Optical Proximity Sensor Phase Shift Distance Measurement
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Solution Overview
Problem
Existing optical proximity sensors, particularly those using time-domain and frequency-domain reflectometry, face challenges in providing low-cost, high-resolution measurements over short distances due to the need for expensive electronics, complex instrumentation, and sensitivity to environmental light conditions, making them unsuitable for low-cost applications in confined spaces.
Innovation Solution
An optical proximity sensor utilizing a solid-state device that functions as both a light emitter and detector, integrated with a driver circuit and signal conditioning components, which emits a modulated optical signal and calculates distance based on phase difference, eliminating the need for mechanical alignment and calibration, and is designed for low-cost, compact, and simplified implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-domain reflectometry is used for distance measurement, then distance resolution can be achieved, but expensive broadband electronics and bulky instrumentation are required
Solution Approach 1:
The patent replaces complex electronic timing systems with a solid-state photonic system. The emitter/detector device uses optical modulation and detection rather than electrical pulse timing, substituting electronic measurement mechanisms with optical ones. This eliminates the need for expensive broadband electronics while maintaining distance measurement capability through phase difference detection of optical signals.
Solution Approach 2:
The patent changes the measurement parameter from direct time-of-flight (requiring picosecond timing resolution) to phase difference of modulated optical signals. By modulating the optical signal at a specific frequency and measuring the phase shift of the reflected signal, the system achieves distance resolution without requiring ultrafast electronic timing circuits, thus reducing device complexity.
2Measurement precision
If frequency-domain reflectometry is used for distance measurement, then phase shift can be determined, but accurate mechanical alignment and temperature calibration are required
Solution Approach 1:
The patent merges the functions of light emitter and light detector into a single solid-state device. This integration eliminates the need for separate alignment procedures between independent emitter and detector components. The unified device structure inherently maintains optical path alignment, removing the complex mechanical alignment requirements present in traditional frequency-domain reflectometry systems.
Solution Approach 2:
The solid-state emitter/detector device performs self-alignment through its integrated structure. The optical path is inherently stable because the emitter and detector are co-located within the same device, eliminating the need for external alignment mechanisms or procedures. The device automatically maintains optimal optical coupling without requiring operator intervention for alignment or temperature calibration.
3Measurement precision
If conventional optical sensors are used, then distance measurement is possible, but sensitivity to environmental light conditions affects measurement accuracy
Solution Approach 1:
The patent employs periodic modulation of the optical signal at a specific frequency. By modulating the emitted light and detecting the phase of the modulated reflected signal, the system can distinguish the emitted signal from ambient environmental light. The periodic modulation creates a frequency signature that filters out unmodulated background light, eliminating sensitivity to environmental lighting conditions while maintaining measurement accuracy.
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 enables low-cost, high-resolution distance measurements over short ranges with improved accuracy and reduced complexity, independence from light intensity, and eliminates the need for temperature calibration, making it suitable for various applications including automation and IoT devices.
Implementation Method 1
a solid-state emitter/detector device configured to operate both as a light emitter and as a light detector
Implementation Method 2
measuring a phase difference between the modulated optical signal emitted by the emitter/detector device and a modulated optical signal received at the emitter/detector device as a result of reflection of the modulated optical signal emitted by the emitter/detector device at the target object
Data Source
AI summary
An optical proximity sensor comprises a solid-state photo-electric converter, a biasing circuit for biasing the solid-state photo-electric converter, and a drive circuit. The drive circuit is configured to control the biasing circuit to apply to the photo-electric converter a bias signal modulated between a first value and a second value, the second value different from the first value, wherein a modulated optical signal is emitted by the solid-state photo-electric converter towards a target object. The drive circuit is configured to receive an electrical output signal from the solid-state photo-electric converter, the electrical output signal being a function of a modulated optical signal received at the solid-state photo-electric converter as a result of reflection of the emitted modulated optical signal at the target object. The drive circuit is configured to perform a phase comparison of the modulated bias signal against the electrical output signal and produce, as a result of the phase comparison, a phase shift signal. The drive circuit is configured to compute a distance between the optical proximity sensor and the target object as a function of the phase shift signal.