Holographic Display Expanding Viewing Window via Off-Axis Diffraction
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Solution Overview
Problem
Current holographic display technologies have a limited viewing window due to focusing on a single point, causing discomfort and restricting the number of viewpoints, and existing methods fail to align the depth perceived by the brain with the focus of the eyes effectively.
Innovation Solution
The proposed holographic display apparatus employs an off-axis method using higher-order diffraction, gratings, and beam displacers to widen the viewing window by deflecting and refocusing holographic images, allowing multiple images of different orders to be observed simultaneously, thereby expanding the observable area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-point focused holographic image is used, then the image quality and depth perception are improved, but the viewing window becomes narrow
Solution Approach 1:
The patent divides the single holographic image into multiple separated images by introducing a grating that diffracts light into different orders. This segmentation allows each diffracted image to be viewed from different angles, effectively expanding the viewing window while maintaining image quality through the off-axis method.
Solution Approach 2:
The patent transitions from a single-point focus to a multi-dimensional viewing approach by using higher-order diffraction. The grating creates multiple image positions in the spatial dimension, allowing observers to view the holographic image from multiple angles simultaneously, thus expanding the viewing window without sacrificing image quality.
2Area of stationary object
If higher-order diffraction is used to enlarge viewing window, then the observable area is expanded, but lattice spots and distortion may be introduced
Solution Approach 1:
The patent extracts and removes the harmful lattice spots by using a spatial filter or aperture stop that selectively blocks the zeroth-order diffraction component and unwanted higher-order components. This allows only the desired off-axis diffracted images to pass through, eliminating lattice spots and distortion while maintaining the expanded viewing window.
Solution Approach 2:
The patent converts the potentially harmful higher-order diffraction effects into beneficial outcomes by using the off-axis method. The higher-order diffraction, which could cause distortion, is instead utilized to create multiple separated images that expand the viewing window. By carefully controlling the diffraction angles and using appropriate filters, the harmful effects are transformed into useful image separation.
3Adaptability or versatility
If binocular parallax methods are used, then 3D image generation is achieved, but the number of viewpoints is limited and viewer fatigue occurs
Solution Approach 1:
The patent creates multiple copies of the same holographic image at different spatial positions through higher-order diffraction. Each copy can be viewed from different angles, providing multiple viewpoints without requiring the viewer to switch between different 3D images. This copying approach maintains viewing comfort by allowing continuous observation from various angles.
Solution Approach 2:
The patent introduces dynamic viewing capability by allowing the observer to move their eye or head to view the holographic image from multiple angles. The off-axis method with grating creates a dynamic viewing experience where the image remains stable while the observer can access different viewpoints, improving comfort compared to fixed binocular parallax methods.
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
This approach effectively enlarges the viewing window, allowing a wider area for observing holographic images without the distortion caused by lattice spots, enhancing the comfort and clarity of the 3D image reproduction.
Implementation Method 1
a spatial light modulator for forming a hologram pattern for modulating incident light in accordance with a computer-generated hologram signal
Implementation Method 2
when light is irradiated onto a hologram pattern having recorded thereon an interference pattern obtained by interference between the light and object light reflected from an original object, the light is diffracted and an image of the original object is reproduced
Implementation Method 3
an optical system for focusing the holographic image on a space
Data Source
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AI summary
A holographic display apparatus for providing an expanded viewing window is provided. The holographic display apparatus includes a spatial filter configured to allow a plurality of holographic images generated by 0th order or higher diffraction in a spatial light modulator to pass therethrough, and an image path conversion element configured to adjust a light path of the plurality of holographic images so that the plurality of holographic images are spaced apart from each other on a focal plane of an optical system.