Structured Light 3D Sensing Speckle Noise Reduction
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Solution Overview
Problem
Existing structured light sensing technologies using multiple emitters often suffer from speckle noise due to coherent light interference, which affects the accuracy and reliability of 3D scanning and surface information calculation.
Innovation Solution
The use of independent, mutually incoherent emitters arranged in rows to generate overlapping light patterns, where each emitter emits coherent light but is not coherent with others, reducing speckle noise by ensuring light from different emitters is incoherent along the projected lines, and allowing for variable intensity and angular spread control through collimation and optical element placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple coherent emitters are used to create structured light patterns, then the light pattern can be formed with sufficient intensity, but speckle noise is generated due to coherent light interference
Solution Approach 1:
The patent changes the coherence parameter of the light sources by using multiple independently controlled emitters (such as LEDs or laser diodes) that are mutually incoherent. Each emitter operates independently with its own phase and frequency, transforming the system from coherent to incoherent light combination, thereby eliminating speckle noise while maintaining sufficient illumination intensity through the cumulative effect of multiple emitters.
2Device complexity
If a single emitter is used with optics to create a full pattern, then the system is simpler, but the field of view and pattern coverage are limited
Solution Approach 1:
The patent segments the light source into multiple independent emitters arranged in arrays, where each emitter contributes to creating a portion of the overall structured light pattern. This segmentation allows the system to achieve a larger field of view and more comprehensive pattern coverage by combining the contributions of multiple emitters, while keeping each individual emitter simple in structure.
Solution Approach 2:
The patent merges the output of multiple independent emitters to form a comprehensive structured light pattern that covers a large field of view. By combining the light from multiple emitters in a coordinated manner, the system achieves both extensive coverage and the ability to create complex 3D patterns, overcoming the limitations of a single emitter approach.
3Area of stationary object
If multiple emitters are used to create a large field of view pattern, then coverage is improved, but speckle noise increases due to coherent interference
Solution Approach 1:
The patent applies parameter changes by transitioning from coherent to incoherent light sources. Each emitter in the array operates independently with uncorrelated phases and frequencies, ensuring that when multiple emitters are combined to create a large field of view pattern, the light waves do not interfere coherently. This eliminates speckle noise generation while maintaining extensive pattern coverage through the additive effect of multiple incoherent sources.
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
This approach significantly reduces speckle noise, enhances line uniformity, and improves the accuracy of 3D scanning by ensuring that each point in the projected pattern receives light from multiple emitters, while allowing for dynamic pattern generation and intensity control, thereby improving the reliability of depth and surface information calculation.
Implementation Method 1
at least two independent emitters, each of the independent emitters configured to generate a part of the projected pattern
Implementation Method 2
The emitters may be coherent in themselves but are independent in being mutually incoherent. In other words each emitter produces coherent light. However two different emitters are not coherent with each other
Implementation Method 3
In a first method a single emitter is projected through a series of optics to create a full pattern
Data Source
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AI summary
Apparatus for structured light scanning, the structured light comprising one or more projected lines or other patterns, comprises at least two independent emitters for each projected line or pattern, typically arranged in a row, and a pattern generator for causing light from respective emitters of a given row to overlap along the pattern axis to form the projected pattern. The independent emitters provide incoherent light along the pattern so that speckle noise is minimized despite the overlapping.