A Head Up Display (HUD), comprising: an image display unit, to generate input images; a virtual image generation unit, to receive said input images and generate at least a virtual image; a rotation mechanism, used to make said virtual image generation unit to change its projection angle, to project virtual images to a plurality of transmission mirrors; and a plurality of transmission mirrors, used to receive said virtual images and reflect them into a large area virtual image. Advantage of said HUD is that, size of lens and mirrors is reduced, so said HUD is miniaturized, while realizing large area image display, such that information frame of vehicle match that of outside view, hereby solving problems of single optical route display device of the prior art, that is only capable of displaying a small area image rather than a large area image.