Microscope Phase Shift Control for Refractive Index
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Solution Overview
Problem
Existing microscopes struggle to accurately determine the phase and refractive index of object regions, particularly in semiconductor fabrication, due to limitations in phase reconstruction from intensity recordings, such as defocusing issues that affect low frequencies and require additional optical setups.
Innovation Solution
A method and microscope design that introduces controlled phase shifts into the imaging beam path by manipulating optical elements within the objective, such as displacing or deforming lenses, to generate different imaging properties, allowing for better reconstruction of phase information without changing the focus, using techniques like iterative Fourier transform algorithms or transport-of-intensity equation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase reconstruction is performed from intensity recordings using conventional methods, then phase information can be obtained, but low frequencies are affected by defocusing which deteriorates reconstruction accuracy for slowly changing phase objects
Solution Approach 1:
The patent applies preliminary anti-action by introducing a phase shift element that pre-compensates for the defocusing effect before imaging. The phase shift element introduces a phase shift that is opposite in sign to the quadratic phase front caused by defocusing, thereby canceling out the harmful defocusing effect on low frequencies and improving phase reconstruction accuracy.
Solution Approach 2:
The patent changes the phase parameter of the light wave by introducing a controllable phase shift element in the optical path. By adjusting the phase shift parameter to counteract the defocusing-induced quadratic phase front, the system improves the reconstruction of slowly varying phase objects without being affected by defocusing artifacts.
2Measurement precision
If standard microscope setups are used for phase determination, then intensity recordings can be obtained, but additional optical setups are required to achieve accurate phase information
Solution Approach 1:
The patent merges the phase shifting function with the existing microscope optical system by placing a phase shift element in the optical path between the objective and the detector. This integration allows the standard microscope to perform both intensity imaging and phase determination without requiring separate interferometric setups, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent makes the microscope system universal by enabling it to perform multiple functions: standard intensity imaging and phase determination. The phase shift element allows the same optical setup to extract phase information from intensity recordings without requiring dedicated phase-contrast or interferometric optics, thus achieving multi-functionality with minimal additional components.
3Measurement precision
If multiple intensity recordings are taken with different focusing to reconstruct phase, then phase information can be obtained, but recording time increases
Solution Approach 1:
The patent applies preliminary action by introducing the phase shift element before taking the intensity recordings. This pre-processing of the optical path enables phase information to be extracted from a single or fewer recordings, eliminating the need to acquire multiple recordings at different focus positions and thereby reducing the total recording time while maintaining phase reconstruction 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
This approach enables improved reconstruction of phase and refractive index, especially for slowly changing phase objects, with increased accuracy and reduced recording time, without requiring additional hardware, and can be applied to various fields like biosciences and semiconductor lithography.
Implementation Method 1
different phase shifts which are additionally introduced into the imaging beam path and which are generated differently than by changing the focusing when carrying out the recordings
Data Source
AI summary
In a method for determining the phase and/or refractive index of a region of an object, the object region is illuminated with coherent or partly coherent light and is imaged into the image plane a number of times with different imaging properties and is recorded in order to obtain a plurality of intensity recordings of the object region. The phase and/or refractive index determination is carried out based upon the plurality of intensity recordings. The different imaging properties differ at least in terms of different phase shifts which are additionally introduced into the imaging beam path, and which are generated differently than by changing the focusing when carrying out the recordings. The different phase shifts which are additionally introduced into the imaging beam path are effected by introducing at least one optical element into the objective and/or manipulating at least one optical element of the objective.