Adaptive Metasurface Microlens Array for Ultra-Wide-Angle CMOS Image Sensors

Demand for higher-resolution CMOS image sensors for mobile camera accelerated pixel scaling into sub-micron size. Micro-lens (ML) array, which plays a crucial role of collecting photons and phase-detection auto-focus, its performance degraded as the ML size became comparable to the visible wavelength. This gets worse with ML aberration and increasing light incident angle in ultra-wide-angle image sensors. We propose a metasurface microlens (MML) replacing the conventional spherical ML, employing adaptive design tailored to varying chief ray angle (CRA) across the entire image sensor. We implemented this MML using 0.5 μm pixel prototype, and demonstrated 35% auto-focus contrast ratio enhancement and 49% sub-color-channel difference improvement without any quantum efficiency degradation.