Abstract: A head-up display 2 includes a light source unit 4 and a combiner 9. A control unit 55 of the light source unit 4 displays on the combiner 9 a guide image indicating a letter or a graphic so that the guide image appears to overlap the background visible from a vehicle Ve. On the basis of a detection signal Sd sent from a vibration sensor 3 and the traveling speed of the vehicle Ve, the control unit 55 obtains a smoothness determination index ? that is information on the degree of smoothness of the road surface on which the vehicle Ve is traveling. The control unit 55 changes the size of the letter or the graphic displayed on the combiner 9 in accordance with the smoothness determination index ?.

Abstract: A display system (100) has a navigation device (1) and a head-up display (2) that displays a virtual image (Iv) using a combiner (8). The combiner (8) is equipped with a reflective member reflecting display light, and is supported so as to be openable and closable. The navigation device (1) performs at least one of the opening control and/or the closing control of the combiner (8), and the navigation device (1) carries out the opening/closing control at the time when a predetermined condition is satisfied. For example, the navigation device (1) automatically closes the combiner (8) to enhance the visibility of a driver in an attention necessary section and in a guidance unnecessary section, or automatically closes the combiner (8) to adhere to highway regulations in an HUD restriction area.

Abstract: A head-up display 2 includes a light source unit 4 and a combiner 9. A control unit 55 of the light source unit 4 displays on the combiner 9 a guide image indicating a letter or a graphic so that the guide image appears to overlap the background visible from a vehicle Ve. On the basis of a detection signal Sd sent from a vibration sensor 3 and the traveling speed of the vehicle Ve, the control unit 55 obtains a smoothness determination index ? that is information on the degree of smoothness of the road surface on which the vehicle Ve is traveling. The control unit 55 changes the size of the letter or the graphic displayed on the combiner 9 in accordance with the smoothness determination index ?.