Logitech helped pioneer the mouse industry over 20 years ago with the
introduction of its first mouse in 1981. This mouse was ahead of its time,
and it wasn’t until graphical user interfaces became popular a few years later
that mice became an essential computing tool.

For the next 18 years the basic operating principles of mice remained the
same. Nearly every mouse tracked motion using the familiar ball-based
mechanical tracking system. It wasn’t until a few years ago that a whole new
breed of mouse started to appear, the optical mouse.

Logitech’s optical experience began in 1995 when it introduced its
proprietary Marble™ optical sensing technology for trackballs. Then, in
2000, Logitech introduced a mouse featuring an optical tracking system,
replacing the ubiquitous ball with a tiny digital camera and image
processing system. This new technology revolutionized the way mice work
and eliminated many of the problems associated with ball-based mice.

Despite the advantages of the new optical mice, there were some
limitations. Most notably, they didn’t track well on certain surfaces, and
they had trouble following quick motions.

To overcome these limitations, Logitech worked with partner Agilent
Technologies to develop an entirely new optical system, the MX™
Optical Engine. The first mice to feature the MX Optical Engine are Logitech’s
new MX™ Series of performance mice. These mice provide smooth, precise
tracking on previously difficult surfaces, and respond to even the fastest
hand movements.

This paper explains the factors that contribute to optical performance, and
the advantages of the new MX Optical Engine.

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By their nature, traditional ball-based mice inherently suffer from a couple
of problems. First, as the ball rolls along a surface, it picks up dust or other
contaminants that eventually build-up and affect tracking. Typically this
results in choppy cursor movement, making it difficult to accurately point.

Second, ball-based mice don’t work well unless they are used on a mouse
pad. The pad provides a flat surface so the ball can maintain good traction
and roll smoothly. Otherwise cursor movement will not be fluid and the
mouse will have to be moved farther than necessary to reach a point on the
screen.

Optical mice overcome these problems because they track motion without
the use of moving parts that can become dirty or wear out. Furthermore,
because the optical tracking system doesn’t make physical contact with the
surface, optical mice can be used on a variety of surfaces without a mouse
pad. You can use one on a stack of paper or magazines, or even on surfaces
that aren’t flat.

While optical technology has many advantages, not all optical mice are
created equal. Optical tracking systems are complex designs consisting of
advanced opto-electronic components along with sophisticated software
algorithms. The new MX Optical Engine features improvements to nearly
every aspect of the optical system, outperforming previous designs. To
understand its benefits, it helps to understand how an optical mouse works.

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How an Optical Mouse Works

Optical mice use an LED to illuminate the surface beneath the mouse, a
lens to focus an image of the surface on the sensor of a tiny digital camera,
and a specialized digital signal processor (DSP) with intelligent software
algorithms to analyze the images.

Motion is tracked by taking a continuous series of pictures of the surface
under the mouse. These pictures are taken very quickly so there are
overlapping areas between successive images. The images are fed to the
DSP, which analyzes small surface details to see how their relative position
changes from one picture to the next. From this analysis the direction and
amplitude of movement are determined.

For example, the pictures below simulate two successive images captured by
the digital camera within an optical mouse. Details in image 1 are
compared with image 2, and from the difference in position the DSP
determines the mouse is moving down and to the right.

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As mentioned earlier, optical sensors are complex systems and overall
performance is a combination of many factors. Because of this, nearly every
aspect of the MX Optical Engine was enhanced to set a new benchmark in
performance. Following are some of the key features and improvements.

Image Processing Power
One of the most important metrics of tracking performance is to measure
the amount of image data the optical sensor is capable of processing every
second. This number, Image Processing Power, is measured in megapixels per
second and is a combination of several other metrics.

Image processing power is important because the more image data is
captured and analyzed each second, the more data is available to determine
motion. This increases a mouse’s ability to track on difficult surfaces or
during quick movements.

Logitech’s MX Optical Engine has an image processing power of 4.7
megapixels per second, over 60% higher than other leading mice. This
number attests to the significantly improved tracking capabilities of the MX
Series.

Sensor Size
An optical mouse needs to “see” small surface details to track motion, so it
follows that the more detail captured within each image, the more data will
be available for calculating movement.

The MX Optical Engine captures images that are over 80% larger than
those from other sensors on the market today. This contributes to the
smooth, fluid tracking on traditionally difficult surfaces, such as wood
desktops or other surfaces with repetitive patterns.

