Advancements in LiDAR: How Optical Coatings and Filters are Enabling the Technology of the Future

The potential for light detection and ranging LiDAR-based technology (LiDAR) is nearly endless. Unlike RADAR which uses radio waves to sense the position and distance to objects, LiDAR utilizes much shorter wavelength visible- to- near- infrared light waves. The shorter wavelengths allow for higher resolution imaging of objects in the scene.   

The change from radio to shorter light waves introduces the need for optical systems to manage and control the electromagnetic radiation. The systems consist of lenses and mirrors to bend and reflect the light. Optical interference filters are needed to separate the LiDAR light from the solar background. In the absence of optical filtering, the detector would be swamped with the solar background, rendering the LiDAR invisible.   

LiDAR is a time- of- flight technique capable of measuring the distance to objects in front of the sensor. The LiDAR emits pulses of laser light and measures the time needed to return as a reflection off an object in the scene. It is a relatively straightforward calculation using the speed of light and the time taken to return as a reflection to calculate the distance. The laser is scanned across the scene in azimuth and elevation using a combination of rotating and tilting mirrors to produce a 3D image of all objects in front of the sensor. Depending on the optical design, the emitting and return channels are either separate or combined into one.  

What Are the Benefits of LiDAR?  

According to Statista, the global LiDAR market is set to reach a revenue forecast of 3.7 billion USD by 2027, with a compound annual growth rate (CAGR) of 13.2% from 2020 to 2027. 

Advantages of LiDAR include:  

- Instant and highly accurate measurements in large quantities or data sets   

- Easy 3D modeling and mapping   

- Fast data and direct distance measurement (minimal processing requirements)  

- Automation and autonomous equipment enablement   

- Superior low light performance   

What Applications Can Use LiDAR?  

Many people may not know that LiDAR is already an integral part of society and is embedded into machines and systems being used every day. Currently, the biggest markets for LiDAR are the agricultural industry, law enforcement, military and defense, and the autonomous vehicles sector.   

For agriculture, LiDAR is primarily used for crop viability and mapping. LiDAR creates a 3D digital model of the land, tracking elements such as water flow and plant frequency. This LiDAR enhanced collected data can help increase crop yields and allow farmers to use their land more efficiently. Not all farmland is uniform – it is common to have natural variation in soil, moisture levels, ground composition, and other environmental factors.  LiDAR can help the agricultural industry adjust to these variables in farms and push forward feeding the world more efficiently. 

For the growing autonomous vehicle industry, LiDAR is used for navigation and collision avoidance. LiDAR serves as the “eyes” of the vehicle allowing human eyes and minds to be less of a factor in fatal accidents. Passenger vehicles, snow blowers, and lawn mowers are already being equipped with LiDAR technology.  

Other applications that are already using LiDAR include:   

- Green Energy (for wind turbines and solar energy planning)  

- Law Enforcement (for forensics, mapping fingerprints, and in solving missing persons cases by detecting unmarked graves)  

- Astronomy (for planet and moon topography and lunar laser-ranging)  

- Conservation and Ecological Research (for coastline management and modeling flood and earthquake damage)  

How Does Optical Equipment Affect LiDAR Performance?   

As an active form of remote sensing, LiDAR uses collected light information to deliver environmental data to be analyzed and then reacted to by the full LiDAR integrated system. That visual sensing ability is dependent on components such as coatings, prisms, sensors, and filters, as well as the overall optical design of the sensing system. If your optics are not specified correctly, or if your system is poorly designed for integration, your LiDAR system will not work as it should. Here are some of the optical coatings and strategies that engineers use to improve LiDAR system performance. 

Bandpass Filters  

The cleaner your wavelength, the better your light reflection will be. Bandpass filters are used to clean up the edges of a laser for better resolution of the feedback signal, achieving more accurate and undistorted information.   

The goal of a bandpass filter is to prevent any contaminating signals and block out other unwanted areas of light. A bandpass filter’s performance is largely determined by the transmission of the bandpass, ripple, and bandshape or how effective it is at blocking out light outside of the bandpass.  

Absorbing Glass Filters 

High-performance Anti-Reflective (AR) coatings that reduce reflection even at high angles can improve the performance of the LiDAR system by removing unwanted light.  Absorbing coatings and filter glasses can do this as well. Colored filter glass can block shorter wavelengths, which is especially useful for LiDAR. LiDAR technology often operates in the 850-1550 nm range, which means that colored glass can block any visible light that you do not want interfering with your system.   

Beam Splitters  

Optical design engineers use beam splitters for polarization management. LiDAR systems have an output channel and receiving channel, creating two sets of optics. Polarization tricks can combine those two channels into one by altering the polarization of the light as it goes out and comes back in. Beam splitter coatings, done correctly, can limit the number of optical components in a LiDAR system. Polarization rotators can do this also by rotating the polarization state, turning S into P.   

Mirrors and Other Scanning Module Optics   

If you look inside the optics of a scanning module, you are likely to find several specially placed mirrors. These mirrors reflect light within the scanning module, essentially moving the light into the correct focal path. Metal or dielectric mirrors are often used, since they reflect well over varying angle ranges.  

The Andover Advantage: Better LiDAR Through Advanced Optical Filters  

Andover Corporation specializes in creating custom optical filters and coatings for a variety of optical needs. For anyone looking to use LiDAR technology, Andover has the engineering acumen and production capability to optimize the performance of your systems.   

Standard, “off the shelf” bandpass filters often will not work for high-level LiDAR applications. With the right optics, Andover can address any design limitations and help to determine the best placement and design for your system, combining both mechanical and optical components.   

Andover has full-service capabilities for polarizing, beam splitting, and breaking up an optical signal for your desired requirements. As the leading expert in polarization management, Andover can ensure that your beam splitters and other polarization tools are used correctly. We can also increase the capabilities of the beam splitter, allowing it to do more than just splitting light.   

When you work with Andover, you can count on us to deliver the quality that you require and, assist with custom assemblies and the alignment of your optics. If you want to learn more about how our experts can help improve your LiDAR system, contact us today.