Optical Measuring Machine Thermal Distortion Correction
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Solution Overview
Problem
Existing optical measuring machines face issues with thermal distortions and precision due to overheating and uncontrolled lighting, leading to reduced measurement accuracy.
Innovation Solution
An optical measuring machine with a transparent support stage and telecentric optical systems, featuring a single LED light source, a linear camera, and a check master for correction, which allows for precise alignment and movement to capture frames, and a processing unit to calculate correction factors for thermal and systematic distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are used to illuminate the workpiece, then the illumination coverage is improved, but the thermal distortion and measurement precision deteriorate due to overheating
Solution Approach 1:
The patent divides the illumination function into multiple LED modules arranged in a specific geometric configuration. Each LED module contributes to the overall illumination while the segmentation allows for better thermal management and optical control, reducing the negative impact of heat generation on measurement precision
Solution Approach 2:
The patent introduces a telecentric optical system as an intermediary between the LEDs and the workpiece. This optical system controls the light paths to ensure parallel illumination and imaging, which compensates for thermal distortions and maintains measurement precision even with multiple LED sources generating heat
2Area of stationary object
If the camera is made movable to capture multiple frames, then the measuring area is expanded, but the measurement precision deteriorates due to thermal distortion from electric drives
Solution Approach 1:
Instead of moving the camera along with electric drives that generate heat and distortion, the patent inverts the approach by keeping the camera stationary and moving the workpiece support stage. This inversion eliminates the source of thermal distortion in the imaging path while still achieving coverage of a large measuring area through workpiece movement
Solution Approach 2:
The patent replaces the electric drive system for camera movement with a mechanical positioning system for the workpiece stage. The telecentric optical system then optically couples the stationary camera with the moving workpiece, substituting the problematic electric drive in the imaging path with a mechanically isolated positioning system
3Measurement precision
If a Fresnel lens is used to direct light rays, then the video capture quality is improved, but the device complexity increases
Solution Approach 1:
The patent uses multiple LED modules that create multiple virtual images of the workpiece through the telecentric optical system. This copying approach achieves high-quality video capture with uniform illumination without requiring complex light-directing elements like Fresnel lenses, thereby reducing device complexity while maintaining or improving image quality
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
The solution provides high-precision, distortion-free measurements by correcting thermal and systematic errors, ensuring rapid and accurate image capture and processing.
Implementation Method 1
an optical detection unit equipped with lighting means configured to generate a light beam along a predetermined optical path
Implementation Method 2
a support, interposed between the lighting means and the video capturing means, comprising a transparent panel
Implementation Method 3
video capturing means at least partly aligned with the lighting means along the optical path in order to receive the light beam
Data Source
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AI summary
An optical measuring machine comprises an optical detection unit (7) equipped with lighting means (8) and video capturing means (9), a support (4), interposed between the lighting means (8) and the video capturing means (9), comprising a transparent panel (6) defining a supporting stage (A) for a workpiece (100) to be measured and positioned along an optical path (B) to be crossed by the light beam. The machine also comprises a check master (20) connected to the support (4) and placed in a plane located at a distance from the video capturing means (9) equal to the focal length (F), in order to define an element of comparison for correcting a measuring error, wherein said check master (20) comprises a first segment (23a) and a second segment (23b) forming a substantially L-shaped structure disposed along the periphery of the transparent panel (6), at least partly delimiting the measuring area (M), extending along at least one direction transversal to the direction of movement (C) and positioned within the measuring area (M) of the machine.