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Home >> BMW >> 2011 >> X3 xDrive 35i (F25) L6-3.0L Turbo (N55) >> Repair and Diagnosis >> Instrument Panel, Gauges and Warning Indicators >> Heads Up Display Unit >> Description and Operation

Heads Up Display Unit: Description and Operation



Head-Up Display

Head-Up Display
The Head-Up Display shows information, such as instructions given by the navigation system or the driving speed, using the windscreen in the driver's field of view. The Head-Up Display is installed directly behind the instrument cluster in the dashboard. The Head-Up Display is activated by the instrument cluster (KOMBI). The instrument cluster (KOMBI) provides the voltage supply and data for the image display. The image display is switched on or off using the central operating facility. The switch status is sent to the Head-Up Display via the instrument cluster (KOMBI). A full-colour display is available in the F3x for the first time. In addition, there is day and night-time illumination similar to the display in the instrument cluster (KOMBI) and the central information display.
The information continues to be displayed in the instrument cluster and central information display.
The information displayed on the Head-Up Display is dependent on the vehicle equipment. The information can be selected on the central information display using the controller. The information selected in the Personal Profile is stored in the microcontroller on the printed circuit board of the Head-Up Display.
The following information can be shown on the head up display:
- Check Control message
- Driving speed
- Navigation instructions
- Lane departure warning
- Driver assistance systems
- Entertainment lists

The following graphic displays what is shown by the Head-Up Display.







The information appears as a virtual image floating 2.2 meters away from the user at the end of the engine compartment lid. The size of the virtual image is approx. 22 x 6.5 cm (width x height).

Brief component description

Head-Up Display

The Head-Up Display is connected with the instrument cluster (KOMBI) by an electronic connector.







The Head-Up Display consists of the following components:
- Mirror
- Projection light source (LEDs)
- Projection display
- Printed circuit board
- Servomotor
- Temperature sensor

The following graphic shows the design of the Head-Up Display.







Mirrors
The mirrors ensure that the content of the projection display appear at the distance and size required, and that deformations caused by the windscreen are largely compensated for. The folding mirror and concave mirror determine the form and size of the projected image.

Projection light source
The projection light source is the backlighting of the projection display. The projection light source consists of 15 white LEDs that are installed in rows on a printed circuit board surface. The microcontroller on the printed circuit board activates the projection light source and adjusts the display brightness.

Projection display
The projection display with TFT technology (TFT = thin film transistor) is used to show the display content. The microcontroller activates the projection display.

Printed circuit board
A microcontroller is installed on the printed circuit board. The microcontroller reads the sensor signals, thereby controlling the mirror adjustment servomotors. The printed circuit board has an integrated temperature sensor that protects the Head-Up Display against overheating. In the event of faults, the microcontroller stores faults in the fault memory of the instrument cluster (KOMBI).

Servomotor
The servomotor is controlled by the microcontroller and moves the pivoting mirror into the required position (image setting or rest position).

Temperature sensor
2 temperature sensors are installed on the printed circuit board near the LEDs for the backlighting. The LED brightness is gradually reduced if the temperature exceeds approx. 86 °C. The projection light source is switched off if the temperature exceeds approx. 105 °C.

Functional description
The following graphic shows the functional concept of the Head-Up Display.







The Head-Up Display is operated using the controller. The Head-Up Display is switched on or off in the Settings menu in the central information display. The horizontal alignment of the virtual image can be adjusted using the controller. The controller is also used to select the information to be displayed. The Head-Up Display brightness can be adjusted in the central information display using the controller.
The following graphic shows the Head-Up Display menu in the central information display.







The following functions of the Head-Up Display are described:
- Switching on
- Projection
- Automatic adaptation of display brightness
- Prioritization of displays
- Image generation
- Display area setting
- Image position setting
- Switch off

Switching on
The Head-Up Display receives the status "Terminal 30B ON" via the instrument cluster (KOMBI). To protect the projection display against direct solar radiation when parked, one mirror is swivelled away while the vehicle is going to sleep. As of terminal 30B ON, the mirror is swivelled from the parked position into the beam path.
The Head-Up Display is partially operational when terminal R is switched ON. That means:
- The projection display is initialized but information is not yet displayed.
- The Head-Up Display is able to communicate with other bus users via the K CAN.
- The LEDs are off.

