An apparatus capable of high accuracy position and motion control utilizes one or more linear commutated motors to move a guideless stage in one long linear direction and small yaw rotation in a plane. The invention comprises a stack of variable and fixed birefringent elements which introduces, on passage though the stack, wavelength dependent polarization onto a polycromatic optical signal of arbitrary polarization. At least one second semiconductor chip includes an arrangement of contact areas which is mirror-inverted in relation to a first semiconductor chip. Circuitry samples the generated signal at a beginning of the integration period andor at an end of the integration period and generates quantized digital data indicative thereof.