Contactless Thickness Measurement Using Dual Optical Shadow Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring the thickness of thin planar objects, such as paper and plastic, face inaccuracies due to density variations, mechanical wear, and vibrations, especially when requiring micrometer-level precision and contactless measurements.
Innovation Solution
A device using two optical sensor modules with reference shades and lighting to produce shadows, allowing for synchronized distance measurement from both sides of the object, minimizing the effects of heat expansion and vibration, and compensating for optical unlinearities and misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radiation sources are used to measure thickness, then measurement can be performed, but accuracy deteriorates due to density variations and radioactive sources may be prohibited
Solution Approach 1:
The patent replaces radiation-based measurement with a mechanical/optical system using two distance measurements from opposite sides. Instead of using radioactive sources and density calculations, the system uses physical distance measurement from both sides of the material to determine thickness, eliminating reliability issues with radiation while maintaining measurement capability.
Solution Approach 2:
The patent introduces an intermediary mechanical structure (frame with measurement devices on both sides) that mediates the thickness measurement process. Rather than directly measuring thickness through radiation penetration, the system measures distances from both sides through the intermediary frame structure and calculates thickness as the difference, improving both accuracy and reliability.
2Object-affected harmful factors
If contactless optical measurement is used, then tear and wear of measured surface is eliminated, but measurement accuracy deteriorates due to vibrations and temperature changes affecting optics
Solution Approach 1:
The patent implements feedback through synchronized measurement and calculation. By simultaneously measuring distances from both sides and using the known frame distance as a reference, the system compensates for optical movements and environmental changes. The feedback mechanism ensures that vibrations and temperature effects are accounted for in the final thickness calculation.
Solution Approach 2:
The patent segments the measurement process into two independent distance measurements taken from opposite sides of the material. Rather than relying on a single complex optical measurement, the system divides the task into two simpler measurements that can be independently stabilized and then combined through calculation to achieve high precision without contacting the surface.
3Device complexity
If point measurement without inclination information is performed, then device complexity is reduced, but measurement accuracy deteriorates due to uncertainties from unknown web inclination angles
Solution Approach 1:
The patent adds another dimension to the measurement by placing sensors on both sides of the material rather than using a single-sided point measurement. This dual-sided approach provides geometric redundancy that eliminates the need for separate inclination measurements while maintaining simplicity. The thickness is derived from the difference in two distance measurements, automatically compensating for angular deviations.
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 provides accurate, contactless thickness measurement by stabilizing the relative distance between shades and shadows, enhancing precision and reducing errors caused by environmental factors and optical misalignments.
Implementation Method 1
A light source 12 is set at an angle phi1 that is between 5 degrees and 85 degrees, providing effectively linear light beam 62 that lights the shade 13 and creates shadow 63 on the surface 11 of the measured object
Implementation Method 2
The shade and the shadow can be seen 65 simultaneously. The vertical distance d prime between the shade and the shadow is proportional to the distance d between the shade and the shadow seen from the top
Data Source
AI summary
A measuring device for measuring thickness of a planar object, where the measuring device comprises a first optical sensor module and a second optical sensor module that located on opposites of the measured planar object with mutual distance the optical sensor modules having at least one light source, a reference shade with two dimensional pattern and an imaging sensor and computing equipment, where the one light source is set to an angle towards measured object and the reference shade is set between the light and the object so that a shadow forms on the surface of the object and the imaging sensor is set so it can detect the reference shade and the shadow while the computing equipment calculates the distance between the surface of the object and sensor module from the distance between the detected shade and shadow of both optical modules and calculate the thickness of the object.