Proximity Sensing Device Self-Calibration Circuit
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Solution Overview
Problem
Conventional optical sensing devices in smartphones lack self-calibration functions, leading to incorrect distance calculations due to crosstalk noise from second reflective light and ambient light, which interferes with the ability to automatically switch off the touch screen when the phone is brought close to the user's ear.
Innovation Solution
A novel proximity sensing device with self-calibration capabilities, comprising a driving module, lighting element, light receiving module, conversion module, judge circuit, synchronous sequential module, analog front-end module, and analog-to-digital converter, utilizing a signal-amplifying MOSFET, current mirror circuit, cascode MOSFET pairs, and current-to-voltage converting resistor to eliminate noise and accurately determine object proximity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ambient light sensor and proximity sensor are integrated to a single optical sensing module, then device complexity is reduced and space is saved, but measurement precision deteriorates due to crosstalk noise from second reflective light and ambient light interference
Solution Approach 1:
The patent divides the light receiving process into two separate modules: a first light receiving module for receiving reflective light from external objects, and a second light receiving module for receiving ambient light. This segmentation allows independent processing of different light sources, eliminating crosstalk noise and improving measurement precision while maintaining integration benefits.
2Device complexity
If conventional optical sensing devices are used without self-calibration function, then device complexity is reduced, but measurement precision deteriorates due to inability to eliminate crosstalk noise and ambient light interference
Solution Approach 1:
The patent implements a self-calibration function that performs preliminary calibration by measuring and storing ambient light levels before proximity detection. This preliminary action eliminates the need for external calibration equipment and ensures accurate proximity detection by compensating for ambient light interference in advance.
Solution Approach 2:
The patent employs feedback mechanisms where the second light receiving module continuously monitors ambient light levels and feeds this information back to the control unit. The control unit uses this feedback to adjust measurements from the first light receiving module, thereby eliminating crosstalk noise and improving measurement precision dynamically.
3Device complexity
If light receiving element simultaneously receives reflective light and ambient light, then device complexity is reduced, but measurement precision deteriorates due to noise interference in distance calculation
Solution Approach 1:
The patent segments the light receiving function into two distinct modules: the first light receiving module dedicated to receiving reflective light for proximity detection, and the second light receiving module dedicated to receiving ambient light for calibration purposes. This segmentation prevents signal mixing and enables precise distance measurement by processing each light source independently.
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 effectively calibrates noise sources, ensuring accurate proximity detection and enabling reliable automatic touch screen switching off by distinguishing reflective and ambient light signals, thereby enhancing the precision of proximity sensing in smartphones.
Implementation Method 1
controlling and processing unit would drive the lighting element 22′ to emit an object-detecting light to an external object 3′ through the light outlet aperture 12′, so as to facilitate a first reflective light 32′ from the object 3′ be received by the light receiving element 23′
Implementation Method 2
the light receiving element 23′ is configured to detect and receive an ambient light 152′ via the light inlet aperture 13′
Data Source
AI summary
Differing from conventional optical sensing device used in smart phones often lacks self-calibration function, a novel proximity sensing device having self-calibration function is disclosed by the present invention, and comprises: a driving module, a lighting element, a first a light receiving module, a conversion module, a judge circuit, a synchronous sequential module, an analog front-end module, and an analog-to-digital convertor. When executing a noise calibration process, a sensing signal outputted from the first light receiving module is converted to a voltage signal by the conversion signal comprising a signal-amplifying MOSFET, a current mirror circuit, N number of cascode MOSFET pairs, and a current-to-voltage converting resistor. After that, the voltage is transmitted to the judge circuit, and then the noise calibration process would be completed under the cooperation of the judge circuit, the synchronous sequential module, and the analog front-end module.