Dual-Pattern Optical 3D Dimensioning for Thermal Stability
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Solution Overview
Problem
Optical 3D dimensioning systems face accuracy losses due to variations in projector-camera pair positions and orientations, thermal changes, and material thermal expansion, which are difficult to calibrate and control, leading to errors in 3D dimensioning.
Innovation Solution
A dual-pattern optical 3D dimensioning system using two identical projecting patterns to generate 3D depth data, where the camera captures images of the patterns and calculates dimensions based on the separation of pattern elements, allowing for accurate measurements regardless of camera focusing, distortion, or thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard projector-camera pair triangulation is used, then the system structure is simple, but measurement precision deteriorates due to variations in relative positions and orientations
Solution Approach 1:
The patent merges two identical pattern projectors into a dual-pattern system, where both projectors project the same pattern simultaneously onto the target object. This combination allows the system to eliminate the need for complex calibration by using the known separation distance between the two projectors, thereby improving measurement precision while maintaining reasonable system complexity.
Solution Approach 2:
The patent uses two identical pattern projectors that project the same pattern onto the target object. By creating a copy of the projection system with known geometric relationship, the system can calculate depth based on the separation distance between the two projectors rather than relying on complex calibration procedures, thus improving measurement accuracy.
2Measurement precision
If calibration is performed to correct position variations, then measurement accuracy improves partially, but reliability deteriorates due to non-calibratable variations from shock and vibration
Solution Approach 1:
The patent changes the fundamental parameter used for depth calculation from calibrated projector-camera geometry to the fixed separation distance between two identical projectors. This parameter change makes the system immune to shock and vibration effects on the camera, as the projector separation remains constant and can be precisely controlled, thereby improving both accuracy and reliability.
3Measurement precision
If camera focusing and distortion are corrected through calibration, then measurement precision improves, but device complexity increases
Solution Approach 1:
By using two identical projectors instead of one projector with complex camera calibration, the system eliminates the need for focusing and distortion corrections. The identical pattern projection from two known positions provides sufficient information for accurate depth calculation without requiring complex camera characterization, thus reducing device complexity while maintaining precision.
4Measurement precision
If thermal expansion compensation is implemented using multiple materials, then measurement accuracy improves, but manufacturing precision deteriorates due to difficulty in controlling thermal expansion
Solution Approach 1:
The patent changes the reference frame for measurement from the camera (which undergoes thermal expansion) to the projector separation distance (which can be thermally stable). By basing depth calculations on the fixed geometric relationship between two projectors rather than camera-based measurements, the system eliminates the need for complex thermal expansion compensation involving multiple materials, thereby improving manufacturability while maintaining precision.
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 provides accurate 3D dimensioning results by using the ratio of pattern image separation to the pattern image base feature, unaffected by changes in camera position or thermal expansion, offering improved precision and reliability compared to traditional methods.
Implementation Method 1
a first pattern generator to project a first light pattern on a target object; a second pattern generator to project a second light pattern on the target object; and a camera assembly to capture an image of the target object
Data Source
AI summary
An optical dimensioning system includes light emitting assemblies configured to project a predetermined pattern on an object. The optical dimensioning system further includes an imaging assembly configured to sense light scattered and/or reflected of the object, and to capture an image of the object while the pattern is projected. A processing assembly, in the optical dimensioning system, is configured to analyze the image of the object to determine one or more dimension parameters of the object.