Capacitive Key Input Layout With Light Guide Leakage Control
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Solution Overview
Problem
Existing input devices face challenges in individually illuminating keys with non-contact operation detection, leading to increased key spacing, light leakage, and reduced detection accuracy due to light guide sheet configurations.
Innovation Solution
An input device with a circuit board, electrostatic electrode, light guide plate, and light shielding member configuration that prevents lateral light leakage and ensures uniform light emission over a wide area, using a light guide plate with angled side surfaces and a light shielding member to enhance detection accuracy and light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the keys are reduced in size to enable individual light emission and non-contact detection, then the light emission capability and detection capability are improved, but light leakage to neighboring keys occurs and detection accuracy deteriorates
Solution Approach 1:
The light guide plate is divided into multiple light guide portions, each corresponding to a key region. Each light guide portion independently guides light to its corresponding key, preventing light leakage to neighboring keys. The light shielding plate is also segmented with light shielding portions that correspond to the gaps between keys, providing targeted light blocking where needed.
Solution Approach 2:
The light guide plate has different properties in different regions: the light guide portions have high light transmission capability to enable bright key illumination, while the light shielding portions of the light shielding plate have high light blocking capability to prevent light leakage. This local differentiation of optical properties resolves the contradiction between light emission and light leakage prevention.
2Illumination intensity
If the keys are reduced in size for individual illumination, then the light emission is improved, but the detection accuracy of non-contact operations deteriorates
Solution Approach 1:
The electrostatic detection plate is segmented into multiple detection electrode portions, each corresponding to a specific key region. This segmentation allows independent detection of non-contact operations on each key while maintaining high detection accuracy. The segmented structure ensures that detection signals from neighboring keys do not interfere with each other.
Solution Approach 2:
The light shielding plate serves as an intermediary structure that positions the detection electrodes at optimal locations beneath each key. By mediating the spatial relationship between the light guide plate and detection electrodes, it ensures that each detection electrode is precisely aligned with its corresponding key region, maintaining detection accuracy despite reduced key size.
3Device complexity
If a conventional light guide sheet configuration is used with external light source, then the structure is simple, but individual key illumination and non-contact detection cannot be achieved
Solution Approach 1:
The light guide plate serves multiple functions: it guides light from the light source to the keys for illumination, and it also serves as a structural support for positioning the light shielding plate and detection electrodes. This multi-functionality reduces the need for separate components, maintaining structural simplicity while enabling individual key illumination and detection capabilities.
Solution Approach 2:
The light shielding plate and detection electrode plate are merged into a single integrated component. The light shielding portions and detection electrode portions are combined in one structure, reducing the total number of components while achieving both light leakage prevention and non-contact detection functions. This merging maintains structural simplicity despite the enhanced functionality.
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 device achieves improved detection accuracy and uniform light emission over a wide area, reducing light leakage and maintaining key spacing while enabling non-contact operation detection.
Implementation Method 1
a light guide plate provided on a lower side with respect to an operation surface and on an upper side with respect to the electrostatic electrode and having at least one first side surface that faces the light source
Implementation Method 2
a light shielding member having a frame shape surrounding the light guide plate and having a light shielding wall that is in contact with the second side surface of the light guide plate
Implementation Method 3
an electrostatic electrode provided on the circuit board and configured to detect electrostatic capacitance
Data Source
AI summary
An input device includes an input detection unit including a circuit board, an electrostatic electrode on the circuit board for capacitance detection, a light source on the circuit board, a light guide plate provided on the lower side with respect to an operation surface and the upper side with respect to the electrostatic electrode and having a first side surface that faces the light source and a second side surface that does not face the light source, and a frame-shaped light shielding member surrounding the light guide plate and having a light shielding wall in contact with the second side surface. The neighboring first and second side surfaces of the light guide plate form an obtuse angle, the first side surface is perpendicular to upper and lower surfaces of the light guide plate, the second side surface slopes to face downward, and the light shielding wall slopes to face upward.