Self-Mixing Laser Optical Input Device for Two-Dimensional Movement Measurement
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Solution Overview
Problem
Existing input devices require additional sensors to measure movement along the Z-direction, increasing complexity and cost, while existing methods struggle to accurately determine movement and distance between an object and input device along two measuring axes using a single self-mixing laser and radiation-sensitive detector.
Innovation Solution
A method and device that utilize a single self-mixing laser and detector to measure movement and distance along two axes by summing offset frequencies from rising and falling portions of the measurement signal, allowing for the determination of speed and direction of movement in the action plane and compensating for Z-axis movement when the input device is lifted from the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional sensors (third diode laser and photo diode) are added to measure Z-direction movement, then measurement capability along three axes is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing two-dimensional sensor (comprising two diode lasers and two photo diodes) perform three-dimensional measurement by enabling it to detect Z-direction movement in addition to its原有 X and Y direction measurement capability, through signal processing that extracts Z-axis information from the existing sensor outputs
Solution Approach 2:
The patent combines the measurement functions for three axes into a single sensor unit by processing the interference signals from the existing two diode lasers and two photo diodes to extract both two-dimensional position information and Z-direction distance information, thereby integrating three-axis measurement capability without adding a third laser-diode pair
2Adaptability or versatility
If additional sensors (third diode laser and photo diode) are added to measure Z-direction movement, then measurement capability along three axes is improved, but cost increases
Solution Approach 1:
The patent makes the existing two-dimensional sensor (comprising two diode lasers and two photo diodes) perform three-dimensional measurement by enabling it to detect Z-direction movement in addition to its原有 X and Y direction measurement capability, through signal processing that extracts Z-axis information from the existing sensor outputs
Solution Approach 2:
The patent combines the measurement functions for three axes into a single sensor unit by processing the interference signals from the existing two diode lasers and two photo diodes to extract both two-dimensional position information and Z-direction distance information, thereby integrating three-axis measurement capability without adding a third laser-diode pair
3Device complexity
If a single self-mixing laser is used to measure movement along two axes, then device complexity is reduced, but measurement precision along transverse axis becomes difficult to achieve
Solution Approach 1:
The patent enables the single self-mixing laser and two-photo-diode arrangement to perform both two-dimensional position measurement and one-dimensional distance measurement by processing the interference signals to extract multiple measurement parameters, achieving multi-functional measurement with minimal hardware
Solution Approach 2:
The patent measures Z-direction distance by analyzing the amplitude or phase characteristics of the interference signal, effectively adding a third measurement dimension through signal processing rather than through physical spatial arrangement, thereby achieving three-axis measurement capability from a two-dimensional sensor configuration
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
Enables accurate measurement of relative movement and distance along two axes using a single laser, reducing complexity and cost, and providing more accurate determination of movement and distance by using the difference and sum of offset frequencies, effectively suppressing unwanted Z-axis measurements in the X-Y plane.
Implementation Method 1
measuring changes in operation of the laser cavity, said changes being due to laser self-mixing interference of measuring beam radiation re-entering said laser cavity and an optical wave in said laser cavity
Data Source
Figure 1a~1b
Figure 2~4
Figure 5~6
AI summary
An optical input device for measuring relative movement between an object (15) and a sensor unit comprising a laser device (3, 5) having a laser cavity for emitting a measuring beam (13, 17) and a respective radiation-sensitive detector (4, 6) for generating a measurement signal representative of changes in the operation of the laser device (3, 5) as a result of measuring beam radiation re-entering the laser cavity. A sensor unit is provided for measuring relative movement along each measuring axis in an action plane, and the resultant measurement signal from one or each of the sensor units is used to determine distance and/or movement of the input device and the object (15) relative to each other along a measuring axis transverse to the action plane by summing the offset frequency of a rising and falling slope of the measurement signal.