modern sensors

8/12/2019 modern Sensors

http://slidepdf.com/reader/full/modern-sensors 1/36

MODERN DAY SENSORS 2013-2014

Department Of Electrical & Electronics, CPTC 1 | P a g e

ACKNOWLEDGEMENT

First and foremost I thank Almighty for all the blessings on the successful completion

of this seminar.

A seminar in its entire means can only be accomplished with the assistance of many

people. I show my sincere gratitude to all those who contributed in this seminar work, they

can never be forgotten.

I owe a great deal of gratitude towards Head of Department of Electrical andElectronics Engineering, Mrs.Lizz Joseph for her whole hearted support for this seminar. I

express my sincere thanks to the lecturers Fr. Josekutty Chacko, Mrs. Tinu Scaria, and Fr.

Jacob Kurian for their encouragement and support throughout my preparations.

At last, but not the least, I thank Jeji B Chandran Secretary, Electrical Engineering

Association) for making arrangements for the seminar and I also thank all my friends and

well wishers for their cooperation and moral support.





TABLE OF CONTENTS

ABSTRACT ........................................................................................................................................................... 4

INTRODUCTION .................................................................................................................................................. 5

HOW A CAMERA WORKS? ................................................................................................................................. 6

WHAT IS AN IMAGE SENSOR? .......................................................................................................................... 10

HISTORY OF IMAGE SENSORS .......................................................................................................................... 11

TYPES OF IMAGE SENSORS ............................................................................................................................... 11

CHARGE COUPLED DEVICE ............................................................................................................................... 12

Basic Operation of a CCD ................................................................................................................................. 13

TRANSFORMATION OF AN IMAGE USING CCD ARRAY .................................................................................... 15

FRAME TRANSFER CCD IMAGE SENSOR ........................................................................................................... 16

INTERLINE TRANSFER CCD SENSOR ................................................................................................................. 17

INTERLINE TRANSFER VS FRAME TRANSFER .................................................................................................... 17

CMOS SENSORS ................................................................................................................................................ 18

BASIC OPERATION OF CMOS SENSORS ............................................................................................................ 18

COMPARISON OF CCD AND CMOS SENSORS ................................................................................................... 20

ACCELEROMETER SENSOR ............................................................................................................................... 21

MEMS technology ............................................................................................................................................ 22

MEMS ACCELEROMETERS .................................................................................................................................. 24

MEMS f abrication ........................................................................................................................................... 25

GYROSCOPE SENSOR ........................................................................................................................................ 27

PROPERTIES OF A GYROSCOPE ........................................................................................................................ 32

Proximity Sensor .............................................................................................................................................. 36





ACKNOWLEDGEMENT

First and foremost I thank Almighty for all the blessings on the successful completion

of this seminar.

A seminar in its entire means can only be accomplished with the assistance of many

people. I show my sincere gratitude to all those who contributed in this seminar work, they

can never be forgotten.

I owe a great deal of gratitude towards Head of Department of Electrical and

Electronics Engineering, Mrs.Lizz Joseph for her whole hearted support for this seminar. Iexpress my sincere thanks to the lecturers Fr. Josekutty Chacko, Mrs. Tinu Scaria, and Fr.

Jacob Kurian for their encouragement and support throughout my preparations.

At last, but not the least, I thank Jeji B Chandran Secretary, Electrical Engineering

Association) for making arrangements for the seminar and I also thank all my friends and

well wishers for their cooperation and moral support.





ABSTRACT





INTRODUCTION

WHAT IS A 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 thermocouple converts temperature to an output voltage which can be

read by a voltmeter.

For accuracy, all sensors need to be calibrated against known standards.

The following are the different types of sensors:

SENSED QUANTITY SENSOR

Temperature Thermometer, Thermocouple

Heat Bolometer, Calorimeter

Electrical resistance Ohmmeter, Multimeter

Electrical current Ammeter, Galvanometer

Magnetism Magnetometer, Fluxgate compass

RadiationGeiger Counter, Dosimeter, Scintillation

Counter

Acoustic Sound ) Seismometers, Microphones,Hydrophones

Pressure Altimeter, Barometer, Barograph





HOW A CAMERA WORKS

Photography is undoubtedly one of the most important inventions in history -- it has truly

transformed how people conceive of the world. Now we can "see" all sorts of things that

are actually many miles -- and years -- away from us. Photography lets us capturemoments in time and preserve them for years to come.

