Author: Samuel Tonkin
Tonkin, Samuel, 2025 Sulfur-based polymers with long-wave infrared transparency for thermal imaging optics, Flinders University, College of Science and Engineering
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Thermal imaging allows for the visualisation of heat and non-contact temperature measurements. It has long been used in high end applications like military, space exploration and medical thermography but has been prohibitively expensive for most consumer industries. Recent developments in microbolometer sensor technology has dramatically reduced the cost of long wave infrared thermal imaging, sparking interest in many low-cost, high-volume applications like home appliances or the mobile phone industry. However, thermal imaging systems require specialised and expensive optical materials for lenses. These materials have not seen the same decrease in cost, making them the largest obstacle preventing the realisation of the many applications of thermal imaging.
In this thesis, a range of new sulfur-based optical polymers were developed to be used as the lenses or other optics in thermal imaging systems. Novel and creative methods of synthesis were used to prepare polymers which had never been reported in literature. The raw materials used to prepare the sulfur-based polymers were several orders of magnitude cheaper than those commonly used for thermal imaging optics. These polymers were characterised, and a range of optimisation processes were used to prepare materials with some of the highest long wave infrared transmission, refractive index and glass transition temperature in literature.
A range of lenses were designed and fabricated using scalable and low-cost manufacturing methods like melt casting, compression moulding or injection moulding. These fabrication techniques were used to demonstrate how polymer lenses could be made in the quantities required for the emerging high-volume thermal imaging applications. The lenses were fully integrated into a prototype thermal imaging system and demonstrated excellent performance over a range of focal lengths and lens designs.
The research presented in this thesis has direct applications in the thermal imaging industry and could see rapid integration into a range of products. The integration of low-cost polymer optics into infrared imaging systems would make thermal imaging available to many new fields and industries that were not previously possible.
Keywords: Thermal imaging, infrared imaging, sulfur, polymer, sulfur-based polymer, inverse vulcanization, lens, thermal camera
Subject: Engineering thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Justin Chalker