Real-time control of 2D lissajous fibre scanners and multi-wavelength scanning system
File(s)
Author(s)
Xiong, Qiyu
Type
Thesis
Abstract
The design, control, and setup of the two-dimensional (2D) Lissajous fibre scanners were investigated, with focus on real-time control and multi-wavelength operation. The first contribution is a dynamically programmable real-time controller for 2D Lissajous scanning. A dual-core cantilever is fabricated by dip-coating two cylindrical single-mode fibres to obtain two orthogonal bending modes with a frequency ratio close to 2. The cantilever is driven by a single piezoelectric actuator at 45°, and backscattered light is captured through cladding mode detection in a dual numerical aperture confocal scheme. Optical feedback is provided by an amplitude-coded reflecting aperture, allowing low- and high-mode timing pulses to be separated using window detectors. The low-frequency mode is locked to resonance using a phase-locked loop (PLL), while the high mode is driven off-resonance using a voltage-controlled oscillator. Additional PLLs, voltage-controlled phase shifters, and divide-by-N circuits correct amplitude imbalance and synchronise the phases, enabling programmable generation of Lissajous figures with variable scan density. This represents the first demonstration of real-time, dynamically reconfigurable Lissajous scan using intermittent feedback alone. Based on this platform, the second contribution introduces a broadband Lissajous scanner based on photonic crystal fibres (PCFs) and multi-wavelength mode-stripping detection. PCFs are dip-coated in polymer using an additional sealed-tip process to maintain the air holes. Mode-stripping detection is characterised using a monochromator and RGB photodiodes, enabling efficient multi-wavelength operation. A PCF-based scanner is constructed using RGB laser sources, with a colour-coded aperture providing distinguishable feedback for real-time control under both blue-only and multiplexed white-light illumination. The system demonstrates fluorescence imaging of USAF test targets and biological samples, as well as calibrated full-colour imaging. Together, these results establish a compact, programmable, and broadband 2D fibre-scanning microscope capable of real-time operation. The combination of a real-time controller and multi-wavelength detection provides a pathway towards future miniature scanners with multispectral functionality.
Version
Open Access
Date Issued
2026-01-03
Date Awarded
2026-05-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Syms, Richard
Sydoruk, Oleksiy
Publisher Department
Department of Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)