VisionICs is a world leader in single photon ranging technology and practicability, and is one of the first pioneers in the research of single photon dtof 3D imaging technology in the world. The company has the world's leading chip level photoelectric converter design and chip level single photon detection and imaging technology, and is mainly engaged in single photon dtof three-dimensional image sensor chip and big data center ultra-high-speed photoelectric interconnection chip solutions. The single photon dtof chip products developed by the company can be widely used in the fields of lidar, robot positioning and navigation, 3D imaging of mobile phone, space environment mapping, security and security, etc., providing chip level solutions of ranging and 3D imaging for complete machine manufacturers and module manufacturers.
When the light is extremely weak, it will disperse into photons, which are called single photons. Due to the weak intensity and obvious particle, it is difficult to detect single photon signal by conventional technology, which is considered as the limit of photoelectric detection technology. dToF technology overcomes the difficulties of photoelectric detection technology and realizes single photon (SPAD) detection.
Single photon (SPAD) detector can detect the weakest light, which can reach the level of photon. This is mainly due to the avalanche effect of electrons when accelerating from high pressure to high speed. That is to say, a very high reverse bias is applied to the p-n junction of the avalanche photodiode, so that a strong electric field is generated in the junction area. When the photogenerated carrier excited by the light irradiates the p-n junction enters the junction area, it will be accelerated in the strong electric field to obtain enough kinetic energy, collide with the lattice in the high-speed movement, and ionize the atoms in the lattice. The electron hole produced by collisional ionization is symmetrical as a secondary electron hole pair. The newly generated electron hole pair is accelerated under the strong electric field, and enough energy is obtained to collide with the lattice again to generate new electron hole pair. This process is constantly reciprocating, which makes the carrier in the p-n junction increase rapidly, and the current increases rapidly, which becomes the avalanche effect.
Lidar (light detection and ranging) technology determines the distance by measuring the time it takes for light to touch an object and reflect back. Due to the active launch of laser by lidar, it is less affected by the change of ambient light, and the ranging is accurate. Even NASA will use it for the next Mars mission. Single photon dtof technology is a key technology to realize miniaturization, low cost and mass production of lidar in the future. VisionICs single photon dtof lidar chip directly measures the time of flight (dtof) of laser pulse in the air with nanosecond precision, and carries out ultra-high sensitivity light detection from the minimum energy unit of light, namely photon level, so as to realize ultra-low power consumption, ultra-high precision, ultra-small volume accurate ranging and three-dimensional imaging.
At present, Apple has released to integrate lidar (LIDAR light detection and ranging) technology into iPad pro. Based on the newly installed dtof laser radar, it is expected to improve the accuracy and fluency of AR application effect to a new level, at the same time, it can reduce the power consumption of equipment, and open endless possibilities for virtual reality (VR), virtual reality enhancement (AR) and more extensive fields.
The chip VI4310 released by VisionICs also adopts its industry-leading dtof single photon detection technology, and realizes the core photosensitive device SPAD array and precise ranging circuit on a single chip, a variety of ranging accuracy optimization and anti background light interference algorithm, as well as the high integration of the back end and ISP (image signal processing). VI4310 has a high resolution of qqvga (160x120), a refresh rate of 30fps (up to 120fps), and can realize 10 meter long-distance detection under the overall ultra-low power consumption of 200MW (including DSP and ISP algorithm).
At the same time, VI4310 optimizes the wavelength of NIR (near infrared spectroscopy) so that the PDE (photon detection efficiency) of single photon device (SPAD) at 940 nm wavelength is up to 10%. The internal integrated special digital processing algorithm (DSP) and image processing algorithm (ISP) are specially optimized for low power consumption. On the premise of ensuring the ranging accuracy and performance, the overall power consumption of the chip is reduced to the maximum extent. In view of its excellent performance of small size and low power consumption, VI4310 chip and module VM4310 composed of VI4310 (overall size is 22 * 23 * 5.5mm) can achieve 1% RMSE detection accuracy within 5m indoor, which is very suitable for mobile phones, tablet computers and other application scenarios.
（1） VI4310 chip and VM4310 module
（2）RGB image and grayscale image
（3）Depth image and point cloud image
The international mainstream terminal manufacturers and VisionICs agree that the single photon detection technology based on SPAD will become the mainstream scheme of 3D detection in the future. At present, the existing manufacturers have begun to try to apply in large quantities in the newly launched products, which is also crucial for the future application of quantum communication, sensing and computing systems. Let's wait and see.