| 摘要 |
The invention uses acousto-optic interaction and a spatial light modulator to provide a filter whose characteristics can be rapidly changed. An input signal is applied to an electro-acoustic transducer which launches surface acoustic waves along a lithium niobate block. The frequency of the acoustic waves depends on the frequency of the input signal. The acoustic waves interact with light from a laser to deflect the light by an angle depending on their frequency. The deflected light is incident on a spatial light modulator, controlled by control signals so as to determine the relationship between the translucency of the filter and the position in a direction perpendicular to the optical path. This relationship can be a simple one such that light is transmitted only through certain paths of the filter or can be more complex. The spatial filter thus filters by different amounts light modulated by input signals on different carrier frequencies. The light, thus filtered, is then converted back into electrical signals.
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