[Introduction]3D Time of Flight (3D ToF) is a scannerless LIDAR (Light Detection and Ranging, LiDAR) technology that captures depth information (usually short) of the relevant scene by emitting nanosecond high-power optical pulses It has been widely used in consumer electronics, industry 4.0, automotive, medical and health, security and monitoring, robotics and other fields. This article will introduce you to the development of 3D ToF technology and related solutions launched by ADI.

3D ToF technology for precise distance measurement

3D ToF technology uses a ToF camera to actively illuminate an object by using a modulated light source, such as a laser, and then captures the reflected light with a sensor sensitive to the laser wavelength to measure distance. The sensor measures the time delay ∆ between the emitted light from the camera and the time it is received by the camera. 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 is the speed of light.

There are several different methods of measuring ΔT, two of which are most commonly used, including the continuous wave (CW) method and the pulsed method. It is worth noting that the vast majority of continuous-wave ToF systems that have been implemented and used on the market today use CMOS sensors, while pulsed ToF systems use non-CMOS sensors (especially CCDs).

3D ToF is widely used in various key fields

3D ToF technology is widely used in consumer electronics, ranging from AR (augmented reality) and VR (virtual reality) headsets to smartphones with advanced photography and security features, and ToF technology is expected to be the next generation of consumer electronics. important parts of. In AR/VR headsets, the depth information obtained through the ToF system can provide users with an additional dimension of reality. In smartphones, the technology will enable cameras to produce DSLR-quality photography, enable more realistic AR/VR capabilities, and provide additional protection from unwanted external access.

Smart sensors, especially depth sensors, in Industry 4.0 applications are increasingly common in manufacturing as well as in transportation and logistics. From industrial machine vision for quality inspection, capacity inspection for asset management to navigation equipment for autonomous manufacturing, manufacturing is adopting these sensing technologies and driving the development of high-resolution systems suitable for harsh industrial environments.

In next-generation automotive applications, ToF systems in the cockpit will be able to monitor the location and status of the driver and passengers, control and steer the car in the event of a driver incapacitated, and ensure the safety of the vehicle. Gesture control systems enabled by ToF technology will likely be the next generation of automotive user interfaces, allowing drivers to answer incoming calls, switch audio input sources, and even adjust the interior temperature with a simple gesture or touch operation.

Given the recent pandemic, ToF technology for long-range and depth measurement has become even more important in the healthcare sector. Touchless control operations through gestures, remote monitoring of infant breathing, and monitoring of social distancing in various environments can all be achieved using 3D ToF technology.

In security and surveillance applications, 3D ToF’s high-resolution depth-of-field measurement technology has obvious advantages compared to traditional 2D image detection technology. High-resolution depth measurement makes it easier and more reliable to distinguish people and objects, making it ideal for security and surveillance detection at entrances and exits of commercial buildings, as well as detection of patient falls or injuries in medical environments.

In addition, high-resolution ToF systems will be critical in enabling automated machines and robots to sense the environment and plan paths to complete tasks in an optimized, reliable, and safe manner. Additionally, 3D imaging can enable safety functions in applications where humans and cobots work together. In addition to industrial applications, collaborative robots are also moving from the factory floor to new applications (such as healthcare), helping nurses to disinfect spaces and surfaces, or assisting with certain tests, thereby minimizing health risks to workers .

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 the capabilities of advanced ToF systems and cameras, including high-resolution CMOS imaging chips (1 megapixels), depth computing and processing , laser drivers, power management, and development tools and software/firmware to help quickly implement ToF solutions. In addition, ADI leverages a global network of partners to develop ToF modules, cameras and design services that help reduce product development time.

The ADSD3100 from Analog Devices is a CMOS 3D ToF-based 3D depth and 2D visible light imager for integration into 3D sensor systems. The functional blocks required for readout, including analog-to-digital converters (ADCs), pixel bias circuits, and sensor control logic, are built into the chip for a simple, cost-effective solution in the system.

The ADSD3100 is electrically interfaced with the host system through the Mobile Industry Processor Interface (MIPI), Camera Serial Interface 2 (CSI-2) interface. To complete the working subsystem, lenses and optical bandpass filters for the imager are required, as well as an infrared light source and associated drivers. The ADSD3100 can be used in smartphones, AR/VR, machine vision systems (logistics and inventory), robotics (consumer electronics and industrial), and more.

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 adjustment of the CCD horizontal clock and LD output with approximately 174 ps resolution when operating at 45 MHz.

