Negative Pixel Compensation in Touch Sensors
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Solution Overview
Problem
Touch sensitive devices experience erroneous or distorted touch output values due to poor grounding of users or objects, particularly when multiple simultaneous touches occur, leading to negative pixel effects.
Innovation Solution
The device measures both the grounding condition and touch event concurrently or sequentially, calculates a compensation factor based on the ratio of these measurements, and applies it to the touch signals to correct for the negative pixel effect by switching drive and sense lines between different coupling states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the device uses standard touch detection configuration, then the device can detect touch events, but erroneous or distorted touch output values occur due to poor grounding of users or objects
Solution Approach 1:
The patent introduces an intermediary measurement process that detects grounding conditions separately from the main touch detection. By measuring the grounding condition of the user or object first, the system can then compensate for poor grounding effects on the touch output values, thereby improving measurement precision without sacrificing reliability
Solution Approach 2:
The patent changes the operational parameters of the touch detection system by switching between different configurations. The drive and sense lines are switched between various coupling states (stimulation signal input, capacitance signal output, ground coupling, touch signal output) to separately measure grounding conditions and touch events, allowing the system to adapt to varying grounding conditions and improve touch output accuracy
2Adaptability or versatility
If the device performs multiple simultaneous touch detections, then multi-touch functionality is enabled, but negative pixel effects cause apparent negative touch amounts to be sensed
Solution Approach 1:
The patent uses an intermediary grounding measurement as a mediator to identify and compensate for negative pixel effects. By measuring the grounding condition before touch detection, the system can distinguish between actual negative touch amounts and artifacts caused by poor grounding, thereby maintaining multi-touch versatility while improving measurement precision
Solution Approach 2:
The patent performs preliminary action by measuring grounding conditions before conducting touch detection. This preliminary grounding measurement allows the system to prepare compensation factors in advance, preventing negative pixel effects from corrupting the touch amount measurements during multi-touch events
3Measurement precision
If the device switches between different configurations to measure grounding and touch, then compensation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the drive and sense lines multi-functional. The same lines are used for both touch detection and grounding condition measurement, depending on their coupling state. This eliminates the need for separate dedicated lines for each function, thereby improving compensation accuracy without proportionally increasing device complexity
Solution Approach 2:
The patent uses periodic action by switching between different configurations in a systematic sequence. The drive and sense lines are periodically switched between stimulation signal input, capacitance signal output, ground coupling, and touch signal output states, allowing the system to gather necessary measurements through time-division multiplexing rather than requiring all measurements simultaneously
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
This approach enhances the accuracy and speed of touch detection, reduces the need for repeated measurements, and improves the device's robustness in handling varying grounding conditions, leading to more reliable touch sensing.
Implementation Method 1
The touch sensor panel can include an array of pixels 106 that can be formed at the crossing points of the row lines 102 and the column lines 104. Each pixel 106 can have an associated mutual capacitance Csig 114 formed between the crossing row line 102 and the crossing column line 104.
Data Source
AI summary
Negative pixel compensation to compensate for a negative pixel effect in touch signal outputs due to poor grounding of an object touching the device is disclosed. To do so, the device can switch to a configuration to measure the grounding condition of the touching object and use the measurement to compensate the touch output values. In the switched configuration, a first set of lines of the device can be switched between a coupling to a stimulation signal input to drive the device, a coupling to a capacitance signal output to output a signal indicative of the object's grounding condition, and a coupling to ground. A second set of lines of the device can be coupled to a touch signal output to output a signal indicative of the object's touch at the device. The grounding signal can be applied to the touch signal to compensate for the negative pixel effect.