SPECTRAL IMAGING FOR RESEARCH
Hyperspectral imaging is used increasingly in many research areas, such as life sciences, vegetation research, precision agriculture, forensics, food and feed analysis, mineral exploration, and for developing new recycling research methods. In each application area, a spectral camera is used to identify, measure, and map the biological, chemical, and physical properties of the objects.
Fluorescence map by Forschungszentrum Jülich
BENEFITS OF SPECTRAL IMAGING
Hyperspectral imaging offers reliable and highly advanced tools for researchers and scientists as well as different governmental authorities and decision-makers. It is a fast, accurate, reliable, and multidisciplinary way to analyze and test targets from minor samples to large areas in a non-invasive, non-destructive manner, which makes it an excellent research tool.
Over the last few years, hyperspectral cameras and systems have become more and more compact, economical, and more comfortable to use. In addition to traditional chemometric methods, the development of artificial intelligence has enabled data processing and analysis methods like neural networks to be used for hyperspectral data interpretation. Hyperspectral technology is now well available for scientific research with excellent performance – to – cost ratio with supporting robust analysis tools.
Hyperspectral imaging expands traditional optical spectroscopy from instruments measuring a single spot at a time to a rapid analysis of non-homogeneous samples and targets. Single-camera operating in a specific wavelength range can be used for various applications like in food research to measure fat, moisture, or protein distribution, or in geology to map the distribution of different minerals on a geological site. The same camera can also be applied in various environments: in laboratories, field, industrial pilot lines, and airborne. With the newest mobile, handheld cameras, the researcher can easily take it to the samples without the need to bring the samples to a lab system.
Both in research and practical applications, one of the critical benefits of hyperspectral imaging is the ability to detect problems early, allowing for preventive measures to be taken to limit and reduce possible damage or loss of quality in the final product, whether it was about the total yield of a farming site, detecting illegal logging or inspecting quality deviations in food production.
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SPECIM EXCELLENCE IN SPECTRAL IMAGING
For the last 25 years, Specim has been pioneering and leading hyperspectral imaging system development. More than a thousand scientific research articles have been published using Specim technology. Much research has been done with Specim products, especially on food science and environmental research.
Specim has the broadest spectral imaging product portfolio and covers wavelengths from visible and near-infrared to the thermal range. Specim spectral cameras are based on our proprietary line scan (push-broom) technology. This design selection ensures their flexible adaptability to different operating environments with no compromise on performance.
Another cornerstone in our spectral camera design is optimized performance to cost ratio. In addition to the spectral cameras, Specim offers standard scanner setups that enable fast sample data collection, application development, and validation in a laboratory or field.
Application transfer to an airborne environment is also straightforward and cost-efficient. As a result, Specim products are widely operated globally in laboratories, field experiments, and airborne missions.
Specim has excellence in designing and manufacturing ground-breaking products. The latest ones include SpecimIQ, launched in 2017, the first truly mobile hyperspectral camera with built-in data processing and analysis capability.
Several innovative Specim products have emerged from the needs addressed by the scientific community. The remote sensing system AisaIBIS is a good example. It was designed and validated together with Juelich Research Centre from Germany, as the Hyplant sensor, an airborne precursor for the European Space Agency’s (ESA) Earth Explorer program called FLEX. The project aims at providing global maps of vegetation fluorescence.
In 2019 Specim delivered a highly advanced multisensor system equipped with our standard AisaFENIX 1K, AisaOWL, and AisaKESTREL sensors to Diamond Aircraft as part of their airborne platform to the Government of Malaysia for forestry management. Most recently, in 2020, SPECIM launched the AFX series, a highly advanced hyperspectral system for airborne and UAV use. Being based on our market-leading industrial FX series cameras makes the AFX sensors very cost-competitive for drone applications.
The first use cases of hyperspectral imaging were remote sensing applications, but as the sensors became smaller and more affordable, the HSI use expanded to other application areas and locations.
Hyperspectral imaging offers advanced tools for environmental care or predicting, monitoring, assessing, and aftercare of different ecological catastrophes. Sensors available on a wide wavelength range enable the application of various parameters and variables indicating the state of the environment. Large-scale mapping of the environment is typically done satellite or airborne, and the application is often brought to field level for more details. When satellite imagery provides information with tens of meters resolution, airborne data can bring its level to 1 cm. With the latest drone-use developments, spectral imaging sensors can deliver data even on the sub-centimeter level.
Oil leakages and illegal deposits
Mineral-based fluids and materials have very distinctive spectra in SWIR, MWIR, and LWIR range. When these materials get loose in nature, they need to be identified fast to prevent potential danger to the environment. Airborne or field spectral imaging is often used for the purpose as it can detect contamination even when invisible to the eye.
