Near infrared ray is a limited ray (a bite) that is only longer than the wavelength of the red line, that is, the infrared ray that is not too long is called near infrared ray; Similarly, there are far infrared rays (that is quite long). As we all know, infrared rays will heat objects, so near infrared nondestructive testing is to control radiation (trace) to detect human body (such as lens inspection of eyes)

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