光点消失方式による不透明体の輪郭の位置の検出法と精密気圧計への応用

抄録

A new detecting method and an optical element realizing the method are invented for the non-contact precise detection of positions of contours of opaque bodies. The method is applied to a barometer to detect the position of the mercury surfaces.
The principle of detection of this method is to catch the instant of disappearance of light in a dark field of view. This method has not the weaknesses which the usual sighting ring has intrinsically, that is, the disadvantages of penumbra, of diffraction of light, of double focussing and of finite aperture of sighting elements, and of dazzling light remaining in the field of view.
The optical element named Complex Slit is a set of slits composed of a triangurar slit and a rectangular one, the component slits being fixed opposite to each other with sufficient spacing on a rigid body. The summit point of the triangular slit and the summit side of the rectangular one form the detecting plane. When the Complex Slit is driven so that the detecting plane approaches an object placed between the component slits, a triangular spot of light is formed by the silhouettes of the slits and that of the object. A sighting element follows to be kept in the extention of the detecting plane. While the approach proceeds, the sighting element observes that the light spot becomes smaller and smaller and then disappears. The position where the spot of light just disappears is adopted as the detecting point. The precision of detection of this method by unaided eye is proved to be several micrometres in terms of standard deviation, and the personal errors to be of the same order.
A self-calibrating type precision barometer with four Complex Slits is manufactured on trial, whose precision is proved to be about twelve micrometres.