Dual-VCSEL Proximity Sensing With Reference-Path Calibration
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Solution Overview
Problem
Conventional proximity sensors are highly susceptible to temperature changes, leading to variations in electrical and optical properties due to thermal expansion or contraction, which increases design complexity, component cost, and power consumption, and requires additional compensation systems.
Innovation Solution
An optical proximity sensor using two discrete vertical cavity surface-emitting lasers (VCSELs) for self-mixing interferometry, where one VCSEL illuminates an object to determine distance and velocity, and another VCSEL illuminates a fixed internal surface to calibrate measurements, making them independent of temperature and environmental effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional proximity sensors are used, then distance measurement function is provided, but measurement precision deteriorates due to temperature changes
Solution Approach 1:
The patent implements a feedback mechanism where the second VCSEL continuously monitors the optical path length to a fixed internal surface and provides real-time calibration data. This feedback loop compensates for temperature-induced drift in the first VCSEL's measurements, maintaining measurement precision across varying thermal conditions without requiring additional compensation systems.
Solution Approach 2:
The patent utilizes parameter changes by monitoring the optical path length variations in the second VCSEL's fixed reference path. These parameter changes, caused by thermal expansion or contraction, are used to dynamically adjust and calibrate the measurement parameters of the first VCSEL, thereby compensating for temperature effects on measurement accuracy.
2Measurement precision
If additional temperature compensation components are added, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the calibration function into the existing sensor system by integrating a second VCSEL that serves dual purposes: it provides reference measurements for temperature compensation while sharing the same optical detection infrastructure as the first VCSEL. This consolidation achieves temperature compensation without requiring separate compensation systems, thus avoiding increased device complexity.
Solution Approach 2:
The second VCSEL is designed with multi-functionality, serving as both a reference measurement source for temperature calibration and as part of the overall optical sensing system. This universal component performs multiple functions within the sensor, providing temperature compensation while maintaining system simplicity and avoiding the need for dedicated compensation hardware.
3Reliability
If additional compensation systems are incorporated, then measurement reliability improves, but power consumption increases
Solution Approach 1:
The patent implements self-service by enabling the sensor system to automatically calibrate itself using the second VCSEL's reference measurements. The system autonomously detects and compensates for temperature-induced drift without requiring external compensation systems or additional power-intensive components, thereby maintaining measurement reliability while minimizing power consumption.
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 reduces variability due to environmental conditions, providing accurate and reliable distance and velocity measurements by leveraging self-mixing interferometry to calibrate measurements in real-time.
Implementation Method 1
Both vertical cavity surface-emitting lasers are configured for self-mixing interferometry. The first vertical cavity surface-emitting laser is configured to illuminate an object to determine a distance to and/or a velocity of that object based on self-mixing interferometry.
Data Source
AI summary
An optical proximity sensor includes a first vertical cavity surface-emitting laser configured for self-mixing interferometry to determine distance to and/or velocity of an object. The optical proximity sensor also includes a second vertical cavity surface-emitting laser configured for self-mixing interferometry to determine whether any variation in a fixed distance has occurred. The optical proximity sensor leverages output from the second vertical cavity surface-emitting laser to calibrate output from the second vertical cavity surface-emitting laser to eliminate and/or mitigate environmental effects, such as temperature changes.