Dual-Axis 3D Inspection Apparatus for Shadow-Free PCB Measurement
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Solution Overview
Problem
Existing automatic optical inspection systems face challenges in accurately measuring complex electronic assemblies due to issues like shadow effects, multiple reflections, and the need for fast, highly accurate, and repeatable measurements in the micrometer field.
Innovation Solution
The apparatus employs a dual-camera system with a first camera having a vertical optical axis and a second camera with a horizontal optical axis, along with a dual objective optical group and an optical beam splitter to acquire three-dimensional information. This setup allows for compact, efficient, and accurate measurements by splitting the light beam into vertical and horizontal optical arms for each camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference plot is projected at an angle to inspect electronic assemblies, then the inspection system can detect manufacturing defects and quality defects, but high sections cast shadows that prevent measurement of neighboring low sections
Solution Approach 1:
The patent transitions from two-dimensional image analysis to three-dimensional scanning technology. By using structured light projection and capturing depth information, the system creates a 3D model of the electronic assembly, allowing measurement of components regardless of their height differences. This eliminates the shadow effect problem that plagues 2D inspection systems when viewing angled surfaces.
Solution Approach 2:
The inspection system divides the electronic assembly into multiple measurement zones or segments. By projecting structured light patterns and analyzing the deformation of these patterns across different regions, the system can independently measure each segment's three-dimensional coordinates, ensuring that shadowing in one area does not prevent measurement of other areas.
2Illumination intensity
If multiple light reflections occur between shiny components, then the inspection system can capture reflected light from various angles, but multiple specular reflections cause distortions in the fringe pattern and errors in height measurements
Solution Approach 1:
The patent acknowledges that specular reflections from shiny components like metal oscillators and tinned cables cause measurement errors. The system compensates for this by using multiple projection angles and advanced algorithms that identify and correct for reflection artifacts in the captured fringe patterns, converting the harmful reflection effect into manageable data that can be processed and corrected.
Solution Approach 2:
The system varies multiple parameters including projection angle, wavelength of structured light, and camera positioning to capture the same surface from different conditions. By collecting data under varying parameters, the system can identify consistent features versus reflection artifacts, thereby improving height measurement accuracy despite the presence of specular reflections.
3Device complexity
If traditional two-dimensional automatic optical inspection technology is used, then the system structure remains simple, but the system cannot provide fast, highly accurate, and repeatable measurements in the micrometer field for complex electronic assemblies
Solution Approach 1:
The patent combines multiple functions into an integrated three-dimensional scanning system that merges structured light projection, multi-angle camera capture, and real-time 3D reconstruction algorithms. This consolidation achieves micrometer-level measurement precision for complex electronic assemblies while maintaining a compact system structure that can be implemented in production environments.
4Measurement precision
If the inspection system uses larger dimensions to avoid interference between components, then component interference is reduced, but the overall system size increases and full measurement of low components near high components becomes difficult
Solution Approach 1:
The patent uses three-dimensional scanning to capture complete surface information without requiring physical separation between components. By projecting structured light patterns and analyzing their deformation in 3D space, the system can measure both high and low components in the same field of view simultaneously, eliminating the need for increased system dimensions to avoid component interference.
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
The apparatus achieves fast, highly accurate, and repeatable three-dimensional measurements, effectively addressing the limitations of existing systems by ensuring full measurement of low components near high components and minimizing errors from multiple reflections.
Implementation Method 1
an optical beam splitter configured to split the light beam reflected by said object into a first light beam directed along said first optical arm and a second light beam directed along said optical second arm
Data Source
AI summary
An apparatus for acquiring three-dimensional information of objects and surfaces comprising a first camera having a vertical optical axis, a first flat sensor having orthogonal axes lying in a horizontal plane, a second camera having a horizontal optical axis, a second flat sensor having orthogonal axes lying in a vertical plane, a plurality of light projectors angularly spaced around the vertical optical axis of the first camera, a first vertical optical arm associated with the first camera and coaxial with the vertical optical axis, a second horizontal optical arm associated with the second camera and coaxial with the horizontal optical axis, an optical beam splitter splitting the light beam reflected by the object into first and second light beams directed along the first and second optical arms, wherein the first and second flat sensors have the same shape and arranged to acquire the object with the same field of view.