Understanding Hyperspectral Imaging and its Applications
Hyperspectral imaging is a technique combining spectroscopy and latest digital imaging technology imaging, where each image is acquired at a narrow band of the electromagnetic spectrum. As an example, the human eye sees light in three bands (red, green and blue) of the visible spectrum while hyperspectral imaging divides the spectrum in more bands, typically covering the visible and near-infrared range.
The term hyperspectral imaging refers to the continuous acquisition of narrow bands (< 10 nm) across the electromagnetic spectrum. With unique technology from Photon etc., we are able to obtain bands of 2nm-4nm wide and even 0.3nm. On the contrary, multispectral imaging covers only a discrete number of bands, and is often performed with a filter wheel.
With hyperspectral imaging, you can find objects, identify materials, and detect processes within a given image. Through the analysis of the spectral and spatial information contained in each pixel of the image, it is possible to identify unique spectral signatures and assign them to the components of the sample under investigation. For example, the material or tissue analyzed can be mapped according to its molecular components.
A Deeper Look at Hyperspectral Imaging
For each of the individual pixels in an image, the use of a hyperspectral camera allows viewers to acquire the light intensity (or radiance) from a wide array of contiguous spectral bands. Each pixel in the image contains a continuous spectrum of light that can be used to characterize the objects in the image with a great deal of precision and detail.
The human eye, for comparison's sake, can only see colors of visible light across three bands. Hyperspectral imaging advances camera technology to capture and record far more spectra, and can be programmed to ranges from 380 nm to as high as 2500 nm.
A normal camera can only capture three separate spectral channels that correspond to the primary visual colors of red, green, and blue. A hyperspectral camera, by contrast, can capture a larger number of color variances from a few tens to several hundred. This provides for vastly improved classification of the objects in the image based upon individual spectral properties.
Advances in Hyperspectral Cameras
Hyperspectral cameras, like many other photographic technologies, was once limited to bulky equipment with limited applications in the field. However, there are exciting advances available in hyperspectral imaging that resulted in the development of smaller, powerful, and more mobile hyperspectral cameras.
Hyperspectral imaging is changing the way photographs are analyzed, revealing levels of detail never before seen by the human eye. Across a variety of industries, hyperspectral cameras are helping to improve the world by securing food chains in various nations, improving the viability of seeds and yield of annual crops. The healthcare field can now detect diseases earlier, improving the ability of doctors to effectively treat patients and increasing the lifespan of those patients with earlier detection.
Hyperspectral Camera Ranges
Whereas the human eye sees the color of visible light in mostly three bands (red, green, and blue), spectral imaging divides the spectrum into many more bands. HSI offers a straightforward way to monitor the quality of TV and computer screen, tablets and cell phones.
This technique of dividing images into bands can be extended beyond the visible. In hyperspectral imaging, the recorded spectra have fine wavelength resolution and cover a wide range of wavelengths:
VIS cameras (380 - 800 nm)
VNIR cameras (400 - 1000 nm)
NIR Cameras (900 - 1700 nm)
SWIR Cameras (1000 - 2500 nm)
MWIR Cameras (3 - 5 µm)
LWIR Cameras (8 - 12.4 µm)
Applications of Hyperspectral Imaging
There are countless examples of viable applications for hyperspectral cameras. The number of industries which could benefit from the advances in hyperspectral imaging include, but are not limited to the following:
- Forensic Science
- Water Control & Purity
Even within these individual fields, there are varying specific examples of how hyperspectral imaging can be used to the benefit of multiple parties.
Take, for example, medical and healthcare fields. Providers and drug manufacturers can use hyperspectral imaging to analyze wounds and detect illegal counterfeits. Patients benefit from receiving safer, more accurate care for their medical needs. The following will focus on some of the specific applications of hyperspectral technology.
Hyperspectral imaging can be used to help detect diseases earlier than other technologies, helping doctors catch severe issues such as cancer before the disease progresses to a critical stage. This enhances the ability of doctors to treat a patient before the disease becomes too advanced, which not only increases the odds of survival but also improves the overall health of the patient in questions.
There is already great use of hyperspectral cameras in the pharmaceuticals industry. The cameras are used by in large to enhance quality control within the industry by examining pills and packaging to detect counterfeit of illegal drugs, while also increasing the security of the packaging and the actual mixture of powders within certain drugs.
Fake Pharmaceutical Sample Detection
Hyperspectral imaging can clearly visualize substituted tablets.
The agricultural field might offer one of the most diverse applications of hyperspectral imaging. From planting of seeds and land preparation to the food that results from farming, hyperspectral cameras have a big role to play in securing food chains around the world. In the case of the finished product, hyperspectral imaging can be used to analyze the quality of food before it reaches market.
- Detecting bruises on an apple
- Determining the freshness of fish
- Inspecting citrus fruits
- Evaluating the distribution of sugar in melons
- Sorting potatoes
Taking this example a little further, hyperspectral cameras can be used to detect bruises on an apple that aren't yet visible. In this early stage, the bruise can exist without visible signs and take days to show an actual dark color mark. Hyperspectral imaging enables quality control to catch that bruise before it is visible.
As already alluded to, hyperspectral technology has a lot of benefits to offer the agricultural industry. It can also be used in seed viability studies. Using a hyperspectral image, seed providers can determine the viability of seed before it is even planted. Even the health of crops in the field can be determined using hyperspectral imaging. Farmers can get real-time solutions to monitor the vigor and disease-resistance of high-value crops to track progress and health as it grows.
Hyperspectral imaging is a powerful tool to monitor food quality, composition and attributes. It can be used to verify food safety and manufacturing consistency.
Hyperspectral cameras can also be used by military and law enforcement agencies around the globe with great benefit. One of the leading uses of hyperspectral imaging in defense has to do with the removal of landmines from conflict zones around the globe. The possibility for landmines not only renders usable land unusable, it poses a significant risk to the individuals living in the area who have no idea of their location.
Law enforcement can use hyperspectral imaging in concert with remote sensing to locate illegal drug farms around the globe. Regardless of the size and scale of various illegal farms around the globe, hyperspectral imaging gives law enforcement the power to detect anomalies and boost drug prevention efforts by tracking down farms to eliminate the problem at the source.
Due to the fine spectral resolution of hyperspectral imaging, this camera technology allows forensic laboratories to perform detailed analyses of varying types of content. These labs can now more accurately question document viability, aid in arson investigations, compare fibers, and more accurately determine gun powder residue existence.
Last, but certainly not least, hyperspectral imaging can be used to aid in environmental monitoring. In an era of increased concern regarding global climate change, hyperspectral cameras aid environmental monitors in the task of tracking changes to the environment. The technology can be used to track and better understand the accumulation of surface CO2 emissions, map water formations around the globe, and track the source of pollution to various regions around the world.
Hyperspectral imaging was originally developed for the mining and geology industries. It is an ideal method for identifying commercially valuable minerals in core samples or identifying the presence of ore or oil.