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as the cell phone have driven linear CCD array detectors down to the point where they use very little power and are very small. These detectors are being mass-produced, even in the small form factor, making it easy to acquire high-quality detectors at a reasonable price.

‘Once you have a very small detector, the other optical components can be easily miniaturised and scaled down,’ said Allen. ‘Really you’re just leveraging all of the miniaturisation and low-power efforts from all of the individual components of the spectrometer to be able to put that into a very small form factor device.’ Not only are spectrometers becoming ever

more compact, but they are being designed to be faster and more robust to perform analysis on food production lines. Spanish flour supplier Emilio Esteban uses a NIR spectroscopic system to inspect the flour that flows through its pipes at a rate of 25 metres per second. The spectrometer in the system, supplied by Ibsen Photonics, is placed on one side of the flow opposite a lamp on the other side, and a measurement is taken that lasts for one tenth of a second. Compared to conventional methods where samples had to be taken to a spectrometer in a laboratory, the processing time is significantly reduced.

‘Most of the reason to do in-line process control is to shorten the feedback link – you can immediately stop the production line if there is a problem,’ said Dr Thomas Rasmussen, vice president of sales and marketing at Ibsen Photonics. ‘This allows you to create more consistent products.’

throughput with no changes in the angle of the diffracted light.’

As seen with the Raman device, it is high- volume mass production of miniature components that has led to compact and cost-effective NIR spectrometers. ‘We make the transmission gratings ourselves, by producing 200 to 300 gratings on a single wafer and then dicing them out,’ said Rasmussen. ‘Similar approaches can be used to produce the lenses and mirrors and, also, very small standard mirrors can be supplied in high volume by lots of Chinese suppliers.’

A similar technology suited to the high speeds of In the future,

spectrometers used in food quality control will be able to analyse different types of food samples at once

The development of grating-based NIR spectrometers with non-moving parts has been significant in making it possible to measure at these high-speeds. ‘In the larger bench- top devices, the technology involves a moving part or a scan, which would take seconds or minutes,’ said Jason Pierce, director of business development at StellarNet. ‘Our devices use a grating and a detector array, where you have a set exposure time to be able to capture the same amount of information in milliseconds.’ Moreover, the type of grating used can make a

difference to its performance in a food production environment. ‘Transmission gratings made out of glass help with the speed – the more light you get through, the shorter time it takes to measure,’ explained Rasmussen. ‘These gratings are also thermally stable, which means that even with vibrations and temperature variations that exist in an industrial setting, you still get the high | @electrooptics

a production environment is integrated wavelength- selective detectors. The PixelSensor from Pixelteq has the option to place eight narrow bent spectral filters in front of an array of eight photodiodes. So, a food supplier is able to select and measure only the wavelengths related to their food item instead of measuring the whole spectrum, which reduces the cost, size and time of measurement. ‘In the future I think this kind of technology will be used very heavily for in-line inspection because a company will know exactly what wavelengths they are looking for,’ said Marco Snikkers, director of sales and marketing in Europe at Pixelteq. ‘The device is limited to eight critical wavelengths, so the analysis can be carried out at very high speeds because the processing time goes down.’ In the future,


spectrometers used in food quality control will be able to analyse different types of food samples at once, according to Rasmussen. ‘I think that the same spectrometer will be capable of monitoring several process


lines at the same time. So, there would be five optical fibres as input to the spectrometer, and the ends of these fibres would be placed at different locations for testing.’ Pierce agreed that the way forward is for a single spectrometer to be capable of testing different food samples: ‘StellarNet is currently making case-carrying systems that have everything included in it. The same device could be used to do quality control both at the production line and at the agricultural field. Companies will be able to monitor products several times during production by using the same spectrometer. ‘I definitely feel that miniature spectrometers are going to revolutionise production and efficiency,’ Pierce added. ‘The entire industry, from the field in agriculture, all the way to the inspection line of a final product, is going to be affected by these low- cost mini spectrometers being implemented in all these steps in production.’l

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