Optical Lens Metrology for Miniaturized Camera Assemblies
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Solution Overview
Problem
Conventional metrology equipment is inadequate for achieving the required measurement reproducibility and accuracy for the complex optical assemblies in miniaturized cameras, particularly in characterizing the geometry and optical properties of molded lenses and diamond-turned molds, due to tightening manufacturing tolerance budgets and the lack of commercially available tools for measuring properties like refractive index and birefringence on the production floor.
Innovation Solution
An optical metrology system combining 3D surface topography with 2D images to evaluate the dimensional and optical properties of lenses, using coherence scanning interferometry and other techniques to measure the relative location of nominally parallel surfaces, refractive index, and birefringence, with a fixture for supporting the lenses and adjusting light coherence properties for enhanced signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metrology equipment (contact probes, tactile profilers, inspection microscopes) is used, then the equipment is simple and readily available, but the measurement precision and reproducibility are insufficient for tight tolerance budgets
Solution Approach 1:
The patent replaces mechanical contact measurement systems (probes, tactile profilers) with optical measurement systems. The optical system uses light-based techniques including coherence scanning interferometry and phase-shifting interferometry to measure lens surfaces, thickness, and optical properties without physical contact, thereby achieving higher precision and reproducibility while avoiding mechanical wear and contact-induced errors
Solution Approach 2:
The patent employs multiple optical parameters and wavelengths to characterize lens properties. By varying the wavelength of light and analyzing different optical parameters (interference patterns, phase shifts, reflectivity), the system achieves comprehensive measurement of lens geometry and optical properties with high precision, resolving the contradiction between measurement capability and system complexity
2Measurement precision
If conventional metrology equipment is used, then the equipment is commercially available, but the capability to measure optical properties (refractive index, birefringence) is lacking
Solution Approach 1:
The patent creates a universal optical measurement system capable of performing multiple measurement functions: geometric surface measurement, thickness measurement, refractive index determination, and birefringence measurement. By integrating various optical techniques and analysis methods, the system provides comprehensive lens characterization across all critical parameters, making it adaptable to diverse measurement needs while maintaining high precision
Solution Approach 2:
The measurement system combines multiple optical measurement techniques and data analysis methods into a composite measurement approach. By integrating interferometry, reflectometry, and optical property analysis, the system achieves the versatility needed to measure both geometric and optical properties of lenses, resolving the limitation of conventional single-purpose equipment
3Manufacturing precision
If tight manufacturing tolerance budgets are applied, then the manufacturing precision is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent performs preliminary optical measurements and characterizations during the manufacturing process itself, rather than as a separate final inspection step. By measuring lens properties in-situ or at intermediate stages, the system enables real-time process control and adjustment, making tight tolerance achievement more manageable while reducing the difficulty of detection through integrated measurement capabilities
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 provides sub-micrometer accuracy in thickness and refractive index measurements, reducing systematic errors and improving process control for lens manufacturing, ensuring precise alignment and imaging performance in miniaturized camera assemblies.
Implementation Method 1
directing measurement light to the lens; detecting measurement light reflected from at least one location on the first surface of the inactive portion; detecting measurement light reflected from the second surface of the inactive portion
Implementation Method 2
coherence scanning interferometry and other techniques to measure the relative location of nominally parallel surfaces
Implementation Method 3
evaluate the optical and dimensional properties of the sample using the information derived from the calculated optical and physical thickness
Implementation Method 4
measuring the relative location of nominally parallel surfaces, refractive index, and birefringence
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A method for determining information about a transparent optical element including a lens portion and a plane parallel portion, the lens portion having at least one curved surface and the plane parallel portion having opposing first and second surfaces, includes: directing measurement light to the transparent optical element; detecting measurement light reflected from at least one location on the first surface of the plane parallel portion; detecting measurement light reflected from the second surface of the plane parallel portion at a location corresponding to the at least one location on the first surface; determining, based on the detected light, information about the plane parallel portion; and evaluating the transparent optical element based on the information about the plane parallel portion.