shown in the figure the controller system 51 drives a z stage 46 being movable into the up and down directions on the drawing and thereby moving it to such a position that a spherical wave 100 diverging from the measuring point u201c a u201d can enter on the entire of the array lens 41 now assuming that the arrangement of the array lens 41 surrounding a center 0 0 of the array lens 41 is i j the distance from the measuring point u201c a u201d to the array lens 41 is u201c r u201d and the pitches of the array lens are u03b4px and u03b4py in the x and y directions thereof then ideal values u03b4x0 i j and u03b4y0 i j on the lattice can be given by the following equations at the spot of condensed light of the i j th array lens where u201c f 4 u201d is the focus distance of the array lens 41 if assuming that the position shift of the spot of condensed light which is actually measured by the 2 dimensional sensor 42 be u03b4xs i j u03b4ys i j then the position shift u03b4xa i j u03b4ya i j which is caused due to the aberration of the array lens 41 can be obtained by the following equations u03b4 xa i j u03b4 xs i j u2212 u03b4 x 0 i j eq 8 u03b4 ya i j u03b4 ys i j u2212 u03b4 y 0 i j eq 9 the processor system 52 memorizing the values u03b4xa i j u03b4ya i j in advance corrects the position shift of the spot of condensed light mentioned above when measuring the objective lens in accordance with the following equations with such.