Proximity Sensor Circuit for Disturbance Light Rejection
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Solution Overview
Problem
Conventional proximity sensors face decreased detection precision due to the influence of disturbance light, such as ambient light, in reflected light.
Innovation Solution
A proximity sensor design incorporating a converter circuit, differential converter circuit, and correlated double sampling circuit to convert current output from a photodetector into voltage, and subtract differential voltage values sampled at different phases of a light emission pulse, reducing the impact of disturbance light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional reflected light sensing is used, then object detection is achieved, but detection precision decreases due to disturbance light influence
Solution Approach 1:
The patent applies periodic action by emitting light in pulsed manner rather than continuous illumination. The light emission unit emits light pulses at specific intervals, and the control unit measures reflected light intensity during the pulse duration. This periodic illumination separates the measurement signal from ambient disturbance light, allowing precise detection of object proximity by comparing reflected light intensity during active illumination periods versus ambient light periods.
Solution Approach 2:
The patent implements feedback through the control unit that continuously monitors reflected light intensity and compares it against reference values. The control unit adjusts measurements based on the detected light intensity variations, using the reflected light signal feedback to determine object proximity. This feedback mechanism enables the system to distinguish between disturbance light and actual reflected light from the object, maintaining high detection precision.
2Reliability
If ambient light is included in reflected light sensing, then continuous detection is possible, but detection accuracy deteriorates
Solution Approach 1:
The patent applies the extraction principle by separating the measurement of reflected light from ambient light through temporal gating. The control unit extracts only the reflected light component by measuring during the light pulse emission window, excluding ambient light that occurs outside this window. This extraction of the useful signal from the total light input eliminates ambient light interference while maintaining reliable detection 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
Enhances detection precision of object proximity by minimizing the effect of disturbance light, improving the accuracy of proximity detection.
Implementation Method 1
a photodetector sensing the reflected light
Data Source
AI summary
A proximity sensor for detecting proximity of an object, by sensing reflected light coming from an object on which a light emission pulse is reflected, the proximity sensor includes: a converter circuit configured to convert a current output from a photodetector sensing the reflected light into a voltage, and to output the voltage, magnitude of the current depending on a degree of the proximity of the object; a differential converter circuit configured to convert the voltage output by the converter circuit into a differential voltage, and to output the differential voltage; and a correlated double sampling circuit having a differential configuration, and configured to subtract a value of the differential voltage output by the differential converter circuit, sampled at falling of the light emission pulse, from a value of the differential voltage sampled at rising of the light emission pulse.