Wide field of view lens design with uniform image illumination in capsule endoscope system

Abstract

This paper proposes a wide-angle lens design with uniform image illumination for a capsule endoscope (CE) system. Most endoscopies require the field of view (FOV) and aperture size as large as possible to capture more symptom information in the dark circumstance, which results in a big challenge in lens design. There are six aspheric surfaces applied in the proposed CE lens to improve the image quality under the specification with FOV 140° at F-number 2.8. The modulation transfer function of the proposed CE lens image quality at 82 lps/mm is more than 40% for pixel size 3.0 µm × 3.0 µm in 640 × 480 resolution image sensor. The relative illumination (RI) is still larger than 30% for the wide FOV lens design. A lighting distribution with regarding to the RI is constructed to improve the illumination uniformity in the image plane. As a result, the proposed CE has excellent image quality under 4 mm overall length.