Optical Pulse Width Modulation for Proximity Sensing
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Solution Overview
Problem
Conventional optical sensing arrangements are bulky, expensive, and vulnerable to interference from ambient light noise, making them inefficient for detecting object movement and proximity.
Innovation Solution
A method using an optical reflection arrangement that transmits a train of pulses and evaluates movement or proximity characteristics by measuring the variation in pulse width between transmitted and reflected pulses, with optional modulation by a carrier frequency and adjustable beam spot size to mitigate interference and improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical sensing arrangements use an optical source and detector positioned on opposite sides of the object, then detection capability is achieved, but the device becomes bulky and expensive
Solution Approach 1:
The patent inverts the conventional optical sensing arrangement by using optical reflection instead of transmission. The optical source and detector are positioned on the same side, and the system detects objects by analyzing reflected light rather than transmitted light. This inversion simplifies the device structure, reduces size and cost, while maintaining detection capability through pulse width modulation analysis of reflected optical signals
Solution Approach 2:
The patent replaces complex mechanical positioning and alignment systems with an optical reflection-based detection method. By using pulse width modulation of reflected optical pulses, the system achieves accurate object detection without requiring precise mechanical alignment between source and detector, thereby reducing device complexity and cost
2Reliability
If conventional optical sensors monitor optical signals transmitted through objects, then movement detection is possible, but the system becomes vulnerable to interference from ambient light noise
Solution Approach 1:
The patent employs periodic modulation of the optical source at a specific frequency and uses pulse width modulation of reflected pulses. By detecting the modulated reflected signal at the known modulation frequency, the system can distinguish the transmitted signal from ambient light noise, thereby eliminating interference while maintaining movement detection capability
Solution Approach 2:
The system uses feedback by comparing the width of transmitted optical pulses with the width of reflected optical pulses. This pulse width comparison provides a reference-based detection method that is insensitive to ambient light levels, as the measurement is based on the temporal characteristics of the modulated signal rather than absolute intensity, thus rejecting ambient light interference
3Ease of operation
If optical pulses are transmitted at wider intervals to simplify detection, then detection mechanism becomes simpler, but detection speed decreases
Solution Approach 1:
The patent uses dynamic pulse width modulation where the width of each reflected optical pulse encodes movement information. This dynamic encoding allows the system to process information continuously at high speeds without requiring wide intervals between pulses, achieving both high detection speed and simplified detection mechanism through real-time pulse width analysis
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 results in a more compact and reliable optical sensing system capable of faster and simpler movement detection, reducing interference from background light and allowing for adjustable resolution and sensitivity.
Implementation Method 1
transmitting a train of optical pulses towards a destination, sensing optical pulses reflected from said destination
Implementation Method 2
An optical detector is positioned on the other side of the object to monitor the detection or reception of optical signals
Data Source
AI summary
A method of sensing movement or proximity of objects by optical reflection is provided. The method includes the steps of transmitting a train of optical pulses towards a destination, sensing optical pulses reflected from the destination, and sensing and evaluating movement or proximity characteristics of objects at the destination with reference to variation in pulse width between transmitted and reflected optical pulses.