Multi-Wavelength 3D Shape Measurement Resolving Phase Ambiguity
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Solution Overview
Problem
The conventional phase shifting method for measuring three-dimensional shapes using Moire patterns faces a 2π ambiguity issue, limiting the measurement range and requiring frequent grating changes when height differences exceed a multiple of the equivalent wavelength, restricting the maximum measurable height of objects.
Innovation Solution
The method employs multi-wavelength pattern lights with different equivalent wavelengths to irradiate a measurement object, allowing for increased maximum height measurement, warpage information acquisition, and shadow region removal by using a combination of first and second pattern lights, which are projected and captured using a camera system with a control unit to analyze the resulting phase information and remove ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional phase shifting method is used to measure three-dimensional shape, then the measurement precision is improved, but the measurement range is limited due to 2π ambiguity
Solution Approach 1:
The patent applies parameter changes by utilizing multiple wavelengths (different equivalent wavelengths) to project patterns onto the measurement object. By changing the wavelength parameter and combining measurements from different wavelengths, the system resolves the 2π ambiguity and extends the measurable height range while maintaining measurement precision through phase analysis
2Device complexity
If a single grating is used for measurement, then the device complexity is reduced, but the adaptability is worsened due to the need for grating changes
Solution Approach 1:
The patent implements universality by designing a measurement system that can handle multiple measurement scenarios using a single grating. Through multi-wavelength projection and phase analysis, the system adapts to different measurement ranges and object types without requiring physical grating changes, making the device universally applicable while maintaining 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 effectively increases the measurable height range, removes shadow regions, and provides accurate warpage information by using the multi-wavelength technique to resolve the 2π ambiguity, enabling more comprehensive three-dimensional shape measurement of objects.
Implementation Method 1
a three-dimensional shape of a measurement object is obtained using a pattern image formed when a pattern light is reflected by the measurement object
Implementation Method 2
there is a method using projection of Moire pattern
Implementation Method 3
the plurality of pattern images is analyzed considering a form of the interference signal and a height of a measurement point
Data Source
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Figure 3B
AI summary
An apparatus and a method for measuring a three-dimensional shape are disclosed. The apparatus includes a transfer stage, a first projector, a second projector, a camera unit and a control unit. The transfer stage transfers a measurement object to a measurement position. The first projector irradiates a first pattern light having a first equivalent wavelength toward the measurement object in a first direction. The second projector irradiates a second pattern light having a second equivalent wavelength that is different from the first equivalent wavelength toward the measurement object in a second direction. The camera unit takes a first pattern image that is generated when the first pattern light is reflected by the measurement object, and a second pattern image that is generated when the second pattern light is reflected by the measurement object. The control unit controls the first projector and the second projector, and obtains a three-dimensional shape of the measurement object through the first pattern image and the second pattern image.