基于滤波成像的大视角数字全息技术

Digital Holographic Technique with Large Viewing Angle Based on Image Filter

为提高数字全息再现像视角,提出一种基于滤波成像的数字全息技术来实现大视角的三维物体面型测量.利用离轴像面数字全息技术,通过在4F相干图像处理系统的空间频谱面处放置可移动的低通滤波器,使满足CCD分辨率的物光波与参考光波干涉形成全息图,并控制低通滤波及成像区域分别记录不同谱段的子全息图.再现时,首先对子全息图进行数字傅里叶变换,重构对应频谱段,并对频谱段进行拼接形成完整的物光频谱;而后通过数字再现获得大视角的数字全息再现像.利用该方法测量了圆柱形表面(光滑的缝纫针)的三维形貌,并取得了较好的实验结果.

To generate digital holograms with a large viewing angle,a digital holographic technique based on filter imaging is proposed.Using the off-axis image plane holography,a low-pass filter is placed at the spatial frequency plane of the 4F coherent imaging system,in order to make the object wave（satisfied CCD resolution ratio） interfere with the reference wave,and the loss-pass filter and imaging areas are controlled to record the sub-holograms for different spectra in turn.In digital holographic reconstruction,all sub-holograms are carried on numerical Fourier transform,and the corresponding spectra are reconstructed which are also stitched to form a whole spectrum of object wave.Then,a large viewing angle reconstruction image can be obtained by digital holography.The proposed technique is applied to the three-dimensional profile measurement of a sewing needle,and the experimental results prove the accuracy of this technique.