Intended for automotive LiDAR systems, it delivers both high-resolution and high-speed performance and the sensor 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, the company’s proprietary device structure enables a frame rate of up to 20 fps, which is the fastest for such a high-resolution SPAD depth sensor having 520 dToF pixels.
LiDAR technology plays an important role in high-precision detection and recognition of road conditions and the position and shape of objects, such as vehicles and pedestrians, and there is a growing demand for further technical advances in LiDAR toward Level 3 automated driving, which allows for autonomous control.
SPAD depth sensors use the dToF measurement method, one of the LiDAR ranging methods, 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 the backside 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 product has been able to achieve 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 delivering enhanced 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 essential for automotive LiDAR, including objects as high as 25cm (such as a tyre or other objects in the road) at a distance of 250m.
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 5cm intervals.
Above: SPAD pixel cross sectional structure
This product features an uneven texture on both the incident plane and the bottom of the pixels, along with an optimised on-chip lens shape. Incident light is diffracted to enhance the absorption rate to achieve a high, 37% photon detection efficiency for the 940nm wavelength, which is commonly used on automotive LiDAR laser light sources. It allows the system to detect and recognise objects with high precision up to 300m away even in bright light conditions where the background light is at 100,000 lux or higher.
