Conference Review
by Matt Wilkinson
Focus Sharpens on Miniature Optical Spectrometers at Pittcon®
O
ptical spectroscopy often seems to be somewhat overlooked at Pittcon®, with much of the attention focusing on hyphen- ated technologies such as GC/MS or ultrahigh-performance liquid chromatography (UHPLC)-MS/MS. Over recent years, renewed interest in the area has been largely led by those products that could ei- ther reduce sample volumes or take the analyzer to the sample. This year, there was also activity in combined imaging and spectroscopy instruments, many of which were covered in Barbara Foster’s review:
http://www.americanlaboratory.com/913-Technical-Articles/156565- Integrating-Microscopy-Into-the-Analytical-Scheme-A-Pittcon-2014- Microscopy-Review/.
Miniaturizing the future of spectrometer design There were several innovations on display that promise to further miniatur-
ize and reduce the cost of future optical spectrometers.
This year’s winner of the Pittcon Editors’ Gold Award was the DLP® NIRscan™ evaluation module from semiconductor expert Texas Instruments (Dallas, TX;
www.dlp.com), which is a complete optical unit that contains no me- chanical parts. The DLP NIRscan is based upon the company’s DLP4500NIR microelectromechanical system (MEMS) device, which is optimized for use with near-infrared (NIR) light in the 700- to 2500-nm range. The MEMS device contains more than1 million digitally programmable micromirrors that can be easily controlled to employ adaptive scanning techniques to optimize material analysis.
Around the micromirrors, the company has assembled optical slits, diffrac- tion gratings, detectors, and embedded processors to provide an integrated optical unit without mechanical parts to give spectrometer developers a working central unit, around which they can build their specific NIR spec- troscopy instrument.
When paired with a single element detector, the DLP4500NIR can replace expensive linear array detectors to create high-performance yet affordable spectrometer designs. The micromirrors enable spectral resolution and wavelength range refinement, adjustment of integration time, and equalize light throughput such that signal-to-noise ratios greater that 30,000:1 can be achieved.
Si-Ware Systems (SWS) (La Cañada, CA;
www.si-ware.com) showcased its 2014 SPIE Prism Award-winning MEMS-based single-chip FTIR spectrom- eter that can be integrated into a wide variety of systems for applications that require qualitative and/or quantitative material analysis.
The first generation of the spectrometer is delivered as a module that consists of a MEMS-based monolithic Michelson interferometer chip that measures just 1 × 1 cm2
, an application-specific IC (ASIC) that provides the electronics interface, a single photodetector, and optical fibers.
The spectrometer module operates in the NIR range, and achieves resolu- tions greater than 30 cm-1
for 2-sec integration time. It measures just 8 × 6.5 × 4.5 cm3
and a signal-to-noise ratio of greater than 1500:1 , weighs less than
150 g, and is powered by a USB interface consuming just 750 mW. Further developments are in progress to operate in other wavelength ranges and to achieve even smaller sizes for the module in upcoming generations.
The FTIR spectrometer is the first product to be developed and released based upon Si-Ware’s SiMOST platform, which enables the miniaturization of optical benches on silicon chips using semiconductor microfabrication techniques. SWS is currently providing evaluation kits for its NIR modules, and targets production next fall.
Taking a different approach to the miniaturization challenge was SpectroClick (Champaign, IL;
www.spectroclick.com), which announced technology that could potentially build your cell phone into the heart of a spectrometer, using the camera’s built-in complementary metal–oxide– semiconductor (CMOS) sensor as the detector. The company is currently targeting applications in absorption, reflectance, surface plasmon reso- nance, and fluorescence. Initially, the instrument uses an external CMOS camera operated from and powered by a USB 2.0 port. The spectrometer requires an external package that combines a light source, collimation optics, sample cell, and dispersion device. A prototype of this package was on display at the SpectroClick booth.
In order to overcome the challenges of stray light, inadequate dynamic range, and poor mechanical stability of the CMOS sensors used in phone cameras, the company has developed a patent-pending grating that cre- ates a “SpectroBurst.” This enables the dynamic range of the system to be the product of the dynamic range of the camera and the wide range of grating and optics throughput. The team is currently tackling wavelength calibration and CMOS sensor characterization challenges and plans to have an alpha testing program in place during summer 2014.
Taking the lab to the sample During the event, SciAps (Woburn, MA;
www.sciaps.com) launched the
first high-performance, handheld laser-induced breakdown spectroscopy (LIBS) instrument, the Z. SciAps expects the Z to extend the applications for handheld elemental analyzers, especially for alloy producers, positive material identification (PMI), and nondestructive testing (NDT) companies because it can quickly and accurately analyze light in every element from hydrogen to uranium. This significantly extends the range of measurable elements to low-atomic-number elements that are out of the reach for handheld X-ray fluorescence (XRF) instruments. Of particular note is the Z’s ability to measure C, Al, Si, and Mg with similar performance to mobile opti- cal spectrometers. In addition, the instrument interface is based on Google’s
AMERICAN LABORATORY • 18 • MAY 2014
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