The work of a camera – photography is considered to be one of the greatest inventions of

mankind. It has not only helped us see the entire world through a click, but has also

transformed how people conceive the world. They can also be kept as a remembrance for

the rest of our life.

Camera can be defined as a device that is used to capture and record photos or videos.

EARLY USE OF CAMERA

Nowadays we see a lot of advanced cameras that are used to capture motion as well as

images from a very far distance. During the time of its invention images could be taken

only in a room and could not be portable. The instrument should be kept in a dark

chamber or box and the room should function as a real-time imaging system. Thus the

camera was earlier called “camera-obscura” which meant “dark chamber”. The first of this

kind was invented by a scientist called Johannes Kepler. But this apparatus was very huge

and could be portable only as a tent. For this instrument to work the light was passed onto

it through a convex lens. Thus an image consisting of external objects would be formed

which was subjected to the surface of a paper or glass, placed at the focus of the lens. A

much compact and portable camera was introduced in 1685 by Johann Zahn.

After years of work by many prominent people the first colour photo was invented by the

famous physicist James Clark Maxwell along with Thomas Sutton. Then came theinvention of the video made in cameras during the early 1920s. This technology has

eventually grown to such heights that in this 21st century, these ordinary film cameras

have been replaced by digital cameras.

PARTS OF A CAMERA

A camera has mainly three parts. They are

Mechanical part or the camera body





Optical part or the lens section

The chemical part or the film

The way in which these three parts are connected represents the different types of

cameras. Thus by combining these three parts and using them under the correct

calibration produces a correct picture. They are capable of working in both the visible

spectrum as well as in other portions of the electromagnetic spectrum. The basic shape of

a camera needs an enclosed hollow chamber with an opening at one end. This opening,

also called aperture helps in the entrance of light. This light is the actual image that has to

be captured. So a capturing mechanism is set at the other end. All cameras have the lens

assembled in the front. This lens helps in capturing the light, which is in turn captured

and stored by the recording surface. Most ordinary cameras can take one image at a time.Most video cameras can take a

maximum of 24 film frames/sec.

MECHANISM OF A CAMERA

To know the complete mechanism

of the camera, it is better to know

each and every parameter of thecamera.

1. Focus

A camera’s focus greatly depends on the clarity of the picture taken. But the focus can be

limited only to a certain distance. This range is limited to the range of the lens. This range

when adjusted to get a perfect image is called the focus of the camera. For accurate

focussing of cameras, the device is comprised of a fixed focus and also consists of a wide-angle lens and a small aperture in front of the camera. The range of focus will be clearly

indicated in the camera with symbols like two people standing upright, mountains and so

on. For a simple camera, a reasonable focus of about 3 meters to infinity is available. The

focus available on each camera is different. Single-lens reflex (SLR) cameras have a focus

that can be changed according to our like. This is done by providing a objective lens and a

moving mirror so as to projecting the image to a ground glass or plastic micro-prism

screen. Similarly each camera has different settings which will be explained briefly later.

The focus of a camera depends on two main features. They are





The structure and position of the lens.

The angle in which the light beams enter into the lens.

Consider a pencil kept at a short distance from the lens. When the distance is altered, that

is kept near and then farther away from the lens, the angle of entry of the light changes

accordingly. This light is hit on the film surface kept inside the camera. The angle becomes

sharper when the image is close to the lens and will become narrower when the image is

kept far away. Thus when the lens is focused farther and then nearer from the pencil, the

image is actually moving closer or farther away from the film surface. The correct image

will be obtained when the focus is adjusted in such a way that you can line up the focused

real image of an object so it falls directly on the film surface.

