Symmetric Machine Vision Substrate Alignment System
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Solution Overview
Problem
Conventional substrate alignment methods face limitations due to the bulky lens barrels of coaxially oriented microscope objective lenses, which restrict the detection range and alignment accuracy, especially when trying to increase resolution without compromising depth of field.
Innovation Solution
A machine vision system with symmetrically arranged illumination sources, reflectors, objective lenses, and detectors, allowing for reduced footprint and expanded detection range by using a driving mechanism to move the components in X, Y, and Z axes, and employing beam splitters to direct light effectively between substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microscope objective lenses are coaxially oriented horizontally to detect alignment marks on substrates, then the detection function is achieved, but the bulky lens barrels take up much space between the substrates, resulting in limited detection range
Solution Approach 1:
The patent changes the orientation of microscope objective lenses from horizontal (coaxial) to vertical arrangement. The objective lenses are positioned above and below the substrates, with their optical axes perpendicular to the substrate surfaces. This dimensional change allows the lens barrels to extend in the vertical direction rather than horizontally between substrates, significantly reducing the space occupation in the critical horizontal region while maintaining full detection capability through vertical optical paths.
2Measurement precision
If higher-resolution microscope objective lenses are adopted to increase alignment accuracy, then resolution is improved, but the depth of field decreases, making it difficult to obtain clear images when substrates are separated by spacers
Solution Approach 1:
By arranging objective lenses vertically above and below substrates with perpendicular optical axes, the system creates independent optical paths for each substrate. This vertical arrangement allows each high-resolution lens to focus on its respective substrate surface without being constrained by the presence of the other substrate, effectively decoupling the depth of field requirement from the substrate separation distance imposed by spacers.
3Reliability
If a spacer is inserted between substrates to ensure non-contact during alignment, then substrate protection is achieved, but a large gap greater than 0.4 mm is created, limiting the detection capability of conventional microscope objective lenses
Solution Approach 1:
The vertical arrangement of objective lenses with perpendicular optical axes allows each lens to independently access its target substrate surface from opposite directions. The spacer creating a horizontal gap no longer obstructs the vertical optical paths, as light travels perpendicular to the substrate surfaces rather than horizontally across the gap. This enables high-resolution detection to proceed uninterrupted despite the presence of spacers maintaining substrate separation.
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 design enhances alignment accuracy and efficiency by reducing the footprint of the lens barrels, allowing for improved detection range and precision in substrate alignment.
Implementation Method 1
light beams emitted from the first and second illumination sources are irradiated on and reflected by the respective substrates
Implementation Method 2
amplified by the respective objective lenses
Data Source
AI summary
A machine vision system for substrate alignment includes first and second illumination sources (11, 12), first and second reflectors (21, 22), first and second objective lenses (31, 32) and first and second detectors (41, 42), each of which pair is symmetric with respect to an X-axis. Light beams emitted from the first and second illumination sources are irradiated on and reflected by respective substrates (1, 2), amplified by the respective objective lenses and received and detected by the respective detectors. An alignment apparatus is also disclosed. Disposing each of the pair of the first and second illumination sources, the first and second reflectors, the first and second objective lenses and the first and second detectors in symmetry with respect to the X-axis results in a significantly reduced footprint of the machine vision system along the orientation of lens barrels of the objective lenses and hence an expanded detection range thereof and improved alignment efficiency and accuracy.