Reflectivity Measurement via Bright Area Change
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Solution Overview
Problem
Image processing systems in machine tools face challenges when dealing with highly reflective workpiece surfaces due to the limitations of small incident light illumination, leading to difficulties in setting correct exposure times and preventing meaningful automatic exposure settings.
Innovation Solution
A method using an image processing system with reflected light illumination and a camera to determine reflectivity by taking multiple images at varying exposure times, evaluating bright areas, and calculating the change in bright surface area over exposure time to measure reflectivity, which can be automated and software-based.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If incident light illumination with small spatial expansion ratios is used in image processing systems, then the system can be used in machine tools with limited space, but highly reflective workpiece surfaces cannot be properly measured due to overwhelming reflections
Solution Approach 1:
The patent inverts the illumination approach by using reflected light illumination instead of incident light illumination. The light source is positioned to illuminate the workpiece from above, and the camera captures light reflected from the workpiece surface at angles different from the illumination angle. This inversion of the light path geometry eliminates direct reflections into the camera sensor while maintaining measurement capability for highly reflective surfaces.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the change in bright surface area over exposure time as an intermediate parameter. Instead of directly measuring reflectivity which fails for highly reflective surfaces, the system measures how the bright area changes with exposure time, and uses this change rate as a proxy for reflectivity. This intermediary measurement enables quantification of reflectivity where direct measurement fails.
2Ease of operation
If automatic exposure setting is attempted with highly reflective surfaces, then exposure time adjustment is needed, but the high reflectivity prevents meaningful automatic exposure setting
Solution Approach 1:
The patent applies preliminary action by first determining the reflectivity of the workpiece surface using the reflected light illumination method and bright area change analysis before performing the actual measurement task. This preliminary reflectivity determination allows the system to pre-calculate appropriate exposure times based on the measured reflectivity value, ensuring reliable exposure settings before the main measurement occurs.
Solution Approach 2:
The patent implements feedback by using the measured reflectivity information to adjust and optimize the exposure time for subsequent measurements. The system measures the bright area change over exposure time, calculates reflectivity from this change, and then uses this reflectivity value as feedback to determine the optimal exposure time for the actual measurement task, creating a closed-loop control system.
3Measurement precision
If multiple images are taken at varying exposure times to determine reflectivity, then accurate reflectivity measurement is achieved, but the process complexity increases
Solution Approach 1:
The patent applies self-service by enabling the image processing system to automatically perform the entire reflectivity measurement process without external intervention. The system autonomously captures multiple images at different exposure times, processes the images to determine bright surface areas, calculates the change over exposure time, and derives the reflectivity value. This automation reduces operational complexity despite the multi-step measurement process.
Solution Approach 2:
The patent replaces manual mechanical adjustment of exposure settings with an automated computational system. Instead of requiring operators to manually adjust exposure times and interpret results, the system uses software-based image processing to automatically analyze the bright area changes and calculate reflectivity, substituting mechanical/manual operations with computational automation.
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 the recognition and measurement of highly reflective workpiece surfaces, allowing for successful measurement tasks with correct exposure times, and provides a measure of reflectivity independent of absolute light changes, effectively differentiating between reflective and matte surfaces.
Implementation Method 1
The device includes incident light illumination 3 to illuminate the surface 2 and reflected light illumination 3 to illuminate the surface 2
Data Source
Figure 1~2
Figure 3~4
AI summary
In a method for determining the reflectivity of a surface (2) which is illuminated by means of an incident lighting unit (3), images of the surface (2) are recorded, said images having respectively different exposure times. Thereafter, the bright surface area in which a predetermined minimum brightness is reached is determined in each of the recorded images, and the bright surface area is used to determine the reflectivity of the surface (2) depending on the differing exposure times. A device (1) suitable for this comprises an incident lighting unit (3) for illuminating the surface (2), a sensor (4) for capturing an image from the surface (2) and an image processing system (7) for processing the recorded images, wherein the image processing system (7) is designed to determine the bright surface area in which a predetermined minimum brightness is reached in each of the recorded images, and to use the bright surface area to determine the reflectivity of the surface (2) depending on the different exposure times.