| 摘要 |
A distortion distribution of an entire vitreous silica crucible is measured in a non-destructive way. A distortion-measuring apparatus comprises: a light source 11 which irradiates the vitreous silica crucible 1 from outside; a first polarizer 12 and a first quarter-wave plate 13 disposed between the light source 11 and an outer surface of the vitreous silica crucible 1 wall; a camera 14 disposed inside of the vitreous silica crucible 1; a camera control mechanism 15 configured to control a photographing direction of the camera 14; a second polarizer 16 and a second quarter-wave plate 17 disposed between the camera 14 and an inner surface of the vitreous silica crucible 1's wall. An optical axis of the second quarter-wave plate 17 inclines 90 degrees with respect to the first quarter-wave plate 13. The camera 14 conducts photographing of a light which is emitted from the light source 11 and passes through the first polarizer 12, the first quarter-wave plate 13, the wall of the vitreous silica crucible 1, the second quarter-wave plate 17, and the second polarizer 16. |
