  The spiral phase contrast microscope can clearly distinguish the
morphological information of the low contrast objects (i.e., biological
samples) because of the isotropic edge-enhancement effect, while the bright
field microscope can image the overall morphology of amplitude objects.
However, the imaging resolution, magnification, and field of view of
conventional spiral phase contrast microscopes based on 4f filtering
configuration are limited by the system's complexity. Here, we reported compact
dual-mode microscopes working at near-infrared using the engineered metalens
which can be tuned between the spiral phase contrast imaging and bright field
imaging by polarization control. The metalens combines the high-resolution
objective lens and polarization-controlled phase filter into a single-layer
nanofins array. We demonstrated two infinity-corrected microscope systems to
achieve subwavelength resolution (0.7 times of wavelength), large magnification
(58X), and large field of view (600um times 800um). Unstained onion epidermal
is imaged by the microscope to show the dual-mode imaging ability for the
biological sample. Finally, a singlet dual-mode microscope system is
demonstrated to show the edge-detection application for industrial standards.
Our results could open new opportunities in applications of biological imaging,
industrial machine vision, and semiconductor inspection.
