- 學位論文
光學顯微鏡去迴旋積檢測技術
Deconvolution Inspection Technology for Optical Microscopy
摘要
一般遠場光學顯微系統取像過程中，光訊號自樣本表面發散後到達物鏡時，由於物鏡尺寸與焦距的限制，必然存在信號損失，導致還原之影像呈現模糊發散，此即任何電磁波都有的繞射現象，當使用光學顯微系統擷取成像點間距過小的樣本影像時，繞射現象會使得各成像點無法有效辨識，通常稱此為光學系統之繞射極限，乃光學顯微量測系統之最大瓶頸，本論文之主要目的即在結合影像處理和模式化去迴旋積技術，期盼在以光學影像技術檢測樣本尺寸時，其分辨率可以達到突破繞射極限限制的目標。 基於光學系統繞射理論，一光點訊號經過光學系統成像後將導致模糊發散，此一過程可視為點擴散函數(point spread function, PSF)，而光學系統成像則可視為點擴散函數之迴旋積，因此藉由正確的PSF估測作影像去迴旋積處理，可強化樣本之影像分辨率，即可進一步檢測奈米級尺度之物體。本論文一方面利用模式化參數模擬光學系統估測PSF，另一方面使用最大可能性估測(maximum likelihood estimation, MLE)盲目估測PSF，配合干涉顯微鏡取像與影像處理技術，以此兩種估測PSF分別對觀測樣本之繞射模糊影像作非線性去迴旋積處理。在模擬評估部分，本論文以理想光學系統驗證，已確認可檢測至100奈米以下線寬；在實測實驗部分，本論文採用了一組白光光源和0.55數值孔徑鏡頭之干涉顯微系統，在放大倍率100倍時之像素解析度為74奈米，應用本論文之技術檢測平面200奈米線寬圖形時，得到線寬值為3像素，350奈米線寬檢測結果則為5像素，整體誤差不大於1像素，顯示本技術已能大幅提升系統退化影像之檢測分辨率，達到次像素檢測精度與突破繞射極限的檢測目標。
關鍵字
去迴旋積檢測技術並列摘要
In the imaging formation of far-field optical microscopy system, for the limit of lens size and focal distance, there certainly is the loss of signal in the light diffuse from the object surface to the objective lens, this phenomenon is called as diffraction of optical system. Diffraction would blur the system images, when the sample size is nearly 1/2 of the wavelength of the light source, the sample image would be hard to identify. The limit is called the Abbe diffraction limit, at present, the Abbe diffraction limit is the thorny problem in the automated optical inspection system. The major purpose of this thesis is to combine the image processing and model-based deconvolution technology to recover the sample image, and expect the resolution of the recovered image of the optical inspection system that can break the diffraction limit. By the optical diffraction theory, we know when a single point light signal imaging through the microscopy system, it will spread as an Airy disc image, it also is called PSF (point spread function), and the imaging formation of optical microscopy can be seen as the convolution of the PSF. Therefore, we can restore the image by deconvolution with the true PSF, and to inspect the object small than the diffraction limit. In this thesis, we deconvolute the far-field optical microscopy images by Richardson–Lucy algorithm with the model-based PSF and the blind guess PSF, and use some image pre-processing technique to analysis and compare the result data. The system is confirmed that can inspect 100 nm linewidth object with the ideal conditions by computer simulation, we also prove the model-based deconvolution can inspect 200 nm linewidth sample with white-light source, NA0.55, and 100X Mirau interference objective, the resolution of the system is 74 nm/px, the inspection data for 200 nm is 3 px, the data for 350 nm is 5 px, the error for all data does not exceed 1px. It means the model-based deconvolution that can substantially improve the resolution of the degenerative inseption images, to attain the purpose for sub-pixel inseption precision and breaking the diffraction limit of the optical inspection system.
參考文獻
延伸閱讀
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