  Complex amplitude measurement is an essential prerequisite for light field
characterization. In this work, we propose a one-time measurement method to
characterize the complex amplitude of symmetry superposed optical vortices
(SSOVs) with only one picture registered by CCD. This method includes two
strategies we proposed. One is the ring extraction strategy for amplitude
measurement, and another is the rotational measurement strategy for phase
measurement. In the proof-of-concept experiment, the complex amplitude is
characterized, and the mode purity is well measured. This method has excellent
flexibility, rapidity, and robustness, which can be applied to various
occasions and harsh conditions. Careful alignment and optimized error analysis
allow us to generate and measure a single component with mode purity as high as
99.99%.
