3D Measurement Dynamic Exposure for PCB Brightness Saturation
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Solution Overview
Problem
Existing three-dimensional measuring devices face challenges in achieving high accuracy and efficiency due to low contrast image data from printed circuit boards with varying colors, leading to difficulties in standardizing height measurements and requiring prolonged image acquisition and processing times.
Innovation Solution
A three-dimensional measuring device that performs first and second image processing with specific exposure times to prevent brightness saturation in bright and dark areas, combining image data to prepare images with extended dynamic range, allowing for accurate measurements using either unsaturated or summed values, thereby reducing overall measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate imaging is performed for solder printing region and background region with different exposure times, then measurement accuracy is improved, but measurement time is prolonged
Solution Approach 1:
The patent implements dynamic exposure time adjustment by controlling the imaging device to capture images at multiple exposure times (first exposure time for bright solder regions, second exposure time for dark background regions). The control device dynamically selects and combines appropriate image data based on brightness characteristics, resolving the contradiction between measurement accuracy and acquisition time by adapting exposure parameters to local image characteristics rather than using a single static exposure time for the entire field of view.
Solution Approach 2:
The patent divides the image processing into segmented steps: first acquiring images at multiple exposure times, then separating and identifying bright and dark region pixels, and finally combining only the necessary unsaturated pixel data from appropriate exposure time images. This segmentation allows the system to process only relevant data portions rather than handling complete images at all exposure times, reducing overall processing time while maintaining accuracy.
2Reliability
If multiple images are taken at same exposure time to increase dynamic range, then brightness saturation is avoided, but number of imaging operations increases
Solution Approach 1:
The patent applies partial action by taking multiple images at the same first exposure time (excessive for dark regions, partial for bright regions) and then selectively using only the unsaturated pixel data from these images. Rather than processing all image data completely, the system identifies and combines only the necessary unsaturated portions, achieving reliable brightness measurement without the full overhead of processing multiple complete images.
Solution Approach 2:
The patent changes the exposure time parameter dynamically based on regional brightness characteristics. By acquiring images at different exposure times and then selecting data based on saturation levels, the system adapts the exposure parameter to match local image characteristics, improving reliability for both bright and dark regions while maintaining imaging efficiency through selective data combination.
3Measurement precision
If standard exposure time is used for bright region, then solder printing measurement is accurate, but background region becomes too dark for height standardization
Solution Approach 1:
The patent performs preliminary action by acquiring images at multiple exposure times before final measurement processing. The first images at first exposure time capture bright solder regions with appropriate brightness, while second images at second exposure time capture dark background regions with sufficient brightness. This preliminary multi-exposure acquisition ensures both regions have usable data before the combination step, preventing information loss in either region.
Solution Approach 2:
The patent adds the time dimension to the imaging process by capturing images at multiple exposure times rather than relying on a single exposure time. This temporal dimension allows the system to obtain both bright and dark region information that would be unavailable in a single exposure, effectively adding a new degree of freedom to resolve the brightness information loss problem.
4Measurement precision
If longer exposure time is used for background region, then height standardization is possible, but solder printing region becomes saturated
Solution Approach 1:
The patent extracts and separates pixel data from different exposure time images based on brightness characteristics. It identifies bright pixels from the first exposure time images and dark pixels from the second exposure time images, then combines only these extracted portions. This extraction approach allows the system to use the longer second exposure time for background regions without saturating solder regions, since the solder region data is extracted from the shorter first exposure time images where saturation does not occur.
Solution Approach 2:
The patent performs preliminary classification of pixels by brightness level before combination. By first identifying which pixels are bright versus dark, and which images contain unsaturated data for each region type, the system prepares the data in advance to prevent saturation information loss. This preliminary sorting ensures that solder printing brightness information is preserved from the first exposure images while background height information is obtained from the second exposure images.
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 enables faster and more accurate three-dimensional measurements by reducing the time required for image data acquisition and processing, improving measurement precision while maintaining data quality, with a total time reduction of approximately 11% compared to previous methods.
Implementation Method 1
an imaging means for imaging light reflected from the measurement object irradiated by the light
Data Source
AI summary
A board inspection device includes an irradiation device for irradiating light on a printed circuit board, a CCD camera for imaging the irradiated part of the circuit board. First image processing is performed for a first exposure time such that an inspection target region is free of brightness saturation, and second image processing is performed using a second exposure time corresponding to the insufficiency of the first exposure time relative to a certain exposure time appropriate for measurement of a measurement standard region. Thereafter, image data for three-dimensional measurement is prepared for the inspection target region using the value of image data obtained by the first image processing, and image data for three-dimensional measurement is prepared for the measurement standard region using a value obtained by summing the image data value acquired by the second image processing and the image data value acquired by the first image processing.