Head-Up Display: Construction: Notes

Fig 1: Identifying Head-Up Display System Components

Courtesy of BMW OF NORTH AMERICA, INC.

The key components of the head-up display are:

• Four Mirrors

  The 4 mirrors ensure that the contents of the projection display appear at the distance and in the size required, and that deformations caused by the windscreen are largely compensated for.

• Light Source

  The light source is the back lighting of the projection display. This light source is a number of coloured LEDs laid out in rows over a certain area. The light source is actuated by the electronic circuitry in the head-up display, which also controls the brightness of the display content.

• Projection Display With Cover Panel

  The projection display with TFT technology (TFT = thin-film transistor) is used to show the display contents. The projection display is activated by the electronic circuitry of the head-up display.

  A cover panel protects the projection display when it is switched off.

  A stepper motor folds the cover panel out of or into the beam. The stepper motor is actuated by the electronic circuitry in the head-up display.

• Electronic Circuitry

  The electronic circuitry has the following tasks:

  • Activation of the projection light source and the stepper motor for the cover panel. The electronics include a temperature sensor which protects the head-up display from overheating. The projection light source is switched off if the temperature exceeds approx. 105 °C.
  • Evaluating and processing incoming image information
  • Generating display content

A power supply in the head-up display provides the light source with a voltage of 42 volts, transformed from the on-board supply voltage.

A 12-pin connector on the head-up display creates the connection to the vehicle electrical system. The MOST data bus is connected to the head-up display via a 2-pin connector.