Touchpad

Closeup of a touchpad on anAcerCB5-311 laptop

Closeup of a touchpad on aMacBook2015 laptop

Atouchpadortrackpadis a type ofpointing device.Its largest component is a tactile sensor: an electronic device with a flat surface, that detects the motion and position of a user's fingers, and translates them to 2D motion, to control apointerin agraphical user interfaceon acomputer screen.Touchpads are common onlaptop computers,contrasted withdesktop computers,wheremiceare more prevalent. Trackpads are sometimes used on desktops, where desk space is scarce. Because trackpads can be made small, they can be found onpersonal digital assistants(PDAs) and someportable media players.Wireless touchpads are also available, as detached accessories.

Operation and function

Touchpads operate in several ways, includingcapacitive sensingorresistive touchscreen.The most common technology used in the 2010s senses the change ofcapacitancewhere a finger touches the pad. Capacitance-based touchpads will not sense the tip of a pencil or other similar ungrounded or non-conducting implements. Fingers insulated by a glove may also be problematic, and capacitive touchpads are rarely used as pointing devices for medical hardware.

Like touchscreens, touchpads sense absolute position but their resolution is limited by their size. For common use as a pointer device, the dragging motion of a finger is translated into a finer, relative motion of the cursor on the output to the display on the operating system, analogous to the handling of amousethat is lifted and put back on a surface. Hardware buttons equivalent to a standard mouse's left and right buttons are sometimes positioned adjacent to the touchpad.

Some touchpads and associateddevice driversoftware may interpret tapping the pad as amouse click,and a tap followed by a continuous pointing motion (a "click-and-a-half" ) can indicate dragging.Tactile touchpads allow for clicking and dragging by incorporating button functionality into the surface of the touchpad itself.To select, one presses down on the touchpad instead of a physical button. To drag, instead of performing the "click-and-a-half" technique, the user presses down while on the object, drags without releasing pressure, and lets go when done. Touchpad drivers can also allow the use of multiple fingers to emulate the other mouse buttons (commonly two-finger tapping for right click).

Touchpads are called clickpads if they rely on software buttons rather than physical buttons. Physically the whole clickpad formed a button, logically the driver interprets a click as a left or right button click depending on the placement of fingers.

Some touchpads have "hotspots", locations on the touchpad used for functionality beyond a mouse. For example, on certain touchpads, moving the finger along an edge of the touch pad will act as ascroll wheel,controlling thescrollbarand scrolling thewindowthat has thefocus,vertically or horizontally. Many touchpads use two-finger dragging forscrolling.Also, some touchpad drivers support tap zones, regions where a tap will execute a function, for example, pausing a media player or launching anapplication.All of these functions are implemented in the touchpaddevice driversoftware, and can be disabled.

History

In 1980,Xeroxoffered one of the first, if notthefirst, touchpads on a computer system with theirXerox 860,a word processing workstation aimed at medium- and large-sized businesses.Embedded on the Xerox 860's keyboard, to the right of the keys, is the circular touchpad, which Xerox dubbed the "Cat" (short forcapacitance-activated transducer). Xerox offered the Cat as an alternative input method for selecting strings of text to copy, delete, insert, or move around the document.

By 1982,Apollodesktop computers were equipped with a touchpad on the right side of the keyboard.Introduced a year later, in 1983, the first battery-powered clamshell laptop, theGavilan SCincluded a touchpad, which was mounted above its keyboard, rather than below, which became the norm.

Psion'sMC 200/400/600/WORD Series,introduced in 1989, came with a new mouse-replacing input device similar to a touchpad,although more closely resembling a graphics tablet, as the cursor was positioned by clicking on a specific point on the pad, instead of moving it in the direction of a stroke.

Laptops with touchpads were launched byOlivettiandTriumph-Adlerin 1992.Cirqueintroduced the first widely available touchpad, branded as GlidePoint, in 1994.Appleintroduced touchpads with modern placing in thePowerBook 500series in 1994, using Cirque's GlidePoint technology,which Apple refers to as a "trackpad"; it replaced thetrackballof previousPowerBookmodels. Since 2008, Apple's revisions of theMacBookandMacBook Proincorporated a "Tactile Touchpad" design with a button integrated into the tracking surface(the lower part of the touchpad surface acts as a clickable button).

