建立了一种激光扫描共聚焦显微镜三层介质中点扩展函数的计算模型。在Hammoum 分式的基础上得到三层介质中的理论公式，对比分析探测光路中的偶极子振动方向对点扩展函数的影响以及各种点扩展函数，讨论针孔对点扩展函数、收集的能量和信噪比的影响。计算表明，振动方向平均化的偶极子的探测点扩展函数优于沿x 轴、z轴振动的偶极子的探测点扩展函数；综合点扩展函数小于照明和探测点扩展函数，且针孔越小，经过针孔过滤后的综合点扩展函数更小；方形针孔和圆形针孔的收集能量曲线类似，但方形针孔的曲线靠右，圆形针孔的信噪比曲线总体上优于方形针孔的信噪比曲线。

A model for laser scanning confocal microscopy with three media is given to calculate the point spread functions. (PSFs) According to Hammoum’s representations, we obtain the representations for three media. The effect of the dipole orientation on the PSFs is discussed. Several PSFs are compared. Then we analyze the effects of the pinhole on the PSFs, the energy collected and the signal to noise ratio. Calculations show that the detection PSF for the dipole averaged over all orientations is better than those for the dipoles along the x axis and the z axis. The total is smaller than the illumination PSF and the detection PSF. The total PSF after the pinhole diminishes as the pinhole decreases. The curves of the energy collected for the circular pinhole and the square pinhole are similar, but the signal to noise ratio for the circular pinhole is better than that for the square pinhole.