Latest Image Sensor (SPAD sensor)
One of the key components that will change society as we know it is the sensor, a device that changes light into electronic signals. Canon has successfully developed an ultra-small 13.2mm x 9.9mm *1 SPAD sensor capable of capturing the world’s highest *2 resolution of 3.2-megapixel images – a higher resolution than Full HD (approximately 2.07 megapixels), even in low-light environments.
SPAD (Single Photon Avalanche Diode) sensors are a type of image sensor. The term “image sensor” probably brings to mind the CMOS sensors found in digital cameras, but SPAD sensors operate on different principles.
Both SPAD and CMOS sensors make use of the fact that light is made up of particles. However, with CMOS sensors, each pixel measures the amount of light that reaches the pixel within a given time, whereas SPAD sensors measure each individual light particle (i.e., photon) that reaches the pixel. Each photon that enters the pixel immediately gets converted into an electric charge, and the electrons that result are eventually multiplied like an avalanche until they form a large signal charge that can be extracted.
CMOS sensors read light as electric signals by measuring the volume of light that accumulates in a pixel within a certain time frame, which makes it possible for noise to enter the pixel along with the light particles (photons), hence contaminating the information received. Meanwhile, SPAD sensors digitally count individual photon particles, making it hard for electronic noise to enter. This makes it possible to obtain a clear image.
The SPAD sensor newly developed by Canon employs a proprietary pixel architecture that reflects photons inside the pixel in order to effectively detect photons across the entire range of effective pixels. Under equivalent light, this SPAD sensor can capture the same images as a conventional CMOS sensor while requiring only 1/10 of imaging area. This makes possible an ultra-small design that can be installed even in small devices and greatly increases sensitivity. By equipping cameras designed for low-light and monitoring applications with this new SPAD sensor, even video footage of low-light environments can be viewed as if it were recorded in bright areas, enabling identification of subject movement as though viewing with the naked eye in well-lit environments.
In conventional backlit SPAD sensors, only photons within the space covered by an electrical field (sensitivity field) can be detected, creating a challenge requiring pixel size to be shrunk and as a result, sensitivity to be lowered. With the proprietary voltage accumulation architecture of this new SPAD sensor, the space within the sensitivity field covers the entire pixel area, increasing the amount of photons that reach the light-receiving pixels. This makes possible a photon use efficiency of 100%, including within the near-infrared range, with a pixel pitch of 6.39 μm, realizing both miniaturization and high sensitivity.
Cross-sectional views and top-view layouts of conventional BSI SPAD array (left) and BSI charge focusing SPAD array (right).
As a result, clear images with the world’s highest resolution of 3.2 megapixels can be captured under environments equivalent to starless night skies.
Color images at a resolution of 3.2 megapixels greater than Full HD
The SPAD sensor that Canon developed has a time resolution as precise as 100 picoseconds, which enables extremely fast information processing. This makes possible capture of the movement of objects that move extremely quickly, such as light particles.
Enables capture of slow-motion images of highs-speed phenomena that occur nearly instantaneously
Source：École polytechnique fédérale de Lausanne(EPFL) and Canon Inc.
In addition to high-resolution and high-sensitivity, it is also capable of capturing light trails moving at a speed of approximately 300,000 kilometers per second (7.5 times the Earth’s circumference). Taking advantage of its high-speed response, it is expected to be used as a sensor for driverless vehicles, medical diagnostic imaging equipment, scientific measurement equipment, etc.
For example, thanks to temporal resolution and high sensitivity, there are expectations that this technology may be used in the process of obtaining high-speed, high-precision 3D special information for such applications as distance measurement for automated vehicles, Augmented Reality (AR), Virtual Reality (VR) and Mixed Reality (MR). What’s more, in the field of medicine, this sensor holds the potential for use in camera components of medical diagnostic imaging devices, microscopes and other equipment. Such devices may be used to determine the behavior and position of fluorescent substances in patient bodies that emit faint light in extremely brief time spans, thereby potentially helping to identify early-stage cancer cells or other illnesses or localized afflictions in their initial stages.
Ultra-high sensitivity, ultra-high resolution: the ongoing commercialization of specialized sensors.
Continuous progress through the mass mobilization of Canon Group technologies.
A lunar rainbow deep in the night: Capturing a world too dark for human eyes to see