Inexpensive polymer-based optics
The TECH_TIR project introduced several innovations in the fields of optics, optomechanics, actuation and sensor technologies to develop two new products. One of these innovations involved the development of low-cost high-density polyethylene (HDPE) lenses. Until this development, the HDPE material had not been used as an optical material in high-end imaging applications, despite its extensive use in low-end non-imaging applications. This limitation was mainly due to its poor transmittance properties by comparison with semiconductor crystals or chalcogenide glasses. A key prerequisite for the production of HDPE lenses as thin Fresnel elements of less than 1mm was to bring the radiation throughput to its maximum potential. Two manufacturing techniques can be employed for fabrication of HDPE Fresnel lenses, hot pressing and injection moulding. The first one is suitable for flat lenses and offers a good moulding accuracy, while the second is more appropriate for curved lenses with limited accuracy. The limited accuracy of the second technique comes from shrinkage of the material that results in rounding of the microreliefs and deformation of the substrate. Answering this need, hot-pressed chalcogenide glasses were utilised, in particular a doublet of chalcogenide material was used for a lower cost product. Lenses based on chalcogenide material cost less than those based on crystalline semiconductors, because of the inexpensive raw materials used and the cost-effective manufacturability (through moulding). The outcome was the design, testing and manufacture of low cost HDPE solutions. The huge cost reduction in the production of optics using plastic-based micro-optical parts opens new avenues in imaging and detection capabilities. These can find numerous applications ranging from medical imaging to surveillance.
