The evolution of CMOS image sensors

Previous video cameras were big and heavy. However, CCD image sensors (CCD-ISs) replaced video camera tubes, so that video cameras became smaller and lighter, and video cameras as consumer products were introduced. Moreover, CCD-ISs created a market for digital still cameras and they replaced film cameras because of they were easy to use. However, CMOS image sensors (CISs) were incorporated into cellular phones that did not require high image resolution. CCD-ISs were then used for digital still cameras; however, their market share drastically declined with the appearance of back illuminated CMOS image sensors (BI-CISs) that had a better signal to noise ratio than CCD-ISs. LOGIC chip stacked BI-CISs were launched after that, which could improve the characteristics of cameras, increase their functions, and enable them to be miniaturized. This paper describes the evolution of CISs and their applications utilizing image quality, 3D integration, and wavelength.