Canon Develops 'Global Shutter'-based CMOS Sensor With Wide Dynamic Range (1)
Canon Inc developed a CMOS image sensor that supports the "global shutter (GS)" technology and has a dynamic range of 111dB and announced it at ISSCC 2017 (lecture number: 4.5).
The size, pixel count, pixel pitch and power consumption of the sensor are 2/3 inches, 2,592 x 2,054, 3.4μm and 450mW, respectively. In a demonstration after the lecture, the company used the sensor to take a picture of an electric fan whose blades are turning.
Conventional CMOS sensors use the "rolling shutter" technology, which exposes lines of pixels in series (one after another). It causes a time lag when reading signals from each pixel, sometimes distorting the image of a fast-moving subject.
On the other hand, the GS technology exposes all the pixels at the same time and is suited for taking images of fast-moving subjects. However, its dynamic range is narrow. To solve this problem, Canon made two major improvements.
Saturated amount of electric charge doubled
First, within time for one exposure, the value calculated by accumulating the electric charge from the light-receiving part (PDs: photo diodes) twice is stored in the memory and processed. To read out the electric charge at a high speed, Canon used its own A-D (analog-digital) converter called "SSDG-ADC". The converter was announced at ISSCC 2014.