Single-sided Infrared Sensor Reflective Substrate Measurement
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Solution Overview
Problem
Existing single-sided sensors for measuring coat weight and other characteristics on layered products are not suited for reflective substrates, as they are sensitive to the surface finish, orientation, and distance of the substrate, leading to inaccurate thickness and weight measurements.
Innovation Solution
An optical sensor with a reflective member and a diffusing element is used to reflect radiation multiple times through the material, reducing the impact of specular reflection and enhancing sensitivity by using Lambertian-type light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard single-sided sensor uses near normal diffusion scattering geometry, then the sensor can detect scattered light signals, but the sensor becomes extremely sensitive to surface finish, orientation, and distance of the reflective substrate, leading to inaccurate measurements
Solution Approach 1:
The patent changes the light propagation dimension by using multiple reflections between parallel reflective members, causing light to travel through the material layer repeatedly in a path perpendicular to the surface. This dimensional change eliminates sensitivity to surface orientation and finish, as the light interacts with the material through its thickness rather than relying on scattered reflection from the surface.
Solution Approach 2:
The patent introduces reflective members (mirrors) as intermediaries between the light source and the material layer. These reflective members create a controlled optical path that guides light through the material multiple times, mediating the interaction between light and material to eliminate the harmful effects of surface reflectivity variations.
2Device complexity
If a sensor uses specular reflection geometry for reflective substrates, then the measurement is sensitive to orientation and distance, but the setup is simpler without additional diffusing elements
Solution Approach 1:
By transforming the optical geometry from surface-parallel scattering to through-thickness multiple reflections, the patent achieves measurement independence from surface orientation and finish. The light path is confined between parallel reflective members, creating a controlled dimension that eliminates the harmful sensitivity to surface variations.
3Reliability
If light passes through the material layer once, then the interaction time is short, but the sensor sensitivity to components within the layer is reduced
Solution Approach 1:
The patent implements continuous useful action by arranging multiple reflections between parallel reflective members, causing light to pass through the material layer repeatedly. This continuous interaction through multiple passes enhances the sensor's ability to detect components within the layer, improving sensitivity and measurement reliability.
Solution Approach 2:
The light undergoes periodic passage through the material layer via multiple reflections between the parallel reflective members. This periodic interaction increases the cumulative exposure time of light to the material components, enhancing detection sensitivity without requiring a more complex sensor system.
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 configuration improves the accuracy of coat weight and thickness measurements by minimizing the effect of specular reflection and ensuring consistent interaction with the material, regardless of surface finish or orientation.
Implementation Method 1
positioning a reflective member, such as a specular mirror, between the main body of the sensor and the sensor radiation source and sensor radiation receiver so that incident radiation from the radiation source propagates through the layer of material being monitored
Implementation Method 2
a diffusing element is positioned between the reflective member and the layer of material. The diffusing element, along with the light source, functions as a diffuse source of illumination as light that travels toward the detector in the machine direction. The Lambertian-type light scattering generated by the diffusing element affords many benefits
Data Source
AI summary
An optical, non-contact sensor for measuring the thickness or weight of layered products and particularly those that contain a light-reflective substrate incorporates a reflective surface to cause incident radiation from a light source to plurality of time within the layered products before being detected in a receiver. A diffusing element can be incorporated as a diffuse source of illumination. The Lambertian-type light scattering generated by the diffuse element causes the incident light to interact multiple times with the layered product resulting in enhanced sensor sensitivity to selected components in the layered product and measurement error induced by specular reflection of the light from the reflective substrate is minimized.