  Lenses with dynamic focal length, also called zoom functionality, enable a
variety of applications related to imaging and sensing. The traditional
approach of stacking refractive lenses to achieve this functionality results in
an expensive, heavy optical system. Especially for applications in the
mid-infrared, light weight and compact form factor are required. In this work,
we use a meta-optic triplet to demonstrate zoom imaging at mid-wave infrared
wavelengths. By varying the axial distances between the optics, the meta-optic
triplet achieves high quality imaging over a zoom range of 5x, with 50$^\circ$
full field of view in the widest configuration and an aperture of 8 mm. This
triplet system demonstrates the potential for meta-optics to reduce
conventional components in complex and multi-functional imaging systems to
dramatically thinner and lighter components.
