Quantitative Comparison of Glass and Plastic Optical Components in Mass-Produced Imaging Applications
Juutilainen, Oula Tapio
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Lasisten ja muovisten optisten komponenttien kvantitatiivinen vertailu massatuotetuissa kuvantamissovelluksissa
Plastics have, in imaging applications, mostly replaced glass as the most common optical material. However, as there is a constant demand for better and better cameras, manufacturers are starting to hit limits of optical qualities of current polymer materials. This has raised interest towards hybrid optics, meaning lenses of a camera comprise of both glass and plastic elements rather than just one or the other. In this thesis a wide range of physical and optical qualities of different optical glasses and plastics were studied via in order to later determine possible applications, in which hybrid optics could produce added value to the consumers. To achieve this goal, first a broad understanding on materials' properties was gathered via literature review, after which the two most promising topics were studied more in detail. At first it was settled upon a decision to compare short wavelength transmittance and its effects on noise creation in final image formation with a MATLAB simulation. Also the effects of temperature changes on focal length were studied. It was found, that glasses are much more resistant to thermal defocus: in 10--50 °C temperature range plastics were at least ten times more affected. Also this difference would increase slightly exponentially, if temperature range was increased. High transmittance was verified to reduce noise in final image. The biggest relative advantage was achieved in low light scenarios. As material differences go, for thin, well AR-coated plastics and glasses, transmittance differences are so tiny, that they only produce at maximum 0.8 % SNR difference for glass's advantage with six 0.4 mm lens stack. In one case, plastic even prevailed glass. However, it was found, that transmittances of plastics drop, when they are thermally aged, whereas glasses sustain high heats considerably better. Also AR-coatings for plastics may not be as efficient as ones for glasses. Thus results in this thesis are considered a best case scenario in terms of noise performance of plastics.