technology Portable sPectroscoPy
we’re trying to quantify the light signals arriving at the eye,’ Navvab explains. ‘The perception of those signals as colour or brightness is through the brain, not by the mechanics of the eye. In the virtual world I can create different conditions to test peoples’ perception of those stimuli.’ The CAVE has also been used to design the lighting for psychology experiments into syndromes such as Seasonal Affective Disorder (SAD), insomnia and depression. Two test apartments have been set up in the psychology department whereby the lighting is manipulated to study its effects on
study was to measure the amount of light falling on the plants and how much is refl ected from the leaves and how much is absorbed. The research involves creating different lighting scenarios in the botanical gardens and measuring the radiance levels and light distribution over the plants using the portable spectrometer.
the equipment is almost at
the point where they could put it in a backpack, but it’s not quite there yet
the subjects living in the apartments. The lighting regimes were designed inside the CAVE, simulated to mimic day/night as well as other conditions. Elsewhere, Ocean Optics’ spectrometers were used to test the lighting conditions in University of Michigan’s Matthaei Botanical Garden Conservatory, with an aim to understand how plants grow and acclimatise to indoor lighting. The data from this will be used to advise architects and building designers on daylight and indoor lighting designs for healthy plant growth. The
‘In some commercial buildings or shopping atriums, for example, the lights are never switched off,’ comments Navvab. ‘If you constantly feed the plant with light, it’s going to die. In these scenarios, a fi lter can be placed in front of the light to cut out certain portions of the spectrum during the night.’
Being able to take the spectrometer to the sample has, according to Morris of Ocean Optics, opened up hundreds, if not thousands, of different applications. Other spectroscopy techniques
generally have technical barriers to making them portable, in that some require large power supplies or larger instrumentation. Morris also feels there has to be a need to make it portable in the fi rst place. Laser induced breakdown spectroscopy (LIBS), for instance, which uses a laser to ablate a sample and then detect the constituent elements, can be used to detect chemical and biological warfare agents, and explosives, and so, Morris says, has an appeal as portable instrumentation in military and defence applications. ‘It’s starting to become more portable, but one of the challenges with LIBS is that the laser draws a lot of power,’ he says. ‘The equipment is almost at the point where they could put it in a backpack, but it’s not quite there yet. You can see that something like that, which you would never have thought would be moved out of the lab, has matured to the point where the idea of being portable is not out of the question.’ More in-depth analysis typically has to be carried out in the laboratory, but as a fi rst line of investigation, portable spectrometers are a useful tool. l
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May 2011 l electro oPtics
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