3D Shape Measurement Using Multi-Pitch Light Patterns
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Solution Overview
Problem
Conventional three-dimensional shape measurement devices using the phase shift method face challenges in achieving high precision and wide dynamic range due to limitations in resolution and measurement range, particularly when dealing with objects having varying heights and complex shapes like cream solder on printed boards, as they often result in shadowed areas and incomplete data acquisition.
Innovation Solution
A device employing multiple irradiation units with different light patterns of varying pitches, positioned to irradiate the object from distinct angles, and an image processing unit that acquires and supplements measurement data to cover entirely and partially irradiated regions, allowing for precise height data acquisition across a wide range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gap between lines of the irradiated light pattern is widened to accommodate maximum height objects, then the measurement range increases, but resolution ability deteriorates
Solution Approach 1:
The measurement process is segmented into multiple stages using light patterns with different pitches. A first light pattern with a smaller pitch is used for high-resolution measurement of smaller objects, while a second light pattern with a larger pitch is used for measuring taller objects. This segmentation allows the system to achieve both high resolution and wide measurement range by selecting appropriate light patterns based on object characteristics.
2Measurement precision
If the gap between lines of the irradiated light pattern is narrowed to improve precision, then measurement precision improves, but the range of height capable of measurement decreases
Solution Approach 1:
The system dynamically selects and switches between light patterns with different pitches based on the measurement requirements. The pitch selection is not fixed but adapts to the object being measured, allowing the system to optimize between resolution and measurement range for each specific measurement task.
3Device complexity
If a single light source is used, then the device complexity is reduced, but shadowed parts occur where the light pattern does not irradiate the object
Solution Approach 1:
Different regions of the object are irradiated by light patterns with different pitches tailored to their specific measurement needs. The system applies local quality by matching the light pattern pitch to the local characteristics of the object surface, ensuring optimal measurement coverage for each region while minimizing shadowed areas.
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 enables high-resolution, accurate three-dimensional measurement over a wide dynamic range by combining data from multiple light patterns, ensuring comprehensive coverage and improved precision, even for complex shapes with significant undulations.
Implementation Method 1
uses an irradiation unit composed of a light source and a sinusoidal wave pattern filter and irradiates a light pattern having a sinusoidal wave-shaped (i.e., stripe shaped) light intensity distribution upon an object being measured
Implementation Method 2
a point on the board is observed using an imaging unit disposed directly above the board. A CCD camera or the like composed of a lens, and imaging element, or the like is used as the imaging unit
Implementation Method 3
the phase is changed, for example, in 4 stages as φ+1, φ+π/2, φ+π, and φ+3π/2. Images of the corresponding intensity distributions (I0, I1, I2, and I3, respectively) are read, and the modulated component a is found based on the below listed formula. α=arctan {(I3−I1)/(I0−I2)}
Data Source
AI summary
A device for measuring three dimensional shape includes a first height data acquisition unit for acquiring a height data specified from measurement values according to a multiplicity of light patterns related to an entirely irradiated region irradiated by all of the multiplicity of light patterns, and for using an acquired specified height data as a height data for the entirely irradiated region; a supplemental data acquisition unit for acquiring, based on the height data for the entirely irradiated region, a supplemental data relating to a partially irradiated region that is irradiated by only part of the multiplicity of light patterns; and a second height acquisition unit for specifying a fringe order of the measurement values for the partially irradiated region based on the supplemental data, and for acquiring as height data for the partially irradiated region a height data corresponding to the measurement values of the specified fringe order.