Abstract
Compound eyes found in insects provide intriguing sources of biological inspiration for miniaturised imaging systems. Here, we report an ultrathin arrayed camera inspired by insect eye structures for high-contrast and super-resolution imaging. The ultrathin camera features micro-optical elements (MOEs), i.e., inverted microlenses, multilayered pinhole arrays, and gap spacers on an image sensor. The MOE was fabricated by using repeated photolithography and thermal reflow. The fully packaged camera shows a total track length of 740 μm and a field-of-view (FOV) of 73°. The experimental results demonstrate that the multilayered pinhole of the MOE allows high-contrast imaging by eliminating the optical crosstalk between microlenses. The integral image reconstructed from array images clearly increases the modulation transfer function (MTF) by ~1.57 times compared to that of a single channel image in the ultrathin camera. This ultrathin arrayed camera provides a novel and practical direction for diverse mobile, surveillance or medical applications.
Highlights
The ultrathin arrayed camera involves the microfabrication of micro-optical elements (MOEs) and the camera packaging (Fig. 2a)
The inverted microlens arrays (iMLAs) were further formed on the multiple layers by using photolithographic patterning (AZ9260, MicroChem a i) Black polymer spin coating ii) UV patterning b iii) SU-8 coating and UV exposure iv) Oxygen plasma treatment
The captured cross-sectional image of the MOE clearly demonstrates that the multilayered aperture arrays (MAAs) have been successfully fabricated by using repeated photolithography (Fig. 2d)
Summary
Microlenses comparable to insect facet lenses have a relatively small focal length as well as low aberration[12,13], which can substantially reduce the total track length, i.e., the distance from an image sensor to a lens top, of a camera[14–16] These lenses can provide a large DOF due to a small focal length and a small aperture diameter, which allows near-to-infinity imaging[17]. Diverse microfabrication methods of microlens arrays, such as thermal reflow, inkjet printing or 3D direct laser writing, have been actively incorporated with biologically inspired cameras[15,18,19] These methods are still under development to prevent optical crosstalk between microlenses for high-contrast imaging. Xenos peckii’s eyes contain pigmented cups surrounding each eyelet to block the incoming off-axis light[8] Light absorbers such as pigment cells serve as a crucial optical element for highcontrast and high-resolution cameras by reducing the. A single high-resolution image can be reconstructed from the array images by using a multi-frame super-resolution algorithm (Fig. 1c)
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