| 摘要 |
The invention relates to an overhead projector in which all disturbing light on the projection screen (12) from the parts of the picture plate (2) of the projector which surround the projected document (10) and the light on the screen which arises when documents are being changed on the picture plate has been eliminated. According to the invention, this has been attained by covering the picture plate (2) with a first polarising layer (3) which is a supporting surface for the document, by placing a second polarising layer (9) in the path of the light close to the projector head (6, 7) and by arranging the polarising directions of these polarising layers (3, 9) perpendicular to each other so that all light which first passes the first polarising layer where no document is placed and thereafter passes the second polarising layer (9) is absorbed.
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