Mechanics and optics of stretchable elastomeric microlens array for artificial compound eye camera

Abstract

Compound eye-inspired imaging devices can find vast applications due to their remarkable imaging characteristics, such as extremely large field of view angle, low aberrations, high acuity to motion, and infinite depth of field. Recently, researchers have successfully developed a digital camera that resembles the structure and functions of apposition compound eyes of arthropod, by combining an elastic array of microlenses with a stretchable array of photodetectors in their planar form and then transforming into a hemispherical shape. Designing an elastomeric microlens array that can be mechanically stretched to very large extent without deteriorating the optical performance is critical to this development. In this study, mechanics and optics of the stretchable microlens array, in which each hemispherical microlens sits on top of a supporting post connected to a base membrane, are studied. The results show that proper designs of the microlenses, supporting posts and base membrane are critically important to meet both mechanical and optical requirements simultaneously. This study can have important implications in not only the design of artificial compound eye cameras, but also other developments that require stretchable optical elements.

Strain tunable optics of elastomeric microlens array

“…where r is the radius of curvature of the microlens surface, n = 1.43 is the refractive index of PDMS [6,7]. This equation, however, does not work when the light beam is large, i.e.…”

“…The change of the microlens surface profile is studied as it directly affects the optical properties [7]. Under equibiaxial tension, the shape of the microlens surface keeps hemispherical but becomes more oblate, as demonstrated in Fig.…”

“…The shape of each microlens surface changes from hemispherical to ellipsoidal. Therefore, each microlens possesses different focusing power along different directions [7,23]. Fig.…”

“…Optical microlens arrays (MLAs) have been playing important roles in many fields, such as photolithography [1], optical communication [2], organic light emitting diodes (OLEDs) [3], thin film organic photovoltaic cells [4,5], and biomimetic artificial compound eye cameras [6,7]. Some recent advancement in photonics and optoelectronics [8][9][10][11][12][13][14] requires tunability of the optics of MLAs, and therefore, a lot of research has been invested to realize tunable MLAs.…”

Application of tot’hema eosin sensitized gelatin film for adaptive microlenses

“…In most optical devices, microlenses have an important role in a focusing, imaging, detection, etc. Different variants of adaptive microlenses arrays were proposed [25,26].…”