LiDAR (Light Detection and Ranging) has become a key technology in ranging applications. With the technology becoming more mature and the product price becoming more reasonable, its application is more and more extensive. This article will show you the development of LiDAR technology and the laser diode solution from ROHM.
LiDAR technology capable of accurately sensing the distance between objects
LiDAR is composed of ToF (Time of Flight) system (light source, ToF sensor or image sensor, etc.), used to sense the surrounding conditions. Usually, a pulsed laser is used to measure the distance and other parameters of the target. LiDAR has applications in surveying and mapping, archaeology, geography, geomorphology, seismology, forestry, remote sensing and atmospheric physics. In addition, this technology is also used in airborne laser mapping, laser altimetry, LiDAR contouring and other specific applications.
The most basic working principle of LiDAR is no different from that of radio radar, that is, a signal sent by the radar transmitting system is collected by receiving system after being reflected by the target, and the distance of the target is determined by measuring the running time of the reflected light. Because the speed of light is known, the distance between the laser and the object can be calculated according to the time difference between the emitting time of emitted light and the receiving time of backscattered light, which is the principle that LiDAR can measure distance.
Laser diode (LD) is the key device of LiDAR. It is a kind of laser generator whose working substance is semiconductor, which belongs to a solid-state laser generator. Most laser diodes are similar to general diodes in structure. This kind of electronic device appeared as early as 1962. It can only emit low-brightness red light in the early stage, and then develop other monochromatic versions. Today, the light it can emit has spread all over visible light, infrared light and ultraviolet light, and the brightness has also increased to a very high degree. Laser diodes have the advantages of high efficiency, small size and long life.
Laser diode with farther, more accurate and lower power consumption
In recent years, LiDAR, which can accurately measure distance and identify space, has become increasingly popular in a wide range of applications requiring automation, such as sweeping robots, AGVs (automated guided vehicles) and self-driving vehicles. In this context, in order to detect information farther, more accurately and with lower power consumption, higher requirements are put forward to improve the performance of laser diodes as light sources.
ROHM, a world-renowned semiconductor manufacturer, has been committed to developing and supplying FP laser diodes, including LED and VCSEL (Vertical Cavity Surface Emitting Laser) products. Recently, such products have become increasingly popular in applications such as ToF sensor light sources in the fields of sweeping robots and surveillance cameras.
At the same time, ROHM uses the development experience and technology of optical components accumulated in the process of launching various products, and continuously promotes the research and development of exerting the performance of components to a greater extent and further improving the output power. ROHM also develops many sensor light source products with different advantages by developing components and their application in modules, which contributes to improving the accuracy of ranging and spatial recognition systems.
Laser diode with 75W high output power
Recently, ROHM has developed a semiconductor laser diode with high output power - RLD90QZW3, which is very suitable for AGVs,service robots in the field of industrial equipment with LiDAR for ranging and space identification, sweeping robots in the field of consumer electronics, and other applications.
ROHM has its own patented technology to achieve narrower laser emission width, which helps LiDAR support longer distances and achieve higher accuracy. RLD90QZW5, a laser diode with 25W high output power, has been mass-produced since 2019, and is increasingly used in applications mainly in the field of consumer electronics. This time, in order to expand the application to the industrial equipment field with a growing market, ROHM has developed RLD90QZW3, a laser diode with 75W high output power.
RLD90QZW3 is an infrared laser diode with 75W high output power, which is developed for LiDAR for ranging and space identification using 3D ToF system. Using ROHM's component development technology, an ultra-narrow emission width of 225 μm is achieved in laser diodes with the equivalent output power in the industry. Compared with conventional products with a emission width of 290 μm and a temperature correlation of 0.25 nm/℃, the emission width is narrowed by 22%, achieving high beam performance.
At the same time, by making the luminous intensity more uniform and taking advantage of the low temperature correlation of laser wavelength, the temperature correlation of laser wavelength is as low as 0.15 nm/℃, which can be reduced by 40% compared with conventional products, and is insusceptible to temperature changes, so it can stably exert high performance, which is helpful for LiDAR to achieve long-distance application in various environments, and also helps to achieve higher accuracy under the condition of equal measurement distance. In addition, the photoelectric conversion efficiency (PCE), which has a trade-off relationship with the narrow emission width, also reaches the same 21% as that of conventional products (when the forward current is 24A and 75W), so there is no need to worry about increasing power consumption when adopting RLD90QZW3. For more information, please visit the RLD90QZW3 product page: https://www.rohm.com/products/laser-diodes/high-power-lasers/rld90qzw3-product.
At present, ROHM is developing laser diode products with a high output power of 120W and automotive sector (AEC-Q102 standard qualified). In the future, ROHM will continue to contribute to the development of safe and convenient LiDAR application products, including the automotive field.
Diversifying support tools to speed up product development
In order to assist customers in new product development and support the rapid introduction of products into the market, ROHM provides rich design data required for evaluating and introducing new products free of charge on the official website, including an application guide that contains driving circuit design method, data for circuit board development and simulation models (SPICE model, Ray data), etc.
In addition, ROHM also introduces the single-channel LiDAR (REFLD001) reference design, which is a single-channel LiDAR demonstration board, allowing you to check the operation of the high-speed optical front end using LiDAR ToF range technology, and the measurement distance can reach 50m.
The REFLD001 reference design is based on LiDAR ToF technology and is easy to use for further development by customers. In addition, long-ranging with low power consumption can be realized by high-speed switching. REFLD001 uses ROHM 905nm 75W RLD90QZW3 invisible laser diode, which can support long-ranging, provide more power-saving 15nsec pulse laser under the same LD power condition, and all systems use a single power supply. LiDAR ToF architecture can be applied to automotive, consumer and industrial machinery. It can be widely used in LiDAR, ranging tool, safety sensor/proximity sensor, BIM (Building Information Model), parking assistance system, robot vacuum cleaner, AGV and other products.
Conclusion
With the introduction of high-power laser diodes, the performance of LiDAR applications is getting better and better, and the market acceptance is gradually rising. The infrared laser diode with 75W high output power introduced by ROHM has higher precision and lower power consumption. It provides complete technical support, which will be the best device choice for LiDAR applications.