Holographic Interferometry Aperture Off-Axis Phase Extraction
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Solution Overview
Problem
Holographic interferometry methods for fast lateral scanning of objects, such as semiconductor wafers, face challenges in extracting phase information from a single image due to interference line density and resolution limitations, which are not adequately addressed by existing technologies.
Innovation Solution
A holographic interferometer system with apertures located away from the optical axis to separate light beams at different angles, allowing for the creation of multiple interference patterns with varying effective wavelengths from a single light source, enabling phase information extraction without the need for multiple wavelength light sources and improving spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a non-zero angle is introduced between the object beam and reference beam to extract phase information from a single image, then the speed of lateral scanning is improved, but the interference line density becomes too high causing camera pixelization to average them out and lose resolution
Solution Approach 1:
The patent divides the interference pattern capture into multiple images taken at different lateral positions. Instead of attempting to capture all phase information in a single high-density interference pattern, the system segments the measurement process across multiple images, each with manageable interference line density, thereby resolving the contradiction between scanning speed and measurement precision.
Solution Approach 2:
The patent transitions from extracting all phase information in a single spatial dimension (single image) to distributing phase information extraction across multiple spatial samples (multiple images at different lateral positions). This dimensional approach allows phase information to be reconstructed without requiring excessively high interference line density in any single image.
2Measurement precision
If multiple wavelength light sources are used to create multiple interference patterns with different effective wavelengths, then phase information extraction accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the approach from varying light source wavelength to varying the optical path difference between reference and object beams. By manipulating the optical path difference across multiple measurements, the system achieves effective wavelength diversity without requiring multiple wavelength light sources, thus resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent creates multiple copies of the interference measurement process at different optical path differences rather than using multiple wavelength sources. Each copy provides complementary phase information, and combining these copies achieves the same effect as multi-wavelength measurement while using a single light source, reducing device complexity.
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
This approach allows for efficient extraction of phase information from a single image, enhancing the speed and accuracy of lateral scanning while reducing computational costs and eliminating the requirement for expensive multiple wavelength light sources.
Implementation Method 1
the at least one aperture is located away from an axis of the at least one light beam, thus transmitting a subset of the at least one light beam collected at an angle range
Implementation Method 2
at least one imaging device capturing an interference pattern created by at least two light beams
Data Source
AI summary
A holographic interferometer, comprising: at least one imaging device capturing an interference pattern created by at least two light beams; and at least one aperture located in an optical path of at least one light beam of the at least two light beams; wherein the at least one aperture is located away from an axis of the at least one light beam, thus transmitting a subset of the at least one light beam collected at an angle range.