用隐身方法对散射介质后物体非侵入式成像

The ability to noninvasive image through turbid media has long been a major scientific and technological goal in many disciplines. Imaging through scattering medium is an essential observation and diagnostic tool in many fields such as astronomical observations, microscopic imaging in tissues and defects testing of microelectronic devices. A breakthrough has been made to observe objects that were completely hidden behind an opaque scattering medium. However, such approach needs not only to scan both illumination light and detector but further off-line procedures to numerically retrieve the image of the objects. In this project, we will propose an invisibility-based noninvasive method that can hide scattering medium and allows to directly image objects behind. By recording holograms of the objects through a scattering medium and then using the holograms produced time-reversal lights to re-illuminate the objects, we implemented to observe objects clearly that were hidden behind a thick scattering medium. We will also reduce the response time of the imaging system 100 milliseconds for the implementation of imaging the moving objects behind scattering medium. Furthermore, we will synthesis conjugate filters and joint transform filters for pattern recognition of the characteristics of the objects with feature size less than 100μm that were hidden behind scattering medium. Of importance, our method may be of great interest to generalists and specialists in many disciplines ranging from the life sciences and nanotechnology for real-time, high speed biomedical imaging of biological tissues and in-site inspection of integrated devices.

对散射介质后物体的非侵入式成像在科学和技术上一直是许多学科的主要研究目标。对散射介质后的物体成像技术是重要的观测和诊断工具，可以应用到天文观测、生物组织成像、微电子器件检测等领域。近期该领域取得了突破性进展，可以非侵入地观察一个完全隐藏散射介质后的物体。然而这种方法需要多角度地扫描照明和探测，更需要一个离线的数值图像重建步骤。本项目中我们提出用隐身方法屏蔽散射介质，对其后面的物体直接非侵入式成像。通过记录散射介质和它后面的物体的全息图，再用全息图生成共轭光波重新照射到物体上，我们可以清楚地观察厚散射介质后的物体。我们还将减少成像系统的响应时间到100毫秒以下实现对散射介质后的运动物体成像。在此基础上我们通过合成共轭滤波器和联合变换滤波器对散射介质后的100微米以下的物体进行特征识别。具有重要意义的是，我们的方法为实时、高速生物医学成像和集成设备的原位检查提供了新途径。

过散射介质成像技术可以用作为一种重要的观察和诊断工具，被广泛应用于许多领域，例如天文观测、生物组织中的显微成像和微电子器件的缺陷测试等。然而，现有的大多数过散射介质成像的方法通常是侵入性的，因为它们需要通过在散射层后面放置检测器或非线性材料来预先单独获得散射层的信息。此外，这些方法通常具有低空间分辨率的特点，并且也难以分辨细节信息小于散射层的厚度或深度的物体。虽然最近有学者提出了一种突破性的方法来实现非侵入地观察散射层后面的荧光物体，但仍然需要耗费时间的离线计算程序来重建物体的图像。因此，该方法不适用于实时成像和现场测试。在本项目中，我们通过在磨砂玻璃（即散射介质）前面记录物体的全息图，可以获得物光的共轭光波用以通过磨砂玻璃重新照明到物体上，并最终将磨砂玻璃的散射效果隐藏掉。最终，我们得以看见散射介质后隐藏的物体。该方法既不需要任何扫描技术也不需要离线处理的计算机程序。项目实施的实验结果表明，本项目中我们提出的方法可以隐藏散射层，并且直接观察到振幅调制型的物体。物体的特征尺寸远小于100毫米（从39毫到80毫米得到验证），该尺寸小于散射介质的厚度即3毫米的深度。我们相信这种基于经典的傅里叶方法仍然可以在现代科学和技术中找到有趣的应用。

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