The invention relates to an autofocusing method for an imaging device (for semiconductor lithography) comprising an imaging optical unit, an object to be measured and an autofocusing device having a reflective illumination, comprising the following method steps:



a) defining at least three basis measurement points M(xj, yj) on a surface of the object,
b) determining the deviation Az(M)j of a nominal position of the surface of the object from the focal plane of the autofocusing device at the defined basis measurement points M(xj, yj),
c) storing the deviations Az(M)j from at least three basis measurement points M(xj, yj),
d) using the stored deviation Az(M)j for determining a deviation Az(P)k at an arbitrary point P(xk, Yk) of the surface, and
e) using the deviation Az(P)k for focusing onto the point P(xk, Yk).