2. Camera Lens

The quality of the photograph taken largely depends on the type of lens used. The

precision of a lens depends on a factor called “bending angle”. This in turn, depends on the

structure of the lens. If the lens has a flat shape, the bending angle is less. Thus the light

beams will converge a little distance farther away from the lens. Thus the image is also

formed farther away. Thus when the distance increases, the size of the image also

increases, though the size of the film is constant. If the lens has a round shape, the bendingangle will be high. Thus the image will be formed a lot more nearly to the lens.

Costly cameras have a lot of lenses, which are replaced or combined according to the

magnification required. This magnification power of a lens is called the focal length.

Greater the focal length, greater the magnification.

3. Camera Film

For an image to be recorded and viewed it must be stored in a film. When an image is

captured, it is actually being “chemically” recorded onto a film. The film mainly consists of

millions of light-sensitive grains, which are suspended on a plastic strip. These grains

chemically react, when exposed to light. This reaction causes the image to be recorded on

the film. This film is then developed by reacting it with other chemicals. For black and

white films, the chemicals cause the grains to appear darker when exposed to light. Thus,

the darker areas appear lighter and the lighter areas appear darker. This is reversed while

printing out the photos.





For producing colour films, the film consists of light sensitive materials that respond to

colours red, green and blue. When they are washed and chemically reacted, you get a

negative of a colour photo.

DIFFERENT CAMERA DESIGNS

There are a lot of types of cameras like Plate camera, large format camera, medium format

camera, folding camera, rangefinder camera and so on. Out of these the most used ones

are the single-lens reflex camera (SLR) and the point and shoot camera. The difference

comes in the manner in which the photographer visualizes the scene. In a point and shoot

camera, you do not see the real image through the camera lens. Instead, you get to see only

a blurred vision of the image.

In an SLR camera, you can see the

real image of the scee you are about

to capture. It has the same

configuration as that of a periscope.

When the image is seen from the

lens, it hits the lower mirror and

bounces from there. It then hits the

prism. This prism flips the image toform the original image. The mirror

and translucent screen help in

providing the exact image to the

photographer. Thus, you can focus

and compose the image so as to get the exact picture you have in mind.

With upcoming technology, the point and shoot cameras are nowadays fully automatic.

SLR is built with both manual and automatic controls. The only difference between the

manual and automatic cameras is that the former will be controlled by a central

processor, instead of the photographer.

The focus system and the light meter transmit the signals to the microprocessor and thus

activate all the motors accordingly. These motors control the adjusting lens and also open

and close the aperture.





WHAT IS AN IMAGE SENSOR

Unlike traditional camera, that use film to capture and store an image, digital

cameras use solid-state device called image sensor.

Image sensors contain millions of photosensitive diodes known as photo sites.

When we take a picture, the camera's shutter opens briefly and each photo site on

the image sensor records the brightness of the light that falls on it by accumulating

photons. The more light that hits a photo site, the more photons it records.

The brightness recorded by each photo site is then stored as a set of numbers

(digital numbers) that can then be used to set the color and brightness of a single

pixel on the screen or ink on the printed page to reconstruct the image.

PIXELS

The smallest discrete component of an image or picture on a CRT screen is known

as a pixel.

“The greater the number of pixels per inch the greater is the resolution”.

Each pixel is a sample of an original image, where more samples typically provide

more-accurate representations of the original.

FILL FACTOR

Fill factor refers to the percentage of a photosite that is sensitive to light.

If circuits cover 25% of each photosite, the sensor is said to have a fill factor of 75%.The higher the fill factor, the more sensitive the sensor.





HISTORY OF IMAGE SENSORS

Before 1960 mainly film photography was done and vacuum tubes were being

used.

From 1960-1975 early research and development was done in the fields of CCD

and CMOS.

From 1975-1990 commercialization of CCD took place.

After 1990 re-emergence of CMOS took place and amorphous Si also came into the

picture.

TYPES OF IMAGE SENSORS

An image sensor is typically of two types:

1. Charged Coupled Device (CCD)

2.

Complementary Metal Oxide Semiconductor (CMOS)





CHARGE COUPLED DEVICE

CCD Stands for "Charged Coupled Device." CCDs are sensors used in digital cameras and

video cameras to record still and moving images. The CCD captures light and converts it

to digital data that is recorded by the camera. For this reason, a CCD is often considered

the digital version of film.

