VCSEL Swept-Source Interferometer Control for Whole-Eye Scans
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Solution Overview
Problem
Existing semiconductor laser diode-based swept source interferometer systems face challenges in achieving high coherence length, wide wavelength tuning range, and high repetition rates, making them unsuitable for whole-eye biometric measurements due to limitations in sensitivity and resolution.
Innovation Solution
The method involves controlling semiconductor laser diodes using periodic current modulation to tune a highly coherent spectral laser line with the highest possible repetition rate and wide wavelength range, optimizing parameters such as center wavelength, sweep rate, sweep range, optical power, and coherence length, using single-mode VCSEL laser diodes with active semiconductor materials and thermal management.
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 range, then imaging resolution and measurement depth are improved, but device complexity and cost increase
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 the required coherence length and wavelength tuning range through electrical parameter control, simplifying the device architecture while maintaining measurement precision
Solution Approach 2:
The patent replaces mechanical MEMS tuning systems with electrical current modulation of VCSEL diodes. This substitution eliminates moving parts and mechanical complexity while achieving the same spectral tuning function through electrical control, thereby reducing device complexity
2Reliability
If high sweep rates of 10-100 kHz are used to exclude motion artifacts, then measurement reliability is improved, but the laser sweep range is insufficient to achieve required resolution
Solution Approach 1:
The patent applies periodic current modulation to the VCSEL laser diode at sweep rates of 10-100 kHz to exclude motion artifacts. This periodic excitation achieves both high measurement reliability and sufficient wavelength sweep range by optimizing the modulation parameters
Solution Approach 2:
The patent dynamically adjusts the current modulation parameters including sweep rate, amplitude, and waveform to simultaneously achieve high measurement reliability through fast scanning and sufficient wavelength range for required resolution
3Productivity
If VCSEL laser diodes are tuned over wide wavelength range with high repetition rate, then productivity and measurement speed are improved, but coherence length decreases
Solution Approach 1:
The patent optimizes the current modulation parameters including amplitude, frequency, and waveform shape to achieve the right balance between sweep speed and coherence length maintenance. By carefully controlling the modulation depth and rate, both productivity and coherence requirements are satisfied
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 high-resolution, whole-eye scans with improved sensitivity and reduced eye movement artifacts, meeting the requirements for biometric measurements while adhering to laser safety regulations.
Implementation Method 1
a semiconductor laser diode (1) with a control unit (2), wherein the control unit (2) is designed to control an operation of the semiconductor laser diode (1) by means of periodic current modulation so that a highly coherent spectral laser line can be tuned
Implementation Method 2
An interferometer is a technical optical device that uses interference for precision measurements. It measures all effects that change the effective path length of the waves and thus the properties of the superimposed wave
Implementation Method 3
the control unit (2) is designed to control an operation of the semiconductor laser diode (1) by means of periodic current modulation so that a highly coherent spectral laser line can be tuned
Data Source
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AI summary
The invention relates to a method for controlling a semiconductor-laser-diode-based SS-interferometer system (SS = swept source), which allows for a wide range of application and is suitable for use in ophthalmology, in particular for imaging and for determining biometric measurement values of the eye. In the method according to the invention, by means of periodic current modulation, the operation of single semiconductor laser diodes is designed such that a highly coherent spectral laser line can be adjusted with a highest possible repetition rate and over a wide wavelength range. In addition, the following parameters: centre 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. The proposed semiconductor-laser-diode-based SS-interferometer system is provided, in particular, for biometric measuring of the eye. Given that the embodiments are based preferably on optical, coherence tomographic scan images, the main application lies in opthalmological diagnostics, treatment and the preparation of surgical procedures and follow-up thereof.