Margrain T H, Owen C
Department of Optometry and Visual Science, City University, London, UK.
Ophthalmic Physiol Opt. 1996 Mar;16(2):108-14.
When a spectacle wearer enters a warm environment after having been in a cooler one, his/her spectacles may 'mist up' due to the formation of condensation on the lens surface. Both the physical properties of the spectacle lens and a number of environmental factors determine how long spectacles take to demist. The relative misting performance of crown glass, CR39 and polycarbonate spectacle lenses were assessed using a novel technique. A box in which the environmental conditions could be controlled was used first to cool the lens and then to warm it. This change in temperature caused condensation to form on the lens surface. By projecting the image of a grating through the lens onto a linear array of photodiodes it was possible to measure the contrast transmission of the spectacle lens as it demisted. Each lens type misted and demisted in a characteristic way. The polycarbonate lens demisted more rapidly than the CR39 lens which, in turn, demisted more rapidly than the glass lens. This indicates that polycarbonate spectacle lenses should be used in conditions where the adverse effects of spectacle misting need to be minimised.
当一名眼镜佩戴者从较冷的环境进入温暖环境时，其眼镜可能会因镜片表面形成冷凝水而“起雾”。眼镜镜片的物理特性和一些环境因素共同决定了眼镜起雾后多久会消散。采用一种新技术评估了冕牌玻璃、CR39和聚碳酸酯眼镜镜片的相对起雾性能。首先使用一个可控制环境条件的盒子来冷却镜片，然后再加热。这种温度变化导致镜片表面形成冷凝水。通过将光栅图像透过镜片投射到线性光电二极管阵列上，可以测量眼镜镜片在起雾消散过程中的对比度透射率。每种镜片类型起雾和消散都有其特点。聚碳酸酯镜片比CR39镜片消散得更快，而CR39镜片又比玻璃镜片消散得更快。这表明在需要将眼镜起雾的不利影响降至最低的情况下，应使用聚碳酸酯眼镜镜片。
