3D reconstruction Detector Zd 2 Specimen (④ (x,y) Az GD (⑧ ④ 93 ④ ② 20 15 10 5 。=a-+-是2+(--+) 1 CA 14( ) ( ( )) 2 2 2 1 1 1 d t t i i n i D i n r r x y A z n z z + − − +  = − +  = − =  n 3D reconstruction 14