Chromatic Sensor Lens Configuration for Optical Pens
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Solution Overview
Problem
Current chromatic sensor lens configurations in optical pens for chromatic confocal range sensing suffer from limitations in optical throughput, measurement spot size, and resolution, which affect the precision and accuracy of surface height measurements.
Innovation Solution
A chromatically dispersive lens configuration is introduced, featuring a doublet lens element with a low Abbe number near the aperture and a high Abbe number farther away, combined with a positive power lens portion formed from three air-spaced singlet lenses, optimizing axial chromatic dispersion and spherical aberration to enhance measurement resolution and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional chromatic sensor lens configuration is used, then the device complexity is low, but the measurement precision and optical throughput are insufficient
Solution Approach 1:
The lens configuration is divided into multiple discrete lens elements (first lens element, second lens element, third lens element) with different optical powers and Abbe numbers. Each element performs a specific function in the chromatic dispersion process, allowing optimization of measurement precision while maintaining manageable complexity through modular design
Solution Approach 2:
Different lens elements are assigned different local properties: the first lens element has a first Abbe number, the second lens element has a second Abbe number different from the first, and the third lens element has a third Abbe number. This local differentiation of optical properties enables precise control of chromatic dispersion characteristics to improve measurement resolution
2Measurement precision
If the lens configuration is optimized for measurement resolution, then the measurement precision improves, but the optical throughput decreases
Solution Approach 1:
The lens configuration optimizes the relationship between Abbe numbers and optical powers of different lens elements. By carefully selecting and adjusting these parameters, the system achieves high measurement resolution while minimizing optical losses. The patent specifies that the average Abbe number of certain lens elements should fall within a specific range relative to others, demonstrating parameter optimization to balance resolution and throughput
3Measurement precision
If the measurement spot size is reduced to improve resolution, then the measurement precision improves, but the optical throughput is reduced
Solution Approach 1:
The lens configuration dynamically controls the focal properties for different wavelengths through the chromatic dispersion of multiple lens elements. This dynamic optical behavior allows the system to achieve a small measurement spot size for high resolution while maintaining efficient light coupling through the optical fiber, effectively balancing spot size and optical throughput
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 new lens configuration improves optical throughput by 10% to 100% and reduces the measurement spot size by 25%, leading to enhanced measurement resolution and accuracy, while maintaining comparable physical dimensions and costs to existing systems.
Implementation Method 1
The lens configuration receives the source radiation from the aperture, and focuses it with axial chromatic dispersion towards the workpiece surface
Implementation Method 2
The lens configuration receives reflected radiation from the workpiece surface and focuses the reflected radiation proximate to the detector aperture with axial chromatic dispersion
Data Source
AI summary
A chromatically dispersive lens configuration may be utilized in optical pens for chromatic range sensing. The lens configuration may include a negative power doublet lens and a positive power lens portion. The Abbe numbers of lenses included in the positive power lens portion may be between the Abbe numbers of the two portions of the doublet lens. The relationship between the Abbe numbers of the materials used in two portions of the doublet lens is generally opposite to their relationship as used in standard doublet lenses of similar geometry. The doublet lens may have a negative spherical aberration which effectively cancels a positive spherical aberration that arises in the positive lens portion. In one embodiment all of the lens elements in the lens configuration are spherical lenses. The lens configuration can be implemented with dimensions which fit a standard commercial optical pen, while providing improved range sensing performance.