The Head-Up Display is operational when terminal 15 is switched ON. That means:
- If the status "Head-Up Display active" is selected in Personal Profile, the Head-Up Display is switched on automatically.
- The projection light source is switched on or off when the button for switching the Head-Up Display on or off is pressed.
- The automatic adaptation of the display brightness is activated.
- The position of the virtual image can be height-adjusted.
- The information to be displayed can be selected.

Projection
The Head-Up Display projects a virtual image that seems to be generated in the air without a fixed image carrier.
The image is generated on a projection display in the Head-Up Display and deflected by the windscreen in such a way that the driver sees the image floating above the engine compartment lid.The size of the virtual image is approx. 22 x 6.5 cm (width x height). The virtual image can only be seen from a defined area from the driver's side.

Automatic adaptation of display brightness
The automatic adaptation of the display brightness prevents major sudden changes in the brightness of the Head-Up Display when the vehicle moves between different ambient lighting conditions (e.g. from light to dark and from dark to light when driving through a tunnel).
The automatic adaptation of the display brightness depends on the ambient brightness, the brightness adjustment and the dimmer setting of the instrument lighting (only with light ON) or the brightness setting in the Personal Profile of the Head-Up Display.The ambient brightness (day, night, twilight, sunshine, etc.) is recorded by the rain-light-solar-condensation sensor. This also picks up the brightness in the area of the virtual image to ensure optimal brightness control.
When the lighting is switched on (locator lighting, lights ON) the brightness of the Head-Up Display is also influenced by the dimmer setting of the instrument lighting or the brightness setting in the Personal Profile of the Head-Up Display.The brightness adjustment takes into account the individual brightness setting for the Head-Up Display, deviating from the basic setting. The individual brightness setting is made on the central information display using the controller. The set value is stored in the Personal Profile in the Head-Up Display.

Prioritization of displays, switch-on characteristics
The information in the Head-Up Display is classified according to importance for the driver. Displays with low priority are overwritten by displays with higher priority.
- Priority 1:
Warnings of cruise control

- Priority 2:
Check Control messages

- Priority 3:
Navigation instructions

Image generation
The picture signals for the screen mask are transferred from the instrument cluster (KOMBI) via the LVDS data line to the Head-Up Display. The switch-on and switch-off signal as well as the information for the screen mask are output by the corresponding control units (headunit) as a bus signal. The instrument cluster evaluates the bus signals received via the K-CAN and forwards the information to the components of the Head-Up Display.
The background colour of the Head-Up Display is black. The contents of the Head-Up Display are displayed as follows:
- White as standard colour during the day
- Orange as standard colour during the night
- Red or white for warning messages
- Green for set speed
- Blue for navigation and assist systems
- as well as levels of grey and mixed shades of the above colors

The size of the display area for the virtual image is approx. 22 x 6.5 cm (width x height). The display area is split vertically to assist in identifying the display content. Instructions given by the navigation system and Check Control messages are displayed on the right. Speed-related information is displayed on the left. Which display content is shown is set in the central information display using the controller.

Display area setting
The virtual image can only be viewed completely and properly from a certain area on the driver's side. Outside this area, it is not possible to view the virtual image completely. The height of the position of the virtual image can be shifted (± 5 cm). In this way, the user can alter the determined area by horizontal height adjustment and adapt it to his/her requirements (via central information display and controller).

Image position setting
It is possible on the central information display to use the controller to adjust the position of the virtual image to the size and seat position of the driver. The set value is stored in the Personal Profile.

Switch off
The Head-Up Display is switched on or off using the controller. If terminal 15 is off, the Head-Up Display is also switched off.

System overview
The Head-Up Display is connected with the instrument cluster (KOMBI) by a six-pin plug connection.
An LVDS data line is used to transmit the image information from the instrument cluster to the Head-Up Display.
The Head-Up Display is powered via the instrument cluster (KOMBI) using terminal 30B. The instrument cluster (KOMBI) transmits the control signals for stepper motors, sensors and display drivers.







Notes for Service department

Failure of the component
If communication to the Head-Up Display fails, carry out the standard checks (global procedure). If there is a fault, the following behavior is to be expected:
- Fault code entry in the instrument cluster (KOMBI).

There is a service function in the BMW diagnosis system to correct image distortions in the Head-Up Display. The geometric representation of the Head-Up Display can be adjusted with the service function.
Path: Service functions > Driver assistance > Head-Up Display -> Adjust the Head-Up Display.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.
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