Visible smartphone spectrometer based on the transmission grating

In this paper, a portable visible spectrometer using an Android smartphone is proposed, designed and experimentally tested. The entire optical system consists of a 10 μm slit, the collimator lens, a 300 lines/mm transmission grating, and the imaging lenses. The CMOS image sensor of the smartphone is utilized for optical imaging. Then a built-in app will calculate the spectrum. Minimum spectral resolution of 7 nm is achieved according to the ZEMAX simulations. The whole size of the external device is 44*44*50 mm
³
, and can be easily installed on the backside of the smartphone. This visible spectrometer can be applied in various fields, such as food safety, water contamination detection, air quality examination, and so on.