Frame Rate
Frame rate is another important factor of tracking quality. If the mouse is
moved too quickly and successive images don’t overlap, then the DSP will
not be able to determine actual motion and the cursor will move in a
random direction.

What should the frame rate be? The answer depends. Frame rate is
analogous to rpm in car engines, where a small engine needs to run at a
much higher rpm than a big engine to produce the same horsepower.

Therefore frame rates can’t be compared between optical sensors because
there are many differences between sensors. Large images captured by a big
sensor reduce the likelihood that successive images won’t overlap, so just
like a big engine, a big sensor can offer excellent performance with a lower
frame rate. Other factors can have a major effect on the minimum frame
rate, including the quality of the optics and illumination, the computational
power of the DSP, and the sophistication of the software algorithms used to
analyze images.

The MX Optical Engine combines improvements in all these areas with a
significantly increased frame rate for accurate, responsive control under
nearly any circumstance. It’s safe to say that few people will ever move a
mouse faster than the MX Optical Engine can track.

The MX Optical Engine

Resolution
The increasing popularity of large 17 and 19-inch monitors has created a
problem for mouse users. The large screen settings used with these
monitors mean the mouse must be moved farther than normal to point at
something across the screen. The problem is, large movements can be
physically uncomfortable.

Most optical mice have a resolution of 400 DPI (Dots Per Inch), meaning
that without software compensation, the cursor will move 400 pixels across
the screen for every inch the mouse is moved on the desktop. For small
screen settings this is fine, but for large settings it means the mouse must be
moved abnormally far.

To compensate for this, mouse software drivers include speed and
acceleration controls (accessed in the mouse properties dialog) to amplify
how far the cursor moves in response to how fast the mouse is moved.

For example, these controls could be set so when the mouse is moved slowly
across the table for one inch, the cursor will move 400 pixels across the
screen. As the mouse is moved faster, cursor movement will be increasingly
magnified up to the point where it will travel 800 pixels or more per inch of
mouse movement.

The problem with this is, as the settings are increased, pointing accuracy is
decreased and the cursor becomes more difficult to control. In the example
above, when the mouse is moved quickly for one inch, the cursor effectively
skips every other pixel in order to travel a screen distance of 800 pixels.
Thus pointing accuracy is reduced.

Logitech’s MX Optical Engine resolution is 800 DPI, twice that of most
competitor’s optical sensors. This allows smoother, more accurate cursor
control with large screens while minimizing the amount of left-and-right
hand motion. By default, the cursor is also easy to control with smaller
screen sizes, and Logitech’s software enables users to adjust the
responsiveness of the cursor to suit their individual preferences.

The Optical Path
Another fundamental factor that determines how well an optical mouse
performs is the quality of the images it captures. Since the lens is just a
fraction of an inch above the tracking surface, and the actual size of the
images is very small, even slight variations in manufacturing tolerances can
result in blurry images which seriously degrade tracking quality.

Logitech designed a proprietary new lens for the MX Optical Engine that
improves the depth of field. The result: more details are captured in each
image with greater clarity.

Significant improvements have also been made to the illumination pattern
of the LED. Just like a standard film camera, proper lighting makes a big
difference in how well the pictures turn out. For optical mice, the goal is to
generate maximum contrast between small surface details.

This is especially important on dark surfaces, which are challenging because
less light reflects off the surface into the sensor. Bright, even lighting is
important to keep the exposure time short. If the exposure time is too long,
the images will be blurry when the mouse is moved very quickly, reducing
tracking ability.

Logitech’s improved light pipe design ensures bright, even lighting across a
wide area for maximum efficiency and contrast. It also reduces the amount
of power needed, extending battery life for cordless devices.

Software Intelligence
Optical sensors incorporate software algorithms to analyze the incoming
images and determine motion. The intelligence of the algorithms has a
large effect on performance, especially when the mouse is used on difficult
surfaces or pushed to its limits.

The proprietary algorithms used in the MX Optical Engine incorporate
years of extensive research and testing, and contribute to the outstanding
performance on surfaces that traditionally pose problems for other optical
mice.

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Performance Specifications

There are a few common specifications used to indicate mouse
performance. As with cars and stereo speakers, numbers don’t always tell
the whole story, but they can provide a good indication of how well a
mouse will perform.

Acceleration and Speed
Mouse movements are characterized by short bursts of rapid acceleration
and deceleration as the user points to different locations on the screen.
This is especially true while playing games, when the mouse tends to be
moved very quickly.

Thus maximum acceleration and speed figures are frequently used as a
measure of performance. The MX Optical Engine is capable of tracking
movements up to an acceleration of 10g, and a maximum speed of 40
inches per second.

