GUIDE TO DISPLAY TECHNOLOGIES

Touch screens are a great interface for many medical devices. They can simplify complex systems, reduce the chance of mistakes, and provide more-efficient data entry than other input devices. They are much easier to keep clean than keyboards, and they have fewer moving parts, which typically translates into good reliability ratings.

Moreover, touch screens are easy to use and take up little space. The underlying software can be dynamically configured and easily upgraded. Yet with all these benefits, touch screens have been unable to supply the confirming tactile feel that buttons and mechanical controls provide, which has hindered their adoption for medical device applications.

New technology allows tactile feedback to be designed into the touch screen interface to make graphical buttons feel real. Using tactile feedback technology, on-screen buttons feel as if they press and release like mechanical buttons, allowing touch screens to be more effective in environments in which audio cues are inappropriate or difficult to hear, and in situations in which ease of use, error reduction, or glance time can have a significant effect on safety and accuracy.

How It Works

Figure 1. Tactile feedback technology allows several options for positioning and mounting the components to help meet objectives for overall size of the LCD assembly. (click to enlarge)

A tactile feedback system for touch screens includes actuators, controllers, and a software interface for controlling tactile cues from application software (see Figure 1). When a user touches the screen, a signal is sent to the touch screen controller, which supplies information on the precise screen location where contact was made. This location information is sent to the host application, which commands the controller to play a specific vibrotactile effect corresponding to the user's selection (see Figure 2). The tactile cue can be synchronized with audio and on-screen graphical events to provide an effective multimodal response for the user.

Figure 1. Tactile feedback technology allows several options for positioning and mounting the components to help meet objectives for overall size of the LCD assembly. (click to enlarge)

The controller's signal can be independent of other system functions so that the tactile cue can be returned faster than the data requested by the user, providing an immediate tactile confirmation that the user's input has been accepted. This fast confirmation helps solve application latency problems, which can be a key benefit for medical applications.

Focus on the Patient

Closely connected to the need for fast confirmation of a user's press on a touch screen is the medical community's strong desire to put the patient at the center of service delivery. For a modern healthcare service, it's not good enough to simply do things to people. Instead, services need to be performed with patient participation. To do this well—and along with their care-giving activities—doctors, nurses, and technicians need to be able to shift their focus from the electronic display to the patient.

Anything that equipment design engineers can do to promote this shift is an asset, and tactile feedback for touch screen user interfaces is one option.

Improving Usability

A key feature of tactile feedback technology is that tactile feedback events, or effects, can vary in frequency, waveform, magnitude, and duration. This means that all sorts of on-screen buttons, switches, and other controls can supply distinct tactile effects to help the user distinguish between applications or controls within applications. For example, pressing the Enter button, no matter where it appears on the screen, could always produce a consistent, strong, and crisp tactile sensation, while buttons for other actions could have a different feel. Inactive regions of the touch screen may be designed to provide no tactile feedback, which in itself lets users know they have not made a selection. Invalid inputs (such as exceeding minimum or maximum on a function) can provide a distinct warning or error effect.

Effects can be synchronized with sound and graphical screen changes, but an added advantage is that the user may not need to look at the screen to know that they pressed the right (or the wrong) button. The buttons can produce different tactile responses, and users can know (without looking) that their press was accepted. This feature may be especially effective for users whose sense of touch may be somewhat diminished when wearing vinyl safety gloves. Whether gloved or not, users can expect a very definite and confirming tactile response from the system to quickly verify their actions.

Tactile-feedback confirmation may also supply a more-effective system response than sound can in noisy environments, such as the emergency room or in rooms crowded with other loud equipment. Tactile confirmation is directed only at the user, not the entire room, so equipment designed with it can have the added advantage of reducing extraneous noise and avoiding patient disruption.

Medical Equipment and Touch Feedback

The sense of touch provides reflex-rate response, allowing users to understand and act quickly, which may be crucial in life-saving scenarios. Touch feedback can also augment, or even supersede, sound and graphics for providing system confirmation. However, user studies have shown that the best user interface results when touch, sound, and graphics are combined. With the ability to supply the confirming feel of mechanical controls, design engineers can use touch screens, with all their benefits, for many types of medical devices, including:

• Data input-output equipment (drug dispensing and inventory, patient check-in kiosks, medical records management, tablet PCs, wireless portable devices).
• Patient-monitoring equipment (local and remote).
• Diagnostic equipment (CT, MRI, ultrasound, ECG).
• Therapeutic equipment (anesthesia, dialysis, radiation therapy).

  Integration

  Tactile feedback technology can be integrated into flat touch screen sizes ranging from handheld devices to large-format touch monitors. The technology can be applied to most touch screen sensing technologies, including capacitive, resistive, surface acoustic wave, and infrared. Integration kits often include components and a software development kit.

   

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