Development of an Analog Speedometer Mutually Compatible with a Digital Head Up Display

Since Head Up Displays (HUD) were first introduced for automobiles in 1988, they have achieved growing customer acceptance for their superior recognition. In the future, with the heightened need for improved auto safety and increased population of older drivers, the rate of adoption for HUDs will continue to increase. For this trend to materialize, improvements are necessary in order to meet customers' more stringent demands. The most significant challenge addresses the application of HUD to vehicles having conventional analog speedometers.

For current production HUDs, digital speedometers in the instrument cluster are usually adopted in order to have identical display information between the HUD and speedometer. However, the customer must be offered a choice between digital speedometers and analog speedometers. Combining the analog display speedometer with the digital HUD can lead to indication discrepancies. At some point this difference becomes unacceptable to the driver.

The authors have been successful in resolving the error factors related to indication differences between the two displays. The result is a low cost and practical analog meter display plus a compatible digital HUD system.