Abstract: A front projection system comprises a display source and a front projection screen. A rear projection system comprises a display source and a rear projection screen. The display source generates illumination. The front or rear projection screen comprises a plurality of high aspect ratio structures are configured to act as a Bragg selective holographic element. The plurality of high aspect ratio structures are configured to diffract the illumination toward a viewer.

Abstract: Indicating relative speed is disclosed. A first grating coupled to a first moving object is illuminated using a coherent light source to generate a first diffracted beam and a diffracted order beam. A second grating coupled to a second moving object is illuminated using the first diffracted beam and the second diffracted beam to generate a third diffracted beam and a fourth diffracted beam. The third diffracted beam and the fourth diffracted beam are measured. A relative speed of the first moving object with respect to the second moving object is indicated based at least in part on the measured third diffracted beam and the measured fourth diffracted beam.

Abstract: Writing a diffractive structure is disclosed. A reference modulated beam is generated. An object modulated beam is generated. A diffractive structure is written using an interference between the reference modulated beam and the object modulated beam. A system for writing a diffractive structure comprises a reference generator for generating a reference modulated beam; an object generator for generating a object modulated beam; and a writer for writing a diffractive structure using an interference between the reference modulated beam and the object modulated beam.