Optical mouse
Encyclopedia
An optical computer mouse
or "optic mouse" uses a light-emitting diode
and photodiode
s to detect movement relative to a surface, unlike a mechanical mouse which has a ball which rotates orthogonal shafts which drive chopper wheels for distance measurement.
Early optical mice, first demonstrated by two independent inventors in 1980, came in two different varieties:
Some, such as those invented by Steve Kirsch
of MIT and Mouse Systems Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed with infrared absorbing ink on a special metallic surface. Predictive algorithm
s in the CPU of the mouse calculated the speed and direction over the grid.
Others, invented by Richard F. Lyon
and sold by Xerox
, used a 16-pixel visible-light image sensor with integrated motion detection on the same chip and tracked the motion of light dots in a dark field of a printed paper or similar mouse pad.
These two mouse types had very different behaviors, as the Kirsch mouse used an x-y coordinate system embedded in the pad, and would not work correctly when the pad was rotated, while the Lyon mouse used the x-y coordinate system of the mouse body, as mechanical mice do.
Modern surface-independent optical mice work by using an optoelectronic sensor
(essentially, a tiny low-resolution video camera) to take successive images of the surface on which the mouse operates. As computing power grew cheaper, it became possible to embed more powerful special-purpose image-processing
chips
in the mouse itself. This advance enabled the mouse to detect relative motion on a wide variety of surfaces, translating the movement of the mouse into the movement of the cursor and eliminating the need for a special mouse-pad.
The first commercially successful optical computer mice were the Microsoft IntelliMouse® with IntelliEye™ and IntelliMouse® Explorer, introduced in 1999 using technology developed by Hewlett-Packard. It worked on almost any surface, and represented a welcome improvement over mechanical mice, which would pick up dirt, track capriciously, invite rough handling, and need to be taken apart and cleaned. Instead the reliable performance of the IntelliMouse® allowed relaxed grips which also were less likely to cause repetitive strain injury
. Other manufacturers soon followed Microsoft’s lead using components manufactured by the HP spin-off Agilent Technologies, and over the next several years mechanical mice became obsolete.
The technology underlying the modern optical computer mouse is known as digital image correlation
, a technology pioneered by the defense industry for tracking military targets. Optical mice use image sensors to image naturally occurring texture in materials such as wood, cloth, mouse pads and Formica. These surfaces, when lit at a grazing angle by a light emitting diode, cast distinct shadows that resemble a hilly terrain lit at sunset. Images of these surfaces are captured in continuous succession and compared with each other to determine how far the mouse has moved.
To understand how optical mice work, imagine two photographs of the same object except slightly offset from each other. Place both photographs on a light table
to make them transparent, and slide one across the other until their images line up. The amount that the edges of one photograph overhang the other represents the offset between the images, and in the case of an optical computer mouse the distance it has moved.
Optical mice capture one thousand successive images or more per second. Depending on how fast the mouse is moving, each image will be offset from the previous one by a fraction of a pixel or as many as several pixels. Optical mice mathematically process these images using cross correlation to calculate how much each successive image is offset from the previous one.
An optical mouse might use an image sensor having an 18 x 18 pixel array of monochromatic pixels. Its sensor would normally share the same ASIC
as that used for storing and processing the images. One refinement would be accelerating the correlation process by using information from previous motions, and another refinement would be preventing deadbands when moving slowly by adding interpolation or frame-skipping.
The invention of the modern optical mouse at HP was made more likely by a succession of related projects during the 1990s at its central research laboratory. In 1992 John Ertel, William Holland, Kent Vincent, Rueiming Jamp and Richard Baldwin were awarded US Patent 5,149,980 for measuring paper advance in a printer by correlating images of paper fibers. In 1998 Travis N. Blalock, Richard A. Baumgartner, Thomas Hornak, and Mark T. Smith were awarded US Patent 5,729,008 for tracking motion in a hand-held scanner by correlating images of paper fibers and document features, a technology commercialized in 1998 with the HP 920 Capshare handheld scanner. In 2002 Gary Gordon, Derek Knee, Rajeev Badyal and Jason Hartlove were awarded US Patent 6,433,780 for the modern optical computer mouse using image correlation.
