Development of system measuring and analysing teeth crown form using light cutting method for dental CAD/CAM technology

本研究的目的是利用数码相机和光切法对牙冠形态和牙弓进行测量和分析。此外，我们还考虑直接测量口腔中的牙冠形状。首先，我们制作了一个有6个自由度的特殊舞台。然后，我们研究了利用裂隙光、交叉图案和马鲁提值图案等测量方法。根据结果，我们决定使用多缝图案。该图案由白线(2像素宽)和黑线(32像素宽)交替构成。利用CCD摄像机采集的图像进行动态阈值处理，转换为黑白图像，计算出三维值。在此基础上，分析了光学系统调焦带来的图像弯曲、模糊等问题，得出了基牙粗略形状容易测量，但不能精确测量基牙的结论。如果使用这种方法直接在口腔中测量牙齿的形状，重要的是将该系统制作成可以插入口腔的小尺寸。我们认为这需要新技术来突破这些问题。

The purpose of this study is mesurment and analisys tooth crown form and dental arch using digital CCD camera and light cutting method. Moreover we considered measuring the shape of tooth crown form in the mouth directly. At first, we made a special stage with 6 degrees of freedom. Then we examined the methods of measurments using slit light, cross-pattern, and maluti-value pattern, et al. From the result, we decided to use multi slit pattern. This pattern was constituted alternately white line (2 pixels width) and black line (32 pixels width). The image provided using CCD camera was handled by the dynamic threshold value, and it was converted into black and white image, and 3 dimensional value was calculated. Then, we considerd the problems of crook or dim of image coming from focusing in optics system, and concluded that it is easy to measure rough shape, but not enough to do a minute measurement for abutment tooth. If the shape of tooth is mesured directly in the mouth using this method, it is important to make up this system into small size that is possible to insert in a mouth. We think it need the new technology break through the problems.