Phase-Only CGH Speckle Reduction via Segmented Phase Functions
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Solution Overview
Problem
Current phase-only computer-generated holographic image projection systems suffer from limited image quality due to restricted modulation capabilities and speckle noise, which degrades reconstruction accuracy and requires compromises in field of view and light efficiency.
Innovation Solution
A phase CGH computation method that designs an initial image-specific phase term, imposing it on the target image to compute an initial CGH, which serves as a starting point for iterations, resulting in quick convergence to low-error, speckle-free reconstructions with maximum light efficiency and full field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If phase-only modulation is used on SLM, then device complexity is reduced and diffraction efficiency is improved, but image quality deteriorates due to limited modulation capability
Solution Approach 1:
The image is divided into multiple blocks, and different phase functions are applied to different blocks. This segmentation allows the system to work around the phase-only limitation by creating spatially varying phase patterns that collectively reconstruct the image with reduced artifacts and improved quality.
Solution Approach 2:
The patent changes the phase parameter distribution across different image blocks using specifically designed phase functions. By varying the phase parameters spatially rather than uniformly, the system achieves better image reconstruction quality while maintaining phase-only modulation constraints.
2Manufacturing precision
If random phase function is applied to reduce speckle noise, then image quality is improved, but speckle noise increases significantly
Solution Approach 1:
Instead of applying a uniform random phase function across the entire image, the patent applies different deterministic phase functions to different local blocks. This local differentiation achieves speckle reduction through controlled phase variation while maintaining image quality through optimized phase patterns in each region.
3Object-generated harmful factors
If image area is partitioned for signal and noise windows, then speckle noise is reduced, but field of view and light efficiency decrease
Solution Approach 1:
The patent extracts and removes the need for separate noise windows by integrating speckle reduction functionality directly into the phase modulation process. The designed phase functions inherently suppress speckle noise without requiring dedicated noise suppression regions, thereby maintaining full field of view and light efficiency.
4Device complexity
If conventional phase CGH computation is used, then computation is simpler, but convergence is slow and speckle effects persist
Solution Approach 1:
The patent performs preliminary action by designing optimal phase functions before the iterative CGH computation process. These pre-designed phase functions are incorporated into the iteration algorithm, which significantly accelerates convergence and eliminates speckle effects without requiring complex computational procedures.
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 method achieves unprecedentedly low-error, speckle-free reconstructions with significantly improved image quality and maximum light efficiency, maintaining full field of view without partitioning the image area for signal and noise windows.
Implementation Method 1
phase modulating light from at least one light source by a spatial light modulator
Implementation Method 2
the coherent diffraction field of a target image is calculated and displayed as a computer generated hologram (CGH) on a spatial light modulator (SLM)
Data Source
AI summary
The present invention relates to a system and method for high quality speckle-free phase-only computer-generated holographic image projection. The present invention more particularly relates to a holographic image display system comprising a spatial light modulator to phase modulate light from at least one light source configured to illuminate said spatial light modulator and to provide a phase hologram and projection optics to project said phase modulated light to generate an image formed by said displayed hologram onto an image plane.