  A pseudoscopic (inverted depth) image made with spiral diffracting elements
intermediated by a pinhole is explained by its symmetry properties. The whole
process is made under common white light illumination and allows the projection
of images. The analysis of this projection demonstrates that the images of two
objects pointing away longitudinally have the main features of standard
pseudoscopic image points. An orthoscopic (normal depth) image has also been
obtained with the breaking of the symmetry conditions.
