(254bf) Development of a Cellphone-Based Optical Emission Spectrometer for Analysis of Plasma Optical Emission

Authors: 
Hsu, C. (., National Taiwan University
Yeh, P. W., National Taiwan University
This work presents the development of a cellphone-based optical emission spectrometer for analysis of plasma optical emission. This spectrometer contains a slit, a grating, and utilizes the CCD camera of the cellphone to acquire spectra. The slit determines the amount of the light and defines the cut edge of the light that enters the spectrometer. The grating disperses the light into different wavelengths and greatly influences the spectral resolution of the spectrometer. The main structure of this device is constructed by a 3D-printer using polylactide (PLA) to obtain the customized shape and size. The slit is made by utility knife blade with a slit size of 0.05 to 0.2 mm. 500 and 1000 lines/mm gratings are tested. The spectral graph is acquired by taking images using the cellphone then is converted to intensity vs. wavelength plots by analyzing the image using either cellphone apps or computer-based programs such as Matlab. To calibrate the device and to quantify the full width at half maximum (FWHM) of the device, Hg-lamp is used as the standard light source. We test how device design influences the spectral resolution, the sensitivity, and signal-to-noise ratio of the device. The geometry of the current design is 26 mm * 23 mm * 27 mm with a FWHM of 17.65 nm. Furthermore, we use this device to analyze the optical emission emanating from the plasma. It is shown that with this device, major emission lines between 400 and 700 nm in Ar, He, and air plasmas are observed. Volatile organic compounds in the gas can be detected by the examination of the emission lines for carbon-containing species. We also show the device with extra accessories and designs that allow for more flexible and easier operation.