Fire risk assessment
Airborne spectral imaging is an efficient tool for mapping fire risk power lines. Visually similar tree types and trees of different health status can be reliably identified based on their distinctive spectra. E.g., eucalyptus trees grow fast, and they contain a lot of highly flammable oil. By airborne spectral imaging, cost-efficient forest or power line management plan can be achieved based on real information on the distribution of tree species, their growth rate, and health status, thus allowing preventive measures to minimize fire risk.
Among infrastructure, different types of building materials and roof types pose the other kind of fire risk. Again, visually similar materials can be chemically very different. The presence and distribution of materials with higher fire risk can be efficiently and reliably mapped by airborne spectral imaging.
Water quality is one of the major global concerns. Algae infestations, the effect of chemical effluents by agriculture, and the widely recognized issue of microplastics are typical research questions where hyperspectral imaging can be efficiently applied.
Chlorophyll Map : Pawnee lake, Lincoln, NE, 6th June 2006
Vegetation and agriculture
Vegetation research and agriculture benefit from the scalability of the spectral imaging sensor technology from satellite to airborne and field use. In addition, greenhouse and laboratory use becomes relevant.
Both visible and NIR range are often used to map the plant or vegetation growth, health, and nutritional status. Chlorophyll absorbs light very efficiently until the so-called red-edge around 680 to 730 nm. Beyond 730 nm, much of the light reflects. On the other hand, the NIR range gives information, e.g., on the protein content of cellulose in the plants.
Precision agriculture is a farming management practice that aims to improve yields while minimizing the negative impacts of farming on the environment. Improved results are achieved by operating hyperspectral sensors to obtain information from the conditions in the field (e.g., the moisture content of the soil) in or near real-time. This information can then be used to apply the right amount of seeds, water, and chemical substances to suitable locations at the right time. Hyperspectral imagery acquired and analyzed during the growing season can be used to identify and address problems immediately before they become critical.
Spectral imaging is the most advanced and information-rich technology for detecting diseases in the early phase, weeds and pests, nutrient and water efficiency, and overall yield prediction. The benefits that spectral imaging offers to precision farming are reduced use of chemicals, reduced weed related losses, lowered manual inspection costs, and better yield quality for the higher selling price.
In addition to crops, insects and other pests can attack forests, leading to significant socioeconomic and ecological losses. These infestations can lead to discoloration of foliage and defoliation, eventually weakening and killing vegetation. However, visible damage to the vegetation is often irreversible by the time the human eye can detect it. Infested trees can accurately be seen using high-resolution hyperspectral data, helping to employ informed management strategies and mitigation measures to restrict the extent of the damage.
Hyperspectral imaging is a well-established method for measuring, inspecting, sorting, and grading food products in different stages of the supply chain as it gives reliable information in a rapid, non-destructive and hygienic way, requiring no sample preparation.
HSI is typically used to study food chemical composition, adulteration, ripeness, freshness, or bruising on various fruits and vegetables, seed classification, detection of foreign objects, or different varieties or blend identification. In comparison to many other technologies, hyperspectral imaging can detect all these quality parameters simultaneously. VNIR, NIR, and SWIR wavelength regions are commonly used for this purpose.
Moisture distribution in a fresh slice of bread. Image courtesy of Campden Bri.
The objective of mineral exploration is to find economically viable ore deposits. Short-wave infrared (SWIR; 1300-2500 nm) wavelength region data are commonly used for this end, but the VNIR wavelength region also offers two crucial geological applications:
- The detection of iron oxide minerals
- The detection of rare earth elements
Iron oxide minerals are essential for mineral exploration because they are often the only visible clues to the underlying mineral deposits. Iron oxide minerals have characteristic spectral features in the 800-1000 nm wavelength region, which can be used to identify them by remote sensing.
Iron oxide concentrations are associated with specific rock types (the “host rocks”), which are sometimes linked to potential ore deposits. Recent research has shown that hyperspectral imaging can be applied to classify iron oxide concentrations based on their host rock substrates, increasing the potential to detect rock outcrops that are most likely to be associated with ore deposits.
Rare earth elements (REEs) are a group of metallic elements that are indispensable for the manufacturing of high-technology products such as consumer electronics. These elements occur in certain minerals, and many can be identified due to their key spectral features located in the VNIR wavelength region. Remote sensing provides a potentially cost-saving tool for the exploration of economic concentrations of REE-bearing minerals.
Since hyperspectral imaging is a non-invasive, hygienic, and fast way to study the target, it is well suited in research where human well-being is involved. Hyperspectral imaging provides a reliable way to perform a chemical composition inspection of pharmaceutical products during the production process. This is particularly important with products that are visually similar but have different proportions of active pharmaceutical ingredient (API).
With hyperspectral imaging, each tablet or capsule can be quickly and reliably identified from their active ingredients. 100% of the products can be inspected online, in real-time.
