spectral imaging

spectral image acquisition, X-ray, radiology, photon-counting computed tomography, microscopy, hyperspectral imaging

Spectral imaging uses multiple bands of the electromagnetic spectrum and incorporates a variety of techniques that go beyond human-perceivable light RGB. Appropriate cameras, unlike conventional cameras, do not image the three wavelength regions of the visible spectrum - red, green and blue, but map other regions of the electromagnetic spectrum, such as infrared, ultraviolet, X-rays or a combination of different spectral regions.

Multispectral imaging captures a small number of spectral bands by using different filters and illuminations. For example, a scene can be illuminated with near infra red (NIR) light, and at the same time an infrared pass filter can be used on an infrared-sensitive camera to ensure that visible light is blocked and only NIR is captured in the image. This technique is often used in detecting or tracking military targets and in land mine detection.

Hyperspectral imaging is characterized by a high spectral resolution and involves the combination of spectroscopy and digital photography. It acquires a full spectrum or a portion of the spectral information at each pixel in an image plane. For each pixel, hundreds of wavelength bands can be acquired, which are interpreted as a full spectrum and often represented as an image cube.

Spectral imaging is used in astronomy, solar physics, planetology, space-based imaging, weather forecasting as well as in microscopy, document and art conservation.

Comparison of multispectral / hyperspectral image acquisition techniques. The upper row shows classic setups (1D scan, 2D scans and full 3D capture), below are common alternative approaches using sparse sampling, titlted sampling, multiple cameras or regular RGB cameras.
Comparison of multispectral / hyperspectral image acquisition techniques. The upper row shows classic setups (1D scan, 2D scans and full 3D capture), below are common alternative approaches using sparse sampling, titlted sampling, multiple cameras or regular RGB cameras.

Image Source:

Lucas Bosch, licensed under the Creative Commons Attribution-Share Alike 4.0 International license.