NIR hyperspectral imaging

An alternative approach for NIR hyperspectral imaging to that described above is to use a Fourier transform NIR (FT-NIR) spectrometer. As the design of FT-NIR microspectrometers is more similar to that of instruments for mid-lR hyperspectral imaging than the dispersive instruments described above, they will be described later (see Section 1.6). 

When Should NIR Hyperspectral Imaging be Used in Food and Agricultural Products ... 

This leads to two main types of use for NIR hyperspectral imagers ... 

Descriptions of these two families of NIR hyperspectral imaging usage are provided in the following sections, together with example applications that illustrate today s state-of the art technologies and methodologies. 

Among the above-described advantages of NIR hyperspectral imaging in on-line settings, we can include the following ... 

Within 10 years of the first attempts to use NIR multispectral or hyperspectral imaging for food products, prodigious advances have been achieved such that NIR hyperspectral imaging is now commonly used in both laboratory and on-line applications. Yet, this outstanding technique continues to raise many questions that must be addressed before it is more widely accepted. Such questions relate not only to the hardware and data processing but also to specific issues related to NIR imaging. 

With the introduction of more economical, large-format (320 x 256 pixels) FPA detectors, NIR hyperspectral imaging was also developed into an important tool in selected industrial areas such as the evaluation of food quality (see Chapter 8) or in the pharmaceutical industry. Most likely, the delay in implementation of NIR... 

The NIR hyperspectral images were recorded on a MatrixNIR system (Malvern, formerly Spectral Dimensions, Olney, MD, USA) (see also Figure 9.1) with four... 

Methods for improving image quality and reducing data load of nir hyperspectral images. Sensors 2008, 8,3287-3298... 

Figure 9.23. Schematic of the NIR hyperspectral imaging system for detecting bruises on apples (29).

Wavelength scanning in NIR hyperspectral imaging spectrometers has also been accomplished with both a scanning monochromator and an acousto-optic tunable filter (AOTF). AOTFs are electro-optical devices that function as electronically tunable filters. They rely on a birefringent crystal, the optical properties of which vary upon interaction of the crystal with an acoustic wave. The resulting... 

The NIR hyperspectral imaging spectrometers marketed by Malvern Instruments are equipped with a Stirling-engine-cooled indium antimonide (InSb) FPA detector with 320 pixels in one dimension and 256 pixels in the other (total 81920... 

For short-wavelength NIR spectra (950-1720 nm), where the absorption bands are caused by transitions to the third or fourth vibrational states of C-H, N-H, and O-H stretching modes, along with weak combination bands, the situation is even worse because bands are so weak that the sample thickness must be increased to about 500 pm, even though the diffraction limit is less than 2 pm. It is at least, in part, for this reason that NIR hyperspectral imaging is rarely used for measurements with very high spatial resolution. Thus, for example, the standard... 

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