White-light interferometer polarization correction for orientation-independent measurement
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Solution Overview
Problem
White-light interferometric measuring devices face variations in measured values due to differences in the orientation of the measurement workpiece, leading to reduced accuracy and efficiency, and current solutions like rotating the workpiece increase costs and complexity.
Innovation Solution
Incorporating a polarization correcting mechanism with a non-polarizing beam splitter, a polarizing plate, and a quarter-wave plate to convert the white light beam into circularly polarized light, which reduces polarization imbalances and stabilizes the interference pattern, thereby eliminating orientation-dependent variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measurement workpiece is measured by conventional white-light interferometric measuring device, then the three-dimensional shape can be measured within the field of view, but variation in measured value occurs due to difference of orientation of the measurement workpiece
Solution Approach 1:
The patent changes the polarization state parameter of the light beam by introducing a quarter-wave plate to convert linearly polarized light into circularly polarized light. This parameter change ensures that the light maintains consistent interaction characteristics with the measurement workpiece regardless of its orientation, thereby eliminating orientation-dependent measurement variations while maintaining high measurement accuracy
2Measurement precision
If a mechanism for rotating the measurement workpiece is provided to resolve orientation variation, then measurement accuracy can be improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical rotation system with an optical field solution by introducing polarization correcting means (quarter-wave plate). Instead of mechanically rotating the measurement workpiece to achieve orientation independence, the system uses circularly polarized light to optically achieve the same effect, thereby eliminating complex mechanical structures while maintaining measurement accuracy
Solution Approach 2:
The patent introduces polarization correcting means as an intermediary element between the light source and the measurement workpiece. This intermediary (quarter-wave plate) modifies the light's polarization state to circular polarization, which acts as a mediator that enables orientation-independent measurements without requiring physical rotation of the workpiece, thus simplifying the overall device structure
3Measurement precision
If a mechanism for rotating the measurement workpiece is provided to resolve orientation variation, then measurement accuracy can be improved, but measuring efficiency decreases due to necessity to control the position
Solution Approach 1:
The patent replaces the mechanical rotation and positioning control system with an optical field solution using circularly polarized light. This substitution eliminates the need for position control mechanisms and their associated control systems, thereby maintaining measurement accuracy while significantly improving measuring efficiency and productivity
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 enhances measuring accuracy and efficiency by minimizing variations in measured values without the need for costly workpiece rotation mechanisms, maintaining high-resolution measurements across different orientations.
Implementation Method 1
polarization correcting means that corrects the white light beam to enter the interference objective lens to circularly polarized light
Implementation Method 2
the polarization correcting means includes a beam splitter being a non-polarizing beam splitter, and a polarizing plate and a quarter-wave plate arranged between the white light source and the beam splitter
Implementation Method 3
a beam splitter that reflects the white light beam
Implementation Method 4
a beam splitter being a non-polarizing beam splitter
Implementation Method 5
the interference objective lens generating interference between a measurement light beam obtained by reflection of the white light beam off the measurement workpiece and a reference light beam obtained by branching of the white light beam
Data Source
Figure 1
Figure 2A~4
Figure 5~6
AI summary
A white-light interferometric measuring device (100) includes: a white light source (106) that emits a white light beam (108); a beam splitter (116) that reflects the white light beam (108); and an interference objective lens (120) that collects the white light beam (108) having reflected off the beam splitter (116) in the direction of an optical axis (0) and irradiates a measurement workpiece (102) with the white light beam (108), the interference objective lens (120) generating interference between a measurement light beam obtained by reflection of the white light beam (108) off the measurement workpiece (102) and a reference light beam obtained by branching of the white light beam (108) to be converged on the measurement workpiece (102). Polarization correcting means (112) that corrects the white light beam (108) to enter the interference objective lens (120) to circularly polarized light is arranged between the white light source (106) and the interference objective lens (120).