CMOS image sensor with APS structure for high-speed video cameras

In this paper, we discuss the required specifications, APS (Active Pixel Sensor) technology, and possible problems to be overcome with next-generation CMOS image sensors for digital high-speed video photography. A custom-designed image sensor with parallel-readout, high-speed-operation and other functions, is needed to develop an advanced high-speed video camera, realizing higher frame rates and producing pictures of proper resolution. The CMOS image sensor can be developed at lower cost than CCD sensors, and its peripheral circuits can be integrated on a single sensor chip. Table 1 describes specification and performance of one of the custom CMOS image sensors currently in use for a digital high-speed video camera. This type of CMOS sensor is also called as "Passive Pixel Sensor". The pixel structure of this sensor is very simple, but it requires the Current-to-Voltage Converter (also called as Trans-Impedance amplifier or Pre-Amplifier). This is because the output signal current from the sensor is very small and needs to be amplified. [GRAPHICS] On the other hand, APS includes an amplifier for each pixel, which improves the Signal-to-Noise Ratio (SIN). We discuss the possibility of CMOS image sensors with the APS structure for digital high-speed video cameras based on test chips. Test chips are fabricated by using 0.35um technology. In addition, we show some simulation results of CMOS image sensors in terms of required specification and performance from the viewpoints of application, functionality, and circuit structure.