傳統接觸式儀器在量測結構物位移時，常受限於單點量測、架設位置與接觸條件等因素，難以完整掌握結構之多點動態反應。為改善上述限制，數位影像相關法（Digital Image Correlation, DIC）作為一種非接觸式光學量測技術，具有同步取得多點位移資訊之應用潛力。本研究自行開發一套基於 DIC 技術之位移量測軟體，並搭配人工標靶進行離散點位追蹤，以獲取橋梁模型之多點動態位移反應。
在演算法方面，本研究採用零均值正規化平方差和（Zero-Normalized Sum of Squared Differences, ZNSSD）作為相關性準則，以提升系統於實際量測環境中對光線變化之強健性。同時，為提高長時間影像序列分析之運算效率，本研究導入反向組合高斯－牛頓法（Inverse Compositional Gauss-Newton, IC-GN）進行次像素位移求解。透過預先計算參考影像之空間梯度與 Hessian 矩陣，可降低迭代過程中重複矩陣運算之成本，進而提升整體分析效率。
為驗證自研 DIC 軟體 IC-GN DIC之準確性與實用性，本研究首先透過具已知真值位移之數值影像進行演算法驗證，並將分析結果與施明祥教授所開發之 Series Image DIC Analysis（SIDICA）軟體進行比較，以確認自研程式於次像素位移分析上之可靠性。接著，透過不同幾何標靶之數值分析，評估人工標靶圖案對位移量測精度與穩定性之影響。最後，將IC-GN DIC應用於橋梁模型之靜態與動態實驗，並與雷射位移計及加速度計等傳統量測儀器進行交叉比對。
實驗結果顯示，IC-GN DIC可有效取得橋梁模型之多點位移歷時，且與傳統量測儀器具有良好一致性。在頻率域分析中，DIC 結果亦能準確掌握主要振動頻率，顯示本研究所開發之 DIC 系統具備應用於結構工程非接觸式動態位移監測之可行性。

Conventional contact-based instruments for structural displacement measurement are widely used because of their stable performance and mature measurement procedures. However, they are often limited by single-point measurement, installation constraints, contact conditions, and the need for multiple sensors when simultaneous measurements at several locations are required. These limitations make it difficult to fully capture the multi-point dynamic response of a structure. Digital Image Correlation (DIC), as a non-contact optical measurement technique, provides an alternative approach because it can obtain displacement information from multiple locations within the same image sequence. In this study, a target-based DIC displacement measurement software was developed, and artificial targets were used for discrete point tracking to obtain the multi-point dynamic displacement responses of a bridge model.
In terms of the algorithm, the Zero-Normalized Sum of Squared Differences (ZNSSD) was adopted as the correlation criterion to improve robustness against illumination variations in practical measurement environments. To improve the computational efficiency of long image-sequence analysis, the Inverse Compositional Gauss-Newton (IC-GN) method was introduced for sub-pixel displacement estimation. By precomputing the spatial gradients and Hessian matrix of the reference image, repeated matrix operations during the iterative process can be reduced, thereby improving the overall computational efficiency.
To verify the accuracy and practicality of the developed DIC software, numerical images with known ground-truth displacements were first used to validate the algorithm. The results were compared with those obtained from the existing DIC software SIDICA to evaluate the reliability of the proposed method in sub-pixel displacement analysis. Subsequently, numerical analyses of different geometric target patterns were conducted to investigate the influence of artificial target design on displacement measurement accuracy and stability. Finally, the developed DIC software was applied to static and dynamic tests of a bridge model, and the measured responses were cross-validated with conventional instruments, including laser displacement sensors and accelerometers.
The numerical and experimental results show that the developed DIC software can effectively capture sub-pixel displacements and obtain multi-point displacement time histories of the bridge model. The displacement responses obtained by DIC were generally consistent with those measured by laser displacement sensors. In the frequency-domain analysis, the DIC results were also able to identify the dominant vibration frequencies of the bridge model. Although acceleration obtained through double differentiation of displacement was more sensitive to noise, the main response trend could still be captured after appropriate filtering. These results demonstrate the feasibility of the developed DIC system for non-contact multi-point dynamic displacement monitoring in structural engineering applications.

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