Displacement measurement system and method of use

A method of measuring a displacement, the method comprising:

• directing an optical input beam toward a movable object;
• at the movable object:
• diffracting the optical input beam into sub-beams comprising more than one diffraction order, and reflecting the sub-beams toward a stationary reflective element, the reflective element comprising two reflective surfaces and a diffraction grating on another surface;
• at the reflective element:
• diffracting the sub-beams from the transmission grating, and returning the sub-beams to the movable object;
• at the movable object selectively recombining the sub-beams to form measurement channels;
• and
• directing the measurement beams toward a sensor head.

A measurement displacement system, comprising:

• sensor head configured to transmit input optical beams and to receive a first measurement beam and a second measurement beam, wherein the second measurement beam comprises both zeroth order diffraction components and first order diffraction components;
• a transmission grating configured to diffract the input optical beams into sub-beams comprising more than one diffraction order, wherein the transmission grating is adapted move in a direction;
• and
• a reflective element configured to diffract the sub-beams from the transmission grating and to return the sub-beams to the transmission grating, wherein the sensor head is substantially stationary and the transmission grating selectively recombines the sub-beams to form the measurement beams and returns the measurement beams to the sensor head.