Optical Touch Sensing System Stylus Position Detection
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Solution Overview
Problem
Optical touch screens struggle to accurately determine whether a stylus is in contact with the screen, leading to incorrect stroke connections and image display issues due to the distance between the image capturing plane and the touch surface.
Innovation Solution
An optical touch sensing system that includes a touch panel, optical sensors, a first light source, and a processor, along with a stylus featuring a switch module and a second light source, where the processor determines the stylus position based on the first light and the second light received by the sensors, with the second light generated when the stylus touches the panel or its switch is pressed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical lenses are disposed close to the touch screen to improve detection accuracy, then measurement precision is improved, but the distance between the image capturing plane and the touch surface cannot be eliminated, causing unreliable touch contact determination
Solution Approach 1:
The touch detection process is divided into two independent stages: first detecting the position of the stylus tip using optical lenses, and then separately detecting whether the stylus is in contact with the screen using a contact sensor. This segmentation allows each detection function to be optimized independently, resolving the contradiction between position accuracy and contact determination reliability.
Solution Approach 2:
A contact sensor is introduced as an intermediary element between the stylus and the screen to detect touch contact. This intermediary provides additional information that complements the optical detection, enabling reliable determination of touch contact status without compromising position detection accuracy.
2Ease of operation
If the stylus is held close to the screen without lifting far enough between strokes, then writing continuity is maintained, but the system cannot distinguish between intentional continuous strokes and accidental screen contact
Solution Approach 1:
The system uses feedback from the contact sensor to determine whether the stylus is in contact with the screen. This feedback mechanism allows the system to distinguish between intentional continuous writing (where the stylus hovers close to the screen) and accidental screen contact, resolving the contradiction between writing ease and detection accuracy.
3Device complexity
If a single optical detection system is used to determine both position and touch contact, then device complexity is reduced, but detection accuracy for touch contact is insufficient
Solution Approach 1:
The sensing system is designed with multi-functionality: the optical lenses serve dual purposes of detecting both the position of the stylus tip and providing information for touch contact determination. This universal approach allows a single integrated system to perform multiple detection functions, balancing device complexity with 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
Accurately determines the stylus's touch position, preventing incorrect stroke connections and improving image accuracy by using the second light as a signal to confirm contact, while also allowing for power-saving adjustments in brightness.
Implementation Method 1
The first light source generates a first light periodically
Implementation Method 2
The second light source generates a second light when the stylus touches the touch surface
Implementation Method 3
a plurality of optical sensors... determines a position of the stylus according to the first light and the second light received by the optical sensors
Data Source
AI summary
An optical touch sensing system, an optical touch sensing device, and a touch detection method thereof are provided. The optical touch sensing system includes an optical touch sensing device and a stylus. The optical touch sensing device includes a touch panel, multiple optical sensors, a first light source, and a processor. The touch panel has a touch surface. The first light source generates a first light periodically. The stylus includes a switch module and a second light source. The switch module enables the second light source to generate a second light when the stylus touches the touch surface. The processor determines a position touched by the stylus according to the first light and the second light received by the optical sensors.