3D Measurement Device Using Polarized Light Interference
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Solution Overview
Problem
Conventional three-dimensional measurement devices using interferometers face limitations in measurement range and accuracy due to the wavelength of measurement light, particularly when the height difference of the object exceeds half the wavelength, and using close-wavelength lights complicates wavelength separation and reduces efficiency.
Innovation Solution
A three-dimensional measurement device that splits incident light into two close-wavelength polarized lights, using one as measurement light and the other as reference light, which are recombined and imaged separately to enhance measurement range and efficiency without the need for wavelength separation units, allowing simultaneous imaging and reducing the complexity of optical path adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If two different lights having different wavelengths are used to expand measurement range, then measurement range is improved, but wavelength separation becomes difficult and measurement efficiency decreases
Solution Approach 1:
The patent changes the parameter of light wavelength by using multiple light sources with different wavelengths (e.g., 1500nm and 1550nm) to expand the measurement range. The measurement range is determined by the beat wavelength which is a function of the wavelength difference, allowing measurement of larger height differences while maintaining adequate resolution.
Solution Approach 2:
The patent segments the imaging process by using separate imaging units for different wavelengths. Each imaging unit is dedicated to capturing interference patterns from a specific wavelength, eliminating the need for complex wavelength separation and enabling simultaneous imaging that improves measurement efficiency.
2Difficulty of detecting and measuring
If wavelength separation units are used to separate different wavelengths, then wavelength separation is achieved, but device complexity increases
Solution Approach 1:
The patent uses an optical combiner as an intermediary device that combines multiple wavelengths into a single optical path without requiring complex wavelength separation units. The combiner efficiently directs different wavelengths to appropriate imaging units through optical path division, simplifying the overall system architecture.
Solution Approach 2:
The patent resolves the wavelength separation problem by transitioning from spatial separation (using dichroic mirrors or prisms) to temporal/multiplexed separation where different wavelengths are imaged simultaneously by dedicated imaging units. This dimensional change in the imaging approach eliminates the need for complex wavelength separation optics.
3Ease of operation
If quarter wave plates are used to change polarizing states, then polarizing state control is improved, but device complexity and operational complexity increase
Solution Approach 1:
The patent extracts and removes the quarter wave plates from the optical system, replacing them with a simplified polarizing beam splitter configuration. This extraction eliminates the need for complex polarizing state control while maintaining the necessary optical path separation between reference and measurement beams.
Solution Approach 2:
Instead of using quarter wave plates to change polarizing states to achieve path separation, the patent inverts the approach by using polarizing beam splitters that directly separate polarized components. This inversion simplifies the optical path control and reduces the number of optical components required.
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 expands the measurement range, improves measurement efficiency, and simplifies the device by eliminating the need for wavelength separation units and quarter wave plates, while maintaining high accuracy and reducing operational complexity.
Implementation Method 1
a polarizing beam splitter configured to divide predetermined incident light into two polarized lights having polarizing directions that are orthogonal to each other
Implementation Method 2
an interference optical system configured to combine measurement light and reference light to combined light
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided a three-dimensional measurement device that uses lights of different wavelengths to expand the measurement range and to improve the measurement efficiency. The three-dimensional measurement device 1 includes a polarizing beam splitter 20 configured to split predetermined incident light into two polarized lights having polarizing directions that are orthogonal to each other, to radiate one of the polarized lights as measurement light to a work W and the other of the polarized lights as reference light to a reference surface 23, and to recombine the two polarized lights to combined light and emit the combined light; a first projection optical system 2A configured to cause first light to enter a first surface 20a of the polarizing beam splitter 20; a second projection optical system 2B configured to cause second light to enter a second surface 20b of the polarizing beam splitter 20; a first imaging system 4A configured to take an image of the first light emitted from the first surface 20a of the polarizing beam splitter 20; and a second imaging system 4B configured to take an image of the second light emitted from the second surface 20b of the polarizing beam splitter 20.