Electronic Design

MEMS Helps Slash Food-Processing Analysis Costs

Food and beverage content analysis is an important segment within the industrial-processing arena. Spectrometer instruments mounted on the production line perform this often expensive and cumbersome step for safety and grading purposes. But now microelectromechanical systems (MEMS) have improved and simplified spectrometry, making it more cost-effective in industrial settings.

This year, Polychromix introduced its programmable Digital Transform Spectrometer (DTS). Thanks to MEMS diffraction grating-beam elements, this lowcost near-infrared (NIR) spectrometer is revolutionizing food processing (Fig. 1).

Initially, Polychromix developed it for chemical sensing, with funding from the Defense Advanced Research Projects Agency. Research at Honeywell Research Labs, Sandia National Laboratories, and the Massachusetts Institute of Technology led to development of the DTS. MEMS pioneer and MIT senior professor Stephen Senturia headed the engineering team. (Senturia also founded Polychromix, and he is its chief technology officer and chairman of its board.)

A typical beverage application would be to analyze the components of raw milk—fat, solid non-fats, proteins, and so on. Several NIR milk-analysis spectrometer techniques use alternative NIR spectroscopy technologies, such as detector arrays. Typically, these alternatives cost up to $40,000. Polychromix's DTS systems cost from $7199 to $10,999.

While other spectrometers usually use an expensive diode array, the DTS employs a single low-cost diode and a programmable optical modulator (Fig. 2). It can analyze different types of milk, regardless of its source. Measurement probes connect to the DTS, which is mounted on a production line. The device monitors the milk's flow, and a computer analyzes the milk's contents (Fig. 3).

HOW IT WORKS
The DTS's thousands of individually movable diffracting beam elements provide a fully programmable optical transfer function (Fig. 4). The beams move less than 1 mm. Containing no moving parts, the DTS is insensitive to stray light. Its USB port supports power and communications. A "my instrument" interface allows operation with standard software packages. Its interface software operates in several modes, selected and controlled by software.

The monochromatic mode permits the selection of one filter passband or the scanning of a single passband across the full spectral range. With a non-dispersive IR (NDRI) mode, it's possible to select a sequence of passband filters, equivalent to an NDIR filter wheel.

In the chemometric mode, users can employ the analog control of individual pixels to implement optimum partialleastsquares weighting of multiple wavelengths, where the output is proportional to the concentration of specific species. Also, the digital transform mode uses the programmability of a proprietary diffractive grating method to implement an encoding scheme for 50% throughput.

The DTS chip measures a mere 105 by 85 by 145 mm and consumes less than 750 mW. Other applications include agriculture, online process control, forensics, pharmaceuticals, aerospace applications, and measuring layers of material thicknesses.

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