手機光譜儀檢測食物之品質

Abstract

本研究之手機光譜儀採用簡單的光學元件，基於手機內建的CMOS照相機做為檢測器、市售光柵做為分光元件，透過SolidWorks設計以及3D列印技術，設計製造手機光譜儀之腔體機構，將所有光學元件整合在一起，完成手機光譜儀系統。 光路設計上，由一條光纖將光源傳輸至手機光譜儀系統，經由手機光譜儀裡面的準直鏡出光，在照相機接收訊號之前，會先通過狹縫與柱面透鏡，狹縫的目的在於改善解析度，狹縫的寬度影響著解析度。柱面透鏡與市售光柵夾47度角，當光入射到市售光柵時，在市售光柵上產生繞射，最後，經由照相機接收訊號。藉由光纖傳輸光之關係，光源可使用內建之閃光燈，完成一套便攜性的系統。在系統校正中，使用已知波長之LED燈，對波長與像素位置校正，藉由波長與像素的轉換，便可定義出解析度。 本研究基於手機光譜儀系統，量測不同顏色的香蕉與市售果汁，藉由不同顏色的香蕉含有的葉綠素不同，用來判斷香蕉之成熟度，與量測不同的市售果汁實際含量，驗證此系統在食物檢測之實際應用。未來將可用於食品安全檢測、日常健康檢測、各種疾病篩檢。

In this thesis, a spectrometer using a smartphone built-in CMOS camera as a light detector and diffraction grating as a dispersive element was developed. A handheld case designed with SolidWorks and fabricated by 3D printing was used to assemble necessary components to realize a smartphone spectrometer system. An optical fiber was used to couple the light source and illuminated at the sample. The transmitted or reflected light was then gone through a slit to improve the spectral resolution. The light was then going through a cylindrical lens before incident on the grating. The dispersed light was then measured by CMOS camera. Three LED with known wavelength was used to calibrate pixel and wavelength relationship such that the spectral information can be transferred into spatial information on the CMOS pixels. To demonstrate the capability of the smartphone spectrometer, two different experiments were performed. Based on the absorbance on a particular wavelength due to the chlorophyll content, the smartphone spectrometer was used to determine the state of ripeness. Also, based on the difference in absorbance between pure juice and water, the actual concentration of apple juice from different vendors can be determined. We believe that smartphone spectrometer can be further applied for other applications such as food safety monitoring, disease screening, and etc.