These numbers exceed typical human limits, and are a result of the MX
Optical Engine’s large sensor and high frame rate, the same features that are
responsible for superior tracking on difficult surfaces. While few will
approach the acceleration and speed limits, everyone can appreciate the
tangible benefit of improved tracking on almost any surface.

Surfaces
For most people, the ability to use an optical mouse on a variety of surfaces
is the most relevant aspect of performance. Older optical mice had trouble
navigating surfaces with repetitive patterns, such as wood desktops and half-tone
print.

Some surfaces have limitations that can’t be overcome with any optical
sensor. These include glossy and glass surfaces that are completely smooth
and lack surface details for the mouse to analyze. Mirrors are also
problematic, because too much light reflects off the surface and blinds the
optical sensor.

Aside from extremely smooth glossy or glass surfaces, the MX Optical
Engine is capable of navigating a much broader range of surfaces than
previous generations of optical mice. The benefit to the user is they can use
the MX Series of mice on almost any surface, giving them the freedom to
work where they want..

Graceful Degradation
Older optical mice tended to exhibit erratic cursor behavior when moved
faster than they were capable of tracking. The cursor would move in a
random direction across the screen, if it moved at all.

Graceful Degradation refers to the manner in which cursor control degrades
as a mouse’s tracking limits are surpassed. Ideally, cursor behavior should
degrade in a predictable fashion so some degree of control is maintained.
The ability to do so is largely a result of the intelligence of the software
algorithms within the optical sensor’s DSP.

The outstanding tracking capability of the MX Optical Engine virtually
eliminates the possibility that its tracking limits will be exceeded. Despite
this, Logitech’s advanced 3^rd generation algorithms are used within the MX
Optical Engine to ensure optimal tracking even at the outer limits of
performance.

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Conclusion

While not everyone needs the performance provided by the new MX
Optical Engine, it has been designed with the simple goal of providing the
best possible tracking under all conditions. Any user, whether a serious
gamer or someone who uses their mouse on a variety of surfaces, can
recognize the advantages it offers over other optical sensors.

Simply put, Logitech’s MX Series of mice provide more accuracy and
control on more surfaces than ever before.

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Introduction
In a Nutshell
The Reporting Advantage
Speeding Data Transmission
Delays Eliminated
Rechargeable Power
Conclusion

Introduction

Logitech pioneered the mouse industry more than 20 years ago with the
introduction of its first mouse in 1981. This mouse was ahead of its time,
and it wasn’t until graphical user interfaces became popular a few years
later that the mouse became an essential computing tool.

That happened in 1984, when Apple introduced its first Macintosh
computer, featuring a mouse designed by Logitech. This mouse
connected to the computer with a cable and used a rolling rubber-coated
metal ball tracking mechanism.

Though they worked well, corded, ball-based mechanical mice suffered
from two intrinsic shortcomings: those annoying cords always seemed to
get in the way, and the tracking ball got gummed up with dirt and
required frequent cleaning.

Setting out to conquer both problems, Logitech crafted two battle plans.
In 1992, the company shipped MouseMan® Cordless, the world’s first
cordless mouse. Three years later, they introduced the first optical
tracking technology with the launch of Marble™ technology for trackballs.
Then, in 2001, Logitech achieved the best of both worlds with the
introduction of Cordless MouseMan Optical.

The benefits of “no ball, no cord” proved to be substantial. Cordless mice
‘untether’ computer users, enhancing usability while freeing valuable
desktop real estate. Optical mice offer greater precision and smother
cursor movement, and because there is no ball, no cleaning is necessary.
Now, in 2002, Logitech introduces the MX™700 Cordless Optical Mouse.
Featuring advancements in both optical tracking and digital radio cordless
technology, the MX700 delivers smooth, precise tracking, responding
accurately to the fastest – or slightest – hand movements. A new
benchmark in performance is established.

This paper discusses three factors that contribute to cordless performance
and confirm the technological superiority of Logitech’s new Fast RF
cordless technology. These are reports per second, data-transmission
speed and method, and delay between reports.

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For those who don’t care about technology, the lesson of the MX700 Cordless Optical Mouse is simple: Cordless mice are better and the MX700 with Fast RF is Logitech's best cordless mouse ever.

The advantages are obvious. Cordless mice are easier to use. They don’t get tangled. They’re not limited to one spot on the desktop. Put a book in your lap and you can use the mouse there. Desktop clutter is cleared from messy cables. And cordless mice just look better.

