Build Surface Optical Calibration for Additive Fabrication Drift
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Solution Overview
Problem
Additive fabrication devices, such as those using selective laser sintering, face accuracy issues due to optical system drift over time, caused by thermal changes and physical disruptions, leading to inaccurate part production without proper calibration.
Innovation Solution
An optical system calibration method using image processing to generate and analyze calibration features on the build surface, determining corrections based on the comparison of actual and intended feature positions, with the aid of fiducial targets and precise mappings between image and build surface coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical system operates continuously for extended periods, then productivity is improved, but manufacturing precision deteriorates due to thermal drift and optical misalignment
Solution Approach 1:
The system performs preliminary calibration by generating calibration features at known positions and capturing images before production begins. This preliminary action establishes a reference mapping between image coordinates and build surface coordinates, enabling the system to compensate for drift that occurs during continuous operation without interrupting productivity.
Solution Approach 2:
The system implements feedback by continuously monitoring the positions of calibration features in captured images and comparing them against expected positions. When deviations are detected, the system automatically calculates and applies correction values to the optical system controls, maintaining manufacturing precision throughout continuous operation.
2Manufacturing precision
If calibration features are generated and analyzed to correct optical drift, then manufacturing precision is improved, but loss of time occurs during calibration procedures
Solution Approach 1:
The system performs self-calibration by automatically generating calibration features, capturing images, analyzing positions, calculating corrections, and applying adjustments without human intervention. This automation eliminates manual calibration time and allows the system to maintain precision through rapid, autonomous calibration cycles.
Solution Approach 2:
Instead of performing comprehensive calibration only at setup, the system implements periodic calibration cycles during operation. Calibration features are generated and analyzed at regular intervals or based on drift thresholds, allowing the system to maintain precision through frequent small corrections rather than infrequent comprehensive recalibration.
3Device complexity
If calibration features are generated on the build surface using the optical system, then device complexity is reduced, but measurement precision requirements increase
Solution Approach 1:
The calibration features are designed with distinct visual characteristics (such as high contrast patterns or specific colors) that make them easily distinguishable in captured images. This allows the image analysis algorithm to precisely detect feature positions even with standard image sensors, maintaining measurement precision without requiring specialized expensive equipment.
Solution Approach 2:
The system creates simplified 2D images of the 3D build surface as a copy representation. By working with these 2D image copies rather than directly manipulating 3D spatial data, the system reduces computational complexity while maintaining the precision needed for optical calibration through standard image processing 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
This method ensures accurate calibration of the optical system, preventing drift-induced inaccuracies and allowing for automatic correction, thereby maintaining the precision of part production.
Implementation Method 1
an optical system configured to direct light onto the source material, thereby producing one or more calibration features on the source material
Implementation Method 2
an image sensor configured to receive light produced from the source material, generate an image of the one or more calibration features
Data Source
AI summary
Techniques are described for calibrating an optical system in an additive fabrication device using an image of the build surface within the device. These techniques allow calibration to be performed by imaging one or more calibration features generated on (or at) the build surface, which may include illuminated regions of the build surface, regions of the build surface on which solid material has been formed, and/or regions of the build surface to which energy has otherwise been directed thereby making those regions distinguishable from their surroundings. The calibration features may be produced (at least in part) by the optical system to be calibrated. The location of the calibration features within the image may be compared with the intended location of these calibration features, and corrections to the optical system determined based on any differences between the actual and intended locations.