| 摘要 |
A device for focusing an optical system which consists essentially of a guide cylinder and a coaxial tube guided inside or onto the cylinder and containing at least a portion of an optical system. The guide cylinder and the tube are relatively displaced by a rotational motion converted into a linear motion for the purpose of focusing. The relative displacement between the guide cylinder and tube components (1,2) of the device are produced according to principles practised with ball thread spindles. For complying thereto each component is provided with a guide groove (3,4) helically winding around the axis of rotation (5) of each component (1,2). One of the components (1,2) is provided with a return channel (6) connecting at least two consecutive turns of the guide groove (3). The segment of the guide groove (3,4) bounded by the two junctions (7,8) of the return channel (6) and the return channel (6) are filled with balls (9) having such a thickness that the two components (1,2) which must be displaced with respect to each other are interconnected only by means of the balls (9). |
