Ultrasonic Touch Screen Using Time of Flight for Ghost Touch Removal

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Solution Overview

Problem

Surface acoustic wave (SAW) type touch screens face challenges with low recognition performance due to vulnerability to pollutants and the need for complex designs and high costs, especially in accurately detecting soft touches and preventing ghost touches.

Innovation Solution

A touch screen apparatus utilizing Time of Flight (ToF) measurements of ultrasonic waves to accurately determine touch points, with a processor calculating distances and separating signals from multiple objects to enhance recognition performance and reduce complexity and costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If SAW type touch screen uses ultrasonic waves irradiated along the surface, then light penetrability and accuracy are improved, but vulnerability to pollutants and low soft touch recognition performance occur

Engineering Contradiction:

Improvetouch recognition accuracyVSAvoidvulnerability to pollutants

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the traditional SAW type mechanical ultrasonic wave propagation system with an optical system using light emission and detection. The touch screen emits light toward the touch surface and detects reflected or absorbed light to determine touch position, eliminating the need for mechanical ultrasonic waves that are vulnerable to pollutants while maintaining high measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If SAW type touch screen uses plurality of acoustic reverberators, then ghost touch prevention is improved, but device complexity and cost increase

Engineering Contradiction:

Improveghost touch preventionVSAvoiddesign complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical acoustic reverberators with optical detection methods. By using light emission and detection arrays, the system can identify and filter ghost touches through optical signal analysis without requiring additional mechanical components, thereby reducing device complexity while maintaining ghost touch prevention capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The optical system serves multiple functions simultaneously: it detects touch position, prevents ghost touches, and provides accurate measurement all through the same light emission and detection mechanism, eliminating the need for separate acoustic reverberators and processing systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If traditional SAW type touch screen is used, then touch sensing capability is provided, but recognition performance of soft touch is low

Engineering Contradiction:

Improvesoft touch recognitionVSAvoidsoft touch detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces mechanical ultrasonic wave detection with optical detection that is more sensitive to subtle changes in light reflection and absorption caused by soft touches. The light-based system can detect minimal disturbances on the touch surface with higher precision, improving soft touch recognition while maintaining ease of operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution significantly improves touch recognition accuracy and reduces costs by using ToF measurements to determine touch points and separate overlapping signals, effectively addressing the limitations of SAW type touch screens.

Implementation Method 1

reflected from an object touched on the display, and received by the plurality of ultrasonic sensors

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

determine a touch point of the object based on Time of Flights (ToFs) of the received ultrasonic signals

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Implementation Method 3

an ultrasonic signal being irradiated from the first ultrasonic sensor, refracted from the first object, and received by the second ultrasonic sensor

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS9785288B2Touch screen apparatus and control method thereof

Publication Date: 2017.10.10 SAMSUNG ELECTRONICS CO LTD

AI summary

A touch screen apparatus based on an ultrasonic wave is provided. The touch screen apparatus includes a display, ultrasonic sensors, and a processor. The ultrasonic sensors irradiate ultrasonic signals. The processor, in response to the ultrasonic signals being irradiated from the ultrasonic sensors, reflected from an object touched on the display, and received by the ultrasonic sensors, determines a touch point of the object based on Time of Flights (ToFs) of the received ultrasonic signals.