PROJECTION DEVICE, PROJECTION SYSTEM, AND SPECTACLE TYPE DISPLAY DEVICE

According to conventional retroreflective projection techniques, image light from a projector reaches a viewer after reflecting from or passing through a half mirror, thereby resulting in a significant loss of the image light. For this reason, a large-sized device has been needed to provide a viewer with a bright image. Provided is a projection system comprising: a projection unit for outputting aprojection image; a retardation plate obliquely disposed relative to the optical axis of the projection image and modulating the polarization state of the projection image incident thereon; a reflective polarizing plate superposed on the retardation plate opposite the side whereon the projection image is incident and reflecting a first polarization component in the projection image passing through the retardation plate; and a retroreflective element provided on the side of the reflective polarizing plate wherefrom the projection image is reflected and emitting the reflection light in the incidence direction of the in