运用部分相干理论和数字全息理论,对基于发光二极管的弱相干光数字全息进行了理论分析和实验研究。在假定LED是空间非相干、时间准相干的前提下,研究了互强度在所研究系统内的传播,导出了利用LED重建的物光波和利用完全相干光重建出来的物光波频谱之间的简单线性公式。结果表明,基于LED的数字全息重建的物光波相当于对相干光源下重建得到的物光波进行了低通滤波。散斑噪声等高频噪声受到了极大抑制,重建图像的信噪比得到较大提高,但同时也损失了一定的分辨率。滤波器的带宽与次级光源的大小成反比,并且受到衍射距离的调制。根据理论分析结果,指出了提高系统分辨率的途径,最后用实验证实了理论分析的正确性。

Both theoretical and experimental researches on light-emitting diode (LED)-based digital holography are carried out.The propagation of the mutual intensity of the system is investigated under the premise that the LED is spatially incoherent and temporally quasi-coherent.A simple formula describing holographic fringe formation process with partially coherent illumination is found.The formula shows that the hologram fringe formation process can be presented as a linear space-invariant filtering operation.The filtering operation suppresses speckle noises and is also expected to experience a loss of resolution.The bandwidth of the filter is determined by the bandwidth of the secondary light source as well as diffraction distances of the object.Some methods are proposed to improve the resolution according to the theoretical analysis.Corresponding experiments are conducted and the results demonstrate the validity of the theoretical analysis.