Abstract: A phase unwrapping method for image demodulation comprises receiving a plurality of images of a fringe pattern captured by rotating the fringe pattern by a predetermined rotation angle. The method estimates a first wrapped phase value for a portion of a first image of the plurality of images and a second wrapped phase value for a corresponding portion of a second image, and establishes a first plurality of elements associated with the first wrapped phase value. For a candidate element from the first plurality of elements, the method determines a constraining element associated with the candidate element using the second wrapped phase value, where the association is established using the candidate element and the predetermined rotation angle, and unwraps the phase for the portion of at least one of the first and second images using the candidate element based on the determined constraining element.

Abstract: We describe optical techniques for replicating an image to expand the exit pupil of a head-up laser-based image display system. The system includes image replication optics to replicate an image carried by a substantially collimated beam, the image replication optics comprising a pair of substantially planar reflecting optical surfaces defining substantially parallel planes spaced apart in a direction perpendicular to the parallel planes. The system is configured to launch the collimated beam into a region between the parallel planes such that the reflecting optical surfaces waveguide the beam between the surfaces in a plurality of successive reflections at front and rear optical surfaces. The front optical surface is configured to transmit a proportion of the collimated beam when reflecting the beam such that at each reflection of the collimated beam at the front optical surface a replica of the image is output from the image replication optics.

Abstract: The invention relates to techniques for speckle reduction in holographic optical systems, in particular holographic image display systems. We describe a holographic image display system for displaying an image holographically on a display surface, the system including: a spatial light modulator (SLM) to display a hologram; a light source to illuminate said displayed hologram; projection optics to project light from said illuminated displayed hologram onto said display surface to form a holographically generated two-dimensional image, said projection optics being configured to form, at an intermediate image surface, an intermediate two-dimensional image corresponding to said holographically generated image; a diffuser located at said intermediate image surface; and an actuator mechanically coupled to said diffuser to, in operation, move said diffuser to randomise phases over pixels of said intermediate image to reduce speckle in an image displayed by the system.