Raman Spectroscopy Line Focus Scanning
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Solution Overview
Problem
Raman spectroscopy mapping of large sample areas is time-consuming and faces challenges in data stitching due to varying laser intensities and ambient condition changes, leading to discontinuities and difficulties in comparing spectra from different positions.
Innovation Solution
The apparatus uses a two-dimensional photodetector array to acquire spectra simultaneously across a line focus, with data shifting synchronously with the sample movement, integrating intensity variations and allowing seamless data assembly by moving the line focus continuously in the Y direction, reducing the need for stripe stitching and minimizing the impact of bleaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a line focus is used to illuminate multiple points simultaneously, then the acquisition speed is improved, but the intensity uniformity across the line deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the integration time for each detector element based on its received light intensity. Elements receiving weaker light (typically at line ends) are given longer integration times, while elements receiving stronger light use shorter integration times. This compensates for the non-uniform intensity distribution across the line focus, enabling uniform spectral quality across all positions while maintaining fast line-focus acquisition speed
2Area of stationary object
If the line focus length is increased to cover larger areas, then the mapping efficiency is improved, but the intensity variation across the line increases
Solution Approach 1:
The patent implements position-dependent integration time adjustment where each detector element's integration time is tailored to its specific location along the line focus. Elements at the ends of longer lines, which receive significantly less light, are assigned proportionally longer integration times. This allows the system to use longer line focuses to cover larger sample areas efficiently while maintaining uniform spectral quality across the entire line through adaptive temporal compensation
3Area of stationary object
If raster scanning is performed to cover large areas, then the coverage is improved, but the stitching accuracy deteriorates due to intensity drops and ambient changes
Solution Approach 1:
The patent applies continuity of useful action by performing continuous line-focus scanning without stopping between stripes. The line focus continuously illuminates successive regions, and spectra are continuously accumulated in the detector array. This eliminates gaps and transitions between discrete scan steps, ensuring that ambient conditions remain stable throughout the entire scanning process and enabling seamless stitching of large-area maps with high precision
4Measurement precision
If the integration time is increased to improve signal quality, then the spectral quality is improved, but the total acquisition time increases
Solution Approach 1:
The patent applies local quality by assigning different integration times to different spatial positions along the line focus based on their local light intensity conditions. Rather than using a uniform long integration time across the entire line, each detector element uses the minimum integration time necessary to achieve adequate signal quality at its specific position. This enables high spectral quality throughout the line while minimizing the overall acquisition time
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 method enables efficient, seamless data acquisition and analysis of large sample areas with reduced scanning time, integrating intensity variations and detector element differences, resulting in accurate and comparative molecular analysis without the need for edge data removal.
Implementation Method 1
A cylindrical lens (34) is present in the optical path between the laser and the sample, with its axis oriented transverse to the direction of relative movement, so that a line focus is produced
Implementation Method 2
a diffraction grating disperses this scattered Raman spectrum across a two-dimensional photodetector array
Implementation Method 3
a dispersive device such as a diffraction grating disperses this scattered Raman spectrum across a two-dimensional photodetector array
Data Source
Figure 1~2
Figure 3~5
Figure 4A~4C
AI summary
In a Raman spectroscopy apparatus, exciting light is focussed on a sample (26) as a line focus (38). Spectra from points in the line focus are dispersed in rows (46) on a CCD detector (34), having a two-dimensional array of pixels. The line focus moves longitudinally in a direction Y (arrow 48) relative to the sample. Simultaneously and synchronously, charge is shifted in a parallel direction Y' (arrow 50) within the CCD, so that data from a given point in the sample continues to accumulate. This ensures that the data from each sample point arises from illumination which is integrated along the line focus, and makes it easier to stitch the data together subsequently to form an image of the sample.