But CMOS sensors fall behind when it comes to picture quality, especially in a dim light, because of the noise in each pixel. All were key breakthroughs, said Shigeyuki Matsumoto, senior general manager at Canon's device development center. The new sensor has an amplifier in each pixel to convert optical signals to electronic signals. The unevenness of those amplifiers causes noise that has a fixed pattern. When the pure noise is subtracted from the mixture, a pure optical signal remains.
Random noise is another problem.
The noise is due to the unevenness of the initial level of optical signals at each pixel. Canon engineers improved the pixel structure by transferring electronic charges completely to reset the initial levels of optical signals and noise in each pixel. The programmable gain amplifier is the first block integrated on the sensor chip to take advantage of the CMOS process. The amplifier eliminates noise and reads out signals at a speed of 12 MHz. Moving forward, Canon engineers have two major goals in mind for the next step in CMOS sensor development.