Palm vein imaging using a polarization-selective metalens with wide field-of-view and extended depth-of-field

Metalens is a flat, lightweight optical element that may replace traditional bulky refractive lenses and other components in imaging systems. However, a number of critical challenges still remain for most metalenses demonstrated to date, including limited field-of-view (FOV), depth-of-field (DOF), and working bandwidth, which restrict their use in a real-world application. Here, we propose and experimentally demonstrate a compact imaging system equipped with a metalens that simultaneously features a wide FOV of 140° and an extended DOF ranging from 33 to 150 mm. The metalens further allows polarization selectivity, which can be used to remove unwanted surface reflection of the target scene. Using a narrowband vertical-cavity surface-emitting laser for illumination, we show that the system is well-suited for near-infrared palm vein imaging, an emerging modality for biometric identification. The metalens-integrated imaging system provides uncompromised performance with a greatly simplified form factor compared to a traditional system, which may also be adopted for other applications such as depth sensing and endoscopy.