Dot-Based Time of Flight 3D Imaging Depth Accuracy
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Solution Overview
Problem
Conventional time-of-flight (TOF) imaging systems face challenges in accurately determining depth due to multi-path reflections and ambient light interference, which requires high-intensity output light and struggles with low-reflection and specular reflective objects.
Innovation Solution
A TOF 3D imaging system that uses a structured light illuminator to emit a dot-pattern output light, coordinated with an imaging sensor and a time-of-flight controller to calculate the time-of-flight and depth information, and applies a detection threshold based on peak intensity to filter out ambient and scattered light, enhancing signal-to-noise ratio and depth accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional broad beam light emission is used to illuminate the field, then the field of illumination is adequately lit, but the system cannot positively discern reflected light from ambient light and suffers from multi-path reflections
Solution Approach 1:
The patent segments the broad beam illumination into discrete dot patterns projected onto the field. Each dot represents a localized light source that can be individually tracked and measured, allowing the system to distinguish between direct reflected light from specific dots and ambient or multi-path reflected light. This segmentation enables precise depth calculation by correlating the known dot positions with their detected locations and intensities.
Solution Approach 2:
The patent applies local quality by concentrating illumination power at specific dot nodes rather than uniformly distributing light across the entire field. This creates high-intensity localized spots that stand out against ambient light backgrounds. The structured light pattern ensures that each dot has sufficient intensity to overcome ambient light interference while maintaining spatial discrimination capability.
2Illumination intensity
If high-intensity output light is used to overcome ambient light and illuminate low-reflection objects, then the signal strength is sufficient, but the system still struggles with specular reflective objects and multi-path errors
Solution Approach 1:
By segmenting the illumination into discrete dots, the system can track each dot's reflection independently. This allows the system to identify and filter out specular reflections and multi-path errors by analyzing the spatial and temporal characteristics of each dot's reflected signal, rather than being overwhelmed by collective reflections from a broad beam.
Solution Approach 2:
The system uses feedback by comparing the known dot pattern positions with the detected reflected light positions and intensities. This feedback mechanism allows real-time correction and filtering of erroneous measurements from specular or multi-path reflections, improving the reliability of depth measurements while maintaining high illumination intensity.
3Area of stationary object
If flood illumination is used to illuminate the entire field, then all areas are visible, but the system cannot achieve precise depth measurements due to inability to distinguish reflected light from ambient light
Solution Approach 1:
The patent maintains full field coverage by projecting a pattern of multiple discrete dots across the entire illumination area. Each dot provides localized precision measurement capability, while the collection of dots collectively covers the complete field. This segmentation approach preserves both wide coverage and precise measurement by treating each dot as an independent measurement point.
Solution Approach 2:
The system applies local quality by ensuring each dot in the distributed pattern has sufficient intensity and spatial definition to enable precise depth measurement. While the overall field coverage remains broad, each local dot region provides high-precision measurement capability, resolving the contradiction between wide coverage and measurement precision.
4Measurement precision
If structured light pattern with dots is used to concentrate illumination power, then depth calculation accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent changes the spatial distribution parameter of the illumination from uniform flood to discrete dot patterns. This parameter change enables concentration of illumination power at specific nodes, improving depth calculation accuracy through better signal-to-noise ratio and ambient light discrimination. The complexity is managed by using regular geometric patterns that can be generated through straightforward optical modulation techniques.
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 system improves depth calculation accuracy and resolution by concentrating illumination power at nodes, reducing depth errors caused by multi-path reflections and ambient light, while maintaining efficient use of illumination power.
Implementation Method 1
measuring the elapsed time between the emission of light from the light source and the reception of the light that is reflected off of the objects
Implementation Method 2
receiving a reflected portion of the dot-pattern output light
Data Source
Figure 1~2A
Figure 2B~3
Figure 4A~4B
AI summary
A system for three-dimensional imaging includes a structured light illuminator, an imaging sensor, and a time-of-flight controller in data communication with the structured light illuminator and the imaging sensor. The structured light illuminator provides an output light in a structured light pattern and the imaging sensor receives a reflected portion of the output light. The time-of-flight controller coordinates the structured light illuminator and imaging sensor and calculates a time-of-flight of the output light and the reflected portion.