Optical Touch Screen Ambient Light Compensation
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Solution Overview
Problem
Existing touch screen systems for mobile devices face challenges in reliably detecting input commands due to variations in ambient light conditions, such as those encountered in direct sunlight, which affect the accuracy of light obstruction detection.
Innovation Solution
The system records an initial measurement value of ambient light intensity before transmitting light pulses and compares it with secondary measurement values during light emission to determine if a light-obstructive object is present, thereby canceling out the effects of varying light conditions by using a processing unit to control arrays of light sources and detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light receiving elements are used to detect touch input on the display unit, then touch commands can be detected, but the detection accuracy deteriorates when ambient light conditions vary (e.g., direct sunlight vs. dark environment)
Solution Approach 1:
The patent applies preliminary action by recording an initial measurement value of ambient light intensity before transmitting the light pulse. This initial measurement is stored and later used to compensate for ambient light variations. By performing this measurement in advance, the system prepares the reference data needed to accurately detect touch input regardless of changing ambient light conditions.
Solution Approach 2:
The patent applies parameter changes by using the initial measurement value to dynamically adjust the interpretation of the secondary measurement value. Instead of using a fixed threshold, the system calculates the difference between the secondary measurement (taken during light pulse emission) and the initial measurement (taken before light pulse emission). This parameter adjustment compensates for ambient light variations and maintains measurement precision across different lighting conditions.
2Volume of moving object
If the device is made physically smaller to improve portability, then device size is reduced, but the functionality and processing capacity must be maintained
Solution Approach 1:
The patent applies universality by implementing a touch screen that serves multiple functions: it acts as both a display unit and a touch-sensitive input device. The same display area is used for presenting information and for detecting touch commands through optical sensing. This multi-functionality allows the device to maintain comprehensive interface capabilities while keeping the physical size small, as separate input devices would not be needed.
3Adaptability or versatility
If more functionality and processing capacity are added to mobile devices, then device capabilities are enhanced, but the physical size increases
Solution Approach 1:
The patent applies merging by combining the display function and touch input detection function into a single integrated component. The display unit serves dual purposes: visual output and touch sensing through integrated light sources and light receiving elements. This consolidation eliminates the need for separate input devices, thereby enhancing device functionality while maintaining a compact form factor.
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 ensures reliable and efficient detection of input commands regardless of ambient light levels, maintaining accuracy and data quality by accounting for initial and secondary measurement values.
Implementation Method 1
arrays of light sources arranged along a respective side of the display device and arrays of light detectors arranged along a respective side of the display device. Each light source in the arrays of light sources is configured to transmit light pulses, here exemplified by ΛemX and ΛemY, across the display device towards the arrays of light detectors
Implementation Method 2
based on light energy registered by the receiving elements, it is determined whether or not a light-obstructive object (e.g. a fingertip) is present on the display unit
Data Source
AI summary
A user interface for receiving input commands in a mobile terminal includes a display device for presenting visual information. Arrays of light sources and arrays of light detectors are arranged along respective first and second sides of the display device. Each array of light sources is configured to transmit light pulses over the display device, and each array of light detectors is configured to receive a part of the energy in the transmitted light pulses. A processing unit controls the light sources such that a light pulse is repeatedly transmitted from each source according to a predefined sequence. Based on an ambience light intensity and a measurement value registered by at least one light detector during transmission of light from the light source, the processing unit determines whether or not a light-obstructive object is present on the display device between a given light source and at least one light detector.