Optical Profilometry Height Mapping with Multiplexed Illumination
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Solution Overview
Problem
Existing optical profilometers face limitations in throughput, making them unsuitable for fast or in-line measurements despite achieving high resolution.
Innovation Solution
A method using a structured illumination microscope with multiplexed optical patterns, such as MURA patterns, to determine a height map by projecting and measuring optical patterns with different spatial frequencies or orientations, allowing for increased throughput and high accuracy through a pre-scan and high-accuracy scan combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical profilometry methods are used to achieve high resolution, then measurement precision is improved, but productivity deteriorates due to limited throughput
Solution Approach 1:
The sample surface is divided into multiple patches, and multiple optical patterns with different spatial frequencies are projected and measured separately. This segmentation allows parallel processing of different spatial regions and frequency components, enabling high resolution measurement while improving throughput by avoiding sequential scanning of the entire surface at maximum resolution.
Solution Approach 2:
The invention introduces a temporal dimension by measuring multiple optical patterns with different spatial frequencies at different time points. This allows the system to reconstruct high-resolution height maps by combining information from multiple lower-resolution measurements taken at different times, thereby achieving high resolution without sacrificing throughput.
2Productivity
If multiple optical patterns with different spatial frequencies are projected simultaneously, then productivity is improved through increased throughput, but device complexity increases
Solution Approach 1:
Multiple optical patterns with different spatial frequencies are merged into a single multiplexed pattern that is projected onto the sample surface simultaneously. This combining approach allows the system to capture information from multiple patterns in a single measurement, improving throughput while managing device complexity through efficient pattern multiplexing rather than requiring separate measurement systems.
Solution Approach 2:
The optical measurement system is designed to handle multiple optical patterns with different spatial frequencies using a single measurement apparatus. The system can project and measure various patterns (e.g., MURA patterns, fractal patterns) without requiring separate dedicated systems for each pattern type, thereby improving productivity while keeping device complexity manageable through multi-functional capability.
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
Enhances throughput for optical profilometry, enabling efficient in-line measurements while maintaining high resolution and accuracy by determining a height map using a calibration relationship between pattern contrasts and defocus positions.
Implementation Method 1
Optical means, such as lenses, may be used to guide light reflected by the sample surface to the optical sensor for measuring the optical pattern projected on the sample surface
Data Source
Figure 1~2b
AI summary
The current invention relates to a method for determining a height map of a sample surface of a sample. The invention further relates to a method for determining a height map of a sample surface comprising a pre-scan step and a high-accuracy scan step. The invention further relates to an optical profilometry device configured for determining a height map of the sample surface. The invention further relates to a computer readable data carrier comprising a computer program.