DEVELOPMENT OF SOFT X-RAY CT FOR DETECTION OF NON-METALLIC FOREIGN MATERIALS IN FOOD AND AGRICULTURAL PRODUCTS

为了开发检测外来非金属材料的软x射线CT系统，通过多种方法收集软x射线性质的基本数据，结果如下：1.软x射线检测系统为了提高当前异物探测器的检测精度，利用x射线图像增强器和图像分析系统对软x射线投影图像进行了测量和分析。分析后的图像比原始图像更容易检测出异物。然而，通过材料的x射线投影法并不能检测到各种异物。为了解决x射线CT检测异物的准确性问题，采用医用x射线CT扫描仪。基于点扩散函数的系统误差和基于比尔定律的分类误差明确了CT扫描仪对异物的检出限。为了检验异物的可探测性，测量了软x射线的透射和反射光谱。通过测试材料的软x射线透射光谱，对异物的检测精度较好。通过测试材料的软x射线反射光谱，获得了软x射线材料的独特性能。组装了一台带有微聚焦系统的软x线CT试验机，对一张CT图像进行了500张图像重构。微聚焦系统实现了小于100微米的分辨率，被认为能够检测食品中细小的非金属材料。

In order to develop soft X-ray CT system for detecting foreign non-metallic materials, basic data for soft X-ray properties were collected by various approaches and the results were shown as follows;1. In order to improve the detection accuracy which is one of major problem in recent detector for foreign material, the soft X-ray projection images were measured and analyzed by X-ray Image Intensifier and Image Analyzing System. The foreign materials were able to be detected by the analyzed image easier than the original image. However, it could not be detected all kinds of foreign materials by using X-ray projection method through materials.2. In order to clear the accuracy problem of X-ray CT for detection of foreign materials, the X-ray CT scanner for medical use was used. It was cleared that the CT scanner had detection limit for foreign materials by systemic error on point spread function basis and classification error on Beer's law basis.3. In order to examine the detectability of foreign materials, the soft X-ray transmission and reflection spectra were measured. By the soft X-ray transmission spectra through test materials, the detection accuracy for foreign materials was better. And by the soft X-ray reflection spectra from test materials, unique properties of materials for soft X-ray were obtained.4. A trial machine of Soft X-ray CT with micro focus system was assembled and 500 image shots were re-constructed for a CT image. The resolution of less than 100 micro-meter was realized by micro focus system and it was considered to be able to detect thin and small non-metallic materials in food.