基於數位微鏡陣列的自適應光學顯微鏡開發研究

Abstract

自適應光學顯微技術(Adaptive Optics Microscopy)為自適應光學的重要應用之一，透過補償因光學元件造成的波前畸變，抑制光傳播過程中遇到的像差，從而提高對樣品觀察的解析度與銳利度。在自適應光學系統中，人們常選用可變形鏡與矽基液晶當作空間光調製器，而夏克-哈特曼波前感測器則常用於波前感測，以了解相差程度並進一步校正；然而，可變形鏡與矽基液晶有解析度、耐用度、更新率與適用波長的問題，夏克-哈特曼波前感測器也有採樣點的限制需要克服。 本研究顯微系統參考Olympus BX71的光路架構，透過聚光鏡增加光的使用效率，並在光路中的物鏡之後引入影像系統與波前校正系統，影像系統透過成像透鏡拍攝樣品影像，波前校正系統則是整合了型號為DLP 6500 BFYE的數位微鏡陣列與橫向剪切干涉儀設計而成。DLP 6500 BFYE具有1920×1080像素的高解析度與9523 Hz的高更新率，透過與電腦生成全像圖的結合進行高解析度可以更精準的補償波前，本研究中將這項特點應用在高階像差的校正。高更新率可加速剪切干涉的相移法進行，再透過二維剪切干涉與K-mirror的設計，達到使用單一剪切片進行二維的波前重建，並進一步進行波前校正，最後透過影像系統觀察影像品質的變化。 實驗結果顯示，無論是數位微鏡陣列的繞射模型探討、全像圖的原理與驗證、K-mirror對於影像旋轉與偏振態的需求、二維剪切干涉儀的量測與驗證和影像品質的提升，都達到了預期的效果。這套系統可以減少傳統剪切干涉儀因為相移法需要機械轉動造成的不穩定性，且在單純使用分光鏡、反射鏡與剪切片材料即完成干涉儀的架設，相較於夏克-哈特曼波前感測器有更好的經濟效益。

Adaptive Optics (AO) Microscopy stands as a crucial application of adaptive optics technology. It effectively compensates for wavefront distortions introduced by optical elements, thereby suppressing aberrations during light propagation. This ultimately leads to a significant improvement in both the resolution and sharpness of sample images. In the Adaptive Optics system, deformable mirrors and Liquid Crystal on Silicon devices are commonly chosen for spatial light modulation and are used to correct wavefront distortion. In order to determine the wavefront’s condition and the needed correction, the Shack-Hartmann wavefront sensor plays an important role. However, both deformable mirrors and Liquid Crystal on Silicon devices face inherent limitations in terms of resolution, durability, refresh rate, and wavelength range that need to be overcome. Similarly, the Shack-Hartmann wavefront sensor is restricted by its sampling points. The optical path architecture of the microscope system in this research is based on the OLYMPUS BX71 microscope. A condenser is introduced to enhance light efficiency. Following the objective lens, an imaging system and a wavefront correction system have been integrated into the optical path. The imaging system captures sample images via an imaging lens and the wavefront correction system is combined with DLP 6500 BFYE Digital Micromirror Device and a lateral shearing interferometer. The DLP 6500 BFYE has a high resolution of 1920x1080 pixels and a rapid refresh rate of 9523 Hz. If the computer-generated holograms are combined, the high resolution enables more precise wavefront compensation so the high-order aberration can be corrected in this research. Moreover, the fast refresh rate accelerates measuring rate of the phase-shifting method used in shearing interferometry. Through a design incorporating two-dimensional shearing interferometry and a K-mirror, the system has achieved two-dimensional wavefront reconstruction and wavefront correction by using a single shear plate. Finally, the changes in image quality has been observed through the imaging system. The experimental results confirmed that all aspects of the system performed as expected. This includes the exploration of the digital micromirror device's diffraction model, the principles and validation of holograms, the requirements of image rotation and polarization state through the K-mirror, the measurements and validation of the two-dimensional shearing interferometer, and the improvement in image quality. Furthermore, this system effectively reduces the instability typically associated with the mechanical rotation required for phase-shifting in traditional shearing interferometers. Besides, by simply utilizing beamsplitters, mirrors, and shearing elements to construct the interferometer, the developed system offers a more economical solution compared to Shack-Hartmann wavefront sensors.