The chemical analysis allows:
- Qualitatively to identify pharmaceutical products with different active principles.
- Quantitatively to identify pharmaceutical products with a different dosage, and to measure the uniformity of the active ingredient distribution.
Since hyperspectral imaging is a non-invasive, hygienic, and fast way to study the target, it is well suited in research where human well-being is involved and shows high potential as a diagnostic tool in medical applications. It helps to quickly and accurately identify the condition of the patient and then provide timely and appropriate treatment, reduce unnecessary surgeries, and shorten the duration of hospitalization.
Non-contact skin measurements with a spectral camera can give reliable information about tissue health through e.g., oxygenation and blood circulation efficiency, help in an open wound and burn wound diagnostics, and identify cancer tumors or blood circulation problems related to diabetes.
Finger occlusion and related blood volume fraction and skin blood saturation studied with a spectral camera
Art and Archeology
Preservation of cultural inheritance like paintings, manuscripts, maps, and old photos through documenting and transforming to digital form for archives, research, conservation, or for display is increasing remarkably. Museum laboratories and university researchers use a wider range of analytical instruments to study collections. There is a need to study, for example, materials like pigments, dyes, and binding media. These are not only to observe possible degradation or changes due to aging or environmental conditions but also to reveal the artist’s painting technique and methods used in the work of art.
Hyperspectral imaging (HSI) is gaining wide acceptance as one of the most valuable optical tools for art archiving and restoration. As a non-invasive and non-destructive imaging technique, hyperspectral imaging is safe for even the most fragile samples. It is used remotely to scan all parts of the sample with a high spatial resolution (down to 15 µm pixel size). HSI records both spatial and spectral information, which can be used to classify the chemical, physical, and/or biological properties of the object.
In the visible range, it gives improved precision in color measurement for recording pigment color-change, which is essential for conservation. In near-infrared, the information hidden behind the outer layer or written text that has deteriorated and faded under environmental conditions may be revealed. Besides, fluorescence investigation is prone to highlight different solvent and binders.
Above all, there are many other applications and application fields where Specim cameras are and could be used. Specim keeps this in mind, providing researchers with performant and highly flexible instruments, allowing scientists to break the boundaries of the current knowledge. To ensure customer success, Specim also offers well established after-sales support as well as online and onsite training concepts based on customer needs.
Much of the hyperspectral imaging is done in laboratories, where the conditions can be reliably regulated. This requires a specific setup, at least:
- HSI sensor
- Data-acquisition computer
Specim offers several turn-key laboratory scanner systems for exploring different size samples. As most Specim cameras can be equipped with different front optics, the scanning systems can be optimized to analyze the samples at a required resolution, starting from a micrometer scale.
The scanner systems are easy to use as they are delivered with proper illumination for the specified spectral range. A single software provides a user interface to control the camera parameters, automatically collects image data with correct aspect ratio, and makes both raw and reflectance data available immediately after the scan.
Sometimes it is not feasible to take the targets to the laboratory. Instead, the measurements are done in the field conditions, which set specific requirements for the hyperspectral imaging equipment.
In the field conditions, ambient light typically makes the illumination (sunny conditions being optimal for collecting reflectance data), though artificial illumination may also be an option. For field/outdoor use, Specim offers the spectral camera with a radiometric calibration. Applying the calibration to the collected data will provide the highest image data quality and allows us to measure the actual spectral radiance from the target. To further obtain reflectance data, there are two options. Either apply an atmospheric correction or have a known reflectance reference plate in the imaged scene.
A line-scan spectral camera is usually installed on a rotary stage for imaging a stationary target from a stationary camera position. Like the linear laboratory scanners, Specim rotary scanner systems provide automatic data collection with the scan. As Specim spectral cameras are robust, it is also possible to install the cameras on vehicles or move them with cable sliders.
The Specim IQ camera is the most compact and mobile option for fieldwork. It provides all the line scan (push-broom) advantages in a handheld device without any external scanner as the scanning mechanism is integrated into the camera. Additionally, the IQ camera includes the capability to obtain processed results immediately after the data collection, based on a processing model uploaded in the camera.
Any material that is detectable either directly or indirectly based on its spectral features can be mapped with an airborne hyperspectral camera. The point of airborne hyperspectral imaging is in creating a material map of the study area, land, or water surface. Taking the sensor in the air gives you a vantage point to search these materials, plant species, etc. from the much larger area than what is immediately visible on the ground – easily hundreds of square kilometers, only limited by altitude and time spent flying.
Specim offers turn-key airborne systems to cover all the spectral regions from visible to thermal infrared Most of our cameras, originally obtained for lab or field can also be upgraded to full-scale airborne systems. Being based online scan camera(s) and fully calibrated, Specim systems suit ideally for airborne data collection and provide the highest image quality, spectral purity, and signal-to-noise ratio.