Touch Screen Parallax Compensation via Dynamic Coordinate Mapping
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Solution Overview
Problem
Touch screens in self-service terminals, such as ATMs, experience parallax errors due to the spacing between the display and the touch sensitive film, leading to misregistration of user touches, especially affecting users of varying heights or those with different viewing perspectives, resulting in transaction failures and user dissatisfaction.
Innovation Solution
A touch screen unit with a processor that receives alignment signals to generate offsets, allowing for the compensation of co-ordinates to ensure accurate registration of user interactions with displayed objects, using cameras, sensors, and card readers to determine user position and adjust display co-ordinates vertically or horizontally to maintain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch sensitive film is spaced apart from the display by a protective screen, then the display is protected, but registry between user touch point and displayed icons is lost due to parallax error
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the offset values in the coordinate mapping algorithm based on detected user position parameters. The system modifies the transformation parameters from touch film coordinates to display coordinates according to the user's viewing angle and position, thereby compensating for parallax errors while maintaining the protective screen spacing.
2Measurement precision
If the touch screen is pivotally mounted to rotate up and down, then vertical parallax error is compensated, but device complexity and risk of mechanical failure increase
Solution Approach 1:
The patent replaces the mechanical rotation system with an electronic/software-based solution. Instead of physically rotating the touch screen to compensate for parallax, the system uses coordinate mapping algorithms that calculate and apply offset adjustments based on user position detection, thereby eliminating complex mechanical components while achieving the same functional goal.
Solution Approach 2:
The patent introduces an intermediary coordinate mapping algorithm that acts as a mediator between the touch film and display coordinates. This software intermediary processes touch inputs and applies calculated offsets based on user position, serving as a virtual layer that compensates for parallax without requiring physical movement or complex mechanical structures.
3Measurement precision
If coordinate mapping with offset compensation is implemented, then touch registration accuracy is improved, but processor complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing offset values for different user positions and viewing angles. The system prepares compensation parameters in advance based on detected user position, so that when a touch occurs, the appropriate offset can be quickly applied without complex real-time calculations, thereby reducing processor complexity while maintaining accuracy.
Data Source
AI summary
A touch screen unit comprises a touch sensitive layer, a display and a processor. The processor is arranged to receive a signal indicative of a parallax error between a user's view of the touch sensitive layer and the user selectable objects displayed on the display and to correct for this parallax error.