Integrated Imaging System Enhances Detection Capabilities

August 1, 2008

A technology that picks out minute abnormalities in forged documents or suspicious biological spores has been developed by Chem - Image Corp. of Pittsburgh, PA through funding from the Missile Defense Agency (MDA).

The technology integrates two specialized types of imaging — luminescence and Raman — into spectroscopes to provide high-throughput screening for defects or anomalies in microscopic semiconductor materials such as gallium nitride (GaN). Abnormalities in large, visible items such as paper documents also can be screened by these spectroscopes as part of forensic trace evidence testing. MDA predecessor BMDO originally funded the technology for GaN screening through an SBIR (Small Business Innovation Research) Phase I contract in 2000. Though ChemImage received only Phase I funding from MDA, company scientists were determined to press on and develop a commercially available system. ChemImage soon integrated the fundamental concepts addressed in the Phase I contract into three systems that are now commercially available: the Falcon™, Condor™, and CI Vision™ multimodal hyperspectral imaging systems.

How it Works

Scientists use luminescence imaging — or ultraviolet excitation — to find or target the anomaly or defect of a particular semiconductor or material. Raman imaging then provides specific identification of these undesirable occurrences. ChemImage has designed special software that integrates luminescence and Raman into a dynamic imaging system to find and identify an abnormality.

Detection of a defect or anomaly (such as dislocations, micropipes, and low-angle boundaries) in a GaN semiconductor or other object starts with a luminescence imaging device that floods ultraviolet (UV) light onto the material with wavelengths between 250 and 350 nanometers (nm). The UV illumination causes the device or object to glow, revealing any abnormalities. An imaging spectrometer then captures images of the material being examined, with images gathered at wavelengths of greater than 350 nm. After the images are taken, ChemImage applies a technique known as multivariate image analysis. This technique processes every pixel in each of the images independently (see photos).

Each pixel has a luminescent spectrum associated with it. The imaging system generates a digital image showing all aspects of the object in question — including defect density — once the individual pixels are processed. After the luminescence system completes its digital imaging of a particular object, the data are transferred within the platform to the Raman device, which confirms defect types or other anomalies through what is known as hyperspectral imaging. Hyper - spectral imaging provides quantitative analysis of the chemical makeup of an abnormality in a material.

For the commercial customer, speed is a key factor. ChemImage's integrated luminescence-Raman process reduces hyperspectral image acquisition time from as long as a week to as short as a few minutes. Time reduction is primarily a result of not having to laboriously scan submicron areas of either a semiconductor component or other material, or use wide-field illumination with one spectroscopic device.

ChemImage's spectroscopic devices also display threedi men sional images, rather than flat, two-dimensional images. These 3D images allow for volumetric defect screening — a feature not commonly available in competing imaging systems.

Where it Stands

ChemImage's systems have broad applicability. The company's luminescence-Raman imaging technology has been successfully demonstrated and is being used in the fields of forensics, homeland security, law enforcement, medicine, and pharmaceuticals. After the 2001 anthrax scare, the Department of Defense used Raman and luminescence imaging systems to detect potentially harmful chemical and biological substances. The Secret Service also used the technology for its forensic capabilities, particularly as an ink-analysis tool for evaluating counterfeit documents in several high-profile cases.

Medical and pharmaceutical industries can use the technology in stents — small wires or tubes inserted into blood vessels or arteries to prevent or reduce localized flow restriction — as well as for screening inhaled drugs. Many stents have drugs implanted on their surface. The ChemImage system provides volumetric imaging of these drugs to ensure application of the correct dosage.

For inhaled drugs, ChemImage, working with the Food and Drug Administration (FDA), has developed and is working to further validate imaging for ingredient-specific particle-sizing tools. The concept relies on the fact that a patient taking an inhalant inhales release agents and stabilizers, in addition to the actual drug. Imaging will help pharmaceutical companies and the FDA determine the dosage and particle-size distribution of the ingredients in the inhalers. The goal is to control the size of the active ingredient to get reliable performance and to ensure patient safety.

The company envisions its imaging systems in all hospitals and doctors' offices. The imaging systems would act as a sensor technology to allow physicians to measure disease states quantitatively and to help align a particular therapy to one's body chemistry. The company is also looking to have its imagers become part of future portal screening systems at airports. The systems would allow homeland security officials to discover all types of explosives, beyond what detection systems can currently screen.

ChemImage's greatest challenge is gaining market acceptance for its technologies. The company has only recently begun to explain in peer-review literature the workings of the technology and the performance characteristics of its various spectroscopes. It is now trying to break into the imaging market, primarily through direct sales in North America. Sales have recently been expanded to Europe and Australia, but the company has not tried to tap the potentially large markets of Asia in China, Japan, and South Korea.

More Information

For more information on ChemImage's spectroscopes, click here  . (Source: MDA TechUpdate, Missile Defense Agency, National Technology Transfer Center Washington Operations.)

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