Optical Reflectance Proximity Sensing With Ambient Light Cancellation
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Solution Overview
Problem
Existing optical reflectance proximity sensors are expensive, bulky, and consume high power, making them unsuitable for consumer applications, and they often suffer from spurious triggering and failure to detect radiation-neutral objects due to reliability issues and high cost.
Innovation Solution
A low-cost, small, and low-power optical reflectance proximity sensor design that includes wavelength transmitting and receiving diodes, an ambient correction circuit, and a comparator circuit to detect proximity with improved sensitivity and reliability, capable of operating without a microprocessor and using minimal power, and can provide analog output without a digital-to-analog converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optical reflectance proximity sensors are used, then proximity detection capability is achieved, but cost, size, and power consumption increase making them unsuitable for consumer applications
Solution Approach 1:
The patent combines the transmitting diode and receiving diode into a single integrated sensor unit with shared optical path and electronic components. The ambient correction circuit and comparator circuit are integrated onto the same substrate, reducing overall device complexity and cost while maintaining reliable proximity detection through coordinated operation of merged components
Solution Approach 2:
The sensor design uses universal components that serve multiple functions: the transmitting diode emits light for proximity detection while the receiving diode detects both reflected light and ambient light. The ambient correction circuit processes both types of signals to eliminate false triggering, making the system versatile for various consumer applications with unified hardware
2Reliability
If traditional optical reflectance proximity sensors are used, then proximity sensing is achieved, but power consumption is high
Solution Approach 1:
The patent implements periodic modulation of the transmitting diode at a specific frequency and uses synchronous detection in the comparator circuit. This periodic action allows the sensor to distinguish between modulated reflected light signals and continuous ambient light, improving detection accuracy while reducing average power consumption through pulsed operation rather than continuous illumination
Solution Approach 2:
The sensor operates by changing the modulation frequency parameter of the transmitting diode and adjusting the detection threshold parameter in the comparator circuit. These parameter changes enable the system to maintain high detection accuracy across varying ambient conditions while optimizing power consumption by adapting the operating parameters to the specific detection requirements
3Ease of manufacture
If simple proximity sensors are used, then cost is reduced, but spurious triggering and failure to detect radiation-neutral objects occur
Solution Approach 1:
The patent extracts and separately processes the ambient light component from the total light signal received by the receiving diode. The ambient correction circuit measures ambient light levels during periods when the transmitting diode is inactive and subtracts this extracted ambient component from the total signal, eliminating spurious triggering caused by ambient light while maintaining the ability to detect genuine proximity signals at low cost
Solution Approach 2:
The comparator circuit acts as an intermediary between the receiving diode and the output signal. It introduces a reference threshold level that mediates the comparison between the processed signal and ambient baseline, filtering out false triggers while allowing genuine proximity detections to pass through. This intermediary processing stage significantly improves triggering accuracy without adding substantial cost to the manufacturing process
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 sensor achieves high sensitivity and reliability in detecting proximity with reduced noise interference, enabling its use in consumer applications with improved power efficiency and cost-effectiveness, and can interface with microprocessors for more complex applications.
Implementation Method 1
one or more wavelength transmitting diodes
Implementation Method 2
one or more wavelength receiving diodes
Data Source
AI summary
A method for calibrating an optical reflectance proximity sensor and then measuring proximity in a repeating cycle or on demand, the sensor including one or more wavelength transmitting diodes, one or more wavelength receiving diodes, an ambient correction circuit, and a comparator circuit, and further teaching steps for powering on the sensor, canceling the ambient signal during a calibration period, transmitting wavelengths to and receiving reflectance from an object in the path of the transmitted wavelengths, and measuring a reflectance pulse width and comparing the value to a preset value to determine proximity.