Calibration Target for 3D Scanner Recalibration
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Solution Overview
Problem
Existing calibration methods for portable 3D contour scanners, such as those used in intraoral imaging, are not practical for end-user on-site recalibration and lack precision, leading to inaccuracies and increased costs due to the need for precise manufacturing and custom calibration targets.
Innovation Solution
A calibration target with uniformly spaced 3D features, including oblique surfaces, that can be easily attached to the scanner, allowing for accurate calibration without precise positioning, and a calibration fixture for adjusting the target's distance, enabling end-users to perform recalibration and correct out-of-calibration errors automatically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional calibration tools and techniques are used for portable 3-D scanners, then calibration can be performed, but the process is not practical for end-user on-site recalibration and requires precise positioning
Solution Approach 1:
The calibration target is segmented into multiple identical 3D features (spheres, cubes, or pyramids) arranged in a grid pattern. This segmentation allows the scanner to identify and use multiple features for calibration, making the process more robust and easier to perform without precise positioning requirements.
Solution Approach 2:
The calibration target is designed with universally recognizable 3D features that can be used for multiple calibration purposes. The same target can be used for different types of scanners and multiple calibration operations, eliminating the need for specialized calibration tools for each device or application.
2Measurement precision
If conventional calibration targets are used, then calibration can be performed, but manufacturing precision requirements increase costs and complexities
Solution Approach 1:
The calibration method changes from requiring precise manufacturing of the entire target to requiring only that the 3D features be clearly distinguishable and uniformly spaced. The calibration accuracy is achieved through the scanning system's ability to precisely measure the positions of the features rather than through ultra-precise manufacturing of the target itself.
Solution Approach 2:
The calibration target can be manufactured using inexpensive methods such as 3D printing or molding, rather than requiring high-precision machining. This reduces manufacturing costs and complexities while still providing sufficient calibration accuracy through the use of multiple uniformly spaced features.
3Reliability
If factory calibration is performed, then initial accuracy is achieved, but drift over time and handling changes adversely impact scanner performance
Solution Approach 1:
The calibration system enables end-users to perform self-calibration without requiring specialized service personnel or complex procedures. The user simply attaches the calibration target and runs the automated calibration routine, which the scanner performs independently using its own imaging systems and processing algorithms.
Solution Approach 2:
The calibration target is designed with pre-established uniform spacing and known geometric features, so that when the scanner images the target, the calibration parameters can be directly calculated without requiring iterative adjustment or complex measurement procedures. This preliminary structuring of the target enables rapid calibration.
4Reliability
If multiple patterns of light are used for structured light imaging, then robustness of pattern detection increases, but the complexity of the illumination system increases
Solution Approach 1:
The illumination system uses periodic patterns of light (such as sinusoidal fringes or repeating line patterns) that are projected onto the calibration target. This periodic structure enables robust detection and analysis of the target features while using a relatively simple single-projector system, avoiding the need for complex multi-projector arrangements.
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
Enables accurate and cost-effective on-site recalibration of intraoral scanners by the end-user, reducing manufacturing complexities and increasing the precision of calibration targets, thus improving the accuracy and reliability of surface contour imaging.
Implementation Method 1
Light reflected or scattered from the surface is then viewed from another angle as a contour image, taking advantage of triangulation in order to analyze surface information based on the appearance of contour lines or other patterned illumination.
Data Source
AI summary
An apparatus (70) for surface contour imaging of an object has an illumination apparatus energizable to direct one or more illumination patterns (46) toward a surface position. A sensing apparatus (40) has at least one lens (34) and a sensor (30) that is energizable to obtain one or more images of the surface position corresponding to the illumination patterns (46). A calibration target (100) is detachably coupled to the apparatus (70) in the surface position, wherein the calibration target (100) has a set having a plurality of raised features (50) that are uniformly spaced apart with respect to first and second orthogonal axes that define a first plane and having a uniform height along a height axis that is orthogonal to the first plane. The raised features (50) further have at least a first slanted surface (54) that is oblique with respect to the first plane and oblique with respect to the height axis.