Based on the principle and design of a novel CMOS image sensor 1

Complementary Metal Oxide Semiconductor (CMOS) image sensors and Charge Coupled Devices (CCD) imaging devices started almost simultaneously 20 years ago. CCD is a high-end technology component used in photography and videography, while CMOS is used in products with lower image quality.diode

Due to its high light sensitivity, low noise, and small pixel size, CCD devices have dominated the image sensor market for the past 15 years. On the contrary, CMOS image sensors used to have disadvantages such as large pixels, low signal-to-noise ratio, and low resolution, which have always been unable to compete with CCD technology. However, with the continuous development of large-scale integrated circuit technology, the technical difficulties that were difficult to solve in the manufacturing process of CMOS image sensors in the past can now be found corresponding solutions, greatly improving the image quality of CMOS image sensors.diode

1 CMOS active pixel sensor

The primary reason why CMOS image sensors have received attention recently is that the sensitivity issue, which was significantly lower than CCD in the past, has gradually been resolved. Because compared to CCD, CMOS sensors have better mass production capabilities and are easy to implement production equipment for large-scale products such as SoC (System DRAM), including other logic circuits. In this way, CMOS image sensors may form a completely different cost structure from CCD image sensors.diode

Figure 1 shows the functional structure diagram of an Active Pixel CMOS image sensor (APS), where the imaging part is a Photo Diode Array.diode