Spectrophotometer Signal Correction for Diffracted Light

Solution Overview

Problem

In PDA spectrophotometers, high order diffracted light from the diffraction grating can overlap with first order diffracted light, causing measurement errors, and using a filter to remove this light introduces stray light from frame and window components, complicating the setup.

Innovation Solution

A correction method is implemented where a first and second wavelength range are defined, with the longest wavelength in the second range being approximately twice that of the first, allowing for the determination and application of a correction coefficient to remove the detection signal value from second order diffracted light, thereby improving detector accuracy without the need for a filter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a filter is arranged between the diffraction grating and PDA to remove high order diffracted light, then measurement accuracy is improved, but device complexity increases and stray light enters the PDA

Engineering Contradiction:

Improvemeasurement accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the harmful second order diffracted light component from the detection signal through computational processing. By calculating the contribution of second order light based on the relationship between first and second wavelength ranges, the system subtracts this component from the total detection signal, effectively isolating the first order diffracted light signal without requiring physical filters or additional optical components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/optical filter-based solution with a computational/mathematical approach. Instead of using physical filters that require frame members, window plates, and complex mounting structures, the system uses signal processing algorithms to remove the harmful second order diffracted light component, substituting mechanical complexity with computational simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a filter is arranged between the diffraction grating and PDA to remove high order diffracted light, then measurement accuracy is improved, but stray light enters the PDA from frame and window components

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidstray light

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes the harmful second order diffracted light component from the detection signal through computational processing. By calculating the contribution of second order light based on the relationship between first and second wavelength ranges, the system subtracts this component from the total detection signal, effectively isolating the first order diffracted light signal without requiring physical filters or additional optical components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/optical filter-based solution with a computational/mathematical approach. Instead of using physical filters that require frame members, window plates, and complex mounting structures, the system uses signal processing algorithms to remove the harmful second order diffracted light component, substituting mechanical complexity with computational simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 effectively reduces the influence of high order diffracted light on measurements, enhancing accuracy and eliminating stray light issues by calculating and applying a correction coefficient to the detection signal values, thus eliminating the need for a filter between the diffraction grating and photodiode array.

Implementation Method 1

a diffraction grating configured to spectrally disperse light from a flow cell for each wavelength component

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a photodiode array (hereinafter referred to as "PDA") configured to detect the spectrally dispersed light for each wavelength component

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11002604B2Correction method of detection signal value in spectrophotometer and spectrophotometer having correction function of detection signal value

Publication Date: 2021.05.11 SHIMADZU CORP

AI summary

The purpose is to reduce the influence on the measurement due to high order diffracted light without arranging a filter for removing high order diffracted light between a diffraction grating and a PDA. The correction method includes a correction coefficient determination step of determining a correction coefficient related to a ratio of a portion of a detection signal value to the detection signal value, the portion of the detection signal value being derived from a second order diffracted light of light in the first wavelength range contained in the detection signal value of a long wavelength side photodiode for detecting light in the second wavelength range in the photodiode array, and a correction unit configured to obtain a corrected detection signal value derived from light in the second wavelength range from a different detection signal value of the long wavelength side photodiode by using the correction coefficient determined by the correction coefficient determination step.