Imaging System Optical Beat Frequency Modulation
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Solution Overview
Problem
Existing imaging methods using Michelson interferometers face challenges in achieving high reproducibility due to errors and fluctuations in the modulation frequency of the image sensor's sensitivity, leading to inaccuracies in extracting spectral reflectance and transmittance data, particularly when dealing with continuous wavelength ranges and temporal fluctuations.
Innovation Solution
The proposed imaging system employs a combination of first and second light sources with discrete frequency components, generating optical beats through a mixing optical system, and an imaging element with variable sensitivity modulated at the beat frequency, allowing for precise extraction of specific frequency components and improving reproducibility by using an optical frequency comb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Michelson interferometer is used to measure spectral reflectance and transmittance, then measurement accuracy is improved, but reproducibility deteriorates due to modulation frequency errors and fluctuations in the image sensor
Solution Approach 1:
The patent applies periodic action by using two light sources with discrete frequency components that generate optical beats at specific beat frequencies. The image sensor's sensitivity is modulated periodically at these beat frequencies to selectively detect specific wavelength components. This periodic modulation approach replaces the continuous scanning method of traditional interferometers, eliminating the reproducibility issues caused by modulation frequency errors while maintaining high measurement accuracy through the stable, discrete beat frequencies generated by the dual light source system
Solution Approach 2:
The patent implements parameter changes by switching from a single continuous spectrum light source to two light sources with discrete frequency components arranged at different frequency intervals. This fundamental parameter change creates stable optical beats with well-defined frequencies, allowing the image sensor to selectively detect specific wavelength components through sensitivity modulation at these discrete beat frequencies, thereby improving both measurement accuracy and reproducibility
2Loss of information
If continuous wavelength range light is used for imaging, then spectral information completeness is improved, but frequency fluctuations cause measurement errors
Solution Approach 1:
The patent applies segmentation by dividing the continuous spectrum into discrete frequency components using two light sources with comb-like spectral structures. Each light source provides a series of equally spaced frequency lines, and their combination creates a segmented spectral coverage that maintains completeness while eliminating the frequency drift problems associated with continuous tuning. The image sensor then selectively detects specific segments (wavelength components) through sensitivity modulation at the corresponding beat frequencies
Solution Approach 2:
The patent introduces optical beats as an intermediary mechanism between the light sources and the image sensor. The mixing optical system generates optical beats at discrete beat frequencies that serve as mediators, allowing the image sensor to selectively detect specific wavelength components without being directly exposed to the full continuous spectrum. This intermediary approach enables precise spectral measurement by converting the continuous spectral information into discrete, stable beat frequency signals
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 enables the imaging system to obtain information on objects with improved reproducibility by accurately capturing spectral reflectance and transmittance data, even in the presence of frequency fluctuations, by selectively capturing optical beats at specific frequencies, thus enhancing the reliability of molecular composition and thickness measurements.
Implementation Method 1
the light beams on the two optical paths are reflected on different mirrors and then superimposed. By moving one of the mirrors, the difference between the two optical path lengths changes with time. In this operation, due to the interference effect, the intensity of the light varies between in a strong state and in a weak state
Implementation Method 2
measuring the time variation of the intensity of light with a photodiode
Data Source
AI summary
An imaging system includes: a first light source that emits first light having a spectrum including discrete first frequency components arranged at first frequency intervals; a second light source that emits second light having a spectrum including discrete second frequency components arranged at second frequency intervals, the second frequency intervals being different from the first frequency intervals; a mixing optical system that mixes the first light and the second light to generate third light including at least one optical beat the intensity of which changes at a beat frequency expressed by the difference between at least one of the discrete first frequency components and at least one of the discrete second frequency components; an imaging element having a variable sensitivity in an exposure period; and a control circuit that changes the sensitivity of the imaging element at the beat frequency of the at least one optical beat.