生物柴油光学常数在其成分的定量定性分析、与柴油的混合水平判断以及辐射吸热机理研究等方面具有重要应用。基于射线踪迹法推导得到光学玻璃-生物柴油-光学玻璃三层平板结构的双光程法透射率模型，实验测量了300~2500 nm 波段内生物柴油光学常数随温度的变化规律。实验结果表明，在20 ℃~60 ℃温度范围内，生物柴油折射率随温度的升高而线性减小，吸收指数受温度影响较弱；吸收光谱在1200、1390、1750、2150 和2300 nm 处出现明显的吸收峰，其形成原因主要为C—H 键的倍频以及各原子团伸缩振动的和频作用；生物柴油吸收峰与普通植物油吸收峰的峰值位置基本相同，但数值大小有所区别。

The optical constant of biodiesel plays an important role in quantitatively and qualitatively analyzing its individual constituent, judging the mixed level with diesel fuel, and studying the intrinsic mechanism of radiation transfer. Transmittance model of the three-layer-plate structure (optical glass -biodiesel -optical glass) is derived based on the ray trace method. Experimental measurement by double optical pathlength transmission method is conducted to study the temperature dependence of optical constant of biodiesel in the spectral range from 300 nm to 2500 nm. The results show that the refractive index of biodiesel decreases linearly with temperature increasing from 20 ℃ to 60 ℃, but the absorption index is less affected. Moreover, five main absorption peaks of biodiesel are observed at 1200, 1390, 1750, 2150 and 2300 nm, which are due to overtones and combinations of C—H stretching vibration of various chemical groups. Compared with ordinary vegetable oil, absorption peaks of the biodiesel exhibit the same locations but different amplitudes.