Based on theory of PTR, the linear relative between si g nal phase and modulated frequency under special condition is showed.The therma l diffusivity is determined by fitting the experimental data.

• 从光热辐射理论出发，在一定条件下，推导出位相信号和调制频率的关系表现为线性关系，分析实验数据得出材料的热扩散系数。