Fig. 1. Stitching model of two adjacent sub-apertures in global coordinate

Fig. 2. Flowchart of sub-aperture stitching based on down-sampling particle swarm optimization algorithm

Fig. 3. Surface map of spherical mirror for simulation analysis

Fig. 4. Results after particle swarm optimization

Fig. 5. Residual phase error of the overlapped region after positioning by the proposed method

Fig. 6. Testing results of a 4-inch plane mirror

Fig. 7. Testing of off-axis parabolic mirror by sub-aperture stitching interferometry

Fig. 8. Surface maps of the 7 sub-apertures of tested off-axis parabolic mirror

Fig. 9. Surface testing results of the parabolic mirror