| 摘要 |
An angle indicator for indicating two mutually perpendicular directions and including two moire screen angle indicating devices, each including several screens consisting of opaque lines separated by transparent gaps with the screens of each device positioned parallel to one another to provide a moire interference pattern. One screen can be fixed and the other freely rotatable to adopt a predetermined position relative to the plumb line. The two devices, each with its pair of screens, are positioned in mutually perpendicular planes, and a mirror is fitted and arranged to project a mirror image of one device in a plane in which the pair of screens of the second device is located, and by the side of the second device so the moire patterns formed at both of the angle indicating devices appear to be lying beside each other when the angle indicator is viewed. |
