Optical Gating for Simultaneous Web Color Measurement
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Solution Overview
Problem
Existing methods for measuring the color of a moving paper web struggle with opacity compensation, requiring mechanical changes of backings which slow down the measurement process and reduce usability due to the need for separate reflectance and transmittance measurements from different areas of the web.
Innovation Solution
A method using a backing element with specific translucent properties allows for simultaneous measurement of reflectance and transmittance from the same spot on the web, utilizing a common viewing optics and detector, and pulsating light sources to quickly switch between measurements, eliminating the need for mechanical backing changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical means are used to change backings between measurements, then opacity compensation can be achieved, but the measurement speed decreases and the web position varies between measurements
Solution Approach 1:
The patent replaces the mechanical backing change system with an optical gating system that uses electronic control to switch between transparent and opaque states. This substitution eliminates mechanical moving parts, enabling instantaneous switching between measurement modes and achieving both high measurement speed and accurate opacity compensation without mechanical delays or web position variations.
Solution Approach 2:
The optical gating system changes its optical parameter (transparency) dynamically between transparent and opaque states through electronic control. This parameter change allows the same physical component to serve dual functions: enabling light transmission during transmittance measurement and blocking light during reflectance measurement, thereby achieving opacity compensation without mechanical backing changes.
2Measurement precision
If separate reflectance and transmittance measurements are made at different times, then opacity compensation can be calculated, but the measurements are taken from different areas of the web reducing measurement quality
Solution Approach 1:
The patent implements continuous measurement capability by using the optical gating system to rapidly alternate between transparent and opaque states within the measurement cycle. This allows reflectance and transmittance measurements to be taken essentially simultaneously from the same web position, maintaining measurement position consistency while still enabling accurate opacity compensation calculations.
3Device complexity
If a single backing is used for both reflectance and transmittance measurement, then device complexity is reduced, but the backing must have conflicting optical properties
Solution Approach 1:
The patent applies dynamics by making the backing's optical properties changeable rather than static. The optical gating system dynamically switches between transparent and opaque states, allowing the same backing to provide appropriate optical properties for different measurement modes. This dynamic adaptability eliminates the need for multiple fixed backings with conflicting properties while maintaining device simplicity.
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 fast, simultaneous opacity-compensated color measurement from the same spot on the moving web, simplifying the sensor construction and increasing maintainability by eliminating moving parts.
Implementation Method 1
Optical properties of paper, such as opacity, color, whiteness, brightness and fluorescence index are measured by illuminating the web and detecting the light reflected from and optionally also transmitted through the paper.
Data Source
AI summary
A method and an apparatus for measuring color of a moving web. The web is measured by reflectance measurement and transmittance measurement, wherein the reflectance measurement is carried out by illuminating a surface of the web in a measuring area, where on the other side of the web at the measuring area resides a solidly attached backing element and measuring the radiation reflected from the web. The transmittance measurement is carried out by illuminating the web and measuring the radiation transmitted through the web. The radiation measured in the transmittance measurement is transmitted through the backing element.