Pointing stick

Pointing stick on a Lenovo ThinkPad

Detail: rear side of a Lenovo ThinkPad pointing stick with the strain gauges. Size: 8 x 8 mm

IBM ThinkPad caps (left-to-right): Soft Dome, Soft Rim, Classic Dome, Eraser Head (discontinued)

A pointing stick is an isometric joystick used as a pointing device, as with a touchpad or trackball, typically mounted in a computer keyboard. Movements of the pointing stick are echoed on the screen by movements of the pointer (or cursor) and other visual changes.

The pointing stick senses applied force by using two pairs of resistive strain gauges. A pointing stick can be used by pushing with the fingers in the general direction the user wants the cursor to move. The velocity of the pointer depends on the applied force so increasing pressure causes faster movement. The relation between pressure and cursor or pointer speed can be adjusted, similar to the way the mouse speed is adjusted.

On a QWERTY keyboard, the stick is typically embedded between the G, H and B keys, and the mouse buttons are placed just below the space bar. The mouse buttons can be operated right-handed or left-handed due to their placement below the keyboard along the centerline. This pointing device has also appeared next to screens on compact-sized laptops such as the Toshiba Libretto and Sony VAIO UX.

Variants

Pointing sticks typically have a replaceable rubber cap, called a nub, which can be a slightly rough "eraser head" material (Classic Dome) or another shape (Soft Dome or Soft Rim, or concave).^[1]

The cap is red on ThinkPads, but is also found in other colours on other machines. For example, it may be grey, black or blue on some Dell models, and blue on some HP/Compaq laptops.

Button configurations vary depending on vendor and laptop model. ThinkPads have a prominent middle mouse button, but some models have no physical buttons. Toshiba employs concentric arcs.

In the early 1990s, Zenith Data Systems shipped a number of laptop computers equipped with a device called "J-Mouse", which essentially used a special keyswitch under the J key to allow the J keycap to be used as a pointing stick.

In addition to appearing between the G, H and B keys on a QWERTY keyboard, these devices or similar can also appear on gaming devices as an alternative to a D-pad or analog stick. On a certain Toshiba Libretto mini laptop, the pointing stick was located next to the display. IBM sold a mouse with a pointing stick in the location where a scroll wheel is common now.

Optical pointing sticks are also used on some ultrabook tablet hybrids, such as the Sony Duo 11, ThinkPad Tablet and Samsung Ativ Q.

A similar technology is used on the C Stick featured on the New Nintendo 3DS, which is actually a simple two-axis potentiometer.^[2]

Configuration options

The user can often customize the operation of pointing sticks using software.

The user may be able to adjust the sensitivity of the pointing stick, so that application of a given amount of force moves the pointer a greater or smaller distance across the screen.

On some systems, a user may be able to configure an option to enable "press-to-select", in which a sharp tap on the pointing stick is equivalent to a click of a specified mouse button.

Other configuration options may include swapping middle mouse functionality to that which allows the pointing stick to act as a scroll wheel while the middle mouse button is held. This is frequently set to default behavior in 2013 computers, and makes the middle mouse button not work with 3D design programs or any program that explicitly uses the middle mouse button to perform functions.

Design challenges

The IBM TrackPoint III and the TrackPoint IV have a feature called Negative Inertia that causes the pointer's velocity to "overreact" when it is accelerated or decelerated. Negative Inertia is intended to avoid feeling of inertia or sluggishness when starting or stopping movement.^[3] Usability tests at IBM have shown that it is easier for users to position the pointer with Negative Inertia, and performance is 7.8% better.^[4]

Another challenge with pointing stick design is identification of the zero position (the position where no motion is desired). Because the amount of motion is small, the sensitivity of the sensors must be high, and they are subject to noise interference.

A typical solution, which assumes that pointing sticks frequently go out of calibration, is to interpret a variation below a certain threshold (over a given interval, perhaps one or several seconds) as being a neutral stick. However the recalibration can also allow brief periods of 'drifting' (movement of the cursor while the user is not moving the pointing stick).^[5]

In practice, if the re-calibration interval is set too short and if the user applies moderately consistent pressure to the stick for such an interval, this method results mistakenly re-zeroed the stick and the pointer stops. Additional pressure again moves the cursor, but the calibration may occur again, requiring even more force. If the user releases pressure at this point, the change will be interpreted as an instruction to move the opposite direction. In time, the software will re-calibrate and stop the motion.

Additionally, if "press-to-select" is enabled, the software may generate unexpected click events by touching the pointing stick during typing.

Since ThinkPad computers have a nub that is responsive to pressure in a direction, and there is a patent for this, other companies have made it so a person has to move the finger a large distance to cause the nub to rock from side to side in a much less efficient way.

History

In 1984, Ted Selker, a researcher at PARC, worked on a pointing stick based on a study that a typist needs a relatively long 0.75 seconds to shift the hand from the keyboard to the mouse, and comparable time to shift back. Selker built a model of a device that would minimize this time. It was only three years later, working at IBM, that Selker refined his design, resulting in the TrackPoint product^[6] for which IBM received US patents in 1996^[7][8] and 2000.^[9]

Problem scope

A ThinkPad UltraNav featuring both a red pointing stick (top right) and a touchpad (bottom left)

Space constraints

The pointing stick can be used in ultra-compact netbooks^[10] where there would be no place for a touchpad.

Finger motion reduction

The pointing stick is positioned such that the hands do not need to be removed from the home row to manipulate the mouse pointer.^[11]

Continuous motion

Some people find them more appealing for mobile gaming than a touchpad, because the track-point allows infinite movement without repositioning.^[11]

Fine positioning

Some users claim it is easier to finely position the pointer than when using a touchpad because there is virtually no "dead zone". This is because a user's finger may run off the edge of a touchpad while positioning the pointer, requiring them to reposition their finger in order to continue.^[12]

However, a finger's slipping off of the stick can lead to the accidental pressing of keys.

Ergonomics

Some users feel that pointing sticks cause less wrist strain because a user does not need to avoid resting wrists on a touchpad, usually located just below the keyboard. One criticism is that because the pointing stick depends on the user's applying pressure, it can cause hand cramps (although this can be partly solved by setting the sensitivity higher and lifting the finger when the pointer is not being moved). Another criticism is that it stresses the index finger and may lead to repetitive strain injury.

A number of ergonomic studies to compare trackpoint and touchpad performance have been performed.^[13][14] Most studies find that touchpad is slightly faster; one study found that "the touchpad was operated 15% faster than the trackpoint".^[15] Another study found that average object selection time was faster with a touchpad, 1.7 seconds compared to 2.2 seconds with a trackpoint, and object manipulation took 6.2 seconds with a touchpad, on average, against 8.1 seconds with trackpoint.^[16]

Naming and brands

Informal names

Various informal names have been invented, including "nipple mouse",^[18][19] "clit mouse"^[18][19] and "nub".^[18]

Other uses

While typically employed on a computer keyboard, IBM included one on its Trackpoint Mouse product; suggested uses included scrolling (as with a scroll wheel) or a dual-cursor system.^[20]

References

External links

• Pointing stick USB Keyboard Comparison
• How to configure the TrackPoint under Linux
• Notebook input devices put to the age test : the usability of trackpoint and touchpad for middle-aged adults Ergonomics, 2007, vol. 50, no3, pp. 426–445
• an OEM supplier for nubs: http://sofpoint.com/
• ALPS (manufacturer)
• Synaptics (manufacturer)