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 SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> content, 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.