Display Panel Object Detection Using Periodic Illumination Switching
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Solution Overview
Problem
Existing display-and-image-pickup devices face challenges in stably detecting objects irrespective of use conditions while maintaining low manufacturing costs, due to issues with outside light interference and variations in light-receiving element characteristics.
Innovation Solution
A display-and-image-pickup device with a panel comprising display and image pickup pixels, where illumination light is used to accumulate electric charge based on total light, including reflected and environment light, and the charge is released when light is off, allowing for object information extraction without external light influence, using a reduced number of frame memories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If reflected light from illumination light is used to detect object position, then the detection can be performed without separately arranging a touch panel, but outside light and variations in light-receiving element characteristics cause detection errors
Solution Approach 1:
The illumination light is switched on and off in a periodic manner to create temporal separation between illumination phases and detection phases. During the illumination phase, the display pixels emit light to illuminate the object. During the detection phase, the illumination is turned off and the light-receiving elements capture reflected light. This periodic switching eliminates the influence of outside light and allows accurate detection of object position based on changes in reflected light intensity.
Solution Approach 2:
The system uses the detected light intensity changes as feedback to determine object position. The image processing unit analyzes the signals from the light-receiving elements, comparing the intensity changes during different phases to identify the position of objects touching or approaching the panel surface.
2Reliability
If difference between light-emitting state image and lighting-off state image is detected to remove outside light influence, then outside light and stationary noise are removed, but frame memories for two images are required increasing component costs
Solution Approach 1:
Instead of storing two separate images in frame memories, the system uses periodic switching of illumination light to create temporal separation. The light-receiving elements capture signals during different phases (illumination and detection) without requiring simultaneous storage of multiple images. This approach eliminates the need for dual frame memories while maintaining the ability to remove outside light influence through phase-based differentiation.
Solution Approach 2:
The display pixels serve dual functions: they act as both the display element and the illumination source for object detection. During the detection phase, the same display pixels that would normally show images are turned off to serve as the illumination source, eliminating the need for separate illumination components and reducing overall device complexity.
3Measurement precision
If light-receiving elements are used to detect reflected light, then object position can be detected, but variations in light-receiving element characteristics cause stationary noises
Solution Approach 1:
The periodic switching of illumination light creates distinct temporal phases where the light-receiving elements are stimulated during the illumination phase and read during the detection phase. This temporal separation allows the system to differentiate between signals caused by outside light and signals caused by the illumination light, enabling the removal of stationary noises through phase-based signal processing.
Solution Approach 2:
The system uses feedback from the light-receiving elements during different phases to compensate for variations in element characteristics. By comparing the signals during illumination and detection phases, the system can identify and correct for stationary noises caused by variations in light-receiving element sensitivity and response characteristics.
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 stable object detection regardless of use conditions and reduces manufacturing costs by minimizing the need for additional components to account for external light interference.
Implementation Method 1
a state in which the display surface is touched or approached is detected based on the detection of a difference in the quantities of received light of the two times
Data Source
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AI summary
An image pickup device capable of stably detecting an object irrespective of use conditions while reducing manufacturing costs is provided. When illumination light from a backlight 15 is emitted to a proximity object from an I/O display panel 20, an electric charge for charging is accumulated in each of image pickup pixels 33 in accordance with total light amount as a summation of reflected light Lon originating from the illumination light and environment light (outside light) L0. Moreover, when the above-described illumination light is not emittedd, an electric charge for discharging is released from each of the image pickup pixels 33 in accordance with light amount of the environment light L0. Thereby, a component by the environment light L0 is subtracted in an image pickup signal obtained from each of the image pickup pixels 33, so object information about the proximity object is obtainable without influence of the environment light L0. Moreover, in a light reception drive circuit 13, a smaller number of necessary frame memories 13A for producing a picked-up image from the image pickup signal than that in related art are necessary.