數位變焦光學測距系統於透明物件與3D表面形貌掃描的研發與應用

Abstract

本研究為將可變焦透鏡的連續式變焦技術運用在共焦測距系統上，發展透明待測物與曲面造型量測設備，並透過實驗進行效能的測試與驗證；實驗量測透明待測物與掃描物體表面之形貌並搭配數值校正來達成提高快速量測速率與準確度的目標。本研究的第一部分探討變焦透鏡在兩種驅動模式下進行透明待測物的厚度量測；藉由LabVIEW程式找出透明玻片等待測物的兩個共焦訊號峰值並帶入距離曲線得出未校正的厚度，再經由折射校正公式計算實際厚度值，由此方式量測得出透明玻片等待測物厚度。第二部分探討共焦訊號的偏移原因，本實驗選用可變焦透鏡模組提供的電流與光焦度驅動模式加以分析比較；首先探討兩者對共焦反饋訊號隨溫度變化方面的響應；其次使用正掃描與逆掃描方式擷取信號來觀察兩者對共焦反饋訊號的偏差影響程度。第三部分使用三角波驅動模式搭配DAQ連續接收模式來作資料擷取，本研究設計DAQ操控程序為自啟動後可以連續掃描擷取一整列的待測點資料，搭配程式的訊號分析演算法來提升連續多點的量測速度。在20Hz的三角波驅動下，可以達到每點50毫秒的量測速率，約為改善前的2.6倍。本研究經由觀察不同驅動頻率影響的偏差誤差的狀態，歸納出偏移誤差的形式與數值，並建立校正公式。校正後的量測系統搭配二維移動載物平台對標準階梯鋁塊做形貌掃描。在3D曲面的量測應用方面，用DAQ連續式多重點擷取資料方式來做球面鏡外型的掃描，首先進行移動平台的水平校正，接著運用球面鏡表面幾何特徵快速找到球面頂點，即投影圓心的位置。然後再以再來以圓心為中心進行表面形貌的掃描量測。本研究的實驗數據顯示經過量測速率與精度改善後，應用可變焦透鏡的共焦量測系統可明顯提高量測速度，並可應用於透明玻片與3D表面造型的量測，可做為光電量測設備發展的參考。

The study proposed and applied the innovative confocal optical technique with varifocal lens on confocal displacement sensor system. High speed scanning methology of profile measurement for transparent object was developed. Some typical experiments of transparent object configuration measurement are executed and demonstrated. First of all, the thickness measurement of cover glass and slide glass was illustrated and discussed. Varifocal lens driven by current and focal power mode were adopted for comparision. LabVIEW program was developed to detect two peaks from collected confocal signal and transforms it into two groups of displacement data for calculating the thickness of the transparent objects based on the corrected parameters such as optical reflection parameters, etc.. Secondly, the compensating rules in dealing with the offset error of confocal signal was discoveried. The influence of temperature in current mode was detected and studied while observing the relative changes of confocal signals in different temperature ocnditions. In third part, the study proposed the continuously scanning method by using analog triangle mode assisted by DAQ system. Measuring the data of multiple points based on LabVIEW improves the scanning speed while using 20 Hz triangle driving current with this method. The scan speed could reach near 50 ms per scan point, which increases 2.6 times in speed compared with former method. Based on the above methods, the measurement of step-height of stair configuration object with 2D tracjectory was tested as illustrated samples. Finally the surface profile of convex glass lens by continuously multi-point scanning method was studied and discussed. The results of the experiment show that after thecompensation process of regulating tilt of the measuring platform, the center of the lens can be found. The evaluated results demonstrate the improved and practical performance of the confocal displacement sensor system with varifocal lens. The function and precision of the optical measurement system was also available for applying to the transparent object on geometrical configuration measurement applications.