PEM Phase Difference Control for Continuous-Scanning Spectrometers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing phase difference control devices for spectrometers using photoelastic modulators are limited in responsiveness, making it difficult to handle wavelength variations and temperature changes, which restricts their application to continuous-scanning spectrometers like circular dichroism spectrometers.
Innovation Solution
A phase difference control device and method that incorporates a CPU circuit to monitor wavelength variations and temperature changes, using feedback and feedforward signals to improve responsiveness, enabling stable phase difference control through a feedback control loop and temperature compensating circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback control configuration is used to maintain phase difference by detecting reference light, then phase difference stability is improved, but responsiveness deteriorates making continuous-scanning impossible
Solution Approach 1:
The patent applies preliminary action by predicting wavelength variations before they affect phase difference stability. The CPU circuit generates feedforward signals based on anticipated wavelength changes, allowing the system to proactively adjust the PEM control voltage rather than merely reacting to detected phase errors, thereby achieving both stability and responsiveness
Solution Approach 2:
The patent combines feedback control with feedforward control. The feedback mechanism continuously monitors reference light to detect phase difference deviations, while the feedforward mechanism anticipates wavelength variations and pre-adjusts the control voltage. This hybrid approach maintains phase stability while improving responsiveness beyond what feedback alone can achieve
2Measurement precision
If step-scanning is used to handle wavelength variations, then measurement accuracy is improved, but productivity deteriorates due to inability to perform continuous-scanning
Solution Approach 1:
The system performs preliminary actions by continuously monitoring wavelength and generating feedforward control signals that anticipate upcoming wavelength variations. This allows the phase difference to be maintained accurately during continuous scanning without requiring step-by-step adjustments, thereby achieving both measurement precision and high scanning speed
Solution Approach 2:
The patent enables continuity of useful action by allowing the spectrometer to perform continuous-scanning instead of step-scanning. The feedforward control mechanism ensures that phase difference stability is maintained throughout the continuous wavelength sweep, making it possible to acquire spectral data continuously without interruption while maintaining measurement accuracy
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 solution enhances responsiveness, allowing the phase difference control device to handle both step-scanning and continuous-scanning, achieving stable phase difference control even with wavelength variations and temperature changes, and is applicable to spectrometers requiring continuous-scanning.
Implementation Method 1
The PEM is generally known as an element that uses birefringence to modulate the phase of an incoming polarized light
Implementation Method 2
a splitting polarizer that splits a light incident from a light source into a measurement light and a reference light, both of which are linearly polarized
Data Source
AI summary
A phase difference control device comprises: a splitting polarizer splitting a light incident from a light source into a measurement light and a reference light, both of which are linearly polarized; a PEM imparting a phase difference to the measurement and reference lights to correspond to the spectrometry; a PEM driver supplying a modulation voltage to the PEM; a PEM control circuit inputting the reference light as a feedback signal and outputting a modulation control quantity signal to the PEM driver; and a CPU circuit monitoring the wavelength of the light in the splitting polarizer to input a wavelength variation as a wavelength signal, wherein the CPU circuit converts the wavelength signal to a feedforward signal which is output to the PEM control circuit; and the PEM control circuit performs arithmetic processing by the feedback and feedforward signals to output the modulation control quantity signal to the PEM driver.