FTIR Spectrometer Velocity Control for Spectrum Accuracy
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Solution Overview
Problem
Conventional Fourier transform infrared spectrophotometers (FTIRs) face challenges in accurately computing the absorption spectrum of samples due to external interference and fluctuations in movable mirror velocity, leading to measurement errors and baseline distortion.
Innovation Solution
An FTIR system that includes a control unit which stores a target movable mirror velocity range and employs a correlation function to correct light intensity information, ensuring accurate computation of absorption or transmission spectra by discarding or correcting data outside the target velocity range, thereby maintaining consistent measurement quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the movable mirror velocity is not controlled, then the measurement process is simple and fast, but the absorption spectrum computation becomes inaccurate due to velocity fluctuations and external interference
Solution Approach 1:
The patent implements feedback control by detecting the actual movable mirror velocity and comparing it with the target velocity, then adjusting the driving signal to minimize velocity deviations. This feedback mechanism ensures accurate absorption spectrum computation by maintaining consistent mirror velocity despite external interference
Solution Approach 2:
The patent replaces purely mechanical velocity control with a combined system that uses optical detection (laser interferometry) and electronic control. The velocity detection unit measures mirror position and calculates velocity, while the control unit processes this information to adjust the driving signal, substituting mechanical rigidity with intelligent control
2Measurement precision
If data outside target velocity range is discarded, then measurement accuracy is maintained, but measurement time increases and productivity decreases
Solution Approach 1:
The patent performs preliminary velocity verification during the measurement process by continuously monitoring mirror velocity against the target velocity range. This real-time check allows the system to identify and handle out-of-range data points immediately, preventing the need for complete remeasurement and maintaining measurement efficiency
Solution Approach 2:
The patent changes the approach from discarding data to correcting data by using the correlation function to adjust light intensity information based on actual velocity deviations. This parameter transformation converts velocity error into a correction factor, allowing all measurement data to be utilized effectively
3Measurement precision
If feedback control is implemented to maintain constant mirror velocity, then measurement accuracy improves, but the system becomes more complex and vulnerable to external interference
Solution Approach 1:
The patent transforms the control strategy from rigid velocity maintenance to flexible velocity compensation. By introducing the correlation function that relates velocity deviations to light intensity corrections, the system can tolerate velocity fluctuations without compromising measurement accuracy, thereby improving reliability under external interference
Solution Approach 2:
The patent introduces the correlation function as an intermediary between velocity detection and spectrum computation. This mathematical relationship acts as a buffer that translates velocity variations into appropriate corrections, isolating the final spectrum result from direct exposure to velocity instability and external interference
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 allows for precise computation of absorption or transmission spectra even under external interference, preventing measurement errors and maintaining signal quality without discarding data.
Implementation Method 1
the infrared light reflected back from the stationary mirror and the infrared light reflected back from the movable mirror are combined in the beam splitter and sent along a single optical path... the combined light becomes an interference light signal (interferogram)
Implementation Method 2
when electric current is made to flow via lead wire 273 to voice coil 272, the voice coil 272 receives magnetic force due to the magnetic field formed by magnet 269a, yoke 268 and pole piece 269b
Implementation Method 3
a laser light source which emits a laser light
Implementation Method 4
an infrared light source unit which emits an infrared light
Data Source
AI summary
An interference spectrophotometer including a movable mirror unit having a movable mirror capable of reciprocating movement; a stationary mirror; an infrared light source unit which emits an infrared light; a beam splitter; an interference light detection unit which detects light intensity information of light transmitted or reflected by a sample; a movable mirror velocity information detection unit which detects movable mirror velocity information for movable mirror; and a control unit which acquires the light intensity information and movable mirror velocity information and computes the absorption or transmission spectrum of the sample; wherein the interference spectrophotometer further comprises a storage unit which stores a target movable mirror velocity range, and control unit does not employ light intensity information obtained when the movable mirror velocity of movable mirror was outside the target movable mirror velocity range for computing the absorption or transmission spectrum of the sample.