OSA: Measurement of LiDAR Testing Light Source for Autonomous Driving

Autonomous vehicles (AVs) are transforming transportation, turning futuristic dreams into present-day reality. The global market for AVs is fueled by advances in AI and sensor technology. A key technology in this application is Light Detection and Ranging (LiDAR), essential for precise, real-time 3D mapping and navigation. Companies worldwide are heavily investing in LiDAR R&D, testing, and manufacturing, to ensure their AVs can safely and effectively interact with the environment. This investment is driving rapid innovation, bringing us closer to a future shaped by self-driving cars.

LiDAR for autonomous driving 

Understanding LiDAR Technology

LiDAR works by emitting laser pulses to measure distances, enabling the detection of obstacles and navigation. Elon Musk has criticized LiDAR, favoring a camera-centric approach due to cost and complexity. However, many companies rely on LiDAR for safety and redundancy in their self-driving systems. The debate over LiDAR's role in autonomous driving remains ongoing as the industry continues to evolve.

LiDAR technology operates on the principle of Time of Flight (ToF), where it measures the time it takes for laser pulses to travel to objects and back. From this data, LiDAR generates a detailed 3D map of the environment, including the location, size, and movement of objects. These maps assist vehicles to navigate safely, as they provide information about obstacles, pedestrians, lane markings, and other features in the surroundings.

LiDAR uses a pulsed infrared laser. The main laser wavelength is 800 to 900 nm, but LiDAR using the 1550 nm band laser, which is superior in terms of high output and low cost, is also under development. An optical spectrum analyzer is required to characterize these lasers.

Testing LiDAR Light Sources

While high-resolution mapping and precise object detection are imperative for safe navigation, companies face constraints such as optical power and scanning speed. The level of available optical power directly impacts accuracy; however, higher power also escalates operational costs. Additionally, scanning speed is critical for real-time data acquisition, yet it must be managed cautiously to avoid safety hazards, especially concerning laser frequencies harmful to human eyes.

LiDAR Test Using Optical Spectrum Analyzers

An optical spectrum analyzer (OSA) is used in LIDAR laser testing, offering detailed insights into the optical characteristics emitted by the laser. Here's how an OSA is typically used for LIDAR laser testing:

• Wavelength Analysis: OSAs precisely measure the laser's wavelength, ensuring accuracy for specific LIDAR system requirements.
• Wavelength Stability: OSAs monitor wavelength stability over time to ensure consistent and reliable distance measurements.
• Power Measurement: OSAs assess optical power to verify compliance with safety standards and system performance requirements.
• Spectral Characteristics: OSAs provide insights into spectral characteristics like linewidth and spectral width, essential for assessing laser coherence and accuracy.
• Noise Analysis: OSAs detect and analyze noise in the laser beam, optimizing system performance and minimizing measurement uncertainties.

Optical spectrum measurement of laser for LiDAR

Some OSAs aren't well-suited for LiDAR testing. When selecting the appropriate OSA, it's important to opt for a model compatible with a broad spectrum of wavelengths and capable of accommodating large diameter free space inputs.

LiDAR systems utilize pulsed infrared lasers. Most commonly, the main laser wavelength falls between 800 to 900 nm (infrared), with some LiDAR systems that employ the 1550 nm band laser (short wave infrared. Each wavelength range offers tradeoffs with respect to target reflectance and absorbance, background radiation, atmospheric transmission, and eye-safety.

Additionally, OSA’s are often used in combination with an optical power meter (i.e AQ2200 modular manufacturing test platform) for manufacturing acceptance and shipment inspection of laser parts.

In summary, OSAs are invaluable tools for characterizing and validating the laser's properties, ensuring the accuracy, stability, and safety of the LIDAR system.

Find the Right OSA for LiDAR Testing

Effective LiDAR signal analysis necessitates Optical Spectrum Analyzers (OSAs) with sufficient sensitivity and dynamic range, especially in challenging atmospheric conditions like fog and rain. All Yokogawa OSAs are equipped with grating technology, ensuring superior sensitivity down to -90 dBm. Additionally, the wavelength ranges commonly used in LiDAR (800-900 nm and 1550 nm) precisely align with communications signals. Leveraging over 40 years of experience in communications testing, 6 out of 8 OSA models cover at least one of the LiDAR wavelength ranges. Moreover, our OSAs feature built-in pulsed laser analysis, ensuring consistent and standardized results across the industry.

6 out of 8 OSA models cover LiDAR wavelengths

 

FAQs about OSAs and LiDAR testing

What can LiDAR not detect?

LiDAR has limitations in detecting transparent objects like glass or water, mirrors, fine details smaller than sensor resolution, subsurface features, materials with low reflectivity or high absorbance, and adverse weather conditions such as heavy rain, fog, or snow.

What are the three types of LiDAR?

The three main types of LiDAR are airborne, terrestrial, and mobile. Airborne LiDAR, mounted on aircraft or drones, captures data for large-scale mapping, forestry management, and urban planning. Terrestrial LiDAR, stationary or mobile, is used for detailed mapping of smaller areas like building interiors and archaeological sites. Mobile LiDAR, installed on vehicles or boats, captures data while in motion, commonly used for mapping roadways, railways, and city streets.

What does LiDAR stand for?

LiDAR stands for Light Detection and Ranging.