We are often exposed to infrared light, such as near-infrared wavelengths such as 780nm and 808nm, and the naked eye can see a faint red spot. As we all know, lasers like 915nm are invisible wavelength. So how do we detect it?
In the video below, we use a small infrared detection card to convert 915nm invisible light into visible light. The 915nm laser illuminates the observation card and displays a green visible spot.