jf:n0=20 ±k, constructive nii ±(k+)x, destructive s=nr Optical path length 土A入, constructive bringht δ,-8 +(k+-n, destructive dark     +     −  = ) , destructive dark 2 1 ( k k , constructive bringht 2 1  = nr Optical path length 10 20 if : =       +  − = k destructive k constructiv e n r n r ) , 2 1 ( , 2 2 1 1  