3D time of flight (3D ToF) is a scanner-less LIDAR (light detection and ranging) technology, which captures the depth information of related scenes by emitting nanoseconds high-power optical pulses (usually within a short distance). It has been widely used in consumer electronics, industrial 4.0, automotive, healthcare, security and surveillance, robotics and other fields. This article will show you the development of 3D ToF technology and the related solutions launched by ADI.
3D ToF technology can accurately measure distance
3D ToF technology uses a ToF camera to measure distance by actively illuminating an object using a modulated light source (such as a laser) and then capturing reflected light with a sensor that is sensitive to the laser wavelength. The sensor measures the time delay Δ between the time when the light is emitted from the camera and when the camera receives the light. The time delay is proportional to twice the distance (round trip) between the camera and the object; therefore, the distance can be estimated as depth = cΔ/2, where c represents the speed of light.
At present, there are many different methods to measure ∆T, in which the continuous wave (CW) method and pulse-based method are most commonly used. It is worth noting that most of the CW ToF systems implemented and used in the market use CMOS sensors, while pulsed ToF systems use non-CMOS sensors (notably CCD).
3D ToF is widely used in various key fields
3D ToF technology is widely used in consumer electronics, including AR (augmented reality) and VR (virtual reality) headsets to smartphones with advanced photography and security features. ToF technology is expected to become an important part of the next generation of consumer electronics. In the AR/VR headset, the depth information obtained through the ToF system can provide users with additional reality dimensions. In smartphones, the technology will enable the camera to produce DSLR-quality photography, achieve more realistic AR/VR functions, and provide additional protection to avoid unwanted external access.
Smart sensors (especially depth sensors), which are used in industrial 4.0, are increasingly used in manufacturing, transportation and logistics. From industrial machine vision for quality inspection to volumetric detection for asset management to navigation equipment for autonomous manufacturing, the manufacturing industry is adopting these sensing technologies and promoting the development of high-resolution systems suitable for harsh industrial environments.
In the next generation of automotive applications, the ToF system in the cockpit can monitor the position and status of the driver and passengers, control and operate the vehicle when the driver is unable to drive, and ensure the vehicle's safety. The gesture control system realized through ToF technology may be the next generation of car user interfaces, allowing the driver to answer incoming calls, switch audio input sources, and even adjust the temperature in the car through simple gestures or touch operations.
In view of the recent pandemic, ToF technology suitable for long-distance and depth measurement has become more important in the field of healthcare. Contactless control through gestures, remote monitoring of infant respiration, and social distance monitoring in various environments can all be achieved using 3D ToF technology.
Compared with traditional 2D image detection technology in security and surveillance applications, 3D ToF high-resolution depth-of-field measurement technology has obvious advantages. High-resolution depth-of-field measurement makes it easier and more reliable to classify between people and objects, making it very suitable for security and surveillanceat the entrances and exits of commercial buildings and for the detection of patient falls or injuries in medical environments.
In addition, high-resolution ToF systems that enable automated machines and robotics to perceive the environment and plan paths will become critical to accomplish tasks in an optimized, reliable and safely manner. In addition, 3D imaging can achieve security functions in applications where humans and collaborative robotics work together. In addition to being used in industry, collaborative robotics have also moved from factory workshops to new applications (such as healthcare). They can help nurses disinfect space and surfaces, or assist in completing certain tests in order to minimize the health risks faced by staff.
Industry-leading complete 3D ToF products and solutions.
Seeing the rapid development of 3D ToF technology, ADI also offers a variety of industry-leading products and solutions that directly implement and enhance advanced ToF systems and camera functions, including high-resolution CMOS imaging chips (1 million pixels), deep computation and processing, laser drivers, power management, and development tools and software/firmware to help quickly implement ToF solutions. In addition, ADI uses a global partner network to develop ToF modules, cameras and design services to help shorten product development time.
ADI's ADSD3100 is a 3D depth and 2D visible optical imager based on CMOS 3D ToF that can be integrated into 3D sensor systems. The functional modules required for read out include an analog-to-digital converter (ADC), pixel biasing circuitry and sensor control logic, which are built into the chip to achieve a simple, cost-effective solution in the system.
ADSD3100 electrically interfaces with the host system through the mobile industry processor interface (MIPI) and camera serial interface 2 (CSI-2). In order to complete the working subsystem, lenses and optical band-pass filters for imagers and infrared light sources and related drivers are needed. The ADSD3100 can be used in smartphones, AR/VR, machine vision systems (logistics and inventory), robotics (consumer electronics and industry) and other fields.
