Projection unit for a head-up display

A method comprising:

• emitting a light beam towards a mirror arrangement by means of a projector element;
• and
• projecting the light beam on a projection surface when the light beam leaves the mirror arrangement, wherein:
• the mirror arrangement comprises a first mirror and a second mirror, the first mirror is a flat mirror, the second mirror is a flat mirror arranged distant from and in parallel to the first mirror, the projector element is configured to emit the light beam towards the first mirror at an angle of incidence, the first mirror and the second mirror are arranged at a first distance from each other such that the light beam is repeatedly reflected from the first mirror towards the second mirror, and from the second mirror back towards the first mirror before leaving the mirror arrangement, and
• at least one of the first distance between the first mirror and the second mirror, and the angle of incidence is adjustable.