Precision measurement device for large displacements

摘要

The proposed device measures large displacements (several metres) between two mechanical components with high precision (fractions of mu m) independently of the prior history of the measurement. For this purpose, a plurality of linear scales having precise graduations are juxtaposed in their linear direction and a plurality of linear diode arrays are arranged on the displaceable part of a device in such a way that they can scan the scales at a plurality of points. The scales are precisely divided essentially in uniform increments, but the regularity of the graduation is interrupted at intervals which are somewhat smaller than the length of the arrays by so-called code fields. The latter are recognised by microprocessors, which detect the arrays, as a coding for the absolute displacement of the two components, while the interpolation of uniform graduation ensures the high resolution.