ADI's ADDI9036 is a complete 45 MHz front-end solution for charge-coupled device (CCD) TOF imaging applications. The ADDI9036 includes an analog front-end (AFE), a programmable instruction set architecture (ISA) timing generator (ISATG), a 7-channel laser diode (LD) driver, a 7-channel H driver, and a 16-channel vertical driver (V-driver). The precision timing®; core allows you to adjust the CCD horizontal clocks and LD outputs at a resolution of about 174ps at 45 MHz.
The AFE in the ADDI9036 includes a black level clamping, a correlated double sampler (CDS), a variable gain amplifier (VGA), and a 12-bit ADC. AFE data is output through the MIPI®; CSI-2 transmit interface, and internal registers can also be programmed through the I2C serial interface. The ADDI9036 is packaged in 6 mm × 6 mm 117-ball WLCSP and can operate in the operating temperature ranging from −20℃ to +85℃.
The ADI ADP362x/ADP363x is a series of high-current, dual-channel high-speed drivers that can drive two independent N-channel power MOSFETs. This series adopts industrial standard foot-print, but includes high-speed switching performance and features higher system reliability. The series integrates internal temperature sensors and provides two levels ofovertemperature protection, overtemperature warning, and overtemperature shutdown function when the junction temperature is extremely high.
The SD function generated by the internal precision comparator can quickly turn the system enable or shutdown. This function provides redundant overvoltage protection, complementing the protection inside of the main controller devices, or safely shutdown the system in the event of an overtemperature warning event. A wide input voltage range enables the driver to be compatible with analog and digital PWM controllers. Digital power controllers are powered from low-voltage power supplies and drivers are powered from higher-voltage power supplies. The ADP362x/ADP363x series adds UVLO and hysteresis functions to support safe start-up and shutdown of higher voltage power supplies when used in conjunction with low-voltage digital controllers.
The ADP362x/ADP363x series of devices use heat dissipation enhanced SOIC_N_EP and MINI_SO_EP packages to greatly improve the high frequency and high current switching performance in a smaller printed circuit board (PCB) area. They can be used in AC-DC switching mode power supply, DC-DC power supply, synchronous rectifier, motor drive and other fields.
3D ToF development platform that can speed up system development.
In order to speed up the development of the 3D ToF system, ADI also launched a 3D ToF development platform - AD-96TOF1-EBZ. This modular ToF solution is based on the industry-standard 96Boards platform and can measure the X, Y and Z axis data of objects.
AD-96TOF1-EBZ is a proven depth-aware hardware platform that can be used with processor boards in the 96Boards ecosystem for 3D software and algorithm development. While developing software and algorithms, hardware design can be utilized to realize production.
ADI can recommend third-party developers to help customize the platform to meet a variety of application needs. According to the differences in customer preferences and development experience, different 96Boards processor boards can be used for overall system evaluation and customized development. The Raspberry Pi interface can also be used on the Mezzanine board to further improve customer flexibility.
The solution can achieve compact design and low power consumption features, measure depths up to 6 meters, and have excellent outdoor and indoor performance and VGA resolution. It can be used in robotics, industrial automation, SLAM (simultaneous localization and mapping), AR, VR, drones, automotive sensingand other applications.
Another ToF development kit, AD-FXTOF1-EBZ 3D, is the depth-of-field measurement module, which is ideal for integrating larger systems and end products. It uses VGA CCD and supports capturing 640x480 depth-of-field mapping scenes at 30 frames per second, which in turn provides a resolution of four times higher than many other TOF systems on the market.
AD-FXTOF1-EBZ is a provenproduction module suitable for depth-of-field measurement. It is fully compatible with existing ADI 3DTOF open-source SDK and prototyping software platforms. It can be used in conjunction with existing ADI algorithms for a variety of use cases, including people detection, occupancy and activity sensing, objects detection and classification, autonomous and service robots, as well as volume measurement for logistics and industrial applications and many other machine vision applications. This kit includes an interposer board to adapt the 25-pin interface of the ToF module to the 15-pin interface and is compatible with commonly used development systems such as Raspberry PI, Nvidia Jetson Nano or Nvidia Xavier NX.
ADI also introduces a highly integrated ToF camera module based on ADI's ToF signal chain products and technologies to output depth maps and (710 version) TOF + RGB images (can be disabled). FOV is 70 X 54. Depth cameras support up to 640*480 (at 30 FPS) image size. RGB cameras support up to 1920*1080 (at 30 FPS) image size. It has a built-in USB 2.0 interface. It can run on Android, Linux, Windows 7/8/10 operating systems, and provides Pico depth sensor SDK, sample code and tools (compatible with Open NI SDK), as well as ADI sample application algorithms in Python.
Conclusion
The development of the LiDAR system integrated with 3D ToF technology has been quite mature, and its application is becoming more and more extensive, so it has great potential for market development. ADI has launched complete 3D ToF products and solutions, providing easy-to-use development platforms and modules to speed up customer product development, which will be one of the best choices for you to develop related products.