Calibrated Spectroscopy Instrument Drive Mechanism
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Solution Overview
Problem
Achieving high angular positional accuracy in diffraction grating monochromators for wavelength selection is challenging due to errors introduced by the diffraction grating and imperfections in its drive mechanism, making calibration difficult and time-consuming.
Innovation Solution
A calibration method using a programmable computing apparatus with a calibration equation that includes correction coefficients to accurately rotate the diffraction grating, incorporating a pinion spur gear and main spur gear, and a method to determine these coefficients through a least-squares analysis with known spectral emission lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used for the diffraction grating monochromator, then wavelength selection accuracy can be achieved, but the calibration process is time-consuming and complex
Solution Approach 1:
The patent performs preliminary calibration measurements at multiple known wavelengths before actual operation. The calibration equation is pre-computed and stored in non-volatile memory, allowing rapid wavelength selection without time-consuming recalibration during normal operation. This preliminary action enables the system to achieve high wavelength accuracy quickly.
Solution Approach 2:
The patent replaces complex mechanical calibration procedures with a computational approach. Instead of physically adjusting and measuring the grating position manually, the system uses a calibrated mathematical model (the calibration equation with correction coefficients) to compute the precise grating angle for any desired wavelength, substituting mechanical calibration with electronic computation.
2Manufacturing precision
If the drive mechanism is made more precise to reduce positioning errors, then angular accuracy improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the parameters of the calibration equation by introducing correction coefficients (a, b, c, d) that account for drive mechanism imperfections. Instead of redesigning the mechanical drive mechanism to be more precise, the system adjusts the computational parameters to compensate for existing mechanical limitations, achieving high wavelength accuracy without increasing mechanical complexity.
Solution Approach 2:
The patent converts the harmful effect of drive mechanism imperfections and grating pitch variations into beneficial correction terms in the calibration equation. The errors in the mechanical system are characterized and incorporated as correction coefficients, transforming what would be sources of inaccuracy into accounted-for factors that enable precise wavelength selection despite mechanical limitations.
3Measurement precision
If correction coefficients are added to the calibration equation to account for grating pitch variation, then wavelength accuracy improves, but the calibration complexity increases
Solution Approach 1:
The patent modifies the calibration equation by adding correction terms with coefficients (a, b, c, d) that account for grating pitch variations and drive mechanism errors. These parameter changes enable the equation to model real-world deviations from ideal behavior, improving wavelength accuracy while keeping the mathematical structure relatively simple and manageable.
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 method provides quick and accurate calibration, reducing wavelength errors and enabling precise wavelength selection, as demonstrated by significant reduction in residual errors and completion time.
Implementation Method 1
wavelength selection in a diffraction grating monochromator is achieved by changing the angular position of the grating element
Implementation Method 2
the drive mechanism including a pinion spur gear and a main spur gear
Data Source
AI summary
A calibrated spectroscopy instrument and a method for calibrating a spectroscopy instrument are disclosed. The spectroscopy instrument includes a monochromator having a drive mechanism comprising a pair of spur gears for rotating a diffraction grating of the monochromator for selecting a desired wavelength. The drive mechanism is calibrated to account for eccentricities in the spur gears to provide an accurate conversion between selected angular settings for the drive mechanism and the wavelength of the diffracted light from the monochromator. The drive mechanism comprises a pinion spur gear and a main spur gear which each have an AGMA (American Gear Manufacturers' Association) rating of at least 10, which allows errors due to random tooth to tooth variations to be neglected. A calibration algorithm is derived which is based on the error due to eccentricities in the spur gears following a precise geometric cyclic pattern.