The Material Imaging Analyzer MIA

In this work, Sinewave Pulse Width Modulation (SPWM) of light sources is proposed to be used for spectral imaging and vibrational spectroscopy. Three Light Emitting Diodes (LEDs) transmit SPWM light at different sinewave frequencies and at 1050, 1300 and 1550 nm respectively. A video camera records the active illumination, reflected in the surface to be analyzed and simultaneously for all three LEDs. A similar demodulation method as for lock-in amplifiers is used to demodulate every single pixel into three spectral channels. Experimental results show that this material imaging analyzer, called MIA, can be used for vibrational spectroscopy such that snow, ice, water and plastic are classified from their corresponding spectral signatures at an overall success rate of 92%. Spectral signatures in this particular case are generated from sensing reflection of light at three wavelengths. MIA must thus be configured with LEDs having wavelengths suitable for the particular application. The response of the MIA light sources and the indium gallium arsenide InGaAs detector is close to perfectly linear. Peak signal to noise ratio PSNR was measured to be 54 dB.