| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance the accuracy of measuring rail displacement with a laser beam by reducing optical path interception by raindrops and reducing contamination of glass with rainwater invasion in rainy weather. <P>SOLUTION: Adverse effects of raindrops to reduce the light quantity of irradiation light and reflected light are reduced by further providing cylindrical hood means between hood means and a rail, narrowing the gap between the tip of the cylindrical hood means and the rail and also minimizing the aperture area of the cylindrical hood means, namely the part thereof in contact with the atmosphere. It is sufficient for the cylindrical hood means to have an internal wall face of a size which is enough large to contain the aperture face of a slit provided in the hood means to let irradiation light and reflected light pass therethrough. Without providing conventional hood means, a similar one to the cylindrical hood means can be provided directly on a detector body to further narrow the gap between the tip of the cylindrical hood means and the rail. <P>COPYRIGHT: (C)2012,JPO&INPIT |
