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Touch sensitive screens
Touchsensitive screens In manyindus~al, edu~a~onaland simple menu applications,touchscreenscan be fasterand more accuratethan keyboards --
by KEN RUMSEY
T
ouch screen terminals have a history almost as old as VDUs themselves. Earlier versions, appearing about fifteen years ago, used wires on the screen. By touching an appropriate wire, a command was issued to the computer to transmit the appropriate data to the screen. A few years later the earliest grid systems, based on a 4 x 4 matrix, appeared in process control applications involving simple menu picking or on-off switching. Development of computer-aided learning systems subsequently gave a further boost to research in touch screen terminals. Today, although the technique still remains fairly specialist, it is finding uses in business and industry. Touch screens are particularly useful where personnel have little or no previous experience of computers, or where keyboards represent a rather intimidating prospect to operatives and trainees, with perhaps the additional risk of misuse.
Abstract: There are a vuriety oftechnical approaches to tovch screen terminals. The choice of techm?oB will depend largely upon the desired application. Touch screens are being used in the industrial and process control areas and as a training aid. Keywmis: computer terminals, display devices (computers), terminals(computers). Ken Rumsey is managing director of Brent-Cybemex Ltd.
34
0011-684W83/040034-02$03.00 0
Touch screen technology The benefits of touch screen use have encouraged some manufacturers to produce touch screen terminals as an option on certain terminals in their range. Four main approaches have been adopted. In the first, surface acoustic wave devices, using ultrasonic transponders, create a standing sound wave on the surface of the display. When the wave is disturbed by a finger, the transponder can measure the propagation time of the disturbance from two edges and thus identify the touch position. This system gives excellent resolution but involves many tuneable components which ‘drift’ with time and require close temperature control for accurate touch position identification. Also, surface scratches and marks will upset the wave pattern. A second approach uses linear resistive devices. These units are composed of a glass plate, on which a thin, transparent layer of gold is deposited, and a matching mylar film cover, on which a similar layer is deposited. The glass and mylar are held apart by air pressure until the finger touch makes a contact in one point. An analogue to digital converter circuit measures the resistance from two edges of the display and as this resistance is proportional to the distance travelled through the gold film, is able to identify the touch position. This system is less sensitive to tuning than the acoustic version but
1983 Butterworth 81Co (Publishers) Ltd.
the film resistivity is sensitive to temperature and the deposition of gold must be exactly uniform in order to produce good results. Digital resistive devices are similar to the linear resistive method, but the gold is deposited into vertical strips on one surface and horizontal on the other. When contact is made by a finger depression, the point is identified by scanning the strips until a pair which is short circuited is found. This scanning is effected with a simple digital circuit in the manner of a keyboard. There are no questions of linearity or of uniformity of gold deposition. No analogue to digital converter or tuning if required - all this being replaced by a small digital scanning board. The resolution of digital devices is less than the first two, but is adequate to resolve an area the size of a fingertip. A final method is the use of Inca-red emitters. Here two rows of infrared emitters, mounted on two sides of the display screen, send out a matrix of beams across the screen which are received by detectors on the opposite sides. Touching the screen breaks one or more beams in both directions, allowing the control logic to detect where the screen has been touched. This method is fast, but is sensitive to dirt, good alignment, and the size and angle of the item touching the screen. The particular application that is being considered for touch screen use will obviously govern which method is
data processing
terminals
have proved popular at exhibitions.
