Autofocus Camera Compensation for 3D Measurement Accuracy
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Solution Overview
Problem
Existing 3D measuring instruments face challenges in maintaining compensation parameters, especially when dealing with changing environmental conditions or varying measurement distances, particularly when using an autofocus camera.
Innovation Solution
A method is implemented using an instrument with a registration camera and a surface measuring system, which includes a first camera with an autofocus mechanism. The method involves capturing registration images and surface images, determining 3D coordinates, and adjusting the autofocus mechanism to calculate compensation parameters based on these images and coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an autofocus camera is used to measure nearby or distant objects, then the measurement range is extended, but the compensation parameters become difficult to maintain
Solution Approach 1:
The system performs preliminary autofocus adjustments and compensation parameter calculations at multiple predetermined focus distances before actual measurement. This preliminary action establishes baseline compensation parameters that can be interpolated during real-time measurement, ensuring reliable compensation across the extended measurement range.
Solution Approach 2:
The system dynamically selects and adjusts compensation parameters based on the actual measurement distance. By making the compensation parameters adaptive rather than fixed, the system maintains reliability across varying distances while preserving the extended measurement range capability of the autofocus camera.
2Adaptability or versatility
If the focal length is adjusted to focus on objects at different distances, then the measurement flexibility is improved, but the positions of registration points change causing measurement errors
Solution Approach 1:
The system captures registration images at multiple focus distances and uses these images to calculate compensation parameters. The feedback loop involves comparing registration point positions across different focal lengths and automatically determining the compensation needed to correct position shifts, thereby maintaining measurement precision despite focal length adjustments.
Solution Approach 2:
The system changes the focal length parameter to enable focusing at different distances, which improves measurement flexibility. Simultaneously, it changes the compensation parameters based on the focal length to counteract the resulting registration point position shifts, thus maintaining measurement precision across different focus distances.
3Measurement precision
If compensation parameters are determined at multiple focus distances, then the measurement accuracy across different distances is improved, but the time required for measurement increases
Solution Approach 1:
The system performs the time-consuming task of capturing registration images and calculating compensation parameters at multiple focus distances as a preliminary setup step. Once these compensation parameters are established, they can be quickly applied during actual measurement, thus improving measurement accuracy without significantly impacting real-time measurement speed.
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 allows for the accurate determination and storage of compensation parameters, enabling the instrument to maintain precise measurements across different conditions and distances, thereby enhancing the reliability of 3D measurements.
Implementation Method 1
the autofocus mechanism is adjusted based at least in part on adjusting a focal length to reduce a difference between positions of the first plurality of registration points and the second plurality of registration points
Implementation Method 2
a first light is projected onto an object with the projector and a first surface image of the first light on the object is captured with the first camera
Data Source
AI summary
A 3D measuring instrument and method of operation is provided that includes a registration camera and a an autofocus camera. The method includes capturing with the registration camera a first registration image of a first plurality of points and a first image with the first camera with the instrument in a first pose. A plurality of three-dimensional (3D) coordinates of points are determined based on the first image. A second registration image of a second plurality of points is captured in a second pose and a focal length of the autofocus camera is adjusted. A second surface image is captured with the first camera having the adjusted focal length. A compensation parameter is determined based in part on the captured second surface image. The determined compensation parameter is stored.