Metalenses have emerged as a new optical element or system in recent years, showing superior performance and abundant applications. However, the phase distribution of a metalens has not been measured directly up to now, hindering further quantitative evaluation of its performance. We have developed an interferometric imaging phase measurement system to measure the phase distribution of a metalens by taking only one photo of the interference pattern. Based on the measured phase distribution, we analyse the negative chromatic aberration effect of monochromatic metalenses and propose a feature size of metalenses. Different sensitivities of the phase response to wavelength between the Pancharatnam-Berry phase-based metalens and propagation phase-reliant metalens are directly observed in the experiment. Furthermore, through phase distribution analysis, it is found that the distance between the measured metalens and the brightest spot of focusing will deviate from the focal length when the metalens has a low nominal numerical aperture, even though the metalens is ideal without any fabrication error. We also use the measured phase distribution to quantitatively characterise the imaging performance of the metalens. Our phase measurement system will help not only designers optimise the designs of metalenses but also fabricants distinguish defects to improve the fabrication process, which will pave the way for metalenses in industrial applications.

超透镜作为一种新的光学元件或系统是近年来兴起的，表现出优越的性能和丰富的应用。然而，到目前为止还没有直接测量超透镜的相分布，阻碍了对其性能的进一步定量评估。我们开发了一种干涉成像相位测量系统，通过仅拍摄一张照片的干涉图案来测量超透镜的相位分布。基于测得的相位分布，我们分析了单色超透镜的负色差效应，并提出了超透镜的特征尺寸。在实验中直接观察到基于 Pancharatnam-Berry 相位的超透镜和传播相位相关的超透镜之间相位响应对波长的不同敏感性。此外，通过相位分布分析，发现当超透镜具有较低的标称数值孔径时，被测超透镜与聚焦最亮点之间的距离会偏离焦距，即使超透镜是理想的且没有任何制造误差。我们还使用测量的相位分布来定量表征超透镜的成像性能。我们的相位测量系统不仅可以帮助设计人员优化超透镜的设计，还可以帮助制造商区分缺陷以改进制造工艺，这将为超透镜的工业应用铺平道路。我们还使用测量的相位分布来定量表征超透镜的成像性能。我们的相位测量系统不仅可以帮助设计人员优化超透镜的设计，还可以帮助制造商区分缺陷以改进制造工艺，这将为超透镜的工业应用铺平道路。我们还使用测量的相位分布来定量表征超透镜的成像性能。我们的相位测量系统不仅可以帮助设计人员优化超透镜的设计，还可以帮助制造商区分缺陷以改进制造工艺，这将为超透镜的工业应用铺平道路。