TOF Pixel Offset Compensation for Depth Accuracy
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Solution Overview
Problem
Time-of-flight (TOF) systems face challenges in maximizing space-time resolution, leading to erroneous depth measurements due to motion blur and pixel offsets, which result in bias errors when combining pixel values from different frames or spatial locations.
Innovation Solution
A method and system that intelligently combine pixel values and compensate for individual pixel offsets, allowing for dynamic on-the-fly decisions to maximize either temporal or spatial resolution, using techniques such as offset cancellation and temporal modeling to reduce motion blur and spatial edge artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel values are combined from different frames to improve temporal resolution, then depth measurement accuracy improves, but motion blur increases causing bias errors
Solution Approach 1:
The patent implements dynamic selection of temporal versus spatial combination mode based on detected motion levels. When motion is detected, the system switches to spatial combination mode; when no motion is present, it uses temporal combination mode. This dynamic adaptation resolves the contradiction by selecting the appropriate processing mode based on real-time conditions.
Solution Approach 2:
The patent changes the processing parameter from temporal combination to spatial combination based on motion detection. This parameter change allows the system to avoid motion blur artifacts while maintaining depth measurement accuracy by combining pixel values from different spatial locations rather than different time frames when motion is present.
2Measurement precision
If pixel values are combined from neighboring pixels to improve spatial resolution, then depth measurement accuracy improves, but spatial edge artifacts increase causing bias errors
Solution Approach 1:
The patent dynamically switches between temporal and spatial combination modes based on motion detection. When motion is detected, temporal combination is used to avoid spatial edge artifacts; when no motion is present, spatial combination provides better resolution. This dynamic selection resolves the contradiction between improving spatial resolution and avoiding edge artifacts.
3Measurement precision
If individual pixel offsets are compensated to reduce bias errors, then depth measurement accuracy improves, but processing complexity increases
Solution Approach 1:
The patent performs preliminary offset compensation by calculating average offset values from multiple pixel readings before the main depth calculation process. This preliminary action removes the need for complex per-pixel offset correction during real-time processing, thereby reducing processing complexity while maintaining depth measurement accuracy.
Solution Approach 2:
The system uses the pixel data itself to determine and compensate for offsets through statistical analysis of the captured values. By using the data to self-correct systematic errors, the patent avoids requiring external calibration procedures or complex correction algorithms, thus maintaining simplicity while improving accuracy.
4Measurement precision
If multiple pixel values are combined to reduce noise, then depth measurement accuracy improves, but the time required for processing increases
Solution Approach 1:
The patent implements dynamic mode selection between temporal and spatial combination based on motion detection. This dynamic approach allows the system to use the most efficient combination method for current conditions, reducing processing time while maintaining accuracy. When motion is present, spatial combination avoids the need to wait for multiple frames; when no motion, temporal combination efficiently reduces noise.
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 approach enables accurate depth calculations by removing pixel-dependent offsets, reducing motion blur and spatial edge errors, and allowing for real-time optimization of space-time resolution, resulting in improved depth measurement accuracy.
Implementation Method 1
When reflected optical energy Sin impinges upon the photodetectors, photons within the photodetectors are released, and converted into tiny amounts of detection current.
Data Source
AI summary
Phase-based TOF systems operate with reduced depth error due to motion blur, and/or spatial blur, and/or pixel offset by intelligently determining how best to combine pixel values, and how best to compensate for individual pixel offsets. Such determination(s) may be carried out on a per pixel basis, dynamically, in real-time during TOF operation, or on archived TOF data. Offsets for individual pixels may be dynamically calculated and subtracted from the values acquired by those pixels Individual pixel offsets may be calculated for example by combining data acquired by the same pixel at two acquisitions, 180° out of phase with respect to each other. Calculated offsets may be averaged, or on a per pixel basis, and if target object motion is detected, one or more offset calculations can be discarded rather than averaged to reduce motion blur. Offsets acquired a priori during a TOF system calibration procedure may be used.