PMOLED Illuminance Sensing via Electrode Voltage Control
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Solution Overview
Problem
Passive matrix organic light emitting diode (PMOLED) displays face challenges in implementing illuminance sensing and touch functions efficiently, particularly due to residual capacitance issues and the need for a method to integrate these features without compromising image output.
Innovation Solution
The method involves forming a predetermined voltage difference between transparent and lower electrode patterns in a PMOLED display, using a combination of electrode patterns for illuminance sensing and touch sensing, and time-sharing the display frame time into separate control periods to efficiently measure illuminance and perform touch sensing, while minimizing the impact of residual capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a voltage is applied to horizontal and vertical axes to illuminate intersections in PMOLED, then the structure remains simple and production cost is low, but sophisticated screens cannot be realized
Solution Approach 1:
The patent combines multiple functions (display, illuminance sensing, touch sensing) into the PMOLED structure itself. The transparent electrode patterns and lower electrode patterns serve dual purposes: displaying images and sensing illuminance/touch by measuring current changes, eliminating the need for separate sensing components and enabling sophisticated functionality while maintaining PMOLED's manufacturing simplicity.
Solution Approach 2:
The electrode patterns in the PMOLED are designed to perform multiple functions. The same transparent and lower electrode patterns used for displaying images also function as sensors for illuminance and touch detection, allowing the display to adapt to various applications (display only, illuminance sensing, touch sensing, or combinations) without requiring additional dedicated structures.
2Adaptability or versatility
If illuminance sensing and touch sensing are implemented in PMOLED, then sensing functions are integrated, but residual capacitance affects touch sensing accuracy
Solution Approach 1:
The patent implements time-division multiplexing where the display operation and sensing operations (illuminance sensing and touch sensing) are performed in alternating time periods. During sensing periods, the display is temporarily suspended, allowing accurate measurement of current changes without interference from display driving signals, thereby eliminating residual capacitance effects while maintaining integrated sensing functionality.
Solution Approach 2:
The frame time is divided into separate display periods and sensing periods. This temporal segmentation allows the system to switch between displaying images and performing sensing operations, ensuring that each function operates under optimal conditions without interference from the other, thus resolving the residual capacitance issue while maintaining integrated sensing.
3Device complexity
If electrode patterns are used for both image output and sensing, then device complexity is reduced, but measurement precision deteriorates due to residual capacitance
Solution Approach 1:
The system performs sensing operations during dedicated sensing periods when display driving is suspended. This periodic separation ensures that current measurements for illuminance and touch sensing are taken without interference from display driving signals, maintaining high measurement precision while using the same simple electrode structure for both purposes.
Solution Approach 2:
The patent uses the organic compound layer as an intermediary that enables both display and sensing functions. The same organic compound layer that emits light for display also responds to light and touch stimuli for sensing, allowing a single simple structure to achieve both functions with high precision through appropriate timing and measurement techniques.
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 enables effective implementation of illuminance sensing and touch functions in PMOLED displays, improving measurement efficiency and reducing the influence of residual capacitance, thus enhancing the overall performance of the display.
Implementation Method 1
A light emitting material of the light emitting layer is excited by the energy due to the coupling, and light is generated when the light emitting material returns from the excited state to a ground state again
Data Source
AI summary
Provided is a method of sensing an illuminance in a passive matrix organic light emitting diode display, the display including a plurality of lower electrode patterns arranged in parallel, a plurality of transparent electrode patterns arranged in parallel and being perpendicular to the lower electrode patterns, and an organic compound layer interposed between the lower electrode pattern and the transparent electrode pattern, the method comprising steps of: (a) forming a predetermined voltage difference between at least one electrode patterns of the transparent electrode patterns as anodes and the lower electrode patterns as cathodes; (b) measuring the magnitude of current formed by the transparent electrode pattern and the lower electrode pattern in the step (a); and (c) measuring an illuminance using the measured current, in which a voltage supplied to the lower electrode pattern is relatively higher than that of the transparent electrode pattern in the step (a).