1. Field of the Invention
The invention relates to a head-up display for a motor vehicle, having an image generating device, from which beams of an image are guided, linearly polarized by a polarizer arranged on the light-exit side on the image generating device, via an imaging optical unit to a windscreen, and are directed from the windscreen in the direction of a driver of the motor vehicle.
2. Description of Prior Art
In such a head-up display, a representation of information is projected by a projection system into the windscreen for the driver of the motor vehicle.
The image is generated by the image generating device. Terminating with respect to the observer, an absorbing polarizing film is situated on the image generating device. The light from the image generating device is linearly polarized by the polarizing film. This polarization is perpendicular to the plane of the projection.
Due to the light paths and the reflection of the beam of the projection image at the windscreen, it is possible that the sun shines directly into the image generating device. Due to the focusing of the imaging optical unit, a significant amount of heat is introduced into the image generating device.
To reduce the heating, it is known to arrange a cold mirror, which is transparent or absorbing in the infrared spectral range, in the beam path of the beam between image generating device and windscreen.
Nevertheless, sufficient luminous power can still be incident on the image generating device for the latter to be heated to temperatures which impair the generated image.