VCSEL Sweep Control for Whole-Eye OCT Coherence and Speed
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor-laser-diode-based SS-interferometer systems face challenges in achieving high coherence length and repetition rate over a wide wavelength range, limiting their suitability for whole-eye scans in biometric measurements, particularly in ophthalmological applications.
Innovation Solution
The system employs single-mode VCSEL laser diodes with optimized parameters such as center wavelength (600-1400 nm), sweep rate (100 Hz-100 kHz), sweep range (3-75 nm), and optical power (50-20 000 μW) to enable highly coherent spectral laser lines with a high repetition rate, using periodic current modulation and temperature management to enhance wavelength tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex MEMS laser diode systems are used to achieve high coherence length and wide wavelength tuning range, then imaging resolution and measurement depth are improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent changes the operating parameters of VCSEL laser diodes by applying periodic current modulation instead of using complex MEMS systems. This approach achieves wavelength tuning across a wide range (600-1400 nm) with high coherence length by modulating the current at specific frequencies, thereby resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces mechanical MEMS tuning systems with an electrical current modulation approach. By using periodic current modulation to tune the VCSEL wavelength, the system eliminates complex mechanical components while maintaining high imaging resolution and wide wavelength tuning capability
2Speed
If high sweep rates (10-100 kHz) are used to preclude motion artifacts, then measurement speed is improved, but coherence length decreases limiting measurement depth
Solution Approach 1:
The patent dynamically adjusts the current modulation parameters to achieve optimal performance. By carefully controlling the amplitude and frequency of periodic current modulation, the system maintains high sweep rates for motion artifact prevention while preserving sufficient coherence length for deep tissue imaging, resolving the contradiction between speed and measurement depth
3Measurement precision
If wide wavelength tuning range (25-75 nm) is achieved at 1300 nm, then axial resolution is improved, but absorption in vitreous body increases reducing signal quality
Solution Approach 1:
The patent optimizes the wavelength tuning parameters by selecting appropriate center wavelengths (600-1400 nm) and sweep ranges. The periodic current modulation is configured to achieve sufficient axial resolution while selecting wavelength ranges that minimize vitreous body absorption, thereby resolving the contradiction between measurement precision and signal quality
4Ease of operation
If VCSEL laser diodes are operated thermoelectrically in temperature range 10-40°C, then ease of operation is improved, but wavelength stability decreases
Solution Approach 1:
The patent implements feedback control through periodic current modulation to compensate for temperature-induced wavelength drift. By monitoring and actively adjusting the current modulation parameters, the system maintains wavelength stability across the operating temperature range while preserving ease of operation, resolving the contradiction between operational simplicity and wavelength stability
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 allows for reliable biometric measurements of the entire eye, including myopic eyes, with improved signal/noise ratio and reduced motion artifacts, suitable for ophthalmological diagnostics and surgical interventions.
Implementation Method 1
semiconductor-laser-diode-based SS-interferometer system... highly coherent spectral laser line
Implementation Method 2
periodic current modulation... wavelength range... temperature management to enhance wavelength tuning
Implementation Method 3
periodic current modulation... sweep rate... sweep range
Implementation Method 4
interferometer system... superposed light paths... stable interference pattern
Implementation Method 5
changes in refractive index for measuring material properties... changes in refractive index occurring at optical interfaces
Implementation Method 6
single-mode VCSEL laser diodes... highly coherent spectral laser line
Data Source
AI summary
A method of controlling a semiconductor-laser-diode-based SS-interferometer system (SS=swept source), for a wide range of application suitable for use in ophthalmology, for example for imaging and for determining biometric measurement values of the eye. In a method according to the invention, by application of periodic current modulation, the operation of single semiconductor laser diode is designed such that a highly coherent spectral laser line can be adjusted with a highest possible repetition rate over a wide wavelength range. The parameters: center wavelength, sweep rate, sweep range, optical power in the eye and coherence length are adjusted such that the method is suitable for imaging and biometric applications via whole-eye scans. A semiconductor-laser-diode-based SS-interferometer system is provided, for biometric measuring of the eye. Embodiments are based for example on optical, coherence tomographic scan images. Applications lie in ophthalmological diagnostics, treatment and the preparation of surgical procedures and follow-up thereof.