A simple, low-cost, and portable LED-based multi-wavelength light source for forensic application

Inexpensive LED-based spectrophotometer for analyzing optical coatings

“…To overcome the limitation of a fixed emission band, the use of a switchable multi-channel LED array was introduced. 11-13, [16][17][18] There are various ways to direct light from a multi-channel array towards the test sample. Hauser et al 12 coupled the light from seven LEDs into a seven channel optical fibre coupler, and used an electronic switch to individually activate each LED.…”

“…A wider spectrum of wavelengths made it possible to identify several chemical elements, instead of only one or two, in an unknown solution using standard colorimetric methods. Lee et al 18 demonstrated another way to make a switchable LED array by using a DC servomotor to rotate the appropriate LEDs towards the object under forensic investigation. However, all of these devices were used in absorbance measurements to identify concentrations of specific chemicals, and have not been applied to analyze optical coatings.…”

“…The device costs under three hundred US dollars to build, and only takes a few days to assemble. The design is similar to Lee et al 18 in that we use a small servomotor to rotate a LED board to sequentially position each LED over a test optic, and measure the transmitted light as a function of LED wavelength. We also introduce a simple calibration method to compensate for the extended emission spectra of some LEDs.…”