Abstract: This invention relates to methods, apparatus, and computer program code for the holographic display of images. We describe a method of displaying an image holographically. The method includes displaying a hologram on pixels of a spatial light modulator (SLM) and illuminating the SLM such that the image is displayed in pixels of a replay field (RPF) of the hologram. The method further includes subdividing the replay field into a plurality of spatially interlaced regions, and displaying holograms for each of the interlaced regions of the replay field sequentially at different times such that in an observer's eye the interlaced regions integrate to give the impression of the image and such that interference between adjacent pixels of the replay field is reduced.

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.

Abstract: We describe a method of displaying an image holographically using a spatial light modulator (SLM), the SLM having a plurality of pixels, the method including: displaying a diffraction pattern on the pixels of the SLM; and illuminating the pixels such that light diffracted by said diffraction pattern on the SLM pixels includes a content of said displayed image. A variation in brightness of said displayed image across the displayed image is modulated by an intensity envelope determined by the diffraction pattern of an individual said pixel, for example a sinc envelope. The method further includes moving a peak or centre of gravity of the intensity envelope away from a zero order spot and towards a centre of the displayed image by imposing a pattern of phase delay across the SLM pixels, the pattern of phase delay repeating at a spatial interval corresponding to a pixel interval of the SLM.

Abstract: We describe a holographic image projection system for projecting an image at an acute angle onto a surface, the system including: a spatial light modulator (SLM) to display a hologram; an illumination system to illuminate said displayed hologram; projection optics to project light from said illuminated displayed hologram onto said surface at an acute angle form said image; and a processor having an input to receive input image data for display and an output to provide hologram data for said SLM, wherein said processor is configured to: input image data and convert this to target image data; generate from said target image data hologram data for display as a hologram on the SLM to reproduce a target image; and wherein said target image is distorted to compensate for said projection of said hologram at an acute angle to form said image.

Abstract: This invention relates to methods and apparatus for the holographic display of images. We describe a method of compensating for spatial phase non-uniformities in a holographic image display system, the system including a substantially coherent light source illuminating an SLM (24), the method comprising sequentially displaying substantially the same hologram (40) at a plurality of different positions (40a, 40b) on said SLM (24) such that the displayed holographic images successively replayed by said differently positioned holograms (40a, 40b) average to provide a holographic displayed image with increased uniformity.

Abstract: The present invention relates to a hologram viewing arrangement, to an alignment device, to a display device, to a device for aligning first and second members and to a device for aligning an optical beam with a desired target. A hologram viewing arrangement comprising a pixellated phase mask substrate (20) and a pixellated hologram display substrate (40), wherein the hologram display substrate is arranged to store data representing at least two distinct images (3a-3d), the arrangement being such that disposing the phase mask in a first position with respect to the display substrate enables one of the at least two images to be visible and disposing the phase mask in a second position with respect to the display substrate enables another of the at least two images to be visible.

Abstract: We describe a method of projecting a colour image on a screen holographically. The method includes: inputting colour image data including data for at least two colour planes of said image, a first, longer wavelength colour plane and a second, shorter wavelength colour plane; generating data for respective first and second holograms from said first and second colour planes, said first hologram having a greater resolution than said second hologram; and displaying said first and second holograms in turn on a common spatial light modulator (SLM) illuminated by light of respective said first and second wavelengths to project said colour image onto said screen; and wherein a scaling in resolution between said first and second holograms is dependent on scaling between said first and second wavelengths such that, when projected on said screen pixels of said image generated by said first and second holograms have substantially the same pitch.