IMAGE SENSOR INCLUDING PLANAR NANO-PHOTONIC MICROLENS ARRAY AND ELECTRONIC DEVICE INCLUDING THE IMAGE SENSOR

Smart overview of the Invention

The application introduces an image sensor featuring a planar nanophotonic microlens array. This array is composed of multiple planar nanophotonic microlenses, each designed with a high refractive index nanostructure and a low refractive index nanostructure. These structures are made from dielectric materials with differing refractive indices, enhancing the sensor's ability to manage light effectively. The microlenses are strategically shifted towards the center of the array, optimizing light capture across the sensor's surface.

Background and Innovation

As image sensors become more compact, the chief ray angle (CRA) at their edges increases, leading to reduced sensitivity and potential darkening of image edges. This necessitates additional processing to correct, which can slow down image processing speeds. The proposed design addresses these issues by using a planar nanostructure to determine the optical curvature profile of each lens surface, thereby improving light management and reducing processing demands.

Technical Details

The microlens array includes nanophotonic microlenses that condense light onto corresponding light sensing cells. Each microlens features a high refractive index structure and a lower refractive index structure, creating an effective refractive index peak that gradually decreases toward the periphery. The arrangement ensures optimal light directionality, especially at the sensor's edges where CRA is most problematic.

Structural Features

Each microlens comprises concentric regions with varying effective refractive indices, contributing to its ability to focus light precisely. At the center of the array, microlenses maintain symmetrical refractive index distributions, while those at the periphery exhibit asymmetrical distributions for enhanced edge performance. Additionally, these structures may include nanoposts or arc-shaped elements for further refinement of light control.

Additional Enhancements

The sensor may incorporate a transparent dielectric layer between the substrate and the microlens array, which increases in thickness from the center to the periphery. This layer can have an inclined or stair-step design to further optimize light management. A spherical microlens can also be added on top of each planar microlens to align optical axes and improve overall efficiency.