Determining positional error of an optical component using structured light patterns

A multiple channel interferometer projector for projecting fringes onto a surface of an object, comprising:

• a plurality of interferometer channels each having a spatially separate optical axis, at least one of the interferometer channels configured to project a respective fringe pattern onto the surface of an object;
• a spatial attenuator disposed on one of the spatially separate optical axes to attenuate the respective projected fringe pattern;
• a detector receiving at least a portion of the attenuated fringe pattern and generating image data responsive thereto;
• and
• a processor in communication with the detector to receive the image data and, in response thereto, to determine a positional error of an optical component in at least one of the interferometer channels.

A method for determining a positional error of a diffraction grating, comprising:

• measuring a position of a diffraction grating;
• generating a fringe pattern using the diffraction grating;
• detecting at least a portion of the generated fringe pattern;
• determining from the detected fringe pattern, a position of the diffraction grating;
• and
• comparing the determined position to the measured position, the comparison indicating a positional error.

An interferometer projector for projecting fringes onto a surface of an object, comprising:

• an interferometer channel having an optical axis and configured to project a fringe pattern onto the surface of an object, the interferometer channel including a diffraction grating disposed along the optical axis;
• a positioning stage coupled to the diffraction grating for positioning of the diffraction grating in a plane perpendicular to the optical axis;
• an imager for collecting at least a portion of the projected fringe pattern and generating image data responsive thereto, the imager being substantially fixed in position relative to the diffraction grating;
• a spatial filter to select a pair of ordered diffracted beams to the imager;
• and
• a processor in communication with the imager and the positioning stage, the processor receiving the image data and, in response thereto, determining a positional error of the diffraction grating, the positioning stage adjusting the position of the diffraction grating in response to the determined positional error.