| 摘要 |
The apparatus, designed to adjust the height of a Berens prism bar (7), consists of a foot (1) for an upright guide rail (5) 1m50 in height and of small section. The rail is shaped to receive the smaller side of an H-section sliding support (6) which has the prism bar attached by adhesive to its larger section. The prism bar can be moved up or down by a cord (13) and two pulleys (8) and is held in the required position by a counterweight (20) attached to a loop (16) on the end of the cord. A U-section strip on the front of the sliding support is marked with the prism values, and the lower end of the rail is fitted with a stop (18). |
