These viewing cards contain a smart pigment coated sensor area that changes color when illuminated by mid-IR sources. This allows for the easy location of mid-IR beams and their focal point as well as the visualization of spatial mode patterns.

Low power cards can detect down to 0.2 W/cm² with one sensor area for low powers and a second sensor area for medium powers. High power cards have a damage threshold up to 120 W/cm². The high power sensor card has a larger area and can be used conventionally by directly exposing the sensitive area to mid-IR radiation. For high power densities, the back of the sensitive area (uncolored) is exposed to the radiation and the sensitive area on the front of the card changes color.

The sensor area offers high performance thanks to color change with high contrast. A white spot appears as a result of mid-IR radiation for all sensitive areas. The beam spot size on the sensor card depends on beam diameter and power. The higher the beam power, the larger the beam spot may appear on the senor area due to dispersion. When radiation is stopped, the initial coloring rapidly re-appears. Touching the card to a surface like an optical table helps refresh the card quickly.