Nor is it possible simply to crank up the power of the source beam, because infra-red light at high intensity can cause eye damage.

他说，“多数光不会你想让它到哪它就到里”。 也不可能简单地增强光束的强度，因为高强度的红外光会伤害人眼。

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The fragments, preserved between sheets of glass, respond to the infra-red spectrum - ink invisible to the naked eye can be seen and photographed.

红外线谱把这些保存在玻璃板之间的残片上肉眼无法识别的墨迹显现出来，并拍成照片。

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In this case the operator would wear goggles that convert infra-red light into an image that the eye can perceive.

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