Touch screen applications finally chosen. Infra-red detection is undoubtedly a faster method, but by its very nature it doesn’t allow for the hesitation which often characterizes touch screen applications. A beam must also be broken by the finger at right-angles to ensure correct data display. In contrast, the digital resistive grid wire system, although intrinsically slower, is geared to the ‘stepthrough’ menu picking applications to which touch screens are typically applied. A typical touch screen grid system design would be made up of a 16 x 16 grid covering an 80 x 24 character format area. Here, each segment covers five characters in the horizontal direction and 1.5 display lines in the vertical axis. A critical factor is obviously the geometry of the tube/sandwich overlay. The tube’s display lines must correlate with the correct point on the sandwich. Some manufacturers are now offering add-on touch sensitive kits. One such kit utilizes touch pads on a capacitance sensitive plate which is mounted in front of the monitor.
vol25no4
may 1983
In application the greatest future scope for touch screens lies in the ‘instant information’ area in industrial or process control applications, in simple menu-picking routines as in warehouse stock picking activities, and in teaching operatives how to perform well-defined operations. The touch screen can play a positive role in avoiding the ‘misuse’ and ‘error’ to which a keyboard may be subjected in a scientific or industrial environment. In some process industries, for example, operatives may wear heavy protective clothing, inwhich render cluding gloves, keyboard use a clumsy and errorprone operation. But the benefit of a touch screen in the industrial and scientific sector is far from being confined to making life easier, or avoiding mistakes. Touch screen operation can be significantly faster than pressing a key in an environment where swift reaction is required. A process control engineer scanning banks of displayed information may need to call up a succession of
data displays within a short space of time - a task which is more easily achieved by pressing screen areas than by flitting between keys. In a scientific research laboratory, almost instantaneous response may be necessary when judging the progress of an experiment in order to keep it on course. The training context also offers a promising future for touch screens. In Canada a complete computer-aided learning system has recently been set up by the Canada Post Corporation by coupling Cybernex video terminals fitted with touch sensitive screens to the same company’s LC-3 microcomputer running its CYBOL programming language. 151 of these configurations are used to train postal employees to key in postal codes for mail routeing by the Corporation’s automated sorting equipment. The Corporation’s programme is intended to gradually familiarize employees with computers and, ultimately, use of keyboards. While touch screens may be limited in functional scope, their role promises to be of great importance on both the computer-aided learning and operational fronts. cl Brent-Cybernex Ltd, Sovereign House, Dallow Road, Luton LUI ITP, Beds, UK. Tel: (0582)452020.
35
by KEN RUMSEY
T
ouch screen terminals have a history almost as old as VDUs themselves. Earlier versions, appearing about fifteen years ago, used wires on the screen. By touching an appropriate wire, a command was issued to the computer to transmit the appropriate data to the screen. A few years later the earliest grid systems, based on a 4 x 4 matrix, appeared in process control applications involving simple menu picking or on-off switching. Development of computer-aided learning systems subsequently gave a further boost to research in touch screen terminals. Today, although the technique still remains fairly specialist, it is finding uses in business and industry. Touch screens are particularly useful where personnel have little or no previous experience of computers, or where keyboards represent a rather intimidating prospect to operatives and trainees, with perhaps the additional risk of misuse.
Abstract: There are a vuriety oftechnical approaches to tovch screen terminals. The choice of techm?oB will depend largely upon the desired application. Touch screens are being used in the industrial and process control areas and as a training aid. Keywmis: computer terminals, display devices (computers), terminals(computers). Ken Rumsey is managing director of Brent-Cybemex Ltd.
34
0011-684W83/040034-02$03.00 0
Touch screen technology The benefits of touch screen use have encouraged some manufacturers to produce touch screen terminals as an option on certain terminals in their range. Four main approaches have been adopted. In the first, surface acoustic wave devices, using ultrasonic transponders, create a standing sound wave on the surface of the display. When the wave is disturbed by a finger, the transponder can measure the propagation time of the disturbance from two edges and thus identify the touch position. This system gives excellent resolution but involves many tuneable components which ‘drift’ with time and require close temperature control for accurate touch position identification. Also, surface scratches and marks will upset the wave pattern. A second approach uses linear resistive devices. These units are composed of a glass plate, on which a thin, transparent layer of gold is deposited, and a matching mylar film cover, on which a similar layer is deposited. The glass and mylar are held apart by air pressure until the finger touch makes a contact in one point. An analogue to digital converter circuit measures the resistance from two edges of the display and as this resistance is proportional to the distance travelled through the gold film, is able to identify the touch position. This system is less sensitive to tuning than the acoustic version but
