通过与双光子荧光共焦成像过程比较，研究了非线性二次谐波的强度脉冲响应函数并对它进行频域分析，获得了横向、纵向截止频率和通频带．研究结果表明：二次谐波共焦成像具有更高的分辨率．

The three-dimensional intensity pulse function of a confocal scanning microscope for secondharmonic wave is derived and compared with that of a two-photon fluorescent confocal scanning microscope. By use of Fourier transformation,the three-dimensional intensity pulse function is theoretically investigated in frequency domain where the transverse and axial cut-off spatial frequencies,together with the transmission bands are given. The results show the optical resolution for second-harmonic wave is better than that for two-photon fluorescence. Such conclusion is also proved from the uncertainty principle.