54 R&DMagazine October 2013 www.rdmag.com
Trends in Optical Spectroscopy
As applications for optical spectroscopy expand, instruments keep pace.
Innovations in optical spectroscopy have helped the technology reach a point where performance previously seen only in laboratory settings can be obtained in the field with compact and easy-to-use systems. These improvements, made to detectors, software and overall design,
have greatly affected instrument characteristics such as speed, miniaturization, price and reliability.
As a result, optical spectroscopy has become important for many new
applications. For example, short-wavelength infrared (SWIR) systems
have proven highly effective in sorting, grading and quality control for
material identification and continuous monitoring of a production line.
These systems provide the ability to use faster, wider conveyor belts, or
inspect more complex and varied materials. Multichannel systems, such as
the HyperChannel technology used in the 2012 R&D 100 Award-winning
Hyperspectral Multichannel Spectrometer from P&P Optica, Waterloo,
Ont., are ideally suited for applications where spectrally similar materials
can be distinguished and sub-pixel-scale information can be extracted in
the presence of strong background signal. The small form factor and flexibility of this type of spectroscopy system allows for bedside examination
of patients repetitively or monitored continuously for a long period of
time. Spectroscopy systems are providing more signal, allowing users to
detect more, see more and do more.
Furthermore, access to improved components, such as collection optics
including fibers, diffractive elements, detectors and data-processing algorithms, improve practical application of spectroscopy and reduce cost as
compared to some other sensing and imaging technologies.
Recent trends in market forces are encouraging to the growth of optical
spectroscopy and its applications. A noteworthy trend in the market is the
general globalization of resources and the centralization of processing of
raw materials. For example, just a few companies, such as TOMRA Systems,
Key Technology or John Bean Technologies, are responsible for the processing of a significant amount of the food produced globally. Food-processing
companies acquire food from multiple sources, including large multi-na-tional farms and small operations. Thus, grading of raw materials, in this
case food, is required to achieve efficiencies of production. To do so in a fast
and reliable way is critical. Optical spectrometers offer the ability to quickly
inspect and grade incoming food products by size, origin and consideration
of the chemical composition of food such as starch, water or sugar content.
Another industry where centralization has occurred is oil refining.
Only about 170 refineries were functioning in North America in 2008,
with a total of 700 around the world. These refineries process oil from
many sources, and although they tend to be specialized, the source of
crude dictates refining processes. Most of the oil is transported by trains
and pipelines, and tends to come in many varieties, chemical compositions and complexity. An increasing need exists to analyze oil prior to its
arrival at the refinery. One method of analysis is to introduce optical spectroscopy, from Fourier transform infrared (FT-IR) to near infrared (NIR).
This allows for minimal handling of samples and quick analysis, unlike
the more complex laboratory instruments such as gas or liquid chroma-
tography combined with mass spectroscopy.
Optical spectroscopy, as a traditionally multidisciplinary science, has
lagged behind other technologies in the development of sensitivity, size
reduction and portability. However, in the last two decades, this trend
has reversed. The pursuit of novel manufacturing methods of diffractive
optical elements, including microelectromechanical systems (MEMS) and
reduction in the cost of high-quality lasers, have led to the creation of new
types of gratings, as well as to significant enhancement of existing grating
manufacturing methods to reduce costs and increase efficiencies. Better
detectors, as well as improved mass production of optical elements, have
led to a steady decrease in the size of optical spectrometers, with many
companies, such as Ocean Optics, Thermo Fisher Scientific or P&P Optica, producing smaller, portable systems. Even handheld units, which are
still limited by the amount of light that can be collected by small optical
elements, have been getting steadily better by taking advantage of lower
noise, faster charge-coupled device (CCD) and complementary metal–
oxide–semiconductor (CMOS) detectors.
For example, many traditional spectrometers were limited by poor
optical elements and light scattering on reflective gratings and curved
mirrors. The mass-production of better types of gratings, such as trans-mission-based gel gratings, has enabled the same size of spectrometers to
be limited by detector noise. That means the same-sized optical spectrometer, previously limited by its optical construction to a signal-to-noise
ratio (SNR) of 300:1, can now be expected to stretch a linear detector to
reach a SNR of well over 3000:1.
Applications of optical spectroscopy
are growing, providing more signals,
allowing users to detect more, see
more and do more. Images: P&P