Sjödahl Mikael, Olsson Erik, Amer Eynas, Gren Per
Division of Experimental Mechanics, Luleå University of Technology, SE-971 87 Luleå, Sweden.
Appl Opt. 2009 Dec 1;48(34):H31-9. doi: 10.1364/AO.48.000H31.
A technique to gain depth information from an image-plane digital holographic recording of a transient phase object positioned between a diffuser and an imaging system is demonstrated. The technique produces telecentric reconstructions of the complex amplitude throughout the phase volume using numerical lenses and the complex spectrum formulation of the diffraction integral. The in-plane speckle movements as well as the phase difference between the disturbed field and a reference field are calculated in a finite number of planes using a cross-correlation formulation. It is shown that depth information about in-plane phase gradients can be determined in two planes using reconstructed speckle fields from four different depths. In addition, the plane of optimum reconstruction for calculating the phase difference with maximum contrast is detected from the technique. The method is demonstrated on a measurement of a laser ablation process.
展示了一种从位于扩散器和成像系统之间的瞬态相位物体的像平面数字全息记录中获取深度信息的技术。该技术使用数值透镜和衍射积分的复谱公式，对整个相位体积内的复振幅进行远心重建。利用互相关公式在有限数量的平面中计算面内散斑运动以及受扰场与参考场之间的相位差。结果表明，利用来自四个不同深度的重建散斑场，可以在两个平面中确定关于面内相位梯度的深度信息。此外，通过该技术检测到用于计算具有最大对比度的相位差的最佳重建平面。该方法在激光烧蚀过程的测量中得到了验证。
