要評估一個透鏡成像品質的好壞，可以量測這個透鏡的調制傳遞函數（MTF），以決定透鏡的優劣。量測透鏡MTF的方法主要有：掃描法、干涉法。本文採用直接掃描法為研究主題，以單狹縫掃描一個穿透面積為餘弦變化的光網，由偵檢器接收到的信號變化量，可以直接轉換為透鏡在該空間頻率下的MTF。製作空間頻率為連續變化的光網，使測試的空間頻率不斷地變化，由偵檢器輸出的信號，可直接轉換為MTF圖。 實際製作部份，分別針對光源驅動、光網、影像旋轉裝置、單狹縫製作、馬達轉速、偵檢器頻寬等參數的影響做深入的探討，並依討論要點實際製作出量測儀器，量測出透鏡的MTF值。 For evaluating the image quality of an optical system, one can measure the Modulation Transfer Function (MTF) of this system. The two major methods of measuring MTF are: (1) Direct method, (2) Auto-correlation method. The subject of this thesis is the direct method with scanning. Using a single slit to scan the grating of sinusoidal changing area size, the detector produces an electrical time-dependent signal. This signal is the MTF at the specified spatial frequency. When the grating is produced with decreasing spatial frequency continuously, the electrical signal presents the MTF chart of the lens. In practice, the apparatus is made in consideration for the light source, grating type, image rotating mirror, single slit, motor rotating speed and the bandwidth of the amplifier. After adjusting properly, this apparatus can measure the MTF of a lens.
