An invisible infra-red beam is superimposed over the image and sensors detect the reflections that are created whenever and wherever the image is touched.

有一束看不见的红外线被叠加在了画面上；不论何时、不论何出图像被触摸到，传感器都会侦测出反射。

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So Starkweather fired a laser through the air between the two buildings, an improvised communications system that meant that, if you were driving down the Foothill Expressway on a foggy night and happened to look up, you might see a mysterious red beam streaking across the sky.

NEWYORKER: Creation Myth

In the case of lidar, the waves are in the form of an infra-red laser beam.

ECONOMIST: Forest conservation

LaserMotive uses special cells made with arsenic and gallium, which are better able to capture the near-infra-red wavelengths of its laser beam.

ECONOMIST: Monitor