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Rugged touch screen pinpoints finger contact

DN Staff

October 18, 1999

2 Min Read
Rugged touch screen pinpoints finger contact

New Westminster, Canada-Many touch screens sacrifice ruggedness and durability for optical clarity, or vice versa. Near Field Imaging(TM) (NFI) allows both. A protected and sealed sensing circuit detects the finger or gloved hand with data acquisition and image processing algorithms.

Introduced by Dynapro, the system incorporates an image processing controller and laminated touch screen. Three elements make up the screen: a glass base-plate coated with conductive sensing circuits of Indium Tin Oxide; an optical adhesive layer; and a chemically strengthened glass faceplate.

To operate, the controller applies an excitation waveform to the baseplate. This, in turn, generates a low-strength electrostatic field in the faceplate. Finger contact modulates the "near field" to create a differential signal. The differential signal permits accurate resolution of electrostatic loading on the face of the screen.

Proprietary sensing topology enables the touch screen to recognize the fingers as an input device, yet control equipment consistently and precisely. Gloves will not impede detection, nor will moisture and other contaminants. The sensor's glass construction provides superior optical performance and will continue to operate despite scratching, pitting, and other surface damage from abrasives, chemicals, or vandals.

"The controller continuously compares profiles against set thresholds to determine the start and finish of touch events," explains Director of Marketing Dan Savage. "Baseline profiles are subtracted from touch profiles to improve accuracy and eliminate interference from static and noise."

Image processing algorithms construct the touch profile from a dynamic array of data points; continuous re-imaging of the electrostatic field resolves the profile to an actual touch point. The controller sends touch coordinates back to the operating system as fully compliant Microsoft mouse coordinates.

Once a touch is registered, its effect is zeroed out, so a subsequent touch in another location can be detected. The system also compensates for long-term changes in the electrostatic image to reject false touches from conductive dirt or even from water droplets.

Dynapro's NFI touch screen withstands shock and vibration, operates within a temperature range between -20C and +70C, and resists contaminants like dirt, dust, and water. "We've proved the technology in harsh industrial applications where a rugged touch screen is required," Savage asserts, adding that, "NFI is also ideal for unsupervised outdoor environments where vandalism, inclement weather, or uptime are key concerns."

NFI touch screens can be reliably sealed for applications that require high pressure washdown or protection from contaminant-filled environments.

Additional details...Contact Dan Savage, Dynapro; Tel: (604) 521-3962; Fax: (604) 521-4629; E-mail: [email protected].

Other Applications

  • Food processing plants

  • Heavy industrial equipment

  • Pulp and paper mills

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