Head-up display and program

A head-up display comprising:

• a display unit that displays an image to a display region configured in front windshield of an automobile;
• and
• a display controller configured to control the display unit, wherein
• the display controller includes
• an automobile information acquirer that acquires automobile information representing a traveling state of the automobile,
• a forward environment information acquirer that acquires forward environment information representing an environment forward of the automobile in a traveling direction,
• a display-targeting object detector that, based on the automobile information and the forward environment information, detects a display-targeting object on which guide information is to be displayed to the display region of the front windshield,
• a guide image generator that generates a guide image for overlay-display of the guide information to the front windshield and preforms overlay-display of the guide image to the front windshield with the display unit so that when the display-targeting object detected by the display-targeting object detector is viewed from an inside of a cabin of the automobile, and
• a display luminance setting unit that set a display luminance of the generated guide image,
• the display unit performs overlay-display of the guide image, whose display luminance is set by the display luminance setting unit, on the front windshield by emitting a display light,
• the display region includes a predetermined display-setting area that is smaller than the display region and located near a center of the display region,
• when a position of the display-targeting object is within the display region, the display luminance setting unit sets the display luminance of the guide image for normal display,
• when the display-targeting object approaches the automobile and a distance between the display-targeting object and the automobile becomes smaller than a designated distance, and the position of the display-targeting object goes beyond the predetermined display-setting area, the display luminance setting unit sets a display luminance of the guide image smaller as the distance of the display-targeting object from a center of the predetermined display setting area increases.