In the original image, a white backlight is used without a filter. When a MidOpt® BP850 Near-IR Bandpass Filter is placed over the lens and used with an IR backlight, the filter blocks the visible portion of the spectrum but passes only the ink illuminated by the output wavelength of the IR backlight. This makes the invisible print visible and also creates optimal contrast.

BP850 Near-IR Bandpass Filter

This solution is recommended when using high-power 830-850nm LED or laser diode lighting to improve contrast in surveillance applications or when inspecting in the infrared, this filter features high peak transmission and particularly durable, robust coatings. This filter’s coated surface also greatly inhibits staining due to year-round issues with heat, humidity, and/or air quality that affect uncoated infrared filters.