Abstract
A line-scan hyperspectral system was developed to enable Raman chemical
imaging for large sample areas. A custom-designed 785 nm line laser based on a
scanning mirror serves as an excitation source. A 45° dichroic beam splitter
reflects the laser light to form a 24 cm × 1 mm excitation line normally incident on
the sample surface. Raman signals along the laser line are collected by a detection
module consisting of a dispersive imaging spectrograph and a CCD camera. A hypercube
is accumulated line by line as a motorized table moves the samples transversely
through the laser line. The system covers a Raman shift range of −648.7 to 2889.0
cm<sup>−1</sup> and a 23 cm wide area. An example application for authenticating
milk powder is presented to demonstrate the system performance. In 4 min the system
acquired a 512 × 110 × 1024 hypercube (56 320 spectra) from four, 47 mm diameter
Petri dishes containing four powder samples. Chemical images were created for
detecting two adulterants (melamine and dicyandiamide) that had been mixed into the
milk powder.
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