At the measurements of angles, way straightness and flatness the angle sensitive method is used.

Two optical units are used for this measurement. The laser beam is split in the differential beamsplitter LS 128.1 into two parallel beams which then enter the reflector LS 128.2 with two corner cube reflectors. Reflected beams return back into the differential beamsplitter. Reflector LS 128.2 functions as the angular sensor. At the measurement the differential beamsplitter LS 128.1 is fixed to the stationary machine part and reflector LS 128.2 is fixed to the moving part. Incidental inclination of the moving reflector evokes a path difference between both split laser beams. This path can be evaluated as inclination of the angular sensor.

For these measurements the angular sensor LS 128.2 is fixed on one of the three bases with footspacing 50, 100 or 150 mm according to the total assumed distance travelled. By moving the base with the angular sensor in steps along the particular base footspacing it is possible to obtain the required height profile in one direction (straightness). With the help of one or two auxiliary mirrors which bend the laser beam into the desired directions it is possible to obtain a complete three dimensional height profile of the measured table in different directions.

For the way straightness and flatness measurements with the LS 128F, the LS 128A must be used (except software LS 128.7). The standard configuration for position measurement except the LS 20.1, LS 21.1, LS 70, LS 90.1, LS 90.3 is used.