| 摘要 |
An aspheric screen (12) for visual display apparatus, the aspheric screen (12) being such that it is not a surface of revolution about an axis, and the aspheric screen (12) being such that it comprises first and second parts (6, 8) which are separated from each other by a third part (10), the first and second parts (6, 8) being such that they are curved in cross section and if connected together then they would form a surface of revolution, and the third part (10) being such that it is straight in cross sectional view and i s a short cylindrical centre section.
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