Photo-Sensing Touch Panel Embedded LCD Stabilizing Signal Against Light Interference
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Solution Overview
Problem
Conventional photo-sensing type touch panels embedded in liquid crystal display devices face challenges in accurately detecting touches due to interference from external light, leading to unreliable touch signal recognition and increased complexity in algorithm manufacturing, especially when external light intensity is variable or when sensor transistors degrade.
Innovation Solution
A photo-sensing type touch panel embedded liquid crystal display device with a touch sensor in each pixel, a ROIC read/write part, an ADC conversion part, and a calculation part that subtracts voltage values detected with and without backlight to stabilize touch sensing, ensuring a reliable touch detection regardless of external light intensity, and includes a pair of sensors to differentiate between touch and non-touch points based on voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photo-sensing type touch panel is embedded in the liquid crystal display device, then touch sensing capability is added, but external light interference causes unreliable touch signal recognition
Solution Approach 1:
The patent applies preliminary action by measuring the photoelectric current at a first time point before the backlight is turned on, and measuring again at a second time point after the backlight is turned on. This preliminary measurement of external light interference allows the system to compensate for it later when calculating touch signals, ensuring accurate touch detection regardless of external lighting conditions.
Solution Approach 2:
The patent implements feedback by using the measured photoelectric current values (both before and after backlight activation) to calculate and compensate for external light interference. The system feeds back the interference information to correct the touch signal measurement, thereby maintaining high reliability in touch recognition under varying external light conditions.
2Adaptability or versatility
If sensor transistors are used for photo-sensing, then touch detection is enabled, but sensor degradation leads to decreased sensing accuracy
Solution Approach 1:
The patent measures the photoelectric current at a first time point before backlight activation and uses this preliminary value to establish a baseline for the sensor's current state. By comparing measurements taken before and after backlight activation, the system can detect and compensate for sensor degradation over time, maintaining accurate touch sensing even as the transistor ages.
Solution Approach 2:
The patent utilizes parameter changes by measuring photoelectric current at different time points (before and after backlight activation) to detect changes in sensor response. These parameter changes over time indicate sensor degradation, and the system uses this information to adjust subsequent measurements, thereby maintaining sensing accuracy despite transistor aging.
3Measurement precision
If touch sensor is embedded in each pixel, then touch detection coverage is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies universality by designing the photo-sensing transistor to serve multiple functions: it acts as both a touch detection sensor and a component that can measure external light interference. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall device complexity while maintaining comprehensive touch detection coverage across all pixels.
Solution Approach 2:
The patent merges the touch sensing function with the external light measurement function within the same pixel structure. By combining these functions into a single integrated measurement process, the patent reduces the number of separate components and simplifies the overall device architecture while achieving high measurement precision through the coordinated measurement of photoelectric current at different time points.
4Measurement precision
If algorithm manufacturing is used to compensate for external light, then touch signal accuracy is improved, but processing complexity and time increase
Solution Approach 1:
The patent applies preliminary action by measuring the photoelectric current at a first time point before backlight activation and storing this value for later use. This preliminary measurement captures external light interference information that can be directly used in the calculation process, reducing the need for complex real-time algorithms and minimizing processing time while maintaining high touch signal accuracy.
Solution Approach 2:
The patent ensures continuity of useful action by continuously measuring and storing photoelectric current values at different time points (before and after backlight activation). These continuous measurements provide a complete data set that can be used to calculate touch signals with high accuracy, eliminating the need for complex interruptive algorithms and reducing processing complexity through efficient data utilization.
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 enables stable touch sensing across varying external light conditions and maintains sufficient voltage differences between touch and non-touch areas, even with sensor degradation, improving the reliability of touch detection in liquid crystal display devices.
Implementation Method 1
a photo-sensing transistor for generating a photoelectric current proportional to an amount of incident lights
Data Source
AI summary
A photo-sensing type touch panel embedded liquid crystal display device and a method for driving same are disclosed, where the device includes a liquid crystal panel includes a touch sensor provided in each of n pixels, where n is a Natural Number; a ROIC readout part which receives a readout voltage value from readout lines provided in the touch panel embedded liquid crystal panel; an ADC conversion part which converts an analog voltage value transmitted to the ROIC readout part into a digital value; a calculation part which calculates a calculated value by subtracting a corresponding value detected from the ADC conversion part when no-backlight is applied from a value detected from the ADC conversion part when a backlight is applied; and a position detection part for detecting a touch point on the photo-sensing type touch panel if the calculated value from the calculation part is beyond a predetermined value.