Producing a computer generated holographic image
A method of producing a Computer Generated Hologram (CGH) for producing a 3 dimensional (3D) holographic image, including receiving data describing a 3D scene, producing a first CGH for producing a 2D image of the 3D scene as viewed from a specific viewing direction, the 2D image perpendicular to the viewing direction, decomposing the 2D image to a plurality of slices at different depths along the viewing direction, adjusting the first CGH by making, for at least one of the plurality of slices, a correction to the CGH associated with a depth of the slice along the viewing direction, thereby producing a corrected CGH for producing a 3D holographic image of the 3D scene. Related apparatus and methods are also described.
1. A system for producing a Computer Generated Hologram (CGH), the system comprising:
a first computing device for preparing data for producing a 3 dimensional (3D) holographic image of a 3D scene, the device comprising a first computing unit arranged for:
receiving data describing a 3D scene;
producing one complex amplitude array for a 2D image of the 3D scene as viewed from a specific viewing point; and
producing a depth-map describing depths of points of the 2D image of the 3D scene relative to the specific viewing point;
a second computing device; and
a Spatial Light Modulator (SLM);
wherein:
the second computing device is arranged for:
receiving the one complex amplitude array for the 2D image of the 3D scene and the depth-map;
decomposing the one complex amplitude array for the 2D image of the 3D scene into slices that correspond to a specific depth according to the depth-map;
performing an inverse-Fourier transform of the complex-amplitude array slices, producing inverse-Fourier-transformed complex amplitude arrays;
correcting the inverse-Fourier-transformed complex arrays according to the specific depth of each slice, producing corrected complex amplitude arrays;
summing all the corrected complex amplitude arrays, producing a second complex amplitude array; and
producing a corrected optimized complex amplitude array for producing a 3D holographic image of the 3D scene by using only the phase values of the second complex amplitude array.
2. The system of claim 1 wherein the producing one complex amplitude array for a 2D image of the 3D scene as viewed from a specific point comprises producing one complex amplitude array for a 2D image on a spherical shell which is perpendicular to a direction Z to the specific point.
3. The system of claim 1 wherein the producing one complex amplitude array for a 2D image of the 3D scene as viewed from a specific point comprises producing one complex amplitude array for a 2D image on a plane which is perpendicular to a direction Z to the specific point.
4. The system of claim 1 and further comprising the second computing device is arranged for adding a random phase to the complex amplitude 2D array.
5. The system of claim 1 and further comprising the first computing device arranged for sending only the phase values of the one complex amplitude 2D array for producing the 3D holographic image of the 3D scene to the second computing device.
6. The system of claim 1 and further comprising:
an SLM (Spatial Light Modulator) arranged to receive the corrected optimized complex amplitude array.
7. The system of claim 6 and further comprising a coherent light illuminator arranged for illuminating the SLM with coherent light, thereby producing a 3D holographic image of the 3D scene.
8. The system of claim 1 wherein the first computing device comprises a transmitter arranged for transmitting the one complex amplitude array and the depth-map from the first computing device to the second computing device.
9. The system of claim 8 wherein the first computing device comprises the transmitter arranged for transmitting only the phase values of the one complex amplitude array and the depth-map.
10. The system of claim 1 wherein the first computing device and the second computing device are the same computing device.
11. The system of claim 1 wherein the correcting the inverse-Fourier-transformed complex arrays according to the specific depth of each slice comprises correcting using a quadratic phase correction.
12. The system of claim 11 wherein the correcting using a quadratic phase correction comprises is calculated based on the specific depth divided by a wavelength of light of the SLM, modulo 2n.
13. The system of claim 1 wherein the correcting the inverse-Fourier-transformed complex arrays according to the specific depth of each slice comprises correcting using a Fresnel depth correction.
14. The system of claim 1 wherein the correcting the inverse-Fourier-transformed complex arrays according to the specific depth of each slice comprises correcting using an angular spectrum correction.