PROJECTION DISPLAY DEVICE, AND OPERATION METHOD AND OPERATION PROGRAM FOR PROJECTION DISPLAY DEVICE

An HUD includes a housing that accommodates a light modulation unit that spatially modulates light emitted by a light source; a projection optical system that is accommodated in the housing and projects the light that has been spatially modulated onto a windshield of a vehicle through an opening portion of the housing; a cover that closes the opening portion; a protection member that is movable and is for protecting the cover; a driving unit that drives the protection member; and an object detecting unit that detects an object approaching a front surface of the cover. The driving unit moves the protection member to a position above the cover and causes the protection member to cover the cover when the object detecting unit detects an object, and the driving unit leaves the protection member retracted from the position above the cover to expose the cover when the object detecting unit does not detect an object.