| 摘要 |
PURPOSE:To make it easy to set a light beam in the central part of a visual field by providing two transparent flat plates in an optical path of the light beam to a two-dimensional image pickup element so that the axes of rotation of the plates are specified. CONSTITUTION:The radius of a light beam 10 is magnified by a lens 30 and picked up on a two-dimensional image pickup element 41 of a TV camera 40, a signal from the camera 40 is processed by a beam radius calculating device 42, and the radius of the beam 10 is measured therefrom. On the occasion, two transparent flat plates 20a and 20b are provided rotatably in the course of an optical path of the beam 10, the axes of rotation of the plates are made to intersect the optical axis of the beam 10 perpendicularly, and the axes of the flate plates 20a and 20b are made to intersect each other perpendicularly. |
