The disclosure refers to devices forming mid-air images in free space. The device comprises a projection optical system; a waveguide comprising a first in-coupling diffractive optical element, a second in-coupling diffractive optical element; an out-coupling diffractive optical element; an optical element with a positive optical power. The projection optical system comprises: an image projector, an optical transfer unit, an intermediate image area, a projection unit. When using the invention, the user observes a real image in a large field of view.