Holographic Display Spatial Filter for Lattice Spot Separation
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Solution Overview
Problem
Current 3D image display methods, such as glasses-type and non-glasses-type methods, are limited by binocular parallax and cause viewer fatigue due to inconsistencies between perceived depth and eye focus, while commercial holographic display techniques using computer-generated holograms struggle to effectively separate holographic images from lattice spots generated by spatial light modulators.
Innovation Solution
A holographic display apparatus incorporating a spatial light modulator and a spatial filter with pinholes and color filters or dichroic mirrors to separate and focus holographic images of different colors, avoiding lattice spots and enhancing the viewing window by using an off-axis technique and periodic diffraction patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a spatial light modulator is used to display hologram patterns, then holographic images can be generated, but lattice spots are produced due to the physical structure of the modulator that interfere with image quality
Solution Approach 1:
The patent extracts and removes the harmful lattice spots from the optical path using a spatial filter positioned at the Fourier plane. The filter transmits only the desired holographic images while blocking the lattice spots generated by the spatial light modulator's physical structure, thereby separating useful information from harmful interference.
Solution Approach 2:
The spatial filter acts as an intermediary element between the spatial light modulator and the observer. It mediates the optical field by selectively transmitting certain spatial frequencies (holographic images) while blocking others (lattice spots), thus cleaning up the output without affecting the core holographic generation function.
2Adaptability or versatility
If multiple color images are generated at different positions, then color holographic images can be reproduced, but the viewing window becomes limited due to overlapping lattice spots and images
Solution Approach 1:
The patent segments the optical field into different spatial regions using multiple pinholes in the spatial filter. Each pinhole corresponds to a specific order of diffraction and transmits only the holographic images of that order while blocking lattice spots. This segmentation allows multiple color images at different positions to be transmitted simultaneously without interference, expanding the viewing window.
Solution Approach 2:
The patent utilizes the Fourier dimension (spatial frequency domain) to separate and select different holographic images and lattice spots. By positioning pinholes at specific locations in the Fourier plane corresponding to different diffraction orders, the system selectively transmits desired images while blocking harmful lattice spots, effectively expanding the viewing window in the image space.
3Area of stationary object
If off-axis technique is used to separate images from lattice spots, then viewing window expands, but device complexity increases due to additional spatial filter requirements
Solution Approach 1:
The patent merges multiple functions into a single spatial filter component. The filter simultaneously performs several tasks: blocking lattice spots, transmitting multiple color images at different positions, and separating different orders of diffraction. By combining these functions into one element rather than using multiple separate components, the patent expands the viewing window while minimizing the increase in device complexity.
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 apparatus provides an expanded viewing window by effectively blocking lattice spots and complex conjugate images, reducing noise and improving the observer's experience by allowing clear observation of holographic images without the distractions of lattice spot noise.
Implementation Method 1
the light is diffracted and an image of the original object is reproduced
Implementation Method 2
the spatial filter includes a plurality of color filters or a plurality of dichroic mirrors configured to separate the first color image, the second color image, and the third color image from the first color lattice spot, the second color lattice spot, and the third color lattice spot
Implementation Method 3
the spatial filter includes a plurality of color filters or a plurality of dichroic mirrors configured to separate the first color image, the second color image, and the third color image from the first color lattice spot, the second color lattice spot, and the third color lattice spot
Implementation Method 4
The spatial filter may include a first pinhole transmitting a holographic image generated by a 0th order diffraction in the spatial light modulator, and a plurality of second pinholes respectively transmitting a plurality of high order holographic images generated by a ±1st or higher order diffraction in the spatial light modulator
Data Source
AI summary
A holographic display apparatus for providing an expanded viewing window includes a spatial filter configured to separate a plurality of holographic images generated by the hologram pattern displayed on the spatial light modulator from a plurality of lattice spots generated by a physical structure of the spatial light modulator. The spatial filter includes a plurality of color filters or a plurality of dichroic mirrors separating a first color image, a second color image, and a third color image from a first color lattice spot, a second color lattice spot, and a third color lattice spot.