| 摘要 |
A method for testing injection-molded discs, such as CD or DVD discs, for the presence of residual stress by placing the discs between two polarizers uses a video screen provided as part of the injection machine's display unit as a light source. The screen is preferably made uniformly bright by removing text or drawings and being set to emit bright white light. The disc is set between and parallel to the two polarizing plates, whose axes are crossed. The machine operator views the screen through the crossed polarizers and freshly-made disc. Stress disturbs the polarization of light transmitted through the disc and shows molding defects as bright patches. The screen can be a CRT or a liquid crystal panel. The light is preferably made uniform by temporarily erasing letters or figures, used to show molding data, from the screen. Preferably a push-button activates and deactivates the bright white screen.
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