Segmented Autofocus Optics With Shared Module for Wide-Field Focus
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Solution Overview
Problem
High throughput optical inspection systems face challenges in maintaining consistent focus across large sample surfaces with varying thickness, curvature, or topography, leading to inaccurate or incomplete inspection results due to complex optical arrangements and sensitivity to alignment issues.
Innovation Solution
An auto-focus system utilizing a simplified optical design with field splitting and staggered spot arrays, employing a mask with dual slits and segmented field curvature compensators, minimizes complexity and maintains optical performance while enhancing transmission intensity and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex optical arrangement is used to maintain focus across large sample surfaces, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The collection path is divided into multiple segments (first segment with first spherical telescope, second segment with second spherical telescope, etc.), each handling specific beam collections. This segmentation allows the complex optical function to be distributed across simpler modular components, reducing overall system complexity while maintaining focus consistency across large sample surfaces.
Solution Approach 2:
Multiple beam collections are nested within a shared module that contains common optical components (entrance pupil, condenser lens, field curvature compensator). This nesting allows efficient use of optical paths where inner collections share outer path components, reducing total component count and system complexity while preserving measurement precision.
2Area of stationary object
If multiple beam collections are implemented to cover large fields of view, then area of stationary object is improved, but device complexity increases
Solution Approach 1:
The shared module serves multiple functions by handling beam collections from both upstream and downstream spots simultaneously. The entrance pupil, condenser lens, and field curvature compensator are universally used across multiple collection paths, allowing large field of view coverage without proportionally increasing device complexity.
Solution Approach 2:
Multiple beam collection paths are merged into a shared optical module where they converge at the entrance pupil and share subsequent optical components. This merging allows the system to cover large areas with multiple spot arrays while using a unified optical path structure rather than separate independent paths for each collection.
3Ease of operation
If alignment sensitivity is reduced to simplify operation, then ease of operation is improved, but manufacturing precision requirements worsen
Solution Approach 1:
Field curvature compensators are introduced at specific locations in the optical path to locally correct alignment sensitivities. These compensators provide targeted adjustment capabilities at critical points (object plane, intermediate image plane, sensor plane) without requiring high precision across the entire system, thus improving ease of operation while maintaining manufacturing feasibility.
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 system achieves near-diffraction-limited spot arrays with reduced complexity, improved sensitivity, and expanded field of view capture, simplifying the imaging system design and reducing costs without compromising optical performance.
Implementation Method 1
illuminating a sample with illumination beams that form multiple spot arrays on the sample
Implementation Method 2
focusing the collected beams along a first axis while imaging the entrance pupil along a second axis
Implementation Method 3
a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimated relay
Data Source
AI summary
An auto-focus system that includes (a) an illumination path that is configured to illuminate a sample with illumination beams that form multiple spot arrays on the sample that comprises an upstream set of spot arrays formed on a first side of an imaging area, and a downstream set of spot arrays formed on another side of the imaging area; and (b) a collection path that includes (b.1) a first segment that comprises a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimated relay that consists essentially of a first relay input spherical lens and a first relay output spherical lens; (b.2) a second segment that comprises an second spherical telescope, an second field curvature compensator, a pair of second prisms, and an second collimated relay that consists essentially of a second relay input spherical lens and a second relay output spherical lens; and (b.3) a shared module.