The color of the optical mouse's light-emitting diode
s can vary, but red is most common, as red diodes are inexpensive and silicon photodetectors are very sensitive to red light. Other colors are sometimes used, such as the blue LED of the V-Mouse VM-101 illustrated at right.
laser diode
instead of a LED to illuminate the surface beneath their sensor. As early as 1998, Sun Microsystems
provided a laser mouse with their Sun SPARCstation servers and workstations.
However, laser mice did not enter the mainstream market until 2004, when Paul Machin at Logitech
, in partnership with Agilent Technologies
, introduced its MX 1000 laser mouse. This mouse uses a small infrared laser instead of a LED and has significantly increased the resolution
of the image taken by the mouse. The laser enables around 20 times more surface tracking power to the surface features used for navigation compared to conventional optical mice .
Glass laser (or glaser) mice have the same capability of a laser mouse but can also be used on top of mirror or transparent glass with few problems.
In August 2009, Logitech introduced mice with two lasers, to track on glass and glossy surfaces better; they dubbed them "dark field
" mice.
) has four power states, where the sensor is pulsed at different rates per second:
Movement can be detected in any of these states; some mice turn the sensor fully off in the sleep state, requiring a button click to wake.
Optical mice utilizing infrared elements (LEDs or lasers) offer substantial increases in battery life. Some mice, such as the Logitech V450 848 nm laser mouse, are capable of functioning on two AA batteries for a full year, due to the low power requirements of the infrared laser.
Mice designed for use where low latency and high responsiveness are important, such as in playing computer games, may omit power-saving features to improve performance.
Unlike mechanical mice, which can become clogged with lint, optical mice have no moving parts; therefore, they do not require maintenance other than removing debris that might collect under the light emitter. However, they generally cannot track on glossy and transparent surfaces, including some mouse-pads, sometimes causing the cursor to drift unpredictably during operation. Mice with less image-processing power also have problems tracking fast movement, though some mice can track faster than 2 m/s
(80 inches per second).
Some models of laser mouse can track on glossy and transparent surfaces, and have a much higher sensitivity than other mechanical or optical mice, but are more expensive than their LED-based or mechanical counterparts.
mechanical mice had lower average power
requirements than their optical counterparts; the power used by mice is relatively small, and only an important consideration when the power is derived from batteries
, with their limited capacity.
Optical models outperform mechanical mice on uneven, slick, soft, sticky, or loose surfaces, and generally in mobile situations lacking mouse pads. Because optical mice render movement based on an image which the LED (or infrared diode) illuminates
, use with multicolored mouse pads may result in unreliable performance; however, laser mice do not suffer these problems and will track on such surfaces. The advent of affordable high-speed, low-resolution cameras and the integrated logic in optical mice provides an ideal laboratory for experimentation on next-generation input-devices. Experimenters can obtain low-cost components simply by taking apart a working mouse and changing the optics or by writing new software.
Mouse (computing)
In computing, a mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons...
or "optic mouse" uses a light-emitting diode
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
and photodiode
Photodiode
A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation.The common, traditional solar cell used to generateelectric solar power is a large area photodiode....
s to detect movement relative to a surface, unlike a mechanical mouse which has a ball which rotates orthogonal shafts which drive chopper wheels for distance measurement.
Early optical mice
Some, such as those invented by Steve Kirsch
Steve Kirsch
Steven Todd Kirsch is an American serial entrepreneur who has started six companies: Mouse Systems, Frame Technology, Infoseek, Propel, Abaca, and OneID. He invented and owns a patent on an early version of the optical mouse. After bringing multiple successful startup companies through IPO and...
of MIT and Mouse Systems Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed with infrared absorbing ink on a special metallic surface. Predictive algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
s in the CPU of the mouse calculated the speed and direction over the grid.
Others, invented by Richard F. Lyon
Richard Francis Lyon
Richard Francis Lyon , is an American inventor,scientist, and engineer, noted for having invented the optical mouse.He has worked in many aspects of signal processing and was a co-founder of Foveon Inc.,...
and sold by Xerox
Xerox
Xerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...
, used a 16-pixel visible-light image sensor with integrated motion detection on the same chip and tracked the motion of light dots in a dark field of a printed paper or similar mouse pad.
