The axes of the light rays from the light source (1) and the back-scattering to the light detector (3) have mutually closely adjacent and substantially parallel or coincident portions.

来自光源（1）的光线的轴线以及反向 散射到光检测器（3）的光线的轴线具有彼此紧邻并基本平行或重合的 部分。

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Do the following to ensure the safe operation of your smoke detector: if your smoke detector is working properly, the red light should be on.

为确保您的烟雾探测器的安全运行，请执行以下操作：如果烟雾探测器正常工作，则红灯常亮。

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If your smoke detector is working properly, the red light should be on.

如果你的烟雾探测器运作正常，红灯应当亮起。

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The camera works, the team explained, by bouncing lasers off distant objects, and measuring the time it takes for the light to travel back to the detector.

BBC: Long-distance 3D laser camera unveiled by Edinburgh team

At one end of the tube is a source of ultraviolet light and at the other a detector.

BBC: Hidden graves found using chemical 'sniffer' technology

The light-sensitive area on each CCD detector measures 45.0mm by 59.0mm, encompassing 1, 966 pixels by 4, 500 pixels.

BBC: A billion pixels for a billion stars