For flatness measurements the angular optics plus additional mirrors should be used. Necessary components are:
Optional elements are:
Flatness measurements require that optical elements IK1 and RK1 are aligned along laser beam as shown in the figure below for the first axis. Element IK1 is stationary and element RK1 is moved. Other axes can be measured with the use of one or two beam benders with constant position of the laser head, or by moving the position of the laser head. In both cases realignment of the IK1 and RK1 components is required. It is recommended to use the option with constant position of the laser head because it simplifies the realignment process.