WHAT IS HYPERSPECTRAL IMAGING?
In this tutorial we will shortly introduce what hyperspectral imaging is.
A good way to work with materials, identify them or define their properties is to study how light interacts with them. This study of light interaction with materials is called spectroscopy. Spectroscopy examines how light behaves in the target and recognizes materials based on their different spectral signatures.
These spectral signatures can be identified from the spectrum of the material. Spectrum describes the amount of light in different wavelengths. It shows how much light is emitted, reflected or transmitted from the target. To put in short, the spectrum tells how much of certain color this light contains.
The usual way to present spectrum is a graph on a scale of intensity and wavelength.
Spectral signatures can be compared to fingerprints. Since every material and compound reacts with light differently, their spectral signatures are different too. Just like fingerprints can be used to identify a person, spectral signatures can be used to identify material.
Let’s examine the reflected light in more detail. To study the light one needs an instrument called a spectrometer. It’s an instrument that splits the incoming light in to a spectrum. In this example, the light going through a spectrometer is reflected, and the result is therefore called a reflectance spectrum. Measuring the reflectance spectra is the most common way to use hyperspectral imaging.
Hyperspectral imaging uses an imaging spectrometer to collect spectral information. This device is also called a hyperspectral camera. With hyperspectral camera we are measuring thousands or hundreds of thousands of spectra, Instead of single spectrum. The collected spectra are used to form an image of the target, in a way that each image pixel includes a complete spectrum. By doing this we are able to get answers to questions what, based on the spectrum and where, based on the location. We can pick any position from the target to get the information.
This means big amount of accurate information. The data that hyperspectral imaging provides is called a data cube because the hyperspectral data is actually three dimensional. We will use a book example in the next tutorial called What hyperspectral imaging provides, to explain it.