Displacement measurement Fizeau-type measurement method 2 Measurement methods 2 Measuring ranges 2 Optical configurations 2 Reference grating 2 Scale grating 2 Sensor head 2 Signal encoding 2 Signal interference 2 Surface encoders 2 Two-axis 2 Z-directional measuring range 2 reference grating 2 scale grating 2 surface encoder 2 2-DOF angular displacement measurement 1 Angular displacement measurement 1 Angular sensor 1 Capacitance 1 Capacitive angular sensor 1 Capacitive sensors 1 Degrees of freedom (mechanics) 1 Differential structure 1 Four-quadrant 1 Four-quadrant differential structure 1 Spheres 1 Spherical motion 1 Spherical motion pair 1 Spherical pairs 1