  Single metalenses are limited by their physical constraints, precluding
themselves from achieving high numerical aperture across a wide visible
spectral band in large-aperture applications. A hybrid system that integrates a
metalens with a refractive lens can address this issue, yet previous designs
lacked sufficient flexibility. Here, by reanalyzing the generalized Snell's
law, we introduce a new paradigm for the hybrid metalens design based on
differentiable ray tracing. Through joint optimization of the phase
distribution of the metalens and refractive lens parameters, our system
achieves achromatic performance within the broad spectral range of 440-700 nm,
with an aperture of 1 cm and an f-number of 1.4. Owing to the differentiable
nature of the proposed system, it can be seamlessly integrated as the optical
front-end into any differentiable computational imaging system. Our system
offers unprecedented opportunities for the advancement of metalenses in
innovative optical design and computational imaging domains.
