"Until recently, it was considered difficult to create a high-pixel-count SPAD sensor. On each pixel, the sensing site (surface area available for detecting incoming light as signals) was already small. Making the pixels smaller so that more pixels could be incorporated in the image sensor would cause the sensing sites to become even smaller, in turn resulting in very little light entering the sensor, which would also be a big problem.
Specifically, on conventional SPAD sensors, structural demands made it necessary to leave some space in between the different sensing sites on neighboring pixels. The aperture ratio, which indicates the proportion of light that enters each pixel, would therefore shrink along with the pixel size, making it difficult to detect the signal charge.
However, Canon incorporated a proprietary structural design that used technologies cultivated through production of commercial-use CMOS sensors. This design successfully kept the aperture rate at 100% regardless of the pixel size, making it possible to capture all light that entered without any leakage, even if the number of pixels was increased. The result was the achievement of an unprecedented 1,000,000-pixel SPAD sensor."
"The SPAD sensor that Canon has developed is also equipped with a global shutter that can capture videos of fast-moving subjects while keeping their shapes accurate and distortion-free. Unlike the rolling shutter method that exposes by activating a sensor’s consecutive rows of pixels one after another, the SPAD sensor controls exposure on all the pixels at the same time, reducing exposure time to as short as 3.8 nanoseconds3 and achieving an ultra-high frame rate of up to 24,000 frames-per-second (FPS) in 1-bit output. This enables the sensor to capture slow motion videos of phenomena that occur in extremely short time frames and were previously impossible to capture."
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