Add to that new optical technology that further improves accuracy and responsiveness, and rechargeable batteries, and the urge to get a new mouse becomes irresistible.

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The job of any mouse is simple: track movement and report it to the
computer. The computer processes that information to move the cursor
image on the screen. Crucial to success is how many times per second the
mouse provides this location report. As the number of reports per second
increases, the motion of the cursor on the screen becomes more fluid.
Reports per second is the principal differentiating factor between the
MX700 with Fast RF and mice from other manufacturers.

A good analogy for reports per second is to imagine a circle, defined as a
series of points connected by straight lines. Think of each point as a
report, saying, “I’m here.” With just four points, that circle would be
drawn as a square; with eight points, an octagon—closer to a circle. With
1,000 points, individual lines become virtually invisible. Clearly, as the
number of points increases, the shape of the circle becomes smoother.
Likewise, as the number of reports per second increases, the motion of
the cursor more accurately follows the movement of the mouse.

The single most significant feature of Fast RF cordless technology is the
ability to deliver 125 reports per second, an astonishing 2.5 times
improvement over existing cordless mouse technology. This increase in
the report rate through Fast RF delivers “a corded performance without
the cord.”

Why not more than 125 reports per second? Certainly such a mouse can
be built. The limiting factor isn’t the mouse, but rather, the computer
port that polls the data. For example, the universal serial bus (USB) ports
present in every modern computer are not capable of polling faster than
125 reports per second.

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Every cordless mouse consists of two hardware components: the mouse
itself, which contains a battery-powered transmitter, and the receiver,
which plugs into the mouse port on the computer. Two methods exist for
data transmission, infrared (IR) and radio frequency (RF). Each has pros
and cons.

A television’s remote control unit employs IR technology. IR takes
advantage of the clear line of sight between transmitter and receiver, and
works well at distances of up to 40 feet.

Logitech’s cordless mice opt instead for digital RF technology. Doing so
eliminates the line-of-sight requirement, allowing the receiver to be
placed in a convenient, yet unobtrusive location, perhaps tucked behind a
monitor. And since the mouse and receiver are never more than about 20
inches apart, a low-cost, low-power, short-range signal can be used,
extending battery life significantly.

Of course, with Fast RF and the huge leap in reports per second, Logitech
had to find a way to transmit so much additional data without allowing
delays or backlogs to occur. This was accomplished by increasing the
speed of data transmission. Matching the advancements in report rate,
the bit rate for Fast RF was advanced 2.5 times over previous RF designs.
This faster data-transmission capability would mean nothing if there were
not more data to transmit. It is the mouse’s greatly increased number of
reports per second that was the driving feature in developing Fast RF.

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The third factor in achieving superior cordless mouse performance is the
time between each report transmitted by the mouse. After each report,
the mouse must ready itself for the next report, gathering data about its
motion, comparing it to its last position, and packaging that data in the
correct format. Rapid preparation (or minimizing delay between reports)
ensures a smooth data flow and maximizes reports made per second.

With Fast RF, Logitech has slashed delay time to less than half that
required by other leading mice. Doing so ensures that the mouse’s 125
reports per second are evenly spaced and sent as a series of discrete, yet
smooth, continuous operations.

All three technical advances, increased reports per second, fast data-
transmission rate, and reduced preparation time, work together as a
system to provide a superior user experience.

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Logitech’s MX700 Cordless Optical Mouse introduces another milestone—
the elimination of replacement batteries. Thanks to the use of
rechargeable nickel metal-hydride (NiMH) batteries, users no longer face
the expense of purchasing and inserting replacement batteries, a
significant and environmentally unfriendly inconvenience.

The rapid charge base station doubles as receiver and cradle into which
the mouse nests and recharges. A fast charging system gives the mouse a
day’s worth of power in only 10 minutes of charging. A full charge
provides up to 10 days worth of power – meaning that the mouse is
always ready for work (and play).

Cost savings can be significant. Given the price of AA-size alkaline
batteries, it is possible that, over the course of a mouse’s use life, a user
would spend as much for batteries as for the original purchase price of
the mouse itself.

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Though the benefits of cordless mice became clear years ago, now it can
be said that technology has fully delivered on the vision. The
technological leaps introduced by Logitech in the MX700 Cordless Optical
Mouse deliver a cordless experience punctuated by a silky smoothness of
operation heretofore unknown. Combined with its sophisticated optical-sensing
technology, feature-laden driver software, and rechargeable-battery
capability, Logitech remains a worldwide leader in input-device
innovation.

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