensor system uses two wavelengths of light for the measurement of Hb concentration. This non-invasive optical measurement method is based on radiation of red and near infrared light, emitted by Light Emitting Diodes (LED) in the range of 600nm to 1400nm. The detector detects the light transmitted through the finger. In order to achieve mathematical conversion from detected light intensity at different wavelengths to hemoglobin concentration, extinction coefficients of hemoglobin,  , is used. The Hb sensor developed for this research is fully integrated into a wearable finger clip. 2. Experimental Methods Presently clinically used methods are Spectrophotometry, Hemoglobincyanide and conductivity based method for measurement of hemoglobin. Howerever in this method it is required to eject the blood sample from human body and then it is tested. It causes pain to the patient and results required are delayed. In the developed technique non