Adaptive Proximity Sensing With Detect-Release Mode Switching
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Solution Overview
Problem
Proximity detection systems in mobile devices face reliability issues due to optical noise from sources like grid mains flicker and shot noise in high ambient light conditions, especially when the sensor is located behind the display, leading to increased false detection events.
Innovation Solution
A proximity detection system with infrared emitter and detector, utilizing a signal processing subsystem that switches between detect and release modes by adjusting optical energy output and signal gain, and implementing programmable thresholds and crosstalk calibration to enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the proximity sensor is placed behind the display, then aesthetic appearance is improved (reduced or removed notch), but detection reliability deteriorates due to optical noise and signal attenuation
Solution Approach 1:
The patent applies dynamics by switching between two operational modes: detect mode with higher optical energy for reliable target detection, and release mode with lower optical energy to reduce noise. This dynamic adjustment of emitter power based on operational state resolves the contradiction between maintaining detection reliability and reducing optical noise when the sensor is behind the display
Solution Approach 2:
The patent changes key parameters including optical energy output (reducing by at least 20% in release mode), integration period duration, and signal processing gain. These parameter changes allow the system to adapt to the attenuated and noisy signal conditions when the sensor is positioned behind the display, maintaining reliability while preserving aesthetic appearance
2Reliability
If optical energy output is reduced in release mode, then false detection events are reduced, but detection sensitivity may deteriorate
Solution Approach 1:
The system dynamically adjusts optical energy output based on operational mode - using higher power in detect mode for sensitive detection and lower power in release mode to reduce false detections. This temporal separation of detection requirements resolves the contradiction between sensitivity and false detection rate
Solution Approach 2:
The system employs periodic switching between detect and release modes, with each mode optimized for its specific function. The detect mode prioritizes sensitivity with higher optical energy, while the release mode prioritizes noise reduction with lower optical energy, achieving both requirements through periodic operation
3Speed
If integration period is shortened, then response speed is improved, but shot noise increases in high ambient light conditions
Solution Approach 1:
The patent dynamically adjusts the integration period based on ambient light conditions and operational mode. In high ambient light conditions or release mode, longer integration periods are used to reduce shot noise, while in detect mode or low light conditions, shorter integration periods provide faster response. This dynamic adjustment resolves the contradiction between response speed and shot noise
Solution Approach 2:
The system changes the integration period parameter adaptively - extending it when shot noise is problematic (high ambient light, release mode) and shortening it when fast response is needed (detect mode, low ambient light). This parameter change strategy resolves the trade-off between response speed and noise reduction
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 system reduces false detection events by increasing the difference between detection and release thresholds, thereby improving the signal-to-noise ratio and maintaining accuracy in high ambient light conditions, particularly when the sensor is behind a display.
Implementation Method 1
an infrared emitter to emit infrared light
Implementation Method 2
an infrared detector to detect the infrared light after reflection from a target
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
A proximity detection system for a mobile device. The system comprises an infrared emitter (106) to emit infrared light, an infrared detector (108) to detect the infrared light after reflection from a target and provide a detector signal; and a signal processing subsystem (110). The signal processing subsystem is configured to control the proximity detection system into a first, detect mode for detecting proximity of the target as the target approaches the mobile device, and after detection of the target to control the proximity detection system into a second, release mode for detecting movement of the target out of proximity to the mobile device. The signal processing subsystem also controls the proximity detection system such that, contrary to conventional hysteresis, for a given proximity of the target the detector signal reduces when the mode switches from the detect mode to the release mode, thus increasing reliability.