An important advancement in the field has been accomplished by a research team from the Institute for Laser Technology in Japan, headed by Toshihiro Somekawa. They developed a small hyperspectral imaging lidar system to identify and detect different plastics remotely. The monitoring and management of plastic pollution could be completely transformed by this invention, opening the door for more effective environmental protection initiatives.

An increasing environmental issue, plastic pollution has a disastrous effect on human livelihoods, marine ecosystems, and sectors like shipping, tourism, and fishing. In order to properly measure the amount, concentration, and distribution of plastic pollution in rivers and oceans, new monitoring techniques needed. There is a pressing need for more effective solutions because, despite their accuracy, traditional lab-based approaches, frequently expensive, time-consuming, and labor-intensive.

Innovative for Raman Hyperspectral Imaging Lidar System

The researchers’ novel approach, described in the journal Optics Letters from the Optica Publishing Group, combines lidar technology with hyperspectral Raman spectroscopy to detect plastic remotely. This device makes it possible to remotely identify plastics up to six meters away, in contrast to conventional techniques that necessitate physical contact with samples. It is perfect for drone-mounted applications because of its small size and low power consumption, which increases its applicability in a variety of settings.

“A drone equipped with our lidar sensor can use to assess marine plastic debris on land or in the sea, paving the way for more targeted cleanup and prevention efforts,” stated Somekawa. The technology has the potential for use in monitoring applications other than plastic detection, like identifying dangerous gas leaks.

Innovations and Challenges in Remote Detection

Traditional Techniques’ Drawbacks

Manual collection and lab-based analysis are common components of traditional marine plastics monitoring methods, which are inefficient and not scalable. There have been issues with even earlier lidar systems. For example, the same research team previously demonstrated a flash Raman lidar approach that used bandpass filters suited to particular measurement goals. However, the technique was not feasible for monitoring marine plastic in the real world since it required changing filters for every target, which hampered fast three-dimensional range and detection.

Another viable remedy, Raman Hyperspectral Imaging Lidar System, has also encountered many obstacles. This method produces comprehensive molecular composition maps of samples by fusing imaging and Raman spectroscopy. However, the inability of traditional systems to detect targets at a distance restricts their use for distant marine environment monitoring.

The Solution for Hyperspectral Raman Lidar

The researchers used hyperspectral Raman spectroscopy in conjunction with lidar’s distance measurement capabilities to get around these obstacles. This hybrid method preserves the accuracy of conventional Raman imaging while enabling remote detection. The prototype system consists of a two-dimensional imaging spectrometer with a gated intensified CCD (ICCD) camera and a pulsed 532-nm green laser for lidar measurements. The system can concurrently record spectral and spatial information thanks to this sophisticated configuration.

In range-resolved measurements, the pulsed laser is essential because it enables the system to discriminate between targets at different distances. The system’s capacity to record fine-range resolutions is improved by the ICCD camera, which can function on a nanosecond time scale. Therefore, even at considerable standoff distances, the Raman hyperspectral imaging lidar system can generate detailed images and spectroscopic data on plastic debris.

Prototype Testing: An Exhibit of Precision

A plastic sample with a polyethylene film over a polypropylene sheet used in a series of experiments by the researchers to verify the system’s functionality. The technology effectively obtained the distinctive spectra of every type of plastic from a distance of six meters. The system’s capacity to distinguish between materials based on their distinct Raman spectra was demonstrated by the generated photos, which clearly showed the vertical distribution of the plastics.

The ICCD camera’s imaging pixel size of 0.29 millimeters at a 6-meter standoff distance implies that even tiny plastic trash can precisely measured and examined. This degree of accuracy is especially useful for tracking microplastics, which represent a serious hazard to marine environments and are notoriously hard to find using traditional techniques.

Applications and Potential for the Future

Monitoring of Marine Plastics

Monitoring marine plastic pollution is the main use for the Raman hyperspectral imaging lidar system. The technology, which is mounted on a drone, can use to measure plastic litter in water or on land by flying over rivers, seas, and coastal regions. Its real-time data on the kind, size, and distribution of plastics allows for more focused cleanup operations and helps guide pollution control plans.

Identification of Microplastics

In order to detect microplastics floating or immersed in water, the researchers currently concentrating on modifying their method. The system’s capacity to detect microplastics in aquatic environments improved by the employment of a 532-nm laser, which transmits efficiently through water. Our knowledge of microplastic contamination and its effects on human health and marine life may be greatly enhanced by this development.

More Comprehensive Environmental Monitoring

The hyperspectral Raman imaging lidar system may find use in various environmental monitoring domains besides plastic detection. It can be use, for instance, to monitor the health of vegetation, evaluate air quality, or find dangerous gas leaks. It is a useful tool for tackling a variety of environmental issues because of its portability and versatility.

Benefits Compared to Existing Methods

Compared to conventional techniques and earlier technologies, the  Raman hyperspectral imaging lidar system has the following significant advantages:

• Remote Detection: By removing the requirement for direct sample contact, the technology makes it possible to remotely monitor plastic pollution in locations that are difficult to access.
• High Precision: Even at the microscale, the incorporation of hyperspectral Raman spectroscopy enables thorough chemical analysis and plastic-type identification.
• Scalability: It may deployed on drones because of its small size and low power consumption, which makes it possible to conduct extensive monitoring operations.
• Real-Time Data: By offering immediate results, the system cuts down on the time and effort needed for conventional lab-based analyses.
• Versatility: The system can modified for additional environmental monitoring applications in addition to plastic detection, expanding its use in a variety of domains.  

Conclusion

In combating plastic pollution, the development of the Raman hyperspectral imaging lidar system is a major advancement. This approach overcomes significant drawbacks of conventional monitoring techniques and creates new opportunities for environmental conservation by enabling remote detection and identification of plastics.

It is likely that the system’s influence on marine conservation initiatives will increase as the researchers continue to improve it and investigate its potential for microplastic detection. This cutting-edge technique may be crucial in addressing a variety of environmental issues and opening the door to a cleaner, healthier world, with uses going beyond plastic monitoring.