New Principle for Optical Tomography Based on Synthesis and Control of a Three-dimensional Spatial Coherence Function : A Basic Research

本研究项目的目的是建立一个全新的技术基础，用于合成和控制空间相干函数，这使得有选择地创建一对三维空间中的所需点之间的高相干性。由于该技术利用了准单色光源的空间（而非时间）相干函数，因此为光学相干层析成像开辟了一条新的途径，完全摆脱了现有低相干层析成像技术中不可避免的色散问题。建立了一种用于设计源分布的理论和方法，该源分布产生三维空间中空间相干函数的期望分布。特别地，提出了一种新的条纹形成模型，给出了光源形状与三维相干结构之间关系的清晰直观的图像.提出了一种同时检测物距和物体表面局部倾斜度的新原理，并通过实验验证了该原理的有效性.提出了一种利用空间光调制器对光源形状进行调制的相移技术方案，并进行了实验验证。该方案使相移完全不受机械运动部件的影响，如压电传感器或精密工作台。综合上述结果，开发了一种新的传感系统，成功地演示了由一组标准量块制成的三维结构的形状测量。

The purpose of this research project is to establish the basis of a fundamentally new technique for synthesis and control of spatial coherence function, which enables selective creation of high coherence between a pair of desired points in three-dimensional space. Because the proposed technique uses spatial (rather than temporal) coherence function of a quasi-monochromatic light source, it opens up a new avenue to optical coherence tomography that is completely free from the dispersion problems that are unavoidable in the existing techniques of low-coherence tomography.The main achievements are summarized as in the following :1. A theory and a methodology for designing a source distribution that produces a desired distribution of a spatial coherence function in three-dimensional space were established. In particular, a new model of fringe formation was proposed that gives a clear and intuitive picture about the relation between the source shape and the three-dimensional coherence structure.2. A new principle for the simultaneous sensing of the object distance and the local inclination of the object surface was proposed, and the validity of the principle was verified by experiment.3. A new scheme of phase-shift technique based on a source shape modulation by means of a spatial light modulator was proposed and verified by experiment. The proposed scheme enables phase shift completely free from a mechanically moving component, such as a piezo-electric transducer or a precision stage.Integrating all the above results, a new sensing system was developed that successfully demonstrated the shape measurement of three-dimensional structure made of a set of standard gauge blocks.