The invention relates to a preprocessing circuit for at least one hologram computation circuit that comprises an input interface device for receiving data of a scene to be displayed, a processing device for defined processing of the received data and for converting the data into a system-independent format with incorporation of specific parameters required for displaying the scene, and an output interface device for outputting and transmitting the converted data to at least one hologram computation circuit. An apparatus for computing a hologram for displaying a scene by means of a holographic display apparatus is also disclosed. The apparatus comprises at least one spatial light modulation device and a preprocessing circuit as described, and at least one hologram computation circuit for computing a hologram and for encoding the hologram for the at least one spatial light modulation device.

A method of projecting a first image and a second image using one multi-wavelength hologram. The first image is different to the second image. The multi-wavelength hologram is arranged for illumination by light of a first wavelength to project the first image. The multi-wavelength hologram is further arranged for illumination by light of a second, shorter wavelength to project the second image.

There is provided a holographic projector comprising a hologram engine and a controller. The hologram engine is arranged to provide a hologram comprising a plurality of hologram pixels. Each hologram pixel has a respective hologram pixel value. The controller is arranged to selectively-drive a plurality of light-modulating pixels so as to display the hologram. Displaying the hologram comprises displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many pixel correlation between the hologram and the plurality of light-modulating pixels.

Provided is a complex light modulator including a phase modulator, and an amplitude modulator, wherein the phase modulator and the amplitude modulator are configured to generate a first complex pixel having first complex light modulation characteristics and a second complex pixel having second complex light modulation characteristics, wherein the first complex pixel includes first sub-complex pixels that are provided in a 3×3 format and are configured to implement the first complex light modulation characteristics, wherein the second complex pixel includes second sub-complex pixels that are provided in a 3×3 format and are configured to implement the second complex light modulation characteristics, and wherein the first complex pixel and the second complex pixel respectively include a first overlapping pixel that is included in the first sub-complex pixels and the second sub-complex pixels.

There is provided a holographic projector comprising a hologram engine and a controller. The hologram engine is arranged to provide a hologram comprising a plurality of hologram pixels. Each hologram pixel has a respective hologram pixel value. The controller is arranged to selectively-drive a plurality of light-modulating pixels so as to display the hologram. Displaying the hologram comprises displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many pixel correlation between the hologram and the plurality of light-modulating pixels.

A holographic display method includes calculating a hologram, displaying it on a spatial light modulator (SLM) and illuminating it with coherent light. The hologram includes hologram pixels each having a hologram pixel value. The hologram is calculated using steps including: performing the inverse Fourier transform of the product of an object field and a negative quadratic phase exponential representative of positive optical power; and restricting each calculated hologram pixel value to one of a plurality (greater than two) of allowable pixel values to form a constrained hologram, which is displayed on the SLM. Each light-modulating pixel of the SLM is operable in a plurality of light-modulation levels corresponding to the plurality of allowable pixel values. The SLM is illuminated with coherent light to form a replay field including conjugate images: a real holographic reconstruction and a virtual holographic reconstruction having greater intensity than that of the real holographic reconstruction.

There is provided a method of projection using an optical element (502,602) having spatially variant optical power. The method comprises combining Fourier domain data representative of a 2D image with Fourier domain data having a first lensing effect (604a) to produce first holographic data. Light is spatially modulated (504,603a) with the first holographic data to form a first spatially modulated light beam. The first spatially modulated light beam is redirected using the optical element (502,602) by illuminating a first region (607) of the optical element (602) with the first spatially modulated beam. The first lensing effect (604a) compensates for the optical power of the optical element in the first region (607). Advantageous embodiments relate to a head-up display for a vehicle using the vehicle windscreen (502,602) as an optical element to redirect light to the viewer (505,609).

There is provided a method of projection using an optical element (502,602) having spatially variant optical power. The method comprises combining Fourier domain data representative of a 2D image with Fourier domain data having a first lensing effect (604a) to produce first holographic data. Light is spatially modulated (504,603a) with the first holographic data to form a first spatially modulated light beam. The first spatially modulated light beam is redirected using the optical element (502,602) by illuminating a first region (607) of the optical element (602) with the first spatially modulated beam. The first lensing effect (604a) compensates for the optical power of the optical element in the first region (607). Advantageous embodiments relate to a head-up display for a vehicle using the vehicle windscreen (502,602) as an optical element to redirect light to the viewer (505,609).

There is provided ahead-up display in a vehicle arranged to display a picture, the head-up display comprises a first optical sub-system disposed in an upper region of the windscreen and a second optical sub-system disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen. The first optical sub-system is arranged to output a light field. The first optical sub-system comprises a light source and a spatial light modulator. The light source is arranged to emit light. The spatial light modulator is arranged to receive the light from the light source and spatially-modulated the light in accordance with a computer-generated hologram displayed on the spatial light modulator. The second optical sub-system is arranged to receive the light field from the first optical sub-system and project the light field onto a windscreen of the vehicle to form a virtual image on the windscreen.

Disclosed is a method of generating a volume hologram using a point cloud and a mesh, in which a weight is given to a brightness of a light source according to a direction of a light in order to record a hologram of better quality. The method includes: (a) acquiring multi-view depth and color images; (b) generating point cloud data of a three-dimensional object from the acquired multi-view depth and color images; (c) generating mesh data of the three-dimensional object from the point cloud data of the three-dimensional object; (d) calculating a normal vector of each mesh from the mesh data of the three-dimensional object; (e) extracting three-dimensional data at a user viewpoint from the mesh data of the three-dimensional object by using the normal vector of the mesh; and (f) generating hologram data from three-dimensional data at the user viewpoint.