Laser Engraving Grayscale Mapping for Extreme Contrast Images
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Solution Overview
Problem
Existing laser engraving methods struggle to consistently produce high-quality images with extreme facial contrasts on identification documents using a single laser parameter, leading to issues with visibility and quality.
Innovation Solution
A method involving the generation of a map by calibrating a laser engraving apparatus using a series of calibration images with varying grayscale values, measuring color values, and determining a relationship between color space distances and laser parameters to ensure consistent grayscale representation across the engraving range, allowing for the precise mapping of input image grayscale values to output image grayscale values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single laser parameter is used for engraving, then the engraving process is simple and fast, but the quality of images with extreme facial contrasts deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the laser engraving system with multiple parameter combinations before actual production. A calibration process is performed offline to create a lookup table or mapping that stores optimal parameter settings for different grayscale ranges. During actual engraving, the system simply queries this pre-computed data structure, avoiding real-time complex calculations while ensuring consistent image quality across different facial contrasts.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting laser parameters (such as power, speed, pulse duration) based on the grayscale values of the input image. Different grayscale ranges are mapped to different laser parameter sets, allowing the system to adapt to varying image characteristics while maintaining a relatively simple control structure through pre-defined parameter mappings.
2Reliability
If laser parameters are adjusted for extreme contrast images, then image visibility improves, but the complexity of the engraving process increases
Solution Approach 1:
The patent reduces device complexity by performing the complex parameter optimization work in advance during a calibration phase. The calibration process explores different laser parameter combinations and their effects on image quality, storing the results in a lookup table. During production, the system only needs to perform simple table lookups based on image grayscale characteristics, avoiding real-time complex optimizations while ensuring reliable image visibility.
Solution Approach 2:
The system applies self-service by automatically selecting appropriate laser parameters based on the input image characteristics without requiring manual intervention. The pre-calibrated mapping between grayscale ranges and laser parameters enables the system to self-adjust to different image types, reducing operational complexity while maintaining high image visibility for extreme contrasts.
3Manufacturing precision
If multiple laser parameters are varied, then image quality across different grayscale values improves, but the calibration and control complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the grayscale range into multiple segments or zones, each associated with specific laser parameter settings. Instead of continuously varying multiple parameters, the system discretizes the grayscale space and assigns predefined parameter combinations to each segment. This segmentation approach simplifies calibration by reducing the continuous optimization problem to a discrete mapping task, while still achieving accurate grayscale representation across the full range.
Solution Approach 2:
The patent manages parameter changes by pre-determining optimal laser parameter combinations for different grayscale segments during calibration. The calibration process systematically varies parameters to identify optimal settings for each grayscale range, storing these as discrete mappings. During production, the system changes parameters by selecting from this pre-computed set rather than performing real-time optimization, reducing control complexity while maintaining grayscale accuracy.
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 the engraving of images with extreme contrasts by averaging laser parameters, ensuring good quality and visibility, particularly useful for security documents featuring diverse facial features.
Implementation Method 1
a laser engraving method using such a map
Implementation Method 2
engraving the plurality of calibration images on a predefined substrate surface
Implementation Method 3
A colour value of each of the engraved calibration images and of the predefined substrate surface in a colour space is measured
Data Source
AI summary
A laser engraving apparatus (100) is calibrated using a number of predetermined calibration images (12). The calibration images (12) are engraved on a predefined substrate surface (14, 15) of a substrate (16) by varying only a single laser parameter. Based on measured colour values of the engraved calibration images, a relationship between said colour values and a predefined laser parameter value, for example, a predefined laser power, is established. This relationship is then used to generate a map for mapping a grayscale value of an input image to a grayscale value of an output image, which is then engraved on the substrate (16) while varying the same laser parameter that was varied during the calibration.