Most of the techniques discussed in the above sections had been designed to work in the seen range because of the limited spectral responsivity of the embedded digital camera sensor. As discussed in part 2, because of the presence of the infrared cut- off filter, the camera sensor is responsive only throughout the visible wavelength range, 400 nm to seven hundred nm. Yet a vast number of biomedical purposes require spectral responsivity in the ultraviolet or infrared range. One method to use a smartphone digicam as a detector for such applications is to convert the light to seen vary via optical transduction using nanoparticle-based methods .