Multi-Wavelength Depth Encoding for 3D Range Geometry Compression
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Solution Overview
Problem
Current 3D range data compression methods, particularly those using digital fringe projection, are prone to significant errors when subjected to lossy compression algorithms like JPEG, leading to unusable high-resolution features due to artifacts, which complicates efficient storage and streaming of high-quality 3D geometry data.
Innovation Solution
A multi-wavelength encoding method is introduced, where 3D range data is represented within 2D images, allowing for robust compression using traditional lossless or lossy image compression techniques, such as PNG or JPEG, with minimal filtering required to mitigate artifacts, achieving extremely high compression ratios while maintaining low reconstruction errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mesh formats (OBJ, PLY, STL) are used to store 3D geometry data, then the data can be stored with vertex locations and connectivity information, but the storage space required is very large (e.g., 13 MB for a single 640×480 frame)
Solution Approach 1:
The patent encodes three-dimensional depth information into two-dimensional image format by mapping depth values to pixel intensity values. This dimensional reduction allows the same geometric information to be stored in a compact 2D image (e.g., 640×480 pixels) rather than requiring large mesh data structures with vertex coordinates and connectivity information, achieving compression ratios of 935:1 compared to conventional formats like OBJ
Solution Approach 2:
The patent transforms geometric parameters (3D coordinates) into image parameters (pixel intensity values representing depth). By changing the representation parameter from spatial coordinates to intensity values, the data can be stored efficiently in standard image formats while preserving the essential geometric information for reconstruction
2Productivity
If lossy compression algorithms (e.g., JPEG) are applied to compressed 3D range data, then storage and transmission efficiency is improved, but significant artifacts and errors are introduced that render high-resolution features unusable
Solution Approach 1:
The patent recognizes that lossy compression artifacts, while traditionally harmful, can be tolerated in the encoded depth image because the encoding scheme is specifically designed to be robust against such artifacts. The multi-wavelength encoding and phase unwrapping process can recover accurate depth information even when the compressed image contains JPEG artifacts, effectively converting the potential harm into an acceptable trade-off for achieving high compression ratios
Solution Approach 2:
The patent employs filtering techniques as a preliminary measure to reduce compression artifacts before they can significantly degrade the reconstruction quality. By applying filters in advance during the decoding process, the system cushions against the harmful effects of lossy compression while maintaining high compression ratios
3Adaptability or versatility
If digital fringe projection techniques are used to encode 3D geometry into 2D images, then portability to video storage and streaming is achieved, but common lossy compression algorithms introduce unacceptably large errors that make high-resolution DFP data unusable
Solution Approach 1:
The patent applies filtering operations as a preliminary cushioning measure to mitigate the harmful effects of lossy compression artifacts on digital fringe projection data. By filtering the decoded image before reconstructing the 3D geometry, the system reduces errors introduced by JPEG compression while maintaining the portability benefits of 2D image storage
Solution Approach 2:
The patent demonstrates that with proper encoding and decoding techniques, the harmful JPEG compression artifacts can be tolerated and even exploited. The system achieves high compression ratios with acceptable error rates by designing the fringe projection encoding to be inherently more robust to compression artifacts than conventional 3D data formats
Data Source
AI summary
A method for generating encoded depth data includes receiving digital fringe projection (DFP) data corresponding to a three-dimensional structure of a physical object, and generating first and second fringe encodings for a first predetermined wavelength based on the DFP data at a first coordinate. The method further includes generating third and fourth fringe encodings for a second predetermined wavelength based on the DFP data at the first coordinate, the second wavelength being longer than the first wavelength, and generating a combined fringe encoding based on the third fringe encoding and the fourth fringe encoding. The method further includes storing the first, second, and combined fringe encoding data in a pixel of two-dimensional image data at a pixel coordinate in the two-dimensional image data corresponding to the first coordinate.