Balanced Detection Optical Path Length Adjustment for OCT S/N Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical tomographic image production systems face challenges in maintaining a high Signal-to-Noise (S/N) ratio due to uneven optical path lengths and light amounts in balanced detection during Fourier Domain OCT measurements, leading to reduced image quality.
Innovation Solution
A system that includes a light source with periodically swept wavelengths, light division and combination means, optical path length adjustment for equalizing interference light paths, and light amount adjustment across wavelength bands to ensure balanced detection, thereby improving the S/N ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If balanced detection is performed by splitting interference light into two paths, then the S/N ratio is improved through noise cancellation, but the optical path lengths of the two interference light paths become uneven, causing degradation in detection accuracy
Solution Approach 1:
The patent applies preliminary action by adjusting the optical path lengths of the first and second interference lights to be equal before performing balanced detection. This pre-adjustment ensures that when the interference lights are combined after detection, their optical path lengths are already matched, enabling effective noise cancellation and improving the S/N ratio without compromising measurement precision
2Productivity
If high-speed FD-OCT measurement is performed without mechanical scan, then measurement speed is improved, but the S/N ratio deteriorates due to inability to perform traditional balanced detection
Solution Approach 1:
The patent applies dynamics by enabling balanced detection in the temporal domain for swept-source OCT without mechanical scanning. The system dynamically processes the interference signals from the two detection paths, adjusting and combining them to achieve noise cancellation while maintaining high measurement speed characteristic of FD-OCT methods
Solution Approach 2:
The patent uses an intermediary approach by introducing a detection system that separates interference light into two paths, detects them independently, and then combines the signals. This intermediary detection and combination process enables balanced detection functionality in high-speed FD-OCT measurements, improving the S/N ratio while maintaining measurement speed
3Measurement precision
If optical path length adjustment is performed to equalize interference light paths, then detection accuracy is improved, but device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The patent applies parameter changes by adjusting the optical path length parameter of the interference lights to achieve equality between the first and second paths. By controlling this critical parameter, the system improves detection accuracy and enables effective balanced detection without requiring complex mechanical adjustment mechanisms
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 system effectively adjusts optical path lengths and light amounts to enhance the S/N ratio, resulting in improved image quality and reliability of tomographic images produced by optical tomography.
Implementation Method 1
a light source unit that outputs light, the wavelength of which is periodically swept
Implementation Method 2
low coherent light that has been output from a light source is divided into measurement light and reference light. Then, a measurement target is irradiated with the measurement light, and reflection light that is reflected from the measurement target or backscattered light is combined with the reference light. Further, an optical tomographic image is obtained based on the intensity of interference light between the reflection light and the reference light
Implementation Method 3
reflection light that is reflected from the measurement target or backscattered light is combined with the reference light. Further, an optical tomographic image is obtained based on the intensity of interference light between the reflection light and the reference light
Implementation Method 4
an optical fiber coupler or the like is used, and interference light is split into two so that the light amounts of the split interference light are substantially equal to each other
Implementation Method 5
each of the split interference light is detected by a detector, and a difference between detected signals is detected as an interference signal (balanced detection), as disclosed in Japanese Unexamined Patent Publication No. 2001-264246. According to the method, the interference signal is amplified to twice the value thereof, and same-phase optical noise, other than the interference signals, is cancelled. Hence, the non-interference components are removed, and the S/N ratio is improved
Implementation Method 6
an interference-light optical path length adjustment means that adjusts the optical path length of at least one of the first interference light and the second interference light, which have been obtained by splitting the interference light at the light splitting means, so that the optical path length of the first interference light and that of the second interference light become the same
Data Source
AI summary
In optical tomography measurement using light, the wavelength of which is periodically swept, interference light between reflection light and reference light is split into first interference light and second interference light by a light splitting means. The optical path length of the first interference light and that of the second interference light are adjusted by an interference-light optical path length adjustment means so that they become the same. Further, balanced detection is performed on the first interference light and the second interference light by an interference light detection means.