Optical Sensor Device Nonlinearity Compensation Using Reference Signal
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Solution Overview
Problem
The existing methods for compensating for nonlinearity in wavelength swept light sources in swept source-optical coherence tomography (SS-OCT) devices require significant signal processing loads, increasing computational demands.
Innovation Solution
An optical sensor device configuration that includes a wavelength swept light source, an optical brancher, an optical sensor head, an optical heterodyne receiver, and a signal processor, which uses internal reflection to generate a frequency variation reference signal, allowing for synchronized sampling of reception signals to reduce nonlinearity compensation load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If regression analysis is performed on the beat signal to compensate for nonlinearity of wavelength swept light, then measurement accuracy is improved, but signal processing load increases
Solution Approach 1:
The patent performs nonlinearity compensation in advance by measuring the actual frequency modulation waveform of the laser light source and storing correction data before actual distance measurements are taken. This preliminary action eliminates the need for time-consuming regression analysis during each measurement, thereby resolving the contradiction between measurement accuracy and processing speed
Solution Approach 2:
The patent creates a reference model of the frequency modulation waveform by measuring it in advance and storing it as correction data. This copied reference model is then used to compensate for nonlinearity during actual measurements without requiring repeated complex calculations, thus improving processing efficiency while maintaining accuracy
2Measurement precision
If regression analysis is performed for each measurement to compensate for nonlinearity, then distance resolution is maintained, but processing time increases
Solution Approach 1:
The system performs frequency modulation waveform measurement and correction data generation in advance before actual distance measurements. This preliminary action stores the nonlinearity characteristics in a readily usable format, eliminating the need for time-consuming regression analysis during each measurement while preserving distance resolution
3Measurement precision
If a known frequency modulation waveform is used for regression analysis, then nonlinearity compensation is achieved, but device complexity increases
Solution Approach 1:
The patent makes the laser light source itself serve as the reference by measuring its actual frequency modulation waveform directly. This self-service approach eliminates the need for external reference equipment or complex theoretical models, simplifying the system while achieving accurate nonlinearity compensation
Solution Approach 2:
The system measures the actual frequency modulation waveform of the laser light source and uses this feedback information to generate correction data. This feedback mechanism allows the system to adapt to the specific characteristics of its own light source, improving compensation accuracy without requiring complex external reference systems
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 configuration reduces the signal processing load required for compensating nonlinearity in wavelength swept light, enhancing measurement accuracy and efficiency by synchronizing sampling with the frequency variation reference signal.
Implementation Method 1
an optical heterodyne receiver to multiplex the local oscillation light branched by the optical brancher and the reflected light received by the optical sensor head, and photoelectrically convert the multiplexed light to acquire a reception signal as an electric signal
Implementation Method 2
a wavelength swept light source to output light whose frequency changes with lapse of time
Implementation Method 3
an optical sensor head to emit the signal light branched by the optical brancher toward a measurement target and receive reflected light reflected by the measurement target
Data Source
AI summary
A signal processing device in an optical sensor device further calculates first frequency variation reference signal data serving as a reference for frequency variation of light output from a wavelength swept light source on the basis of an internal reception signal converted into a digital signal by an analog-to-digital converter, a digital-to-analog converter converts the first frequency variation reference signal data calculated by the signal processing device into an analog signal to generate a first frequency variation reference signal as a first clock signal, and the analog-to-digital converter samples a reception signal acquired by an optical heterodyne receiver in synchronization with the first frequency variation reference signal generated by the digital-to-analog converter.