Automated Showthrough Measurement via Pixel Intensity Ratios
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Solution Overview
Problem
Current methods for measuring showthrough of printed images on planar objects, such as paper, are inadequate as they rely on subjective human ratings and small-area opacity measurements, failing to provide a representative assessment of visual appearance uniformity, especially when patterns are printed on the reverse side.
Innovation Solution
An automated imaging system that measures the optical reflectance of the front surface using a photodetector array and lens, creating calibration and sample images to calculate the ratio of pixel intensities, providing a more accurate and representative measure of showthrough by adjusting illumination levels and correcting for dark current signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional opacimeters are used to measure showthrough, then measurement can be performed on a small region, but the measurement does not provide a representative measure of overall showthrough
Solution Approach 1:
The patent transitions from point-based opacity measurement to area-based imaging measurement by capturing two-dimensional images of the entire sample surface. The imaging assembly captures reflectance information across the full sample area, and pixel intensity ratios are calculated to quantify showthrough across the entire surface rather than at isolated points.
Solution Approach 2:
The patent creates digital images (copies) of the sample surface that capture reflectance information. These image copies are then analyzed through pixel intensity ratio calculations to determine showthrough, replacing direct physical measurement with optical copying and digital analysis.
2Measurement precision
If human operators perform visual ratings of showthrough, then subjective assessment can be obtained, but the process is time-consuming and lacks objectivity
Solution Approach 1:
The patent replaces the human visual assessment system with an automated optical measurement system. The imaging assembly captures reflectance data, and a computer automatically calculates pixel intensity ratios to quantify showthrough, eliminating subjective human judgment and significantly reducing measurement time.
Solution Approach 2:
The system performs self-assessment by automatically capturing images, calculating pixel intensity ratios, and generating showthrough measurements without requiring human operators to visually evaluate each sample. The automated processing provides objective, repeatable measurements across all samples.
3Reliability
If illumination level varies during measurement, then measurement flexibility is improved, but measurement reliability decreases due to intensity variations
Solution Approach 1:
The patent employs feedback control where the measured pixel intensity ratios are used to normalize showthrough calculations. By measuring the actual reflectance at each pixel location and using these measurements to calculate ratios against a reference image, the system compensates for illumination variations and maintains measurement reliability despite fluctuations in lighting conditions.
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 system offers stable and uniform illumination, minimizing noise and ensuring showthrough measurements are independent of illumination intensity variations, providing a precise and objective assessment of visual appearance uniformity across larger areas compared to traditional methods.
Implementation Method 1
measuring the optical reflectance of the front surface with a lens and a photodetector array
Implementation Method 2
measuring the optical reflectance of the front surface with a lens and a photodetector array, the lens focusing an image of the object onto the photodetector array
Implementation Method 3
uniformly illuminating, with a diffuse light source, the front surface of a reference object
Data Source
AI summary
An image analysis method to quantify visual showthrough of printed images on the reverse face of planar objects, such as paper. An illumination level is set using a white reference object. A white reference image is stored in a computer memory. An image of a planar object having a printed image on the reverse face is stored in a computer memory. A pixel by pixel ratio of the two images is calculated and a mean value of the ratios is calculated to characterize the visual showthrough. The measurements are substantially independent of both the illumination level and image shading.