| 摘要 |
A microfilm reader is described, in which means are provided with the aid of which it is possible to concentrate the light flux coming from the lamp onto a relatively small portion of the film image or ground glass screen to obtain an increased illumination of this relatively small portion. It is therefore possible with the aid of this reader also to read or recognise microfilm images which have in the details a degree of blackening which under normal illumination would no longer be legible. The means employed are a positive lens which can additionally be folded into the illuminating beam path, or a displaceable lens in the condenser system, or a complete, displaceable condenser system. An additional diaphragm ensures that the more poorly illuminated residual image field is covered.
|