The AFE in the ADDI9036 includes black level clamps, a correlated double sampler (CDS), a variable gain amplifier (VGA), and a 12-bit ADC. AFE data is output through the MIPI® CSI-2 transport interface, and internal registers can also be programmed through the I2C serial interface. The ADDI9036 is available in a 6 mm × 6 mm 117-ball WLCSP package and can operate over the −20°C to +85°C operating temperature range.

The ADI ADP362x/ADP363x are a family of high-current, dual-channel high-speed drivers capable of driving two independent N-channel power MOSFETs. This series uses industry standard dimensions, but adds high-speed switching performance and higher system reliability. The series integrates an internal temperature sensor and provides dual over-temperature protection, over-temperature warning, and over-temperature shutdown when the junction temperature is extremely high.

The SD function is generated by an internal precision comparator to quickly enable or shut down the system. This feature can provide redundant overvoltage protection, cooperate with the protection functions inside the main controller, or safely shut down the system in the event of an overtemperature warning event. The wide input voltage range enables the driver to be compatible with both analog and digital PWM controllers, with the digital power controller powered from a low voltage supply and the driver powered from a higher voltage supply. The ADP362x/ADP363x family adds UVLO and hysteresis to support safe start-up and shutdown of higher voltage supplies when used with low-voltage digital controllers.

The ADP362x/ADP363x device family is available in thermally enhanced SOIC_N_EP and MINI_SO_EP packages to maximize high frequency and high current switching performance in a small printed circuit board (PCB) area. It can be used in AC-DC switch mode power supply, DC-DC power supply, synchronous rectification, motor drive and other fields.

3D ToF development platform for faster system development

In order to speed up the development of 3D ToF systems, ADI has also launched a 3D ToF development platform – AD-96TOF1-EBZ. This modular ToF solution is built on the industry standard 96Boards platform and can measure the X, Y of an object. , Z-axis data.

The AD-96TOF1-EBZ is a field-proven depth-sensing hardware platform for 3D software and algorithm development when used with processor boards in the 96Boards ecosystem. While software and algorithms are being developed, hardware design can be utilized for productization.

ADI can recommend third-party developers to help customize the platform to meet various application needs. Depending on customer preference and development experience, different 96Boards processor boards can be used for overall system evaluation and custom development. A Raspberry Pi interface is also available on the mezzanine board for further customer flexibility.

The solution is capable of very small size and low power consumption, measuring depths up to 6 meters, with excellent outdoor and indoor performance and VGA resolution. It can be used in applications such as robotics, industrial automation, SLAM (simultaneous localization and map building), AR, VR, drones, car inspection, etc.

Another AD-FXTOF1-EBZ 3D ToF development kit is a depth-of-field measurement Module ideal for integration into larger systems and end products. It uses a VGA CCD that supports capturing 640×480 depth-mapped scenes at 30 frames per second, providing 4x higher resolution than many other TOF systems on the market.

AD-FXTOF1-EBZ is a certified production module suitable for depth of field measurement. It is fully compatible with existing ADI 3DTOF open source SDKs and prototyping software platforms. It can be used with existing ADI algorithms for a variety of use cases, including people detection, occupancy and activity detection, object detection and classification, autonomous and service robotics, and volumetric measurement for logistics and industrial applications and many other machine vision applications. The kit includes a breakout board that adapts the ToF module’s 25-pin interface to a 15-pin interface and is compatible with commonly used development systems such as Raspberry PI, Nvidia Jetson Nano or Nvidia Xavier NX.

ADI also launched a highly integrated ToF camera module, which is based on ADI’s ToF signal chain products and technologies, which can output depth maps and (710 version) TOF + RGB images (can be disabled), FOV is 70 X 54, and the depth camera supports a maximum of 640 *480 (under 30 FPS) image size, RGB camera supports up to 1920*1080 (under 30 FPS) image size, built-in USB 2.0 interface, can support running on Android, Linux, Windows 7/8/10 operating systems , and provides the Pico depth sensor SDK, sample code and tools (compatible with the Open NI SDK), and the ADI sample application algorithm provided in Python.

Epilogue

The development of LiDAR systems integrating 3D ToF technology has been quite mature, and its applications are becoming more and more extensive, and it has great market development potential. ADI launches complete 3D ToF products and solutions, and provides easy-to-use development platforms and modules, which can speed up customer product development and will be one of the best choices for you to develop related products.