Computer-Generated Hologram Fabrication Process for Wide Viewing Angles
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Solution Overview
Problem
Computer-generated holograms have limited viewing angles, especially in the longitudinal direction, and fail to display images in white when using white light illumination, due to restricted recording areas and depth-dependent viewing angles.
Innovation Solution
A fabrication process that records amplitude and phase information on a recording surface by setting orthogonal directions, creating diffraction patterns with varying spatial frequencies in one direction, and using point or linear light sources to achieve parallax and wide viewing angles, allowing images to be viewed in white with reconstructing white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a computer-generated hologram is formed using conventional methods with uniform diffraction patterns, then the computation load is reduced and fabrication is simplified, but the viewing angle in the longitudinal direction becomes narrow and images cannot be viewed in white light
Solution Approach 1:
The patent applies local quality by making the diffraction pattern spatial frequency vary in the longitudinal direction (Y-direction) while keeping it uniform in the lateral direction. Specifically, different unit areas along the longitudinal direction have different spatial frequencies, which enables each region to diffract light at appropriate angles for wide viewing while maintaining fabrication simplicity through computational methods
Solution Approach 2:
The patent changes the spatial frequency parameter of the diffraction pattern along the longitudinal direction to achieve wide viewing angles. By gradually varying the spatial frequency from one end to the other in the longitudinal direction, the hologram can display images in white light and provide wide viewing angles without significantly increasing fabrication complexity
2Area of stationary object
If the recording area on the hologram recording surface is limited in the vertical direction, then the device size is reduced, but the viewing angle in the vertical direction changes depending on the depth position of the object
Solution Approach 1:
The patent compensates for the limited recording area by varying the spatial frequency parameter in the longitudinal direction. This allows the hologram to maintain a compact size while achieving depth-independent viewing angles through computational optimization of the diffraction pattern distribution
3Device complexity
If diffracted light from the uppermost unit area is not directed toward the viewing point, then the computational complexity is reduced, but the reconstructed image at the uppermost site cannot be viewed and the viewing angle does not spread
Solution Approach 1:
The patent applies local quality by assigning different spatial frequency characteristics to different unit areas along the longitudinal direction. This enables each unit area to contribute to the wide viewing angle while keeping the overall computational method systematic and manageable through computer-based design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process enhances viewing angles and ensures consistent viewing angles regardless of object depth, enabling wider viewing angles and white image reconstruction with white light illumination.
Implementation Method 1
a first hologram is fabricated on a first hologram recording medium by use of object light that has passed through a first original image and reference light, a second hologram is fabricated on a second hologram recording medium by use of object light that has passed through a second original image and the reference light
Implementation Method 2
creating diffraction patterns with varying spatial frequencies in one direction
Data Source
AI summary
The invention provides a fabrication process for a computer-generated hologram wherein amplitude information and phase information are recorded on a given recording surface by means of computation by a computer. The computer-generated hologram is characterized by having a first direction and a second direction orthogonal to the first direction, and parallax in the first direction X alone. The hologram 1 comprises unit areas B1, B2, B3, . . . , Bm, . . . BM, each one having a given width in the second direction Y. In each unit area B1, B2, B3, . . . , Bm, . . . BM, there is a diffraction pattern having a spatial frequency Cm1, Cm2, Cm3, . . . , Cmt, . . . CmT that varies in the second direction.