Recent Developments in Advanced 3D Sensing Applications

Roman Koerner, Head of Device and Technology Development, Trumpf

VCSELs serve advanced 3D sensing applications

VCSEL (vertical-cavity surface-emitting laser) are a perfect laser light source for 3D sensing applications in smartphones, consumer electronics, automotive as well as for industrial sensing. VCSELs are attractive as they come with a small form factor and the option to integrate various functions. Therefore, the small laser diodes offer benefits to optical engineers such as freedom. While TRUMPF already shipped more than 2 billion VCSELs to the market, product development continuously serves the demanding industries by improving illumination quality and overall performance. General trends go towards smaller and smarter components. In various industries from consumer electronics, to automotive to industrial sensing there is always a demand to reduce footprint and enhance the functionality per VCSEL chip area. TRUMPF therefore offers 3D sensing VCSEL solutions with features such as polarization, integrated lens structures or optics. Another approach to integrate functionalities are VCSELs with integrated photodiodes (ViP). ViP not only emit radiation, but it also detects signals for further processing. This enables the so called self-mixing interference technology (SMI), where a VCSEL projects an infrared laser beam onto the surface of a passing object. An optical resonator catches the reflection of the laser beam and mixes it with the light in the resonator. The photodiode measures the interference, and the system calculates the movement speed from the frequency difference. This is for example interesting for industrial laser sensors to monitor processes to detect speed and position within a production line. The SMI technology is already used in millions of products for around 20 years and proven itself, but still there are interesting new application fields such as for eye-tracking applications in VR/AR.

3D sensing in consumer electronics 

High-end smartphone applications are looking for constant improvements of their functionalities of laser for time-of-flight or structured light sensing technologies for applications as face recognition or laser auto focus. Additionally, there is a common trend of all-screen-display, which challenges system designers to place advanced optical sensing technologies underneath the displays. VCSELs are perfect to integrate under displays due to their vertical laser emission, minimum height and small footprint. By offering even more compact laser components, this trend is addressed to enable an even smaller footprint of the chip and therefore addressing an overall smaller building area. TRUMPF therefore offers compact VCSEL solutions with high power output at the same time. The company recently introduced a new single-mode 940 nm VCSEL array, which consists of twelve quadratic emission zones to generate a high output power of 20 mW with an absolutely symmetrical Gaussian beam shape, also at high pulsed operation.

"VCSELs are perfect to integrate under displays due to their vertical laser emission, minimum height and small footprint"

Another application field for modern advanced optical 3D sensing is under OLED display sensing. To improve illumination quality and resolution in these 3D illumination applications, TRUMPF launches a new multimode 940 nm VCSEL with controllable polarization. Due to the optimized grating design the new polarized VCSELs achieve almost 100 percent of the efficiency compared to standard non-polarized VCSELs. TRUMPF particularly has developed the patented technology of VCSELs with stable polarization for high volume applications. The polarization is locked by a surface grating etched directly into the GaAs. Next generation products in development will address dual polarization on one VCSEL for even more advanced applications and trend towards miniaturization.

3D sensing in automotive

The automotive sector is another growing application field for VCSELs. The trend towards autonomous driving is supported by advanced VCSEL solutions that can take over applications as in-cabin sensing, driver monitoring or LiDAR.

Systems designers get great flexibility with the so called ViBO (VCSEL with integrated Optics) technology developed by TRUMPF. ViBO comes with monolithically integrated optics and creates lighting profiles to illuminate objects at both close and long rates. The very small form factor of ViBO also allows easy integration into system designs. As for applications such as LiDAR higher output power is needed, VCSELs come with the general advantage of easy scalability of the individual emitters to very densely packed arrays. Hence this scales the optical power accordingly to serve these applications. By the way VCSELs and photodiodes also support data transfer in cars and are main components for in-vehicle optical networks, another application field TRUMPF is addressing.

New 940 nm emitting VCSEL array with twelve emitters

New generation of 940 nm emitting VCSEL-array with 12 emitters for high optical output power to enhance the quality in proximity sensing and laser auto focus applications.

Polarization controlled VCSEL

The polarization is locked by a surface grating that is etched directly into the GaAs. Polarization improves the illumination quality and resolution in demanding 3D illumination applications.

ViBO (VCSEL with integrated Backside Optics)

Cost-effective and easy to integrate VCSEL array technology with monolithically integrated micro-optical elements.

 

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