| 摘要 |
PURPOSE:To enable a detailed stress distribution to be obtained in the form of contour lines by providing an image pickup device for forming the photoelastic image of an object to be measured that is inserted in between a first polarizer and a quarter wavelength plate. CONSTITUTION:A parallel light beam reaches an image pickup device 7 via a first polarizer 4, a quarter wavelength plate 5 and a second polarizer 6. An object 10 to be measured is inserted in between the first polarizer 4 and the quarter wavelength plate 5. Therefore, when the rotating angle of the second polarizer 6 is equal to zero, a portion in the object 10 wherein an optical path difference is equal to zero is covered by a black fringe. When the second polarizer 6 is rotated through theta degrees, the black fringe is displaced to a position wherein the optical path difference is equal to (theta X constant), where the constant takes a value determined by a photoelastic instrument. Thus, the second polarizer 6 is rotated and a group of contour lines each connecting the portions wherein the optical path differences are constant can be obtained. Then, when those contour lines are concurrently displayed in different colors, the optical path difference distribution in the object 10 being measured can be displayed by grouping.
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