Method for detecting surface figures of large-aperture off-axis convex aspheric mirror

The invention relates to a method for detecting surface figures of a large-aperture off-axis convex aspheric mirror. The method comprises the following steps of: performing null interferometry on reference sub-aperture regions by using computer-generated holographic elements which correspond to surface figures of the reference sub-aperture regions of an aspheric mirror to be detected; performing null interferometry on off-axis sub-aperture regions by using computer-generated holographic elements which correspond to surface figures of the off-axis sub-aperture regions of the aspheric mirror to be detected: solving the distribution of full-aperture surface figures of the convex aspheric mirror to be detected; converting coordinates of all off-axis sub-apertures in an x-y-z coordinate system into coordinates below an X-Y-Z coordinate system and obtaining the distribution of full-aperture phases of the convex aspheric mirror to be detected by calculation; and removing system adjustment errors from the distribution of the full-aperture phases to obtain the error distribution of the full-aperture surface figures of the convex aspheric mirror to be detected. The invention has the advantages of simple data processing and mathematical operation, easy experiment operation, low detection cost and short testing time.