| 摘要 |
PURPOSE:To enhance reliability, durability and inexpensiveness of the whole system and intend miniaturization as well by employing a varifocal system for a gap measuring device. CONSTITUTION:By fluctuating pressure air 13 periodically, a focal distance lens 9, 11 can be fluctuated periodically. In this case, light imaged on the tip of a moving blade 2 is reflected to pass through the lens 9, 11, and then divided by a half mirror 8 to move in a 90 deg.-bent direction to a projected optical axis and focused by a lens 12 in the vicinity of the entrance of a light-receiving optical fiber cable 14. When an optical beam spot is just brought in focus on the tip level of the moving blade 2, the quantity of light reaches a peak value abruptly, and so the output of a light-receiving circuit 15 also provides a peak value. The focal distances of the lens 9, 11 at this time are at the position of the movable lens 9, that is a function of the pressure of pressure air 13, so that the gap to the tip of the moving blade 2 can be easily detected by measuring this pressure separately. |
