Spectral Imaging describes a spectroscopic image acquisition and analysis method, which combines spectroscopy,
high resolution CCD imaging and computing to delineate the way light reacts with a sample, in order to quantify and
analyze information that might otherwise be missed. The underlying principle is the simultaneous measurement of
the detailed spectrum of every point of a given area (surface), or more specifically of each pixel of a given CCD array.
Spectral Imaging can be used to obtain fluorescence or brightfield spectra, such as absorption, transmission, or
Spectral imaging displays an image and measures its spectra at every point in the image.
Its advantage is that this spectral information lets you distinguish between materials that appear identical.
GenASI’s Spectral platform, the SpectraCube ®, can be considered as an extensive enhancement of the famous
Fourier transform infrared (FTIR) spectrometer. While a FTIR measures a single spectrum by using an interferometer,
the SpectraCube ® uses the same principle to measure many spectra, one for each point in the image. The system
can be attached to a microscope, telescope, lens or any other fore-optics.
The core of the SpectraCube ® system is a common path Sagnac interferometer mounted on a rotatable disk and a
CCD camera is coupled to the system for image registration. The sensitivity range of the spectral image measurements
follows the sensitivity of the camera chip and allows measurements between 400 and 1.000 nm, thus covering the
completely visible as well as the near infrared range (NIR) of the light. A maximum spectral resolution as good as ~2 nm
at short wavelengths increasing to ~25 nm towards the near infrared range can be achieved.
The unique and proprietary design of the SpectraCube ® allows the simultaneous processing of the entire input image
without the need for sequential spatial scanning of the sample or the sample illumination.
In short, the light beam which enters the triangular interferometer is meeting a beam splitter which splits the beam into two
beams (a transmitted and a reflected beam), which are then travelling in opposite directions but in the same path in space
(common path interferometer) between the mirrors of the interferometer. At the exit, the two beams are united again with
an optical path difference (OPD) which is a function of the angle between the incoming beam and the interferometer itself.
The interferometer forms interference fringes at infinity, so that they show up on the CCD focal plane as lines of intensity
modulation superimposed on the image of the sample. When scanning the interferograms (by rotating the interferometer
in small angles), the fringes sweep across the image, but the image itself does not move. Therefore, each pixel of the
CCD correctly collects the interferogram that belongs to the spectrum of the corresponding pixel area of the object itself,
and the CCD data are collected for each position of the interferometer rotation. At the end of the measurement, the system
computes the Fourier transformations to all the pixels (using FFT procedures) with the standard Fourier-analysis
methodology for achieving the best spectrum.
With ASI's SpectraCube®, for example, you can distinguish between different materials even if they look identical. Here, in the
image below, on the left, it is difficult to differentiate between the red dyes. In the image on the right, the three dyes are classified
by the SpectraCube® and then displayed in unique colors. SpectraCube® reveals crucial information that no
other technique can display.
A. Color image
B. Color image after SpectraCube
Three types of red dye were used to stain these chromosomes. (image A.) With the SpectraCube® technology, each dye is displayed as a unique color. (image B.)
One of the applications for the GenASIs Spectral Platform is the SpectraView. This application allows the user to
What is SpectraView?
digbeneath the surface of a sample to identify its true physical and chemical characteristics.
Discover the concealed details that reveal the full picture; you define the areas of interest and SpectraView does the rest.
SpectraView harnesses the way light reacts with a sample in order to quantify and analyze information that might otherwise
be missed. Ultra-accurate quantifications allow the physical and chemical properties to be quickly and
categorically identified, characterized and verified.
What Does SpectraView do?
Uncover chemically similar areas hidden to the eye. Create color-coded maps of chemical similarities
and differences. Compare the chemical makeup of components between different images.
Automatically select areas according to spectra and intensity. Quantify each selected area according to intensity,
area and other parameters.
Separate components to view them as individual image layers. Show or hide image components to view
underlying information. Verify results by displaying the spectral match of each image layer with a reference library.
Enhance images automatically with brightness and contrast tools before using them in customized reports
that include images and notes. Connect with ASI's Database, Case Data Manager, and export the information
to common spreadsheet formats.