Pyroelectric Presence Sensing for Reliable Mobile Switch Actuation
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Solution Overview
Problem
Existing gesture recognition systems for mobile devices face challenges in accurately detecting the presence of a human head, particularly under varying lighting conditions and with different hairstyles or headgear, leading to potential errors in activating or deactivating device functions.
Innovation Solution
A switch actuation device utilizing a presence sensor with pyroelectric pixels made of lead zirconate titanate to detect heat emitted by a human head, featuring an approach and removal phase detection mechanism, which ensures reliable and error-free operation with low power consumption and miniaturized design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical detection is used to detect the presence of a human head, then the gesture recognition device can detect whether the mobile phone is being held to a person's head, but the detection accuracy is affected by lighting conditions, hairstyles, and headgear
Solution Approach 1:
The patent replaces the optical detection system with a thermal detection system using pyroelectric sensors. Instead of detecting reflected light that is affected by lighting conditions, hairstyles, and headgear, the system detects infrared radiation (heat) emitted by the human head. This substitution of detection mechanism eliminates the harmful environmental factors that affect optical detection, as thermal detection is not influenced by visible light conditions or physical characteristics of the head.
Solution Approach 2:
The patent changes the detection parameter from optical properties (reflected light) to thermal properties (infrared radiation). By measuring temperature-related parameters instead of light intensity, the system achieves more reliable detection that is independent of lighting conditions, hairstyles, and headgear, thereby improving measurement precision while reducing environmental interference.
2Measurement precision
If a presence sensor with pyroelectric pixels is used to detect heat emitted by a human head, then detection accuracy is improved and environmental interference is minimized, but the device complexity increases
Solution Approach 1:
The patent extracts and utilizes only the relevant thermal signal from the pyroelectric pixels, focusing on the characteristic temperature rise pattern when a head approaches. By isolating and evaluating only the essential detection function (detecting the thermal signature of a approaching head), the system achieves high detection accuracy without requiring complex additional components or processing systems.
Solution Approach 2:
The pyroelectric pixels inherently generate electrical signals in response to thermal radiation changes, eliminating the need for external illumination sources or complex signal generation systems. The sensor material itself provides the detection mechanism through its pyroelectric properties, simplifying the overall device structure while maintaining high detection precision.
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 provides accurate and reliable detection of a human head, minimizing errors caused by environmental interference and hairstyle variations, ensuring safe and efficient operation of mobile device functions with low energy consumption.
Implementation Method 1
at least one pixel having a thin film made of pyroelectric material and a signal per pixel with signal deflections corresponding to the temporal intensity profile of the heat detected by the pixel
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a switch-actuating apparatus (100) having a presence sensor (1) for actuating a switch (103) by means of the presence of a heat-emitting part (115) at the presence sensor (1), wherein the presence is composed of an approach phase (31), in which the part (115) approaches the presence sensor (1), a waiting phase (44), in which the part (115) remains near the presence sensor (1), and a removal phase (41), in which the part (115) is to be moved away from the presence sensor (1), wherein the presence sensor (1) is designed to detect heat emitted by the part (115) by means of at least one pixel (21 to 24) having a thin film made of pyroelectric material and to output one signal (51 to 54) per pixel (2 to 24), said signal having signal swings (56, 57) corresponding to the intensity curve over time of the heat detected by the pixel (21 to 24), a signal-evaluating unit (101), by means of which the approach phase (31) and the removal phase (41) can be determined from the succession over time and the form of the signal swings (56, 57), and an actuator (104), which is controlled by the signal-evaluating unit (101) and actuates the switch (103) as soon as the approach phase (31), the waiting phase (44), or the removal phase (41) is determined.