Optical translation measurement

A method for determining the relative motion of a surface with respect to a measurement device comprising:

• placing a partially reflecting object, which is part of the measuring device, adjacent to the surface;
• illuminating the object with incident illumination such that part of the incident illumination is reflected or diffracted by the object, as a reference illumination and part is reflected from the surface;
• coherently detecting the illumination reflected from the surface utilizing the reference illumination, to generate a detected signal;
• and
• determining the relative motion of the surface parallel to the surface, from the detected signal;
• wherein the surface has no markings indicating position.

A method for determining the relative motion of a surface with respect to a measurement device comprising:

• placing an object comprising a grating, which is part of the measuring device, adjacent to the surface;
• illuminating the grating with incident illumination such that at least part of the illumination is incident on and reflected from the surface, wherein at least one of the incident and reflected illumination passes through the grating;
• detecting the illumination reflected from the surface;
• generating a signal in response to the reflected illumination;
• and
• determining the relative motion of the surface parallel to the surface, from the detected signal,
• wherein the surface is in the near field of the grating.