Another early adopter of the GlidePoint pointing device was Sharp.Later,Synapticsintroduced their touchpad into the marketplace, branded the TouchPad, andEpsonwas an early adopter of this product with theirActionNote. As touchpads began to be introduced in laptops in the 1990s, there was often confusion as to what the product should be called. No consistent term was used, and references varied, such as: glidepoint, touch sensitive input device, touchpad, trackpad, and pointing device.

Users were often presented with the option to purchase apointing stick,touchpad, ortrackball.Combinations of the devices were common, though touchpads and trackballs were rarely included together.Since the early 2000s, touchpads have become the dominant laptop pointing device as most consumer laptops produced during this period and beyond includes only touchpads, displacing the pointing stick.

Use in devices

Optical trackpadof theBlackBerry Curve 8520in the red circle

AMicrosoft Surfacetablet. The touchpad is the rectangle near the bottom of the keyboard.

Touchpads are primarily used in self-contained portablelaptopcomputers and do not require a flat surface near the machine. The touchpad is close to the keyboard, and relatively short finger movements are required to move the cursor across the display screen; while advantageous, this also makes it possible for a user's palm or wrist to move the mouse cursor accidentally while typing. Laptops today featuremultitouchtouchpads that can sense in some cases up to five fingers simultaneously, providing more options for input, such as the ability to bring up thecontext menuby tapping two fingers, dragging two fingers for scrolling, or gestures for zoom in/out or rotate. The touchpads with physical buttons now are only hi-end business/professional laptops option.

One-dimensional touchpads are the primary control interface for menu navigation oniPod Classicportable music players and additional input method on someWacomdigitizer tablets, where they are referred to as "click wheels", since they only sense motion along one axis, which is wrapped around like a wheel.Creative Labsalso uses a touchpad for theirZenline ofMP3 players,beginning with the Zen Touch. The second-generationMicrosoftZuneproduct line (theZune 80/120andZune 4/8) uses touch for theZune Pad.

Touchpads also exist for desktop computers as an external peripheral, albeit rarely seen. But touchpad layer can be integrated withgraphics tabletas additional input option.

External computer keyboards can be equipped with integrated touchpads(particularly keyboards oriented forHTPCuse), and some keyboards can have only touch input surface instead of hardware buttons (a typical solution for clean rooms).

Optical trackpadsprimary can be used as part of ultraportable electronics; some handheld laptops and early smartphones can be equipped with optical trackpads.

On September 9, 2024, Apple unveiled theiPhone 16, iPhone 16 Plus,iPhone 16 Pro and iPhone 16 Pro Maxto feature the single one-directional trackpad next to the side button called "Camera Control" which allows the users to take an easier way to take a photos and videos, the force sensor to distinguish between the firm press and the light press and the capacitance touch sensor to distinguish sliding with finger for adjusting the zoom, exposure or depth-of-field.

Theory of operation

There are two principal means by which touchpads work: the matrix approach and the capacitive shunt method.In the matrix approach, a series ofconductorsare arranged in an array of parallel lines in two layers, separated by aninsulatorand crossing each other atright anglesto form a grid. A high frequency signal is applied sequentially between pairs in this two-dimensional grid array. The current that passes between the nodes is proportional to thecapacitance.When avirtual ground,such as a finger, is placed over one of the intersections between the conductive layer some of the electrical field isshuntedto this ground point, resulting in a change in the apparent capacitance at that location. This method receivedU.S. patent 5,305,017awarded to George Gerpheide in April 1994.

The capacitive shunt method, described in an application note by manufacturerAnalog Devices,senses the change incapacitancebetween a transmitter and receiver that are on opposite sides of the sensor. The transmitter creates an electric field which oscillates at 200–300 kHz. If a ground point, such as the finger, is placed between the transmitter and receiver, some of the field lines are shunted away, decreasing the apparent capacitance.

Trackpadssuch as those found in some Blackberry smartphones work optically, like an opticalcomputer mouse.

Manufacturing

Major manufacturers include:

• Alps Electric
• Elan Microelectronics
• Cirque Corporation
• Synaptics

See also

• Capacitive sensing
• Graphics tablet
• Kaoss Pad
• List of touch input manufacturers
• Magic Trackpad
• Multi-touch
• Pointing stick

External links

• Annotated Bibliography of References to Gestures, Touchscreens, and Pen Computing
• Notes on the History of Pen-based ComputingonYouTube