With ToF technology, the distance to an object is measured by the time it takes for light from a light source to reach the object and reflect back to the sensor. ToF image sensors detect distance information for every pixel, resulting in highly accurate depth maps. Accuracy can be enhanced even further by ensuring that the reflected light is efficiently received and that the processing required to measure distance is executed at a high frame rate. Additionally, power consumption can be reduced by efficiently collecting and processing the reflected light; the more efficient, the less light source power is needed.
At the heart of the ToF technology in Sony's new product is Softkinetic's proprietary Current Assisted Photonic Demodulator ("CAPD"), which employs a unique pixel architecture capable of high-speed modulation using drift current*3
in the pixel, allowing for detection of the light signal with an improved accuracy. This methodology raises the accuracy of distance measurement at the level of every pixel, thereby delivering accurate measurement and depth map acquisition even at significant distances.
Sony combined CAPD with its back-illuminated CMOS image sensor pixel technology to develop the new back-illuminated ToF image sensor, which features a 10µm pixel pitch, with the industry's smallest.*1
The new sensor builds on the advantages of a back-illuminated pixel structure, which layers the circuitry beneath the photo detector. By optimizing the pixel construction and circuitry for CAPD, the new Sony product delivers improved light collection efficiency and enables high-speed distance measurement processing. The design delivers accuracy equivalent to conventional methods, even at 1.5x the distance.*2
The higher level of light collection efficiency also makes it possible to use a less-powerful light source, and this keeps power consumption down and allows the ToF camera module to be more compact.
In recent years, demand for more accurate depth sensing has been increasing, particularly in the fields of augmented reality (AR), virtual reality (VR), and other applications such as robotics and drones that require autonomous operations. This new sensor is part of the DepthSense® lineup, which makes features such as gesture and object recognition as well as obstacle detection possible. By delivering highly accurate depth-sensing performance in a compact package with low power consumption, the new sensor will help expand the range of applications for ToF image sensors.
*3 Internal pixel drift current: Unlike normal image sensors, this current is generated by the potential difference between two electrodes without forming a depletion layer.