| 摘要 |
A scanning device that includes a pair of opaque members which rotate about a common axis and lie across the path of radiant energy where one member has a transparent area in the form of a straight line and the other member contains a transparent area in the form of a logarithmic spiral so that when the discs are rotated at different speeds they produce a scanning aperture of constant shape and configuration formed by the intersection of the transparent areas.
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