Scanning unit

DETAILED DESCRIPTION The improved scanning unit of this invention provides at least two guide bearings at a bearing location in the scanning unit which are spaced longitudinally from each other along the direction of measurement.
The total longitudinal separation between the bearings of this one bearing location is greater than the width of a joint in the guide surfaces.
A scanning unit having double roller bearings at each bearing location has been shown to be particularly advantageous in many applications.
However, designs with multiple sliding rails, multiple magnetic bearings, multiple pneumatic bearings, and the like also are possible.
The invention, together with further objects and attendant advantages, will be best understood by reference to the following description taken in connection with the accompanying drawings.