Method for determining petal piston in a segmented imaging system

Claim 1

In an imaging system for imaging scene radiation comprising a center mirror and a set of P petals adjacent to the center mirror, a method for determining petal piston for each of the P petals, the method comprising the steps of: 1) separating scene radiation into replicate first, second and third scene radiation beams; 2) processing the first scene radiation beam by (i) dividing the first scene radiation beam into p discrete beams, in correspondence to p areas of the imaging system, such that each area p overlaps a portion of one of the P petals and a portion of the center mirror; (ii) adding or subtracting zero path length difference to that component of each of the p discrete beams that exits the petal relative to that component which exits the center mirror, for creating p discrete zero piston beams; and (iii) outputting the p discrete zero piston beams; 3) processing the second scene radiation beam by (i) dividing the second scene radiation beam into p discrete beams, in correspondence to p areas of the imaging system, such that each area p overlaps a portion of one of the P petals and a portion of the center mirror; (ii) adding path length to that component of each of the p discrete beams that exits the petal relative to that component which exits the center mirror, for creating p discrete positive piston beams; and (iii) outputting the p discrete positive piston beams; 4) processing the third scene radiation beam by (i) dividing the third scene radiation beam into p discrete beams, in correspondence to p areas of the imaging system, such that each area p overlaps a portion of one of the P petals and a portion of the center mirror; (ii) adding path length to that component of each of the p discrete beams that exits the center mirror relative to that component which exits the petal, for creating p discrete negative piston beams; and (iii) outputting the p discrete negative piston beams; 5) photodetecting each of the p discrete zero piston beams, for measuring p discrete variance of intensity magnitude., 6) photodetecting each of the p discrete positive piston beams, for measuring p discrete variance of intensity magnitude; 7) photodetecting each of the p discrete negative piston beams, for measuring p discrete variance of intensity magnitude; and 8) determining petal piston for each of the P petals by (i) generating a petal parabolic function by specifying at least three independent variables derived from steps 5, 6 and 7 respectively, the variables thus comprising the magnitudes of the variance of intensity of the zero, positive, and negative piston beams; and (ii) computing a parabolic function maximum as a measure of petal piston.