Multifunctional imaging that enables the extraction of multiple physical parameters from a single-shot image is highly desirable for compact and integrated optical systems. Here, we present a metalens-enabled double-helix point spread function (DH-PSF) for multifunctional imaging, capable of sensing both depth and wavelength information. By superposing Bessel beams with different transverse wave vectors, we design a DH-PSF metalens with two controllable degrees of freedom, whose rotation angle varies linearly with the axial position and the main lobe spacing is inversely proportional to the axial position, significantly enhancing the robustness of depth estimation. Furthermore, the dispersive property of the DH-PSF is deliberately exploited for wavelength sensing, as the lobe spacing exhibits a linear dependence on the incident wavelength at a fixed depth. We experimentally demonstrate single-shot three-dimensional (3D) imaging and wavelength discrimination, with estimation errors maintained below 5%. This work provides new insights into the construction and engineering of DH-PSFs and establishes a compact and versatile framework for 3D imaging and spectral sensing, offering new opportunities for multifunctional imaging devices in machine vision and microscopy.
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