what are fingerprints and why and how we use them

1. Finger Prints Research
History of finger prints
It is believed that the chines were the first to use finger prints to identify individuals
without realizing that how unique these marks were, there are documents that were
signed three thousand years ago by Chinese culture using finger prints.
William Herschel was an English civil servant who worked at a tea company in India and
his job was to recruit Indians to harvest tea, to do this he had to make them sign a
contract, the problem was that they didn’t know how to write their names, so he had
them signed by butting their right hand in ink and pressing it to the paper.
It wasn’t until the year 1892 that Francis Galton (considered the god father of finger
prints) wrote the book “Finger Prints” in which he discussed the anatomy of finger prints
and suggested methods for recording them, he was the first individual who came up
with the three classifications of finger prints the loops, whorls, and arches which I will
talk about in later on, he also laid down the lows of finger prints which say that no two
finger prints are the same and that a finger print of an individual remain unchanged.
In the early 19’s the US began to use finger prints as an efficient way to identify
individuals followed by the whole world until now, nowadays we use finger prints in
almost every aspect of our lives that need authentication and identification from
unlocking our smart phones to identifying victims and criminal in a police investigation.
How is it that every one of us has a unique finger print?
Finger print is considered a very efficient way to identify individuals because every
individual has his own unique finger print, in fact even identical twins who have the
same DNA have different finger prints and the reason why is that finger prints are
created while the baby is his mother’s whom, the pressure of the fluid inside the whom
on the surface of the hands and finger tips influences the formation of patterns and with
so many factors which determine the shapes of these patterns every ones finger prints
are unique

2. Finger Prints types and Characteristics
Fingerprints are formed from three basic shapes which are ridges, cores and deltas: -
Ridges: are the edged lines on your finger that forms the unique pattern for every
fingerprint.
Cores: are the inner most recurve at the center of the pattern.
Deltas: are the features in a fingerprint where three areas of ridges converge into a
triangle shape.
There are three main types of finger prints that we use to classify every finger print
which are loops, arches and whorls: -
An arch pattern is the simplest type of fingerprints but also the rarest. Only about 5% of
population have arch fingerprints, arch fingerprints have ridges begin in one side and
ends on the other side making a line that looks like a hill, there are usually no cores or
deltas in an arch
Loop patterns are the most common they are found in about 70% of the population,
ridges in a loop pattern begin and end on the same side there are usually one core and
one delta in a loop pattern.
In a whorl pattern the ridges form a spiral that appears to complete a full circle
approximately 25% of the world population has whorl patterns there are usually two
deltas in a whorl pattern.
As you look closer to a fingerprint you will notice that ridges start and stop as they flow
throw the pattern these are the characteristics of a fingerprint ridges.

3. Ridge ending occurs when a ridge stops and
two other ridges on the side converge to fill the
space.
Bifurcation occurs when a ridge splits to form
two ridges at a specific point.
Dot/Scar occurs when a ridge starts and stops
over a short distance making the ridge making
the ridge approximately only as long as it wide.
With these characteristics, we can compare
between two or more fingerprint and recognize
which fingerprint belongs to whom.
Fingerprint scanners
Capacitive Sensors
Capacitive sensors use an array capacitor plates to image the fingerprint. Skin is
conductive enough to provide a capacitive coupling with an individual capacitive
element on the array. Ridges, being closer to the detector, have a higher capacitance
and valleys have a lower capacitance. Some capacitive sensors apply a small voltage to
the finger to enhance the signal and create better image contrast.
Optical Sensors
Optical sensors use arrays of photodiode or phototransistor detectors to convert the
energy in light incident on the detector into electrical charge. The sensor package
usually includes a light-emitting-diode (LED) to illuminate the finger.
Thermal Sensors
Thermal sensors use the same pyro-electric material that is used in infrared cameras.
When a finger is presented to the sensor, the fingerprint ridges make contact with the
sensor surface and the contact temperature is measured, the valleys do not make
contact and are not measured. A fingerprint image is created by the skin-temperature
ridges and the ambient temperature measure for valleys.
Pressure Sensors
Pressure sensing scanners can be made very thin and are often used in electronic
devices. Early pressure sensing scanners had to make a tradeoff between durability
and quality because any protective layer on the detector surface would diminish the
contrast of the impression.

4. RF Sensors
A low radio frequency (RF) signal is applied to the user’s finger and then read by the
detector array, with each pixel operating like a tiny antenna. The advantage of this
detector is that it reads the fingerprint from the dermal layer underneath the surface
making it less susceptible to damaged or dry fingertips.
Ultrasonic Sensors
Ultrasonic scanners have an advantage of being able to see beneath the skin. This
provides not only verification of a live finger, it provides more information as a biometric
measure. But this technology is slow, expensive, bulky, and too data intensive for most
access control applications.
Static Fingerprint Sensor
A Static Fingerprint Reader/Sensor requires the user to place the finger motionless on a
surface. The sensor array must be as large as the area of the image to be captured.
Swipe Fingerprint Sensor
A Swipe Fingerprint Reader/Sensor requires the user drag the upper part of the finger
across the sensor. The complete image is pieced together by accumulating the partial
image as the finger moves across the scan area.