Effects of Aperture Diameter on Image Blur of CMOS Image Sensor With Pixel Apertures

Abstract

This paper presents the effects of aperture diameter on image blur of complementary metal-oxidesemiconductor (CMOS) image sensor with pixel apertures for depth extraction. In a conventional camera system, the aperture is located at the camera lens. However, in the proposed camera system, the aperture is located on the photodiode. The patterns in the pixel array of the fabricated CIS are composed of blue, red, and white pixels, as well as pixel apertures. The pixel apertures are formed by a metal pattern in the white pixels and designed using a metal layer in the CIS process. The focused and defocused images are simultaneously obtained using white pixels with and without the pixel apertures. The focused image can be used as a reference image to extract depth information for 3-D imaging. The sensor was designed and fabricated using the 0.11-mu m CIS process. The image blur as a function of the aperture diameter was measured using the fabricated sensor. In addition, the effects of the F-number of the camera lens, which is defined as the ratio of focal length to the diameter of the camera lens, and variation in the output of the CIS with the angle of incidence were investigated.