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讨论了玻璃内可能出现的各种类型的不均匀性。玻璃的不均匀性取决于:(a)熔炼过程;(b)由热力学不平衡造成的密度差异;(c)在退火区内由温度梯度造成的永久应变。假如想要达到玻璃所允许的最高级光学均匀性,则需要知道(a)、(b)和(c)的影响。消除由(b)和(c)所造成的不均匀性,就可测得由熔炼过程中所造成的不均匀性。为了得到某种特殊玻璃的不均匀性的可靠测试数据,必须用两种不同的测量方法。对于一块直径400mm、
Various types of inhomogeneities that may occur in the glass are discussed. Glass inhomogeneities depend on: (a) the melting process; (b) the difference in density caused by the thermodynamic imbalance; and (c) the permanent strain caused by the temperature gradient in the annealing zone. If you want to achieve the highest levels of optical uniformity allowed by glass, you need to know the effects of (a), (b) and (c). By eliminating the inhomogeneities caused by (b) and (c), the inhomogeneities caused by the smelting process can be measured. In order to obtain reliable test data for the inhomogeneity of a particular glass, two different measurement methods must be used. For a diameter of 400mm,