CCD Spectroscopic Apparatus Synchronous Spectrum Scanning
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Solution Overview
Problem
Existing Raman spectroscopy data acquisition methods, such as the step-and-repeat method, face challenges in stitching together separate blocks of data due to changes in background light levels or other conditions, leading to difficulties in computer processing and increased readout noise.
Innovation Solution
The apparatus moves the spectrum orthogonally to the direction of charge transfer in the CCD, allowing data to be accumulated and read out synchronously with the movement of the spectrum, reducing the need for subsequent data stitching and minimizing readout noise by reading each pixel only once.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the step-and-repeat method is used to acquire data from different parts of the spectrum, then a wider spectrum can be covered, but the data stitching becomes difficult and readout noise increases
Solution Approach 1:
The patent implements continuous scanning where the diffraction grating moves the spectrum across the CCD detector without interruption. The CCD continuously accumulates charge from different spectral regions as the spectrum scans across, eliminating the discontinuous step-and-repeat approach. This continuous action ensures uniform data collection across the entire spectrum without gaps or overlaps that would require stitching.
Solution Approach 2:
The patent replaces the mechanical indexing of the diffraction grating (used in step-and-repeat methods) with continuous grating movement combined with synchronous charge shifting in the CCD. Instead of mechanically repositioning the grating to capture different spectral segments, the system uses continuous grating motion synchronized with charge transfer, eliminating the need for mechanical repositioning and subsequent data stitching.
2Quantity of substance
If multiple exposures are taken to cover the full spectrum, then complete spectral data is obtained, but background light level changes cause processing difficulties
Solution Approach 1:
The continuous scanning method ensures that the entire spectrum is captured in a single uninterrupted sequence. As the diffraction grating continuously moves the spectrum across the CCD, all spectral regions are exposed simultaneously in time, eliminating variations in background light levels that would occur between separate exposures. The synchronous charge shifting ensures that all pixels integrate signals over the same time period.
Solution Approach 2:
The system prepares the CCD detector in advance by ensuring all pixels are ready to receive and accumulate charge simultaneously. The diffraction grating is positioned and the spectrum is allowed to scan across the detector before readout begins, ensuring that the entire spectral range is captured under uniform illumination conditions without requiring post-processing adjustments for background variations.
3Measurement precision
If the spectrum is dispersed widely across the CCD for high spectral resolution, then spectral detail is improved, but only a part of the spectrum can be received at any one time
Solution Approach 1:
The patent employs dynamic movement of the diffraction grating to scan the spectrum across the CCD detector. While the grating disperses the spectrum with high resolution across the detector width, the continuous motion of the grating dynamically shifts different spectral regions across the detector over time. This dynamic approach allows the system to maintain high spectral resolution while progressively capturing the entire spectral range through the scanning motion.
Solution Approach 2:
The patent adds the time dimension to the spectral measurement by implementing continuous scanning. While the spatial dimension across the CCD provides high spectral resolution for a narrow bandwidth, the temporal dimension introduced by continuous grating motion allows the spectrum to scan across the entire detector, effectively extending the spectral coverage without sacrificing resolution. The synchronous charge shifting in the CCD's output register captures this temporal progression.
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 uniform data collection and reduces readout noise, as each pixel is read out of the CCD only once, improving data processing efficiency and accuracy.
Implementation Method 1
a dispersive device such as a diffraction grating disperses this scattered Raman spectrum across a two-dimensional photodetector array
Implementation Method 2
a two-dimensional photodetector array, e.g. in the form of a charge-coupled device (CCD)
Data Source
Figure 1~2
AI summary
A sample (26) is illuminated by laser light and the resulting Raman spectrum (62) is dispersed at a high spectral resolution along one or more rows or columns of detector elements (60) of a CCD (34). The resulting charge is shifted in a direction Y' and binned in an output register 64 of the CCD. The dispersed spectrum is moved along the rows or columns in a direction X', synchronously with the shifting of charge in the output register (arrow 72). Thus, data from a given wavenumber in the spectrum continues to accumulate in the output register during the movement. This enables data from a wide spectrum to be collected at high resolution, without the need to subsequently stitch blocks of data together in a computer, even where the CCD is arranged such that row-by-row transfer of charge towards the output register is orthogonal to the direction of dispersion.