數位Moiré運用在光學振動測試分析;Research and Analysis of Digital Moiré Application in Optical Vibration

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/89343

Title:	數位Moiré運用在光學振動測試分析;Research and Analysis of Digital Moiré Application in Optical Vibration
Authors:	劉昱銘;LIU, Yu-Ming
Contributors:	光電科學與工程學系
Keywords:	疊紋;頻率;強化影像;等高線輪廓;攝影機幀數;非接觸;Moiré;frequency;enhanced image;project gratings;The frame rate of the camera;non-contact
Date:	2022-07-21
Issue Date:	2022-10-04 11:11:33 (UTC+8)
Publisher:	國立中央大學
Abstract:	疊紋光學量測 Moiré 方法具有非接觸、非破壞性、成本較低等特點，同時利用 Moiré條紋計算分析物體表面振動或尺寸細微變化之方法，比傳統的數位影像處理的方法速度與檢測效率更快更精準。現階段的 Moiré都是使用投影機投射光柵，有兩項影響量測品質的重要因子，(1)因為攝影機取樣頻率與投影機投射頻率不匹配，錄製的影像就會因為投影機幻燈片的閃爍造成雜訊，讓最後數據分析產生偏差，(2)投影機與攝影機的夾角並沒有達到適合的角度，使錄製畫面無法產生 Moiré等高線現象，未達到影像特徵值強調效果。本研究優化針對以上缺點依實驗進行優化，(1)將攝影機幀數由 30fps 改為與投影機相同的 60fps。(2)擺設位置採光柵側投影，攝影機正面拍方式。(3)光柵焦距在物體前 0~5cm 處。結果顯示硬體位置調配的改善過去 Moiré沒有等高線輪廓缺點，另外用喇叭輸出固定頻率去驗證此系統的精確度；在 7Hz 振動頻率時，有等高線影像所量測出來的數據，能有效強調待測物之特徵值，優化前的數據在 7Hz 處強度只有在 7.5，並且有 0.6Hz 和 8Hz 的相對值誤差，而優化後的數據顯示 7Hz 處有明顯的波峰，強度甚至快到 17 左右，相當於過去系統的兩倍以上，雜訊減少且整體訊號強度從低於 2 明顯增 ii 加到高於 4，真正達到 Moiré強化影像之效果，成為量測震動的可靠工具之一。;Moiré optical measurement is non-contact, non-destructive, low cost, etc. At the same time, the method of using Moiré fringes to calculate and analyze the surface vibration or subtle changes in object size is faster and more efficient than traditional digital image processing methods. At this stage, digital Moiré uses projectors to project gratings. There are two important factors that affect the measurement quality. (1) Because the sampling frequency of the camera does not match the projection frequency of the projector, the recorded image will be affected by the projector slide. Light flicker causes noise, which cause the result to have image bias during the final data analysis. (2) The angle between the projector and the camera does not reach a suitable angle, so that the Moiré contour line phenomenon cannot be generated in the recording image, diminishing the image feature value emphasis effect. The optimization of this study is based on the experiments according to the above shortcomings. (1) The frame rate of the camera is changed from 30fps to 60fps, which is the same as the projector’s fps. (2) The installation position adopts the grating side projection, and the camera shoots from the front. (3) The focal length of the grating is 0~5cm in front of the object. The results show that the hardware position adjustment has been improved. In the past, the digital Moiré did not have the shortcomings of contour lines. In addition, the speaker output fixed frequency to verify the accuracy of the system. At 7Hz vibration frequency, the data measured by the contour image iv can effectively emphasize the waiting period. For the characteristic value of the measured object, the intensity of the data before optimization is only 7.5 at 7 Hz, and there is a relative value error of 0.6 Hz and 8 Hz. While the optimized data shows that there is a clear peak at 7 Hz, and the intensity increased to 17 Hz, which is quite More than twice the size of the previous system. The noise is reduced and the overall signal strength is significantly increased from less than 2 to more than 4, which truly achieves the effect of Moiré′s enhanced image and becomes one of the reliable tools for measuring vibration.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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