3D Scanner Feedback Control for Heterogeneous Surface Reflectivity
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Solution Overview
Problem
Existing 3D scanners face challenges in accurately capturing three-dimensional models of objects with heterogeneous surface reflectivity due to limited dynamic range of image sensors and issues with specular reflections, leading to inaccurate triangulation and the need for coating objects with diffusely reflecting agents.
Innovation Solution
A scanner system with a laser light source having adjustable power, where the intensity is regulated independently of the image sensor using a photodiode for feedback control, allowing for real-time adjustment of the laser power to maintain intensity within the sensor's dynamic range, and a method involving projection of a moving light pattern onto the object's surface for three-dimensional geometry acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the laser power is increased to capture highly reflective surfaces, then the signal from reflective areas is improved, but the dynamic range of the image sensor is exceeded causing saturation
Solution Approach 1:
The patent implements dynamic adjustment of laser power based on real-time feedback from the image sensor. The system continuously monitors the intensity of reflected light and adjusts the laser power accordingly, transitioning from a static to a dynamic control mechanism. This allows the laser power to be increased for reflective surfaces and decreased for absorptive surfaces, maintaining optimal signal levels across heterogeneous surfaces without saturation or insufficient signal.
Solution Approach 2:
The patent employs a feedback control mechanism where the image sensor monitors the intensity of reflected light and feeds this information back to the laser power control system. This closed-loop feedback allows the system to automatically adjust the laser power in response to the actual reflection characteristics of the scanned surface, ensuring that the signal remains within the dynamic range of the sensor for accurate triangulation.
2Reliability
If the laser power is decreased to avoid sensor saturation, then the dynamic range is maintained, but the signal from absorptive surfaces becomes too weak for accurate detection
Solution Approach 1:
The system dynamically adjusts laser power in real-time based on the reflection characteristics of the scanned surface. When scanning absorptive surfaces that return weak signals, the laser power is automatically increased to ensure sufficient signal strength for accurate triangulation, while maintaining reliable sensor operation within its dynamic range through continuous feedback control.
Solution Approach 2:
The feedback mechanism monitors the intensity of reflected light from the image sensor and automatically adjusts the laser power to compensate for variations in surface reflectivity. This ensures that even highly absorptive surfaces generate sufficient signal for accurate detection and triangulation, while preventing saturation on reflective surfaces.
3Device complexity
If a fixed laser power is used, then the device complexity is reduced, but the scanner cannot adapt to surfaces with heterogeneous reflectivity
Solution Approach 1:
The patent implements a feedback control system where the image sensor continuously monitors the reflected light intensity and feeds this information back to the laser power control. This automatic feedback mechanism enables the scanner to adapt to surfaces with heterogeneous reflectivity without requiring complex manual intervention or pre-programming, achieving high adaptability through a relatively simple closed-loop control structure.
Solution Approach 2:
The system performs self-adjustment of laser power based on the actual scanning conditions detected by the image sensor. The scanner automatically adapts to different surface reflectivity characteristics without external intervention, with the feedback control mechanism enabling the system to serve itself by making real-time power adjustments based on the reflected light intensity measurements.
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 solution enables accurate three-dimensional modeling of objects with varying reflectivity without the need for coatings, expanding the application areas of 3D scanners and reducing time lag between image acquisition and intensity regulation, thus improving scanning speed and accuracy.
Implementation Method 1
detection means, other than the at least one image sensor, for monitoring at least a part of the light pattern reflected from the surface
Implementation Method 2
at least one light source, preferably a laser light source with adjustable power, projection means for directing light from the at least one light source to a moving spot on the surface of the object
Data Source
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Figure 2A~2B
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AI summary
The present invention relates to non-contact optical scanning of an object for generation of a three-dimensional surface model of the scanned object. In particular the invention relates to a scanner for obtaining the three-dimensional geometry of at least a part of the surface of an object, said scanner comprising: - at least one light source, preferably a laser light source with adjustable power, - projection means for directing light from the at least one light source to a moving spot on the surface of the object, - at least one image sensor adapted to record at least one image of at least a part of the surface, - detection means, other than the at least one image sensor, for monitoring at least a part of the light reflected from the surface, - regulation means for adjusting the intensity of the at least one light source based on the amount of light reflected from the surface, and - means for transforming the at least one image to a three-dimensional model of the surface.