1983 Butterworth 81Co (Publishers) Ltd.
the film resistivity is sensitive to temperature and the deposition of gold must be exactly uniform in order to produce good results. Digital resistive devices are similar to the linear resistive method, but the gold is deposited into vertical strips on one surface and horizontal on the other. When contact is made by a finger depression, the point is identified by scanning the strips until a pair which is short circuited is found. This scanning is effected with a simple digital circuit in the manner of a keyboard. There are no questions of linearity or of uniformity of gold deposition. No analogue to digital converter or tuning if required - all this being replaced by a small digital scanning board. The resolution of digital devices is less than the first two, but is adequate to resolve an area the size of a fingertip. A final method is the use of Inca-red emitters. Here two rows of infrared emitters, mounted on two sides of the display screen, send out a matrix of beams across the screen which are received by detectors on the opposite sides. Touching the screen breaks one or more beams in both directions, allowing the control logic to detect where the screen has been touched. This method is fast, but is sensitive to dirt, good alignment, and the size and angle of the item touching the screen. The particular application that is being considered for touch screen use will obviously govern which method is
data processing
terminals
have proved popular at exhibitions.
Touch screen applications finally chosen. Infra-red detection is undoubtedly a faster method, but by its very nature it doesn’t allow for the hesitation which often characterizes touch screen applications. A beam must also be broken by the finger at right-angles to ensure correct data display. In contrast, the digital resistive grid wire system, although intrinsically slower, is geared to the ‘stepthrough’ menu picking applications to which touch screens are typically applied. A typical touch screen grid system design would be made up of a 16 x 16 grid covering an 80 x 24 character format area. Here, each segment covers five characters in the horizontal direction and 1.5 display lines in the vertical axis. A critical factor is obviously the geometry of the tube/sandwich overlay. The tube’s display lines must correlate with the correct point on the sandwich. Some manufacturers are now offering add-on touch sensitive kits. One such kit utilizes touch pads on a capacitance sensitive plate which is mounted in front of the monitor.
vol25no4
may 1983
In application the greatest future scope for touch screens lies in the ‘instant information’ area in industrial or process control applications, in simple menu-picking routines as in warehouse stock picking activities, and in teaching operatives how to perform well-defined operations. The touch screen can play a positive role in avoiding the ‘misuse’ and ‘error’ to which a keyboard may be subjected in a scientific or industrial environment. In some process industries, for example, operatives may wear heavy protective clothing, inwhich render cluding gloves, keyboard use a clumsy and errorprone operation. But the benefit of a touch screen in the industrial and scientific sector is far from being confined to making life easier, or avoiding mistakes. Touch screen operation can be significantly faster than pressing a key in an environment where swift reaction is required. A process control engineer scanning banks of displayed information may need to call up a succession of
data displays within a short space of time - a task which is more easily achieved by pressing screen areas than by flitting between keys. In a scientific research laboratory, almost instantaneous response may be necessary when judging the progress of an experiment in order to keep it on course. The training context also offers a promising future for touch screens. In Canada a complete computer-aided learning system has recently been set up by the Canada Post Corporation by coupling Cybernex video terminals fitted with touch sensitive screens to the same company’s LC-3 microcomputer running its CYBOL programming language. 151 of these configurations are used to train postal employees to key in postal codes for mail routeing by the Corporation’s automated sorting equipment. The Corporation’s programme is intended to gradually familiarize employees with computers and, ultimately, use of keyboards. While touch screens may be limited in functional scope, their role promises to be of great importance on both the computer-aided learning and operational fronts. cl Brent-Cybernex Ltd, Sovereign House, Dallow Road, Luton LUI ITP, Beds, UK. Tel: (0582)452020.
35