新型非侵入式光測量脈搏式血氧偵測電路之設計

Design of a Novel Noninvasive Pulse Oximeter

蕭哲尊(Che-Tsun Hsiao)

指導教授 ： 徐永珍

國立清華大學/電機資訊學院/電子工程研究所/碩士(2014年)

摘要

氧是人體中重要的元素之一，一旦缺少氧，可能導致昏迷、休克甚至是死亡。在醫療技術發達的現代，人們越來越重視健康，使用可攜式血氧濃度計便能隨時監測人體健康狀況，對於老年人更能用於健康追蹤，具有預防功效。
非侵入式血氧濃度計使用紅光與紅外光做為光源，搭配光檢測電路來感測人體動脈中的帶氧血紅素和不帶氧血紅素的濃度變化，其原理是藉由比爾蘭伯特定律(Beer-Lambert law)，以入射光與透射光隨血脈波的變化，推算出血氧飽和濃度。
傳統架構中的光檢測電路使用轉組放大器(TIA)將血脈波放大，但因血脈波的交流成分約只有直流成分的1%~2%，因此光檢測電路必須以大的晶片面積來換取放大倍率；而血脈波頻率很低，約為0.2Hz~5Hz，所以後端的低通濾波和帶通濾波電路，需要使用外接式大電容，暨耗費成本也需要龐大的電路板面積。
本研究使用TSMC 0.35μm CMOS標準製程整合脈動式血氧計與光源驅動電路，有別於傳統TIA架構，本研究以3T Active pixel sensor方式實現光檢測電路，而後方直接使用ADC將訊號轉為數位碼，用處理器推算得血氧濃度值。此架構大大減少電容和電阻的使用，達到縮小面積與高度整合電路之目的，利於實現產品便於攜帶的特性。

關鍵字

血氧計 ； 血氧濃度 ； 光電二極體

並列摘要

Oxygen is one of the most important elements in human body. Lacking oxygen could lead to coma, shock, or even death. Nowadays, the medical techniques are highly developed in Taiwan. The issue of health therefore becomes more and more important. One of the techniques is used to monitor blood oxygen. The portable blood oximeters help to monitor human health conditions, and for the elders, the machines are helpful in health tracking and preventing diseases.

The method of non-invasive oximeters is to use red and infrared lights to detect the dynamic concentration changes of oxygenated hemoglobin and deoxygenated hemoglobin in arteries. The relationship to oxygen saturation is derived based on the Beer-Lambert Law, which is the linear relationship between absorbance and concentration of an absorber of electromagnetic radiation(i.e.light).

Traditional oximeters utilize a circuit architecture with transimpedance amplifier (TIA) to amplify signal. It takes a large chip area in exchange of gain, because the AC signal is only about 1% to 2% of the DC signal. The frequency of the signal is only about 0.2Hz to 5Hz, so the following filter circuit needs more external, large capacitors, which increases the module area and cost.

In this research, the pulse oximeter and drive circuit for light source are integrated in standard TSMC 0.35μm CMOS technology. In contrast with traditional TIA structure, this work uses 3T active pixel sensorstructure and a dual-slope ADC to directly convert the detected signal into digital signal and to allow the level of oxygen saturation in blood to ve calculated by a processor. This structure significantly decreases the use of capacitors and resistances and the module size is shrunk. significantly for better portability.

並列關鍵字

Oximeter ； Oxygen saturation ； PD

參考文獻

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