Spectrometer Wavelength Calibration Using D2 Lamp and Ho Glass Filter
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Solution Overview
Problem
Existing spectrometry devices face calibration inaccuracies due to variability in the absorption peak of commercial Ho glass filters, which affects the reference wavelength for wavelength calibration, especially with the potential prohibition of mercury lamps under RoHS restrictions.
Innovation Solution
A spectrometry device that uses a D2 lamp for calibration and a specific absorption peak of a Ho glass filter as the reference wavelength, with a wavelength calibration unit that adjusts control pulses based on pre-measured values to ensure accurate calibration across varying Ho glass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mercury lamp is used for wavelength calibration, then reference position can be determined accurately, but device complexity increases and environmental compliance becomes problematic due to RoHS restrictions
Solution Approach 1:
The patent extracts the calibration function from the mercury lamp system and implements it separately using a D2 lamp for emission line calibration and a Ho glass filter for absorption spectrum calibration. This separation eliminates the need for mercury lamp while maintaining calibration accuracy through multiple reference sources.
Solution Approach 2:
The D2 lamp serves multiple functions: it provides emission line spectrum for wavelength calibration and can also serve as a light source for sample measurement. The Ho glass filter complements this by providing additional absorption reference peaks, creating a universal calibration system that replaces the specialized mercury lamp.
2Device complexity
If Ho glass filter is used for wavelength calibration, then environmental compliance is improved and device complexity is reduced, but measurement precision deteriorates due to variability in absorption peak position
Solution Approach 1:
The patent implements a feedback mechanism where the actual absorption spectrum of the Ho glass filter is measured and the peak positions are detected. These detected peak positions are then used to generate corrected pulse numbers that compensate for any deviations from standard values, ensuring accurate wavelength calibration despite filter variability.
Solution Approach 2:
The system dynamically adjusts the pulse numbers based on the actual measured absorption peak positions of the Ho glass filter. By changing the control parameters (pulse numbers) according to the actual filter characteristics, the system maintains calibration accuracy despite variations in filter manufacturing.
3Measurement precision
If slit width is reduced to obtain sharp peak waveform, then measurement precision improves, but light intensity decreases reducing the amount of diffracted light transmitted to measurement cell
Solution Approach 1:
The patent uses a D2 lamp that provides excessive light intensity across the UV spectrum, ensuring that even when the slit width is reduced for sharp peak detection, there is sufficient light transmitted to the measurement cell. The strong emission lines of D2 lamp compensate for the reduced light throughput.
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
Enables accurate wavelength calibration of spectrometers using Ho glass filters, even with different absorption peak positions, without relying on mercury lamps, ensuring consistent measurement performance.
Implementation Method 1
Some spectrometry devices include a diffraction grating as a wavelength dispersion element, and by rotating the diffraction grating, select the wavelength of diffracted light that is to emerge from an exit slit.
Implementation Method 2
Calibration of the rotation position of the pulse motor for rotating the diffraction grating is performed, for example, by searching for an emission line in the spectrum of a deuterium (D2) lamp and defining its position as a reference position 656.1 nm on the long-wavelength side
Implementation Method 3
as an alternative to the emission line wavelength of the mercury lamp, use of the peak wavelength of Ho absorption spectrum of a holmium (Ho) glass filter has been considered. The absorption peak of Ho is at 241.7 nm
Data Source
AI summary
The wavelength of a spectrometer is calibrated by using a commercial Ho glass filter. The spectrometer includes a light source including a D2 lamp and not including a mercury lamp, and a reference wavelength input unit for inputting, as a reference wavelength, a wavelength of a specific absorption peak separately measured for an Ho glass filter to be used. To calibrate the wavelength of the spectrometer by using the wavelength of a specific emission line peak of the D2 lamp and the reference wavelength input by the reference wavelength input unit, the wavelength calibration unit holds a conversion table showing a theoretical relationship between the number of control pulses for rotating a diffraction element and the corresponding wavelength of diffracted light, and calibrates the number of control pulses from the conversion table by the wavelength calibration unit.