In order to satisfy high precision and fast optical surface measuring

an iterative algorithm for annular subaperture stitching is discussed

this is based on the subaperture stitching and localization (SASL) algorithm. Firstly

the basic theory of annular subaperture stitching is introduced

this can be divided two parts

one is how to determine the overlapping points precisely and the other is how to find optimal configuration. Then the new problem which was arising in annular subaperture stitching

i.e.

determination of the overlapping points

is studied. The detailed procedure of the iterative stitching algorithm is presented. At last

a paraboloid of 160mm aperture is tested with annular subapertures

which gives consistent result with the auto-collimated full aperture testing. The PV value is 0.186λ and the RMS value is 0.019λ. It proves that the iterative annular subaperture stitching algorithm meets the requirement for high precision testing of aspherical surfaces.