A compact line-detection spectrometer with a Powell lens

Optical spectra are functions of the emitted or reflected light from the object under observation. The investigation of spectral data can facilitate quantitative analysis and material identification. In this paper, we report a portable line-detection spectrometer for non-invasive sensing of samples of interest. The spectrometer relies on a Powell lens to perform a rapid line detection. Through a manual scanning across a sample of interest, a series of spectra could be acquired. After an unmixing procedure is performed on the detected spectra, the reflected (or emission) spectrum of the sample could be obtained. In this work, the feasibility of the line-detection spectrometer was demonstrated by scanning across a LED screen and fruit samples. These spectral results were applied to determine the composition of the scanned objects, such as the colors of a LED screen and the chlorophyll and carotenoid content in bananas. This method is compatible with many kinds of spectrometer, e.g. Raman spectrometer for high spectral resolution sensing, infrared spectrometer for identification of adulteration. Therefore, this portable device can be a versatile tool to carry out a range of in-site studies in the future.