Optical Touch Screen Using Hybrid Display and Image Sensor Pixels
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Solution Overview
Problem
Capacitive touch screens are prone to false detections due to dust, water, and electromagnetic interference (EMI), and struggle to distinguish between actual touches and nearby objects, while also facing challenges in scaling up in size due to signal discrimination issues.
Innovation Solution
An optical touch screen system that utilizes standing wave interference patterns to detect touches by comparing baseline and perturbed patterns, employing a hybrid display and image sensor with a spatial light modulator to accurately locate objects, and repurposing display pixels as light sources for low-cost and robust touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive touch screens are used to detect touches, then multiple touches can be detected with low cost, but false touch detections occur due to dust, water, and electromagnetic interference
Solution Approach 1:
The patent replaces the capacitive sensing mechanism with an optical sensing mechanism. Instead of detecting electrical capacitance changes, the system uses light sources to illuminate the touch screen surface and optical sensors to detect changes in light reflection or transmission patterns caused by touches. This substitution eliminates susceptibility to electromagnetic interference while maintaining the ability to detect multiple touches simultaneously.
Solution Approach 2:
The patent introduces light as an intermediary medium between the user's touch and the detection system. Light sources illuminate the screen, and optical sensors detect modifications in light paths caused by touches. This intermediary approach allows the system to distinguish actual touches from false triggers like dust or water, as these objects do not produce the same optical signature changes as finger touches.
2Ease of manufacture
If capacitive touch screens are used to detect touches, then cost is reduced, but it becomes difficult to discriminate between actual touches and nearby objects
Solution Approach 1:
The patent adds spatial and optical dimensional information to the detection process. Instead of relying solely on electrical field changes, the system captures images or optical patterns at multiple spatial locations and analyzes changes in light distribution. This dimensional enrichment enables precise discrimination between actual touches and nearby objects by examining the spatial pattern and optical characteristics of detected signals.
Solution Approach 2:
The patent utilizes optical properties including color and light intensity changes to distinguish between different types of contacts. By analyzing the optical signature, color, and intensity patterns of reflected or transmitted light, the system can differentiate between finger touches, stylus contacts, and proximity detections, thereby improving measurement precision while maintaining cost-effectiveness.
3Area of stationary object
If capacitive touch screens are scaled up in size, then coverage area increases, but signal discrimination becomes too low
Solution Approach 1:
The patent divides the large screen area into multiple detection zones or pixels, each with its own optical sensors. This segmentation allows the system to maintain high signal discrimination across the entire large area by processing local optical patterns independently. Each segment can detect touches with high precision while the collective system covers the full screen area, resolving the scaling problem.
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 optical touch screen system effectively filters out extraneous objects and detects the presence of electrically insulated objects, provides accurate size and shape detection, and is less susceptible to EMI, enabling reliable and scalable touch detection.
Implementation Method 1
An optical touch screen system relies on the property that light transmitted through an enclosure will exhibit a standing wave interference pattern that can be perturbed by a nearby object such as a finger
Implementation Method 2
In another form, the optical touch screen system activates multiple display pixels and uses the spatial light modulator to create a hologram of a nearby object
Data Source
AI summary
In one form, an optical touch screen system includes a semiconductor body forming a hybrid display and image sensor comprising a plurality of display pixels interspersed with a plurality of image sensor pixels, a spatial light modulator overlying a surface of the hybrid display and image sensor, and a control circuit for driving the plurality of display pixels with a first pattern and measuring a second pattern of the plurality of image sensor pixels, the control circuit analyzing the second pattern to detect a position of an object and selectively detecting a touch location in response to the second pattern.