These two mouse types had very different behaviors, as the Kirsch mouse used an x-y coordinate system embedded in the pad, and would not work correctly when the pad was rotated, while the Lyon mouse used the x-y coordinate system of the mouse body, as mechanical mice do.
Modern optical mice
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
(essentially, a tiny low-resolution video camera) to take successive images of the surface on which the mouse operates. As computing power grew cheaper, it became possible to embed more powerful special-purpose image-processing
Image processing
In electrical engineering and computer science, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame; the output of image processing may be either an image or, a set of characteristics or parameters related to the image...
chips
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
in the mouse itself. This advance enabled the mouse to detect relative motion on a wide variety of surfaces, translating the movement of the mouse into the movement of the cursor and eliminating the need for a special mouse-pad.
The first commercially successful optical computer mice were the Microsoft IntelliMouse® with IntelliEye™ and IntelliMouse® Explorer, introduced in 1999 using technology developed by Hewlett-Packard. It worked on almost any surface, and represented a welcome improvement over mechanical mice, which would pick up dirt, track capriciously, invite rough handling, and need to be taken apart and cleaned. Instead the reliable performance of the IntelliMouse® allowed relaxed grips which also were less likely to cause repetitive strain injury
Repetitive strain injury
Repetitive strain injury is an injury of the musculoskeletal and nervous systems that may be caused by...
. Other manufacturers soon followed Microsoft’s lead using components manufactured by the HP spin-off Agilent Technologies, and over the next several years mechanical mice became obsolete.
The technology underlying the modern optical computer mouse is known as digital image correlation
Digital image correlation
Digital Image Correlation and Tracking is an optical method that employs tracking & image registration techniques for accurate 2D and 3D measurements of changes in images. This is often used to measure deformation , displacement, and strain, but it is widely applied in many areas of science and...
, a technology pioneered by the defense industry for tracking military targets. Optical mice use image sensors to image naturally occurring texture in materials such as wood, cloth, mouse pads and Formica. These surfaces, when lit at a grazing angle by a light emitting diode, cast distinct shadows that resemble a hilly terrain lit at sunset. Images of these surfaces are captured in continuous succession and compared with each other to determine how far the mouse has moved.
To understand how optical mice work, imagine two photographs of the same object except slightly offset from each other. Place both photographs on a light table
Light table
A light table is a viewing device that is used to review photographic film or artwork placed on top of it. It provides even illumination of the subject from below through a translucent cover and fluorescent lights that emit little heat. They can also be found mounted on the walls of hospitals and...
to make them transparent, and slide one across the other until their images line up. The amount that the edges of one photograph overhang the other represents the offset between the images, and in the case of an optical computer mouse the distance it has moved.
Optical mice capture one thousand successive images or more per second. Depending on how fast the mouse is moving, each image will be offset from the previous one by a fraction of a pixel or as many as several pixels. Optical mice mathematically process these images using cross correlation to calculate how much each successive image is offset from the previous one.
An optical mouse might use an image sensor having an 18 x 18 pixel array of monochromatic pixels. Its sensor would normally share the same ASIC
ASIC
ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...
as that used for storing and processing the images. One refinement would be accelerating the correlation process by using information from previous motions, and another refinement would be preventing deadbands when moving slowly by adding interpolation or frame-skipping.
The invention of the modern optical mouse at HP was made more likely by a succession of related projects during the 1990s at its central research laboratory. In 1992 John Ertel, William Holland, Kent Vincent, Rueiming Jamp and Richard Baldwin were awarded US Patent 5,149,980 for measuring paper advance in a printer by correlating images of paper fibers. In 1998 Travis N. Blalock, Richard A. Baumgartner, Thomas Hornak, and Mark T. Smith were awarded US Patent 5,729,008 for tracking motion in a hand-held scanner by correlating images of paper fibers and document features, a technology commercialized in 1998 with the HP 920 Capshare handheld scanner. In 2002 Gary Gordon, Derek Knee, Rajeev Badyal and Jason Hartlove were awarded US Patent 6,433,780 for the modern optical computer mouse using image correlation.
