News: Optoelectronics
27 June 2024
ROHM develops VCSELED infrared light source combining features of VCSELs and LEDs
ROHM says that it has established VCSELED, a new infrared light source technology that encapsulates a VCSEL (vertical-cavity surface-emitting laser) chip in a resin optical diffusion material for laser light. ROHM is currently developing this technology for commercialization as a light source for improving vehicle driver monitoring systems (DMS) and in-cabin monitoring systems (IMS).
Picture: ROHM’s new VCSELED infrared light source, which combines features of VCSELs and LEDs.
To further enhance automotive safety, driver monitoring systems are increasingly being installed in vehicles equipped with advanced driver assistance systems (ADAS) to detect drowsiness, sleepiness and distracted driving. In Japan, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has created guidelines that define the design and functions of the system, and in the European Union (EU) there are plans to make installation mandatory in all new vehicles sold in Europe from July onwards. Auto-makers and suppliers are also developing in-vehicle monitoring systems to detect occupants other than the driver, and there is a growing awareness of the need for high-performance light sources that enable detection systems to function with greater precision.
In response, ROHM has developed VCSELED technology to achieve high-accuracy sensing. Minimal wavelength temperature variation combined with a wide emission beam angle mean not only that it is suitable for in-vehicle monitoring systems but also that it contributes to improving the accuracy and performance of inspection systems for robots and industrial equipment as well as spatial recognition and ranging systems.
Similarly to LEDs, VCSELED extends the beam (irradiation) angle by combining a high-performance VCSEL chip and light diffusion material to enable sensing over a wider area with higher accuracy than VCSELs. Also, the light-emitting element and light diffuser are integrated into a compact package, contributing to smaller, thinner applications.
The VCSEL chip used in VCSELED features a narrow emission wavelength bandwidth of 4nm, which is one-seventh that of LEDs. This characteristic improves resolution performance on the receiving side while eliminating the red glow that is often associated with LEDs. At the same time, a wavelength temperature variation of 0.072nm/°C — less than a quarter that of LEDs (0.3nm/°C) — allows high-accuracy sensing, unaffected by temperature changes. Furthermore, the response time when emitting light is 2ns, which is about 7.5 times faster than LEDs, contributing to higher performance in time-of-flight (ToF) applications that use infrared light to measure distance.
ROHM says that it is working on commercializing VCSELED as a new technology brand for infrared light source components. Prototype samples are available for purchase now, with mass-production samples scheduled for release in October 2024 for consumer applications and in 2025 for automotive applications, respectively.
ROHM adds that, going forward, it will continue to develop laser light source technology for in-vehicle monitoring and other systems.
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