SPECTROPHOTOMETRY: ChromaID scanner challenges traditional spectrophotometry

Traditional spectrophotometers measure reflected or transmitted light from a sample as a function of wavelength, typically by sending broadband light through a prism or diffraction grating and measuring the light with a linear CCD array. But a new lower cost and potentially less bulky method from Visualant (Seattle, WA) eliminates the need for delicate optical components and expensive detectors by using a “virtual” light-emitting diode (LED) source and inexpensive photodiode detectors.1 The technology could be used in a myriad of applications now being addressed by handheld spectrometers and emerging chip-based spectroscopy designs.

Spectral pattern matching
The LED source consists of any number of individual LEDs—from the ultraviolet (UV) through the visible and even into the near-infrared (near-IR) spectrum—incorporated into an emitter module that paints a structured pattern of light onto the sample being measured. The source is described as virtual because the current supplied to the LEDs is varied through a sequence of steps to vary the frequency of the light produced by the emitter.

The virtual LED technique allows Visualant to cover a wider light spectrum using a limited number of LEDs. For example, one prototype source incorporates 34 emitters that are fired through 25 current steps in a sequence that is repeated four times; in effect, a single less-than-one-second scan paints 34 × 25 × 4 = 3400 flashes of light onto the sample. The Rayleigh reflections from these flashes are measured by photodetectors and the data is captured as a two-dimensional profile called a ChromaID.

This ChromaID is plotted on a chart showing the intensity of the reflected light at each wavelength and spectral pattern matching (SPM) is used to compare the pattern to a database of patterns from known substances (see figure). Visualant holds patents describing how these database comparisons are made.

A handheld spectrophotometer device uses a 'virtual' LED emitter and inexpensive photodetectors to scan a sample and create a unique wavelength-vs.-intensity plot or ChromaID that uses spectral pattern matching to compare the plot to a database of known ChromaID signatures to identify the substance under test
A handheld spectrophotometer device uses a “virtual” LED emitter and inexpensive photodetectors to scan a sample and create a unique wavelength-vs.-intensity plot or ChromaID that uses spectral pattern matching to compare the plot to a database of known ChromaID signatures to identify the substance under test.

Field analysis
Operating between 350 and 1450 nm, the ChromaID scanner is handheld and easily operated either in a laboratory setting or in the field. Recent testing on plastic sample bags containing a variety of similar-looking white powders demonstrated that the SPM ChromaID method was able to distinguish between flea powder, household cleaner, ground Tums, Splenda, baby powder, and cornstarch, to name a few.

The Visualant ChromaID technology was developed by University of Washington (Seattle, WA) professors Tom Furness and Brian Showengerdt over a seven-year period at Tom’s skunkworks, the “RATLab.” Visualant has partnered with Sumitomo Precision Products (Tokyo, Japan) to manufacture the initial scan head and further reduce the technology to a reliable and cost-effective form for flat-surface applications.

“Over the last six months we have transferred the technology into a form we can manufacture,” says Richard Mander, vice president of product management and technology at Visualant. “We are excited to now be designing products that customers can use.”

For more information, see http://youtu.be/ddjcafJ-J30.

1. R. Mander, “Introducing Visualant Spectral Pattern Matching Technology,” white paper; see http://bit.ly/STmccA (October 2012).


A long way from the ruby laser

Most Popular Articles


Ray Optics Simulations with COMSOL Multiphysics

The Ray Optics Module can be used to simulate electromagnetic wave propagation when the wavelength is much smaller than the smallest geometric entity in the ...

Multichannel Spectroscopy: Technology and Applications

This webcast, sponsored by Hamamatsu, highlights some of the photonic technology used in spectroscopy, and the resulting applications.

Handheld Spectrometers

Spectroscopy is a powerful and versatile tool that traditionally often required a large and bulky instrument. The combination of compact optics and modern pa...

Fracking, climate change, and lasers:  new tools to reduce fugitive methane emissions

This webcast, sponsored by Hamamatsu Corporation, covers recent developments and field deployments of compact quantum-cascade-laser (QCL)-based methane senso...
White Papers

Narrow-line fiber-coupled modules for DPAL pumping

A new series of fiber coupled diode laser modules optimized for DPAL pumping is presented, featur...

Accurate LED Source Modeling Using TracePro

Modern optical modeling programs allow product design engineers to create, analyze, and optimize ...

Optical Isolators Improve Engraving Performance of Pulsed Fiber Lasers

The deleterious effects of back reflections on pulsed fiber lasers used in marking and engraving ...
Technical Digests

ADHESIVES, SEALANTS, AND COATINGS: Solutions for optical technologies

A vast array of optical systems of various types and degrees of complexity require the use of adh...

WAVELENGTH-SWEPT LASERS: Dispersion-tuned fiber laser sweeps over a 140 nm range for OCT

By eliminating the use of mechanical tunable filters and instead tuning by intensity-modulation i...

Keeping pace with developments in photonic materials research

For demanding or custom spectroscopy solutions, care must be taken in selecting and integrating a...

HIGH-POWER FIBER LASERS: Working in the kilowatt regime

High-power materials-processing fiber lasers are available in an increasing variety of forms, as ...

Click here to have your products listed in the Laser Focus World Buyers Guide.
Social Activity
Copyright © 2007-2014. PennWell Corporation, Tulsa, OK. All Rights Reserved.PRIVACY POLICY | TERMS AND CONDITIONS