VCSEL Self-Mixing Sensor With Frequency-to-Intensity Conversion
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Solution Overview
Problem
Existing self-mixing interferometric sensors face challenges in achieving improved signal quality and reliability for detecting the motion of a moving target, often requiring collimating optics and external photodiodes.
Innovation Solution
A self-mixing interferometric sensor with a VCSEL configured for undistorted and distorted operation modes, utilizing an optical element to convert frequency modulation into intensity modulation, enhancing signal strength and reliability by blocking undistorted radiation and splitting distorted radiation into multiple beams for detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-mixing interferometric sensors use traditional configurations with collimating optics and external photodiodes, then detection capability is maintained, but device complexity and signal quality are limited
Solution Approach 1:
The patent combines the VCSEL and photodiode into a single integrated sensor device, merging the light source and detector functions. The VCSEL emits laser radiation that reflects off the target and is detected by the integrated photodiode, eliminating the need for separate collimating optics and external photodiodes while improving signal quality through the self-mixing interferometric effect
Solution Approach 2:
The VCSEL serves multiple functions: it acts as both the light source for illumination and the detector for receiving reflected radiation. The single device performs both emission and detection tasks, reducing overall system complexity while enhancing signal quality through the interferometric self-mixing mechanism
2Reliability
If the VCSEL operates in distorted mode to detect target motion, then signal strength is improved, but frequency distortion occurs
Solution Approach 1:
The patent introduces an intermediary optical element (such as a diffraction grating or prism) that separates the distorted frequency components of the reflected radiation. This intermediary device redirects different frequency components to different spatial locations, allowing the photodiode to detect the frequency-modulated signal while the system can process the spatially separated components to recover accurate motion information
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 solution significantly improves signal quality and reliability for detecting target motion by converting frequency modulation into intensity modulation, allowing for enhanced detection without collimating optics and external photodiodes.
Implementation Method 1
Self-mixing interferometry is an interferometric technique, wherein electromagnetic radiation of an output beam emitted by a laser device such as a VCSEL, is reflected back into an optical cavity of the laser device, causing a modulation and/or variation of an amplitude and/or a frequency of the electromagnetic radiation of the output beam
Implementation Method 2
an optical element on or over one of the radiation transmission surfaces, the optical element transmits distorted electromagnetic radiation and blocks undistorted electromagnetic radiation
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A self-mixing interferometric sensor with the following features is provided: - a VCSEL (1) having two radiation transmission surfaces (6) and being configured for emitting undistorted electromagnetic radiation (13) of an undistorted frequency (v0) in an undistorted operation mode and configured for emitting distorted electromagnetic radiation (14) with a frequency variation in a distorted operation mode, and - an optical element (10) on or over one of the radiation transmission surfaces (6), wherein - the optical element (10) transmits distorted electromagnetic radiation (14) and blocks undistorted electromagnetic radiation (13), and/or - the optical element (10) splits passing distorted electromagnetic radiation (14) in at least two beams (14') dependent on the frequency. Further, a method for detecting a motion of a moving target is provided.