Achromatic shearing phase sensor for generating images indicative of measure(s) of alignment between segments of a segmented telescope's mirrors

An achromatic shearing phase sensor for generating an image indicative of at least one measure of alignment between two segments of a segmented telescope's mirrors, said sensor comprising:

• an optical grating, positioned in a first plane that is located at one of (i) approximately a pupil plane of a segmented telescope or (ii) approximately conjugate to the pupil plane of the segmented telescope, for receiving at least a portion of irradiance originating at the segmented telescope and incident on said optical grating in the form of a collimated beam, said optical grating splitting said collimated beam into a plurality of diffraction orders thereof;
• focusing optics, positioned to receive said plurality of diffraction orders of said collimated beam, for separating and focusing said plurality of diffraction orders of said collimated beam on a second plane;
• filtering optics, positioned in said second plane, for blocking all of said plurality of diffraction orders of said collimated beam that are (i) greater than a +1 diffraction order of said collimated beam and (ii) less than a −1 diffraction order of said collimated beam;
• imaging optics, positioned to receive said +1 diffraction order and said −1 diffraction order, for re-imaging said +1 diffraction order and said −1 diffraction order in a third plane that is approximately conjugate to said first plane, wherein said +1 diffraction order and said −1 diffraction order are combined;
• and
• imaging means, positioned in said third plane, for generating an image of said +1 diffraction order so-combined with said −1 diffraction order.