| 摘要 |
<p>A scanning assembly for use in optical devices is provided, and a method of varying the size of apertures in the same, the scanning assembly comprising first (10) and second (12) scanning elements and having a plurality of composite apertures effective for transmission of electromagnetic radiation, typically light, the composite apertures being formed by the overlap of respective first (14) and second (16) perforations in the first and second scanning elements, the size of the composite apertures being variable by relative movement of the first and second scanning elements so as to vary the extent to which the first and second perforations overlap. The scanning elements preferably comprise Nipkow discs. The scanning assembly preferably further comprises means for providing relative movement of the first and second scanning elements, which may be a screw means or advantageously may be a thermally expandable material , enabling the size of the apertures to be varied while the scanning assembly is in use in an optical device. At least one of the scanning element may be provided with counterweights to prevent any substantial out of balance forces arising from the location of the means for providing relative movement of the scanning elements, or said means may be located so as to avoid substantial out of balance forces during rotation of the scanning assembly.</p> |
