紅外線輻射感測元之室溫補償方法

Abstract

本論文主要研究電阻式熱型紅外線輻射元之室溫補償方法。感測元的輸出信號對室溫變化非常敏感，會造成室溫飄移雜訊，因此，用熱型感測元件作輻射計量時，以適當電路作飄移的補償是必須的。本論文研究是透過一啞感測元作補償；啞感元以微矽加工技術與感測元同時做在單一矽晶片上十分接近，且使用相同材料，使室溫變化幾近為共模雜訊，而易於消除其效應。實驗所用的元件為白金電阻材，具有十分的溫度線性。文中，感測元與啞感測元皆以定電流方式操作，兩定電流源以一定關係分別通過兩元件形成一電橋，並由橋之兩端輸出信號。經由適量調整啞感測元電流後，對室溫飄移雜訊可被大量地減少。由實驗結果得飄移的效應可降低至0.14uV/□C。透過Spice語言所建立元件之電熱模型可預期模擬驗證本室溫補償理論，結果證實本法之正確性。

The purpose of this research is to study the method of ambient compensation of infrared microbolometer. All thermal-conductivity-type sensors are strongly affected by the ambient temperature variation, which results in thermal drift at sensor output. Hence it is always necessary to provide a way of compensating the drift, when a microbolometer is used for radiation measurement. A special dummy compensation method is used. Using silicon micromachining technique, a sensor and a dummy are made on the silicon die with identical very linearly dependent Pt material. Therefore the temperature variation results in a common-mode noise in both devices and can be easily reduced. The sensor and dummy are drived by two constant current sources forming a bridge. The drift can be reduced by adjusting the dummy current to a specific value related to the sensor current. The results of the experiment shows that the drift can be reduced to an extent of 0.14□V/°C. In the study an electronic thermal model created by Spice language is also built to simulate our circuit and to verify correctly of compensation theory.