| 摘要 |
<p>A very small (13cm x 6cm) pocket viewer is for use with interchangeable film cassettes. There are 35 images, each with an explanatory text, in each roll of film. Each cassette deals with a different theme in the field concerned. The interchangeable film cassette is hermetically sealed and contains two rollers (5) running is opposite directions and in frictional contact with each other. They drive the roll of film running in an elliptical groove (7). At the end opposite the rollers, the roll passes a rectangular aperture (8) which enables the image to be illuminated. The image is viewed after magnification by an objective lens.</p> |
