Head-up display device with reflective optical system for vehicle

Abstract

A head-up display device includes an illumination optical system, an imaging optical system and a reflective optical system. The illumination optical system emits a source light indicating information. The imaging optical system projects the source light to a projection surface. The reflective optical system has a dielectric multilayer film, and is configured so that a retardation of a subject wavelength including at least a part of wavelengths of the source light from the illumination optical system is in a range greater than −π/2 [rad] and smaller than π/2 [rad]. The reflective optical system is arranged on a path from the illumination optical system to the imaging system so that a polarization axis of the source light from the illumination optical system defines an angle α satisfying a relation of 0 degree <α<90 degrees <α<180 degrees, relative to an incident surface.