As artificial intelligence moves toward practical application and is gradually adopted in smartphones, smart homes, industrial robots and future autonomous driving, accurate environmental perception has become increasingly critical for intelligent terminals. As an essential sensor for machine 3D vision, Time-of-Flight (ToF) image sensors based on laser pulse flight time provide an extra dimension of perception compared with traditional 2D CMOS Image Sensors, endowing intelligent terminals with more precise and efficient environmental scene capture capabilities.

However, the high cost of ToF ranging 3D imaging based on pulse flight time is currently a bottleneck restricting the development of artificial intelligence, a typical example being the LiDAR used for autonomous driving today. Though also based on the ToF laser ranging principle, the design with discrete chips and components means a 64-channel LiDAR packs a large number of discrete devices and chips into a narrow cavity, making it difficult to solve numerous mass production challenges related to cost, power consumption, heat dissipation and stability.

To address these key industry pain points, visionICs has launched a laser ranging ToF chip based on single-photon detection. This chip achieves an ultra-high sensitivity, high-resolution single-photon detection array on a low-cost CMOS process, and integrates independently developed ultra-high-precision ranging circuits and anti-interference digital algorithms. Compared with indirect ToF 3D ranging implemented by modifying CMOS pixel image sensors, direct ToF based on a Single-Photon Avalanche Diode (SPAD) array features ultra-high photodetection sensitivity, enabling long-distance detection with low laser power and reducing the overall system's power consumption and cost.

Nanjing visionICs holds a leading position worldwide in single-photon ranging technology and its commercial application. Founded in May 2018, the company boasts advanced optoelectronic conversion device design and single-photon detection imaging technologies, focusing on a portfolio of 1D and 3D ToF sensing chips based on single-photon detection. Its chip products are widely applied in consumer electronics including robot vacuum cleaners, drones and smartphones, as well as in AR/VR, smart home systems and automotive LiDAR for autonomous driving.

visionICs’ core competitive advantages in the LiDAR chip sector are as follows:

1. High cost-performance SPAD single-photon detection array chips based on a low-cost CMOS process. Adopting the direct ToF detection method, the chips offer advantages such as low power consumption, a simplified system, long detection distance and high precision compared with indirect ToF or coherent light solutions.
2. The new single-photon detection technology greatly improves receiver sensitivity, significantly reducing the number and power of lasers on the transmitter side.
3. Independently designed fully integrated receiver chips on the receiving end, which integrate single-photon detection arrays, analog-digital hybrid control circuits for single-photon pixels, anti-sunlight and background light algorithms, as well as memory and high-speed interfaces, leading to a substantial reduction in overall costs.
4. The company’s core team has over a decade of industry experience in optoelectronic integrated circuits and silicon photonics, ensuring high efficiency in product design and manufacturing.

Laser ranging 3D imaging technology is a research hotspot in the field of machine vision. By emitting laser beams to detect targets, acquiring point cloud data from reflected light, and processing the data for imaging, it can generate accurate 3D stereoscopic images with centimeter-level ranging precision. Boasting high accuracy, fast operation and high efficiency, it has important application prospects in automotive assisted/autonomous driving, AR/VR, robot 3D vision positioning and navigation, spatial environment mapping, and security and protection.

The working principle of laser ranging is similar to that of traditional radar wave devices. A laser transmitter emits laser signals that illuminate the target object, and the reflected light signals are collected by a receiver. The precise physical distance is measured by calculating the round-trip flight time (Time-of-Flight) of the light signals in the air. Currently, there are two basic measurement methods.

First, the transmitter irradiates the target with narrow laser pulses, and the receiver uses a Time-to-Digital Converter (TDC) to directly measure the flight time of the laser pulses in the air, known as Direct-ToF (dToF) ranging.

Second, the transmitter modulates continuous light with a sine or square wave, and the receiver indirectly calculates the flight time of the light signals based on the ratio of the phase shift of the modulated light during the round trip to the period of the modulated signal, known as Indirect-ToF (iToF) ranging.

Based on the principle of constant light speed, both methods can calculate the precise distance to the target object. The first method, with its advantages of high signal-to-noise ratio, high precision, large dynamic range and anti-multipath interference, combined with the ultra-high sensitivity detection of single-photon detection devices, is ideal for long-distance detection under low-light conditions, providing an ultra-high sensitivity, low-power solution for laser ranging and 3D detection imaging.

Current laser ranging and imaging systems are limited in their application in the consumer market due to high cost, large size and low integration. The industry expects the development of silicon photonics technology to bring a revolutionary change to laser ranging technology. The integration of large-scale single-photon detection arrays has long been a technical challenge. At present, the mainstream industry solution still uses discrete components to build LiDAR systems. Such systems have a complex structure, and the APD sensors used have low photoelectric conversion current, which leads to crosstalk issues with an increased number of channels and makes it difficult to scale up the channel count. Meanwhile, the growing number of multi-stage amplification components keeps costs high, hindering large-scale mass production and commercialization (Figure 2). Another problem with discrete device solutions is the large measurement error caused by different reflectivity of target objects, which can even reach tens of centimeters and requires resource-intensive algorithm correction. visionICs’ single-chip solution based on single-photon detection (Figure 3) achieves an ultimate measurement error of less than 1 cm for target objects with different reflectivity, reaching an advanced level in the laser ranging field.

The newly launched series of single-photon detection laser ranging and 3D imaging chips (including single-point, 32x32 SPAD array, 256x64 SPAD array and other specifications) is based on the direct Time-of-Flight laser ranging method, providing a one-stop solution for miniature ToF sensing in the market. Relying on independently developed SPAD (Single-Photon Avalanche Diode) technology and unique ToF acquisition and processing technologies, visionICs’ inaugural laser ranging and 3D imaging chips hold significant performance advantages.

Among them, the single-point ranging chip VI4300 series achieves high-precision full-range testing from 0.1 meters to 200 meters, increasing the ranging range of similar chips by 100 times. It can also resist ambient light interference of up to 100 KLux, making it suitable for measurements in outdoor sunlight environments. The VI4300 series chips have a wide range of applications in the ranging field, such as short-distance LDS modules for robot vacuum cleaners and laser autofocus modules for cameras; medium-distance modules for handheld rangefinders, AGV anti-collision modules and lane detection modules; and long-distance automotive LiDAR for autonomous driving vehicles.

Taking the industry-focused autonomous driving LiDAR as an example, compared with cameras and other sensors, the LiDAR system based on the VI4300 single-point ranging chip can not only generate 3D position models, but also offer a longer detection distance, higher measurement precision and faster response speed, while being unaffected by ambient light. It can be said that the VI4300 single-point ranging chip provides an excellent chip solution for LiDAR.

In addition, visionICs has also exclusively launched two fully integrated array single-photon ToF chips (models: VI3810 and VI4320), which lead the industry in performance, ease of use and manufacturability. Array ToF chips also have broad application prospects in spatial perception and 3D modeling. Based on the VI3810 chip, the 32*32 pixel array module co-developed by visionICs and the 27th Research Institute of China Electronics Technology Group Corporation has passed acceptance testing. Meanwhile, visionICs’ array chips have extensive application potential in face recognition, liveness detection, smartphone AR, security and biometric detection.