Laser lighting - safe and efficient

Homogeneous intensity profile in the angular space with high flank quality. This results in high efficiency to make meaningful use of each generated photon and to avoid stray radiation. (Image source: LIMO)

New LIMO Diffuser Technology: The two diffusers each generate a vertical or horizontal line. By overlaying the two functional surfaces, the laser light is shaped into a rectangular field with a steep edge and a user-defined size, e.g., 120 degrees x 25 degrees. (Image source: LIMO)

LiDAR sensors have quickly become a key technology for automated processes and especially for fully autonomous driving. To accurately capture the distances of the static and dynamic environment around the vehicles, the laser beam must be shaped into a light field with a defined field of view. The new wide-angle diffuser from LIMO achieves a constant performance through its hotspot-free beam shaping, even at extreme operating temperatures, and allows for a 360-degree panoramic view with only four LiDAR systems by providing a large illumination field for safe driving.

The development of a state-of-the-art LiDAR system requires more than careful selection of a suitable laser source and a compatible detector. The most critical components are the optics that shape the laser light in the correct direction. Furthermore, safe and reliable operation of the LiDAR system is only possible if the risk of injury from laser photons is eliminated, which requires beam propagation without hotspots.

For this, a consistent intensity distribution of the laser radiation is necessary even at high ambient temperatures. The use of diffractive scattering optical components (DOE) has so far only been suitable for small angles and moderate environmental conditions. Additionally, the optics usually have an intensity distribution that decreases flatly towards the edges.

Illumination angles of more than 100 degrees

In LIMO's diffuser technology, a different approach is used: similar to a homogenization optical, LIMO constructs refractive optical elements from glass that can scatter the laser light in one direction up to a full illumination angle of a few milliradians to over 100 degrees. Combined with a second functional surface, the light can also be shaped in the other direction at any angle to create a rectangular field with a steep edge and a user-defined size, for example, 120 degrees x 25 degrees.

"We can precisely and uniformly illuminate the target area with different angles, and a surface structure defined for the customer application ensures a consistent intensity distribution for each application," explains Dr. Daniel Braam, Product Line Manager Optics at LIMO. "This is advantageous for noise suppression and increases the signal-to-noise ratio, thereby extending the range of the LiDAR sensors. Due to the large illumination angle of the new diffuser of over 100 degrees, an autonomous vehicle only needs to be equipped with four LiDAR systems to capture the entire spatial environment."

The LIMO diffusers can be combined with all types of laser sources with low and high power, even in the range of 1.4 < M² < 15, which is a range where the laser beam is difficult to homogenize.

Large production quantities through wafer technology

The diffusers, like other micro-optics from LIMO, can be manufactured using a novel and highly productive wafer-based processing method. LIMO produces high-quality glass laser optics on wafers up to 300 mm x 300 mm, enabling sustainable reduction of production costs for large series without compromising quality. Since LiDAR systems and 3D sensors are particularly safety-critical components in autonomous driving and require large quantities for this application, the quality and cost structure of the optics are crucial factors for the breakthrough of this technology.