Annular Optical Configuration for Metrology Focus Adaptation
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Solution Overview
Problem
Existing precision non-contact metrology systems face limitations in lighting configurations, particularly in terms of intensity, uniformity, position, and range, when imaging workpieces at different focus positions using variable focal length lenses and interchangeable objective lenses.
Innovation Solution
A metrology system incorporating a variable focal length lens, an annular lighting configuration, and an annular optical configuration, which allows for periodic modulation of the optical power of the VFL lens and redirection of source light to accommodate different working distance focus positions of interchangeable objective lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coaxial light source or stage light source is used for illuminating the workpiece, then the system can provide illumination for imaging, but the illumination intensity and uniformity are limited when imaging at different focus positions
Solution Approach 1:
The patent transitions from conventional point or linear light sources to an annular (ring-shaped) light source configuration. This dimensional change allows light to be emitted from multiple circumferential positions simultaneously, creating a volumetric illumination pattern that maintains uniform intensity across different focus positions along the optical axis, thereby resolving the contradiction between illumination intensity and adaptability to different focus positions.
Solution Approach 2:
The system incorporates a variable focal length lens that can dynamically adjust its focal length to match different objective lens configurations. This dynamic adjustment capability ensures that the annular light source maintains optimal illumination characteristics across varying focus positions, resolving the contradiction by making the illumination system adaptable rather than fixed.
2Adaptability or versatility
If interchangeable objective lenses with different working distances are used, then the system can accommodate different imaging requirements, but the lighting configuration must be adjusted for each lens
Solution Approach 1:
The annular light source configuration serves multiple functions simultaneously: it provides uniform illumination for various objective lenses with different working distances, maintains consistent intensity across different focus positions, and eliminates the need for separate lighting adjustments for each lens. This universal design resolves the contradiction by making a single lighting configuration work effectively for all lens types.
3Adaptability or versatility
If conventional lighting configurations are used with variable focal length lenses, then the system can vary focus position, but the illumination uniformity and position coverage are insufficient
Solution Approach 1:
By configuring the light source in an annular geometry rather than as a point or linear source, the system creates a three-dimensional illumination volume that uniformly covers the entire focus range. This dimensional change allows light to reach all focal planes equally, resolving the contradiction between focus position range and illumination uniformity.
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 improved illumination uniformity and intensity across various focus positions, enabling precise imaging and measurement of workpieces with non-planar surfaces, thereby enhancing the accuracy and efficiency of precision metrology.
Implementation Method 1
The VFL lens controller is configured to control the VFL lens to periodically modulate the optical power of the VFL lens over a range of optical powers at an operating frequency, so as to vary a system focus position over a plurality of positions within a focus range
Implementation Method 2
The annular lighting configuration is configured to provide source light for illuminating the workpiece for producing the image light
Implementation Method 3
The annular optical configuration is configured to be utilized in combination with the second objective lens while the second objective lens is included in the objective lens configuration and to be located in front of the annular lighting configuration to redirect the source light toward a second central volume which includes the second working distance focus position
Data Source
AI summary
An annular optical configuration is provided for utilization in a metrology system to redirect source light. The metrology system includes a camera that provides images of a workpiece at different focus positions through operation of a variable focal length lens and an objective lens configuration (OLC). The OLC includes one of a plurality of objective lenses having respective working distances and working distance focus positions. An annular lighting configuration directs source light toward a first central volume which includes a first working distance focus position of a first objective lens when the first objective lens is included in the OLC. When a second objective lens with a second working distance focus position is included in the OLC, the annular optical configuration is configured to be located in front of the lighting configuration to redirect the source light toward a second central volume which includes the second working distance focus position.