Sony Semiconductor Solutions Corporation (SSS) has announced the upcoming release of its IMX479 stacked, direct Time of Flight (dToF), SPAD depth sensor for automotive LiDAR systems. Through the sensor, SSS is aiming to provide the OEMs and suppliers developing these systems with both high-resolution and high-speed performance.
The new sensor product employs a dToF pixel unit composed of 3×3 (horizontal × vertical) SPAD pixels as a minimum element to enhance measurement accuracy using a line scan methodology. In addition, SSS’s proprietary device structure enables a frame rate of up to 20 fps, which the Sony subsidiary says is the fastest fps for such a high-resolution SPAD depth sensor having 520 dToF pixels.
SSS’s IMX479 likewise enables the high-resolution and high-speed distance measuring performance demanded for an automotive LiDAR required in ADAS and automated driving (AD) systems, contributing to safer and more reliable future mobility practices. SPAD depth sensors use the dToF measurement method, a LiDAR ranging method that measures the distance to an object by detecting the time of flight (time difference) of light emitted from a source until it returns to the sensor after being reflected by the object.
The new sensor harnesses SSS’s proprietary technologies acquired in the development of CMOS image sensors, including an illuminated stacked structure and Cu-Cu (copper-copper) connections. By integrating the newly developed distance measurement circuits and dToF pixels on a single chip, the new product has achieved a high-speed frame rate of up to 20 fps while delivering a high resolution of 520 dToF pixels with a small pixel size of 10 μm square. The new distance measurement circuits handle multiple processes in parallel for even better high-speed processing.
These technologies achieve a frame rate of up to 20 fps, the fastest for a 520 dToF pixel SPAD depth sensor. They also deliver capabilities equivalent to 0.05 degrees vertical angular resolution, improving the vertical detection accuracy by 2.7 times that of conventional products. These elements allow detection of three-dimensional objects that are vital to automotive LiDAR, including objects as high as 25 cm (such as a tire or other objects in the road) at a distance of 250 meters.
The proprietary circuits SSS developed to enhance the distance resolution of this product individually processes each SPAD pixel data and calculates the distance. Doing so successfully improved the LiDAR distance resolution to 5 centimeter intervals.
An uneven texture on both the incident plane and the bottom of the pixels, along with an optimized on-chip lens shape, allows incident light to be diffracted, enhancing the absorption rate and enabling a 37% photon detection efficiency for the 940 nm wavelength, which itself is commonly used on automotive LiDAR laser light sources. It allows the system to detect and recognize objects with high precision up to 300 meters away even in bright light conditions where the background light is at 100,000 lux or higher.
SSS has developed a mechanical scanning LiDAR unit equipped with this new sensor for product evaluation, which will be provided to customers and partners. This will contribute to customer and partner LiDAR development and product evaluation initiatives.
