Optical Computed Tomography by Detection of Photons Preserving initial Polarization Through a Scattering Medium

在基本实验结果的基础上，设计了一种光子保持初始偏振态的光学CT装置。半导体激光器、相位调制器、平移台和探测器安装在一个小的光学面包板上。个人计算机用于三个目的：控制平移台和锁定放大器的增益，采集投影数据和重建光学CT图像。该装置具有抑制透射光中漫射光的能力，最高可达110 dB。(1)水果成分的二维分布将我们的光学CT装置应用于甜椒和夏橙子，并从投影数据重建了它们的光学CT图像。尽管图像的空间分辨率不够，但能够识别内部部分和核心。三个二极管激光器，它们具有不同的发射波长， ...更多信息 分别对应于水、糖（蔗糖）和叶绿素A的吸收线来获取果实的投影数据。再现像吸收系数的二维分布与激光波长有关。这意味着我们的仪器可以获得食品中每种成分的二维分布。(2)食品中异物的检测X射线适用于食品中金属的检测，但对塑料碎片的检测效果不佳。该仪器已应用于食品中异物的检测。将一块塑料设置为异物的瓶中牛奶的投影数据。在重建图像中清楚地识别出塑料片的存在。利用这种方法得到的图像容易受到折射率变化的影响，这是在探测直线附近传播的光子的方法中常见的问题。我们的方法对折射率边界的敏感性也有望用于食品中异物的检测。少

An optical CT apparatus using photons preserving initial polarization was designed on the basis of results of fundamental experiments. A diode laser, a phase-modulator, a translation stages and a detector were mounted on a small optical bread board. A personal computer was used for three purposes; control of translation stages and the gain of the lock-in amplifier, acquisition of the projection data and reconstruction of the optical CT image. The apparatus had the ability to suppress the diffused light in the transmitted light up upto 110dB.The following applications of the optical CT apparatus were investigated.(1) Two dimensional distribution of fruits ingredientsOur optical CT apparatus was applied to a pimento and a summer orange and their optical CT images were reconstructed from projection data. The internal section and the core were able to be recognized, although the spatial resolution of images was not sufficient. Three diode lasers, which had different emission wavelengths in … More dividually corresponding to the absorption lines of water, sugar (sucrose) and chlorophyll A were employed to take the projection data of the fruit. Two dimensional distribution of absorption coefficient of the reconstructed images depended on the wavelength of laser. It means the possibility that two dimensional distribution of every ingredient in food is obtained by our apparatus.(2) Detection of foreign matter in foodX ray is applicable to the detection of metals in food, but is not effective for pieces of plastics. Our apparatus was applied to detection of foreign matter in food. The projection data of the milk in a bottle in which a piece of plastic was set as a foreign matter. The existence of a piece of plastic was clearly recognized in the reconstructed image. The image by our method is easily influenced by the change of refractive index, which is common problem in the methods detecting photons travelling near the straight line. The sensitivity of our method to the boundary of refractive indices is also expected to be used for the detection of foreign matter in food. Less