The quality of an image captured by a CCD depends on the resolution of the sensor. In

digital cameras, the resolution is measured in Megapixels (or thousands of or pixels.

Therefore, an 8MP digital camera can capture twice as much information as a 4MP

camera. The result is a larger photo with more detail.

CCDs in video cameras are usually measured by physical size. For example, most

consumer digital cameras use a CCD around 1/6 or 1/5 of an inch in size. More expensive

cameras may have CCDs 1/3 of an inch in size or larger. The larger the sensor, the more

light it can capture, meaning it will produce better video in low light settings. Professional

digital video cameras often have three sensors, referred to as "3CCD," which use separate

CCDs for capturing red, green, and blue hues.

Charge-coupled devices (CCDs) are silicon-based integrated circuits consisting of a dense

matrix of photodiodes that operate by converting light energy in the form of photons

into an electronic charge.

Electrons generated by the interaction of photons with silicon atoms are stored in a

potential well and can subsequently be transferred across the chip through registers and

output to an amplifier.





HISTORY OF CCD SENSORS

The CCD started its life as a memory device and one could only "inject" charge into

the device at an input register.

However, it was immediately clear that the CCD could receive charge via the

photoelectric effect and electronic images could be created.

By 1969, Bell researchers were able to capture images with simple linear devices;

thus the CCD was born.

It was cconceived in 1970 at Bell Labs.

Basic Operation of a CCD

In a CCD for capturing images, there is a photoactive region, and a transmission

region made out of a shift register (the CCD, properly speaking).

An image is projected by a lens on the capacitor array (the photoactive region),

causing each capacitor to accumulate an electric charge proportional to the light

intensity at that location.

A one-dimensional array, used in cameras, captures a single slice of the image,

while a two-dimensional array, used in video and still cameras, captures a two-

dimensional picture corresponding to the scene projected onto the focal plane of

the sensor.





Once the array has been exposed to the image, a control circuit causes each

capacitor to transfer its contents to its neighbor.

The last capacitor in the array dumps its charge into a charge amplifier, which

converts the charge into a voltage.

By repeating this process, the controlling circuit converts the entire semiconductor

contents of the array to a sequence of voltages, which it samples, digitizes andstores in some form of memory.





TRANSFORMATION OF AN IMAGE USING CCD ARRAY

1- CCD camera, 2- CCD detector, 3- Reading, 4- Amplifier, 5- A/D converter, 6-

Digitization , 7- Download





FRAME TRANSFER CCD IMAGE SENSOR

Top CCD array used for photo detection (photo gate) and vertical shifting.

Bottom CCD array optically shielded – used as frame store.

Operation is pipelined: data is shifted out via the bottom CCDs and the horizontal

CCD during integration time of next frame.

Transfer from top to bottom CCD arrays must be done very quickly to minimize

corruption by light, or in the dark (using a mechanical shutter).

Output amplifier converts charge into voltage, determines sensor conversion gain.





INTERLINE TRANSFER CCD SENSOR

Photodiodes are used.

All CCDs are optically shielded, used only for readout.

Collected charge is simultaneously transferred to the vertical CCDs at the end of

integration time (a new integration period can begin right after the transfer) and

then shifted out.

Charge transfer to vertical CCDs simultaneously resets the photodiodes, (shuttering

done electronically for `snap shot' operation).

INTERLINE TRANSFER VS FRAME TRANSFER

Frame transfer uses simpler technology (no photodiodes), and achieves higher fill

factor than interline transfer.

Interline transfer uses optimized photodiodes with better spectral response than the

photo gates used in frame transfer.

In interline transfer the image is captured at the same time (`snap shot' operation)

and the charge transfer is not subject to corruption by photo detection (can be

avoided in frame transfer using a mechanical shutter).

Frame transfer chip area (for the same number of pixels) can be larger than

interline transfer.

Most of today’s CCD image sensors use interlines transfer.





