Pseudoscopic imaging in a double diffraction process with a slit:   critical point properties
  Pseudoscopic (inverted depth) images that keep a continuous parallax were shown to be possible by use of a double diffraction process intermediated by a slit. One diffraction grating directing light to the slit acts as a wavelength encoder of views, while a second diffraction grating decodes the projected image. The process results in the enlargement of the image under common white light illumination up to infinite magnification at a critical point. We show that this point corresponds to another simple-symmetry object-observer system. Our treatment allows us to explain the experience by just dealing with main ray directions. 
Jose J. Lunazzi and Noemi I. Rivera