What does a dichroic filter in a laser projector?

The dichroic filter is used in an multi color laser system for combining the single colors to one beam. The dichroic filter deflects a certain color spectrum, whereas it lets pass others. Due to that it is possible to have e.g. a red and a green laser source, that is combined: The green light heads straight to the scanner mirrors, whereas the red source is placed 90° to the green beam. With the dichroic filter, the red laser light is deflected to exactly match the green beam and hit the scanner mirrors in the same point as the green laser light.

If colors of a multi color laser systems mismatch, it is necessary to realign the dichroic filters and rematch the colors again.