Netsu Sokutei, 29 (1), p. 11, (2002)



Photo-acoustic Method

原非接触測定法である光音響法の特徴,測定原理,測定装置,測定例について,筆者が関与している固体材料の熱物性値測定に関する研究を中心に解説を進めた。光音響法で関係する光,熱および音の関わり合いを概説した。変調された入射光に対する光音響信号(音波)の位相遅れが,RG(Rosencwaig and Gersho)理論により試料の熱物性値などの関数として導出されることが説明された。入射光の変調周波数を変化させて測定された位相遅れの結果から,基盤の熱物性値が未知の場合にも,試料の熱拡散率が得られることを示した。入射光の変調周波数と試料の厚さ方向の情報の関係,試料の入射光に対する透過性の差異による取り扱いの留意点についても若干の説明を行った。
The characteristics, basic principle, experimental system and measured examples of a non-contact photo-acoustic method are introduced in order to measure the thermophysical properties of thin solid materials on the basis of my recent studies. The relation among light, heat and sound in relation to the photo-acoustic method is described briefly. The phase lag of the photo-acoustic signal for the incident modulated light expressed as a function of some properties such as the thermophysical properties of sample is derived from the RG (Rosencwaig and Gersho) theory. The thermal diffusivity of sample is obtained from the measured phase lag versus the modulated frequency of incident light, even if the thermophysical properties of backing material are unknown. The relation between the modulated frequency of incident light and the obtained vertical information of sample, and the analytical point in accordance with the transparency of sample for the incident light are also explained to some extent.