Koehler Integration Optics for Spectral Analysis Consistency
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Solution Overview
Problem
Existing spectroscopic systems, such as Raman systems, face challenges in achieving consistent analysis of pharmaceutical dosage forms due to variations in sample position, orientation, and movement, leading to intensity fluctuations and peak shifts.
Innovation Solution
The use of Koehler integration optics to spread collected light uniformly, independent of the sample's geometry, ensures that spatial information from the sample surface is not coupled into the spectrometer, thereby reducing the influence of sample position and orientation on the light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional imaging lens systems are used to couple light directly onto the spectrometer, then spatial information from the sample is preserved, but spectroscopic analysis becomes sensitive to sample position, orientation, and movement causing intensity fluctuations and peak shifts
Solution Approach 1:
The patent introduces Koehler integration optics as an intermediary between the sample and spectrometer. This intermediate optical system decouples the direct spatial mapping relationship, allowing light from different sample positions to be mixed and redistributed uniformly across the spectrometer entrance, thereby eliminating sensitivity to sample positioning while maintaining spectral information
Solution Approach 2:
The patent changes the optical parameters by implementing Koehler illumination conditions, which transform the light distribution characteristics. The system adjusts the optical path to ensure that the sample is illuminated uniformly and that the collected light is redistributed to eliminate spatial variations, changing the fundamental parameter of light-coupling geometry
2Device complexity
If light is collected directly from the sample surface without integration optics, then the optical path is simpler, but spatial and angular information from the sample is coupled into the spectrometer causing measurement variability
Solution Approach 1:
Koehler integration optics serve as an intermediate stage that receives light from the sample and redistributes it before entering the spectrometer. This intermediate optical system adds controlled complexity to eliminate unwanted spatial coupling, achieving better measurement consistency through structured light management
Solution Approach 2:
The patent transforms the light distribution from a direct spatial mapping (one-to-one correspondence between sample position and spectrometer input) to a distributed uniform illumination pattern. By introducing the integration optics, the system transitions from preserving spatial dimensions to averaging them out, effectively moving from a spatially-resolved approach to a spatially-integrated approach
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 results in improved consistency of spectroscopic analysis by averaging out spatial and angular information, leading to more uniform light distributions and reduced variability in spectral measurements across multiple samples.
Implementation Method 1
Koehler integration optics, so as to spread collected light from the sample in a uniform manner independent of the geometry of the sample
Implementation Method 2
This ensures that spatial information from the sample surface is not coupled into the input to the spectrometer. This does not necessarily eliminate far-field variances, although these can be addressed using a 'fly's-eye' lenslet array configuration of Koehler optics where a pair of matched lenslet arrays are used to subsample the intermediate aperture
Data Source
AI summary
Apparatus and methods for spectral analysis of a sample are described, for example for carrying out Raman or other optical or spectroscopic analysis of samples such as pharmaceutical dosage forms, including oral solid dosage forms such as tablets or capsules. Such apparatus may comprise delivery optics arranged to direct probe light to a delivery region of the sample, collection optics arranged to collect probe light scattered from a collection region of the sample, and a spectrometer having an entrance port, the spectrometer being arranged to receive the collected probe light from the collection optics at the entrance port of the spectrometer, and to detect spectral features in the received probe light. In particular, the collection optics may comprise Koehler integration optics arranged to process the collected probe light such that the collected light from each point of the collection region is distributed across the entrance port of the spectrometer.