CMOS SENSORS

“CMOS" refers to both a particular style of digital circuitry design, and the family of

processes used to implement that circuitry on integrated circuits (chips).

CMOS circuitry dissipates less power when static, and is denser than other

implementations having the same functionality.

CMOS circuits use a combination of p-type and n-type metal – oxide –

semiconductor field-effect transistors (MOSFETs) to implement logic gates and

other digital circuits found in computers, telecommunications equipment, and

signal processing equipment.

BASIC OPERATION OF CMOS SENSORS

In most CMOS devices, there are several transistors at each pixel that amplify and

move the charge using wires.

The CMOS approach is more flexible because each pixel can be read individually.

In a CMOS sensor, each pixel has its own charge-to-voltage conversion, and the

sensor often also includes amplifiers, noise-correction, and digitization circuits, so

that the chip outputs digital bits.

With each pixel doing its own conversion, uniformity is lower.





COMPARISON OF CCD AND CMOS SENSORS

CMOS image sensors can incorporate other circuits on the same chip, eliminating

the many separate chips required for a CCD.

This also allows additional on-chip features to be added at little extra cost. These

features include image stabilization and image compression.

Not only does this make the camera smaller, lighter, and cheaper; it also requires

less power so batteries last longer.

CMOS image sensors can switch modes on the fly between still photography and

video.

CMOS sensors excel in the capture of outdoor pictures on sunny days, they suffer

in low light conditions.

Their sensitivity to light is decreased because part of each photosite is covered with

circuitry that filters out noise and performs other functions.

The percentage of a pixel devoted to collecting light is called the pixel’s fill factor.

CCDs have a 100% fill factor but CMOS cameras have much less.

The lower the fill factor, the less sensitive the sensor is and the longer exposure

times must be. Too low a fill factor makes indoor photography without a flash

virtually impossible.

CMOS has more complex pixel and chip whereas CCD has a simple pixel and chip.





ACCELEROMETER SENSOR

Accelerometers are one of the simplest but also most applicable microelectro mechanical

s y

st

em

s. Th

e y have b

ec

ome indi

sp

en

sabl

e in

automobil

e indu

stry , comput

er

and

audio-

video technolog y . This seminar presents MEMS technolog y as a hi ghl y developing

industry . Special attention is given to the capacitor accelerometers, how do the y w ork and

their applications. The seminar closes w ith quite extensivel y described MEMS

f abrication.

An accelerometer is an electromechanical device that measures acceleration f orces.

These f orces ma y be static, lik e the

constant f orce of gravit y pulling at our

f eet, or the y could be d y namic - caused b y

moving or vibrating the accelerometer.

There are man y t y pes of accelerometers

developed and reported in the literature.

The vast ma jorit y is based on piezoelectric

cry stals, but the y are too bi g and to clums y .

P eople tried to develop something smaller,

that could increase applicabilit y and

started searching in the field of

microelectronics. The y developed MEMS

(micro electromechanical s y stems)

accelerometers.

The fi

rst micro m

achin

ed

acc

el

erom

et

er w

as d

esi gn

ed in 1979

at

St

anf ord Univ

er

sit y ,

but it took over 15 y ears bef ore such devices became accepted mainstream products f or

lar ge volume applications. In the 1990s MEMS accelerometers revolutionised the

automotive-airba g-s y stem industry . Since then the y have enabled unique f eatures and

applications ranging f rom hard-disk protection on laptops to game controllers. More

recentl y , the same sensor-core technolog y has become available in f ull y inte grated,

f ull-f eatured devices suitable f or industrial applications.

Micro machined accelerometers are a hi ghl y enabling technolog y w ith a huge commercial potential. The y provide low er pow er, compact and robust sensing.





Multiple sensors are of ten combined to provide multi-axis sensing and more accurate

data .

MEMS TE HNOLOGY

What could link an ink jet printer head, a video pro jector DLP s y stem, a disposable bio-

anal y sis chip and an airba g crash sensor - y es, the y are all MEMS, but w hat is MEMS?

Micro Electro

Mechanical S y stems or MEMS is a term co

ined around 1989 b y