本文探討應用高速攝影機補捉振動訊號時，改變攝影機之對焦良好與否的效應，以測試此種影像數據搜集系統的應用範圍。因為是初步研究，本文固定攝影機的焦距於某一固定位置，再改變攝影機鏡頭與被測物的距離，以探討失焦效應。此外本文也討論改變振動物之背景之明暗以襯托影像之明暗效應，以及改變攝影機的取樣頻率和失焦的影響。本文從所攫取的連續明暗影像中，選取相同位置之等比例像素長方形，將該區域內的灰階值累加，可得到時變訊息，經使用快速疊代型率波器移除時變數據串中的趨勢線後，使用傅立葉正弦頻譜產生器求取其頻譜。
分析結果顯示不論在距離較近時，有或沒有正確對正焦距的情形下，高速攝影機仍然有機會補捉到主要的振動訊息。但距離持續遠離量測物時，其能力會因失焦而大幅度降低。這顯示有必要將攝影機加裝遠距離鏡頭的放大功能。本文研究結果顯示，此種遠距離非接觸式的振動數據搜集系統，具有很大的潛力應用到不同的自然或實驗場合。

By varying two conditions, the capability of capturing the vibration signal with the image frames grasped by a CMOS high speed camera is examined. The first one checks the in or out of focusing state of the camera and the second changes the sampling frame rate of the camera. To examine the focusing effect, this study fixed both the focus length and distance between the camera and target at 0.6, 1, 2, and 3m. The frame rate of the high speed camera uses 190, 200, 210, and 232 frame per second. At first, the vibration signals of a vibration exciter with different frequencies were examined. For each image frame captured by the camera, the gray level of pixels within a properly assigned square were summed up and were referred to as the vibration signal at the corresponding time. Subsequently, a time series data string of the image signal was obtained. After filtering out the trend via the fast iterative Gaussian smoothing method, the Fourier sine spectrum of the sinusoidal part was obtained in which the vibration modes can be faithfully obtained. Experimental data showed that, when the degree of losing focus is moderate and the distance between camera and target is short, the capability of capturing the fundamental mode and harmonics is not seriously affect. The capability gradually decays as the degree of losing focus and distance being increase. If the distance is large, say 2 or 3m, the fundamental mode may be lost. By changing the sampling frame rate, the experimental data show that the physical and aliased modes can be easily identify. Moreover, the original frequency of the aliased mode can be calculated. By changing the white background of the target to be gray, the tendency of the capability of capturing the dominant modes is not prominent affected. All the data show that the non-contact type image data acquisition system can grasp vibration signal in the state of properly keeping the focus state, degree of brightness of the target surface, and changing the sampling frame rate. In other words, the image data acquisition system is suitable for a severe environment.

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