Germanium Hemisphere ATR Microscope Image Correction
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Solution Overview
Problem
Conventional ATR infrared chemical imaging systems using a Ge hemisphere suffer from optical aberrations, non-uniform optical throughput, and varying incident angles, leading to distorted and inaccurate chemical images.
Innovation Solution
A method is developed to correct these issues by simulating the movement of a Ge hemisphere in a ray tracing model to determine the mean positions and percentage of rays reaching the detector, using a background spectrum to normalize the data, and applying corrections for incident angle variations, resulting in a more accurate chemical image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Ge hemisphere is used to focus the infrared incident beam at the sample position, then the incident beam is focused at the sample and the infrared beam is totally reflected back from the sample-Ge boundary, but optical aberrations and distortion occur in the chemical images
Solution Approach 1:
The patent applies parameter changes by systematically varying the incident angle of the infrared beam across different sample positions. By modeling how the incident angle changes with position and applying correction factors based on these angle variations, the patent compensates for optical aberrations and distortion while maintaining precise beam focusing at the sample position.
2Productivity
If an array detector is used to obtain infrared spectra from multiple positions, then the measurement time is shortened, but optical throughput variation across different positions affects measurement accuracy
Solution Approach 1:
The patent applies local quality by making the optical throughput correction position-dependent. Each detector element's measurement is corrected using a specific correction factor that accounts for the local optical throughput at that particular position. This allows the system to maintain high measurement speed with an array detector while achieving uniform accuracy across all positions by applying location-specific corrections.
3Adaptability or versatility
If the Ge hemisphere and sample are moved together to change measurement locations, then different sample areas can be analyzed, but loss of optical symmetry changes optical throughput
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction factors for various measurement positions before actual sample analysis. When the Ge hemisphere and sample are moved to different locations, the system retrieves the appropriate pre-computed correction factor for that position, allowing flexible positioning while maintaining measurement accuracy without requiring real-time optical symmetry adjustments.
4Manufacturing precision
If spectra are collected from small area segments to create high resolution chemical images, then fine structures can be studied, but the number of measurements increases and measurement time increases
Solution Approach 1:
The patent applies copying by using an array detector to simultaneously capture spectra from multiple sample positions in parallel. Instead of sequentially measuring each small area segment, the system creates a spatial copy of the sample region across multiple detector elements, acquiring all necessary spectral data in a single measurement pass and then applying position-specific correction factors to generate the high-resolution chemical image.
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 method effectively corrects distortion, energy throughput, and incident angle variations, producing a chemical image representative of the sample's chemical composition, reducing measurement time and improving signal-to-noise ratio.
Implementation Method 1
The use of an array detector reduces the required measurement time because an array detector is composed of multiple detectors. The reflected beam carries the spectral information of the sample. The infrared Ge ATR imaging technique is a popular technique to study fine structures that have a size that is on the order of a few micron, because the refractive index of Ge (n=4) provides additional magnification above the nominal magnification of infrared microscopes.
Implementation Method 2
By utilizing the Ge hemisphere as an additional lens in an infrared microscope system, spectroscopic measurements are affected by optical aberrations and distortion. Ge ATR imaging measurements show significant pincushion type distortion in displayed chemical images.
Data Source
AI summary
A method and corresponding apparatus provide correction of chemical images collected with a germanium hemisphere ATR microscope. A model is developed for rays passing through a simulated germanium (Ge) hemisphere attenuated total reflection (ATR) microscope. The model determines a data set for rays reaching the detector plane. Movement of the hemisphere is simulated along a first axis between each data set determination. A calculated background spectrum is produced by multiplying the percentage of rays by a background spectrum to produce a calculated background spectrum. A real Ge hemisphere ATR microscope having parameters that substantially match those of the simulated Ge hemisphere microscope is then used to collect a chemical image of a sample that is in contact with the Ge hemisphere. The collected image is then corrected to produce a corrected chemical image.