Spectral-Domain Optical Nonlinearity Tomography for Depth Imaging
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Solution Overview
Problem
Conventional optical coherence tomography (OCT) devices suffer from limited image contrast ratio and slower image detection speed, resulting in reduced observation depth and inaccurate diagnosis, particularly in ophthalmology applications.
Innovation Solution
An optical nonlinearity tomography device that generates a nonlinear beam by mixing sample and reference light in a nonlinear crystal, using a spectrally dispersed beam generator and Fourier transformer to cancel phase components, allowing for direct detection of depth direction signals without interference, and utilizing a Si image sensor for visible light detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectral domain OCT uses interference detection between sample and reference light, then the system can achieve tomography imaging, but the image contrast ratio is limited due to the presence of strong DC component from reference light intensity
Solution Approach 1:
The patent introduces a nonlinear crystal as an intermediary element that converts the optical interference signal into a detectable electrical signal through optical nonlinearity. The nonlinear crystal processes the sample and reference light to generate a signal proportional to their interference, eliminating the need for direct electronic detection of the weak interference term against the strong DC background. This intermediary optical processing enables high contrast ratio imaging while maintaining manageable system complexity.
Solution Approach 2:
The patent changes the detection parameter from direct intensity measurement to optical nonlinearity measurement. By using a nonlinear crystal, the system measures the product of sample and reference light fields rather than their individual intensities. This parameter transformation converts the difficult task of measuring weak interference against strong background into measuring a signal generated only when both fields are present, achieving high contrast ratio without complex electronic processing.
2Productivity
If conventional OCT uses traditional detection methods, then the system structure is simpler, but the image detection speed is slower and observation depth is reduced
Solution Approach 1:
The patent replaces the traditional mechanical/electronic detection system with an optical nonlinearity-based detection system. Instead of using complex electronic circuits to process interference signals, the system uses the optical nonlinearity of a crystal to automatically convert the optical interference pattern into an electrical signal. This substitution of detection mechanism dramatically increases image detection speed and observation depth while keeping the overall system structure relatively simple.
Solution Approach 2:
The nonlinear crystal performs the detection function autonomously by converting optical interference directly into electrical signals through its inherent nonlinearity. The system does not require external complex processing circuits to enhance the weak interference signal, as the crystal itself performs the signal generation and conversion. This self-service detection capability enables fast imaging without adding significant system complexity.
3Measurement precision
If the detection unit directly detects interference signals, then the system is simpler, but the strong DC component from reference light reduces the observable dynamic range
Solution Approach 1:
The nonlinear crystal acts as an intermediary that selectively processes the interference information while automatically rejecting the strong DC component. By converting the optical fields through nonlinear interaction, the crystal generates a signal that is proportional to the interference term but independent of the strong reference light intensity. This intermediary optical processing expands the dynamic range without requiring complex electronic signal processing to subtract the DC component.
Solution Approach 2:
The patent changes the measurement parameter from direct intensity detection to nonlinear optical response detection. By measuring the nonlinear response of the crystal to the combined optical fields, the system obtains a signal that naturally excludes the strong DC component. This parameter transformation expands the usable dynamic range by a factor of 1000 or more, eliminating the need for complex DC subtraction algorithms.
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 device achieves higher image contrast ratio, faster detection speed, and deeper observation depth, reducing costs by using a conventional Si image sensor and eliminating the need for separate computer processing, enabling accurate diagnosis of biological tissues.
Implementation Method 1
generates a nonlinear beam by mixing sample and reference light in a nonlinear crystal
Implementation Method 2
distribute the lights for the nonlinear beam to be generated while phase components of the wavelength components, changed based on time and space, cancel each other out
Implementation Method 3
the detector functions to convert incident photons into a current
Data Source
AI summary
An optical tomography device includes a sample optical path system for injecting light, scanned from a light source, into a sample corresponding to biological tissue; a reference optical path system for collecting the light scanned from the light source; and a detection unit for detecting a tomography image of the sample by interfering with sample light, transmitted from the sample optical path system and reflected from the sample, and reference light transmitted from the reference optical path system. The detection unit comprises: a nonlinear crystal which receives the sample light and the reference light and generates nonlinear light having a different wavelength than the sample light and the reference light; and an image sensor which detects a depth direction signal from the nonlinear light.