LED mice
Optical mice often use LED's for illumination, even though they are sometimes colloquially referred to as 'lasers'.The color of the optical mouse's light-emitting diode
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
s can vary, but red is most common, as red diodes are inexpensive and silicon photodetectors are very sensitive to red light. Other colors are sometimes used, such as the blue LED of the V-Mouse VM-101 illustrated at right.
Laser mice
The laser mouse uses an infraredInfrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
instead of a LED to illuminate the surface beneath their sensor. As early as 1998, Sun Microsystems
Sun Microsystems
Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
provided a laser mouse with their Sun SPARCstation servers and workstations.
However, laser mice did not enter the mainstream market until 2004, when Paul Machin at Logitech
Logitech
Logitech International S.A. is a global provider of personal peripherals for computers and other digital platforms headquartered in Romanel-sur-Morges, Switzerland. The company develops and markets products like peripheral devices for PCs, including keyboards, mice, microphones, game controllers...
, in partnership with Agilent Technologies
Agilent Technologies
Agilent Technologies , or Agilent, is a company that designs and manufactures electronic and bio-analytical measurement instruments and equipment for measurement and evaluation...
, introduced its MX 1000 laser mouse. This mouse uses a small infrared laser instead of a LED and has significantly increased the resolution
Image resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
of the image taken by the mouse. The laser enables around 20 times more surface tracking power to the surface features used for navigation compared to conventional optical mice .
Glass laser (or glaser) mice have the same capability of a laser mouse but can also be used on top of mirror or transparent glass with few problems.
In August 2009, Logitech introduced mice with two lasers, to track on glass and glossy surfaces better; they dubbed them "dark field
Dark field microscopy
Dark field microscopy describes microscopy methods, in both light and electron microscopy, which exclude the unscattered beam from the image. As a result, the field around the specimen Dark field microscopy (dark ground microscopy) describes microscopy methods, in both light and electron...
" mice.
Power
Manufacturers often engineer their optical mice—especially battery-powered wireless models—to save power when possible. In order to do this, the mouse dims or blinks the laser or LED when in standby mode (each mouse has a different standby time). A typical implementation (by LogitechLogitech
Logitech International S.A. is a global provider of personal peripherals for computers and other digital platforms headquartered in Romanel-sur-Morges, Switzerland. The company develops and markets products like peripheral devices for PCs, including keyboards, mice, microphones, game controllers...
) has four power states, where the sensor is pulsed at different rates per second:
- 11500: full on, for accurate response while moving, illumination appears bright.
- 1100: fallback active condition while not moving, illumination appears dull.
- 110: standby
- 12: sleep state
Movement can be detected in any of these states; some mice turn the sensor fully off in the sleep state, requiring a button click to wake.
Optical mice utilizing infrared elements (LEDs or lasers) offer substantial increases in battery life. Some mice, such as the Logitech V450 848 nm laser mouse, are capable of functioning on two AA batteries for a full year, due to the low power requirements of the infrared laser.
Mice designed for use where low latency and high responsiveness are important, such as in playing computer games, may omit power-saving features to improve performance.
Optical versus mechanical mice
Metre per second
Metre per second is an SI derived unit of both speed and velocity , defined by distance in metres divided by time in seconds....
(80 inches per second).
Some models of laser mouse can track on glossy and transparent surfaces, and have a much higher sensitivity than other mechanical or optical mice, but are more expensive than their LED-based or mechanical counterparts.
mechanical mice had lower average power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
requirements than their optical counterparts; the power used by mice is relatively small, and only an important consideration when the power is derived from batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
, with their limited capacity.
Optical models outperform mechanical mice on uneven, slick, soft, sticky, or loose surfaces, and generally in mobile situations lacking mouse pads. Because optical mice render movement based on an image which the LED (or infrared diode) illuminates
Lighting
Lighting or illumination is the deliberate application of light to achieve some practical or aesthetic effect. Lighting includes the use of both artificial light sources such as lamps and light fixtures, as well as natural illumination by capturing daylight...
, use with multicolored mouse pads may result in unreliable performance; however, laser mice do not suffer these problems and will track on such surfaces. The advent of affordable high-speed, low-resolution cameras and the integrated logic in optical mice provides an ideal laboratory for experimentation on next-generation input-devices. Experimenters can obtain low-cost components simply by taking apart a working mouse and changing the optics or by writing new software.