| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 100 === A miniature and flexible scanning endoscope based on nonlinear optics has been developed for three-dimensional (3D) optical imaging, such as two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) imaging. A double-cladding fiber is employed to transport femtosecond laser pulses to excite samples in single-mode and collects the nonlinear optical signal by multi-mode. For To improve the collection performance, an assembly of three micro-size doublet achromatic lenses were designed by achieving minimum focal shift between the near infrared excitation and visible collection wavelengths. A grating pair with negative group velocity dispersion (GVD) is utilized to compensate the dispersion induced by the optical fiber. Furthermore, a miniature piezoelectric tube is used to produce the space-filling scanning to achieve two-dimensional optical nonlinear images. Two scanning patterns based on spiral scanning and Lissajous scanning are developed via different driving modes. The spiral scanning provides the field of view approximately of 150 μm, pixels of 290×290, frame rate at 5 Hz, and natural resonance frequency at 905 Hz. The Lissajous scanning based on two driving frequencies close to the resonance frequency offers the same field of view and pixels, frame rate at 1 Hz, rectangular images, and low photodamage. Finally, the z-axis piezoelectric motor is integrated into the system to develop a 3D nonlinear optical endoscope.
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