Interferometer Calibration for Linear Wave Number Variation
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Solution Overview
Problem
Existing interferometer calibration methods require constant feedback control to maintain a linearly varying wave number on the time axis, which is challenging to achieve during measurement, especially when sampling at unequal time intervals.
Innovation Solution
A method involving generating a spectrum interference signal by varying the voltage applied to a wavelength-swept light source, sampling at equal time intervals, Fourier transforming, and using window functions for Hilbert transforms to obtain correspondence voltage that linearly varies the frequency without constant feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedback control is executed to maintain constant frequency of AC component, then wave number varies linearly on time axis, but measurement complexity increases and continuous control is required
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the relationship between drive voltage and wave number before measurement. The calibration process stores correspondence data between drive voltage values and wave number values in advance, eliminating the need for continuous feedback control during measurement. This allows the system to achieve linear wave number variation by simply selecting appropriate pre-calibrated voltage values.
Solution Approach 2:
The patent uses feedback by measuring the actual wave number during calibration and using this information to adjust and store the correspondence relationship between drive voltage and wave number. The system measures the frequency of the AC component, calculates the wave number, and iteratively adjusts the drive voltage to achieve the desired linear relationship, storing the corrected correspondence data for future use.
2Ease of operation
If sampling is performed at equal time intervals, then data acquisition is simplified, but wave number linearity deteriorates without feedback control
Solution Approach 1:
The patent resolves this contradiction by pre-calibrating the drive voltage waveform to compensate for the non-linear relationship between equal time interval sampling and wave number variation. The calibration process determines the specific voltage values to be applied at each equal time interval to achieve linear wave number variation, storing this corrected voltage waveform for subsequent measurements.
3Measurement precision
If continuous feedback control is implemented, then measurement precision is maintained, but measurement time increases and productivity decreases
Solution Approach 1:
The patent eliminates continuous feedback control during measurement by performing all necessary calibration and correction in advance. The pre-stored correspondence relationship between drive voltage and wave number allows the system to achieve high measurement precision through simple voltage application and equal time interval sampling, dramatically improving measurement speed without sacrificing precision.
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 linear variation of the wave number on the time axis without continuous feedback control, improving the quality of tomographic images by reducing distortion in the point-spread-function.
Implementation Method 1
a wavelength-swept light source 200 that sweeps a wavelength of light to be emitted
Implementation Method 2
the reference light reflected on a reference mirror disposed in the reference optical path and the measurement light scattered and reflected on the biographic body as a measurement target disposed in the measurement optical path are again synthesized to be superimposed, so that a time-varying spectrum interference signal (beat signal) is generated
Implementation Method 3
This spectrum interference signal (beat signal) is detected by a detector
Data Source
AI summary
A calibration method for improving distortion of a waveform of a point-spread-function without constantly executing feedback control to a wavelength-swept light source is provided. An interference signal is generated by varying voltage to be applied to a light source within one period, the interference signal is sampled at equal time intervals on a time axis, the point-spread-function is obtained through Fourier transform by multiplying by a first window function, and a complex analysis signal including frequency information of light is obtained through inverse Fourier transform by multiplying the point-spread-function by a second window function. After a variation in a frequency of the light relative to a time within one period is obtained at equal time intervals by unwrapping phase information of the complex analysis signal, a correspondence relationship between the variation in the frequency of the light within one period and a variation in voltage within one period is obtained.