How Hyperspectral Imaging Works

And The Instruments that
Make It Happen

"Analytical Hyperspectral Systems Convert
Spectral Signatures Into Targeted Maps"

Hyperspectral Imaging
Hyperspectral imaging (HSI) originated in the remote Earth sensing community. The goal then, as now, was to convert spectroscopic data into an information-rich image. Landsat, other satellites, and fixed wing aircraft are highly successful uses of Hyperspectral Imaging for remote sensing.

It is well known that most objects present spectral information that correlate well enough to be considered a " fingerprint". Hyperspectral imaging acquires "spectral fingerprints" and creates a spectral "topographical" map showing target spectral objects, or conditions, on a grayscale field of view.

There are two Hyperspectral Imaging methodologies
1. Electronic bandpass filters that characterize a fixed field of view, by acquiring wavelength data sequentially. The instrument is typically a sensitive camera, such as a CCD, with the "Filter Flipper" located between a focusing lens and the camera chip.

Every camera pixel accumulates a wavelength data point (WDP). If 50 filters are needed to obtain the necessary information, then each pixel will step through and acquire 50 WDP.

Electronic tunable filter (ETF) hardware includes:

  • Liquid Crystal Tunable Filters (LCTF),
  • Acousto Optic Tunable Filters (AOTF) or an
  • Interferometer (In this case filters are not involved, but wavelengths are still acquired sequentially over a fixed field of view)

ETF instruments when used in the life sciences typically:

  • Acquire relative, not analytical data.
  • Rarely if ever calibrated or validated for wavelength accuracy
  • In instruments designed for use in the life sciences, it is unlikely that they compensate for variations in camera sensitivity (QE) as a function of wavelength.

Electronic Tunable Filters do not acquire analytical "spectroscopic" data that can quantify differences between objects, or conditions.

2. Wavelength Dispersive Imaging Spectrometers (WDSI) systems use a diffraction grating or a prism to acquire wavelength accurate analytical spectral data in one or other of the following formats:

  • Absorption (measured in optical density)
  • % Reflection
  • Fluorescence
  • Luminescence, phosphorescence, auto-luminescence...
  • Scattered light. Typically in "Dark-field" often used for characterizing nanoparticles.
  • Instruments, such as the PARISS Hyperspectral Imaging System, can be rendered "radiometric" to compensate for variations in wavelength sensitivity (QE) of the camera.
  • Can validated using spectroscopic standards

WDSI instruments acquire all wavelength information simultaneously and acquire an unlimited field of view sequentially

To learn more play the interactive presentations below

Click here for the PARISS Interactive Presentation

      
  Hyperspectral imaging
  Hyperspectral instruments
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