Field Curvature Aberration Correction Using Cylindrically Curved CMOS Image Sensors

We demonstrate the lateral field curvature aberration correction of a lens employing a cylindrically curved complementary metal-oxide-semiconductor (CMOS) image sensor without using multiple lenses. By employing a silicon-on-insulator (SOI) structure and applying etching using xenon fluoride, we fabricated an extremely thin CMOS image sensor with an 11-μm thickness without causing damage to the CMOS circuitry. Because of the structural characteristics of SOI, i.e., extremely small thickness and high SiO2content, the fabricated CMOS image sensor is flexible and does not break easily even when curved. The device was curved on a concave surface, fixed to a cylindrical pedestal, and mounted on a package using wire bonding to implement a cylindrically curved CMOS image sensor with a curvature radius of 20 mm. Using the fabricated CMOS image sensor, we successfully captured video images (320 × 240 pixels). A comparison between these images and those obtained from a flat CMOS image sensor showed that blurring at the lateral periphery of the images can be reduced using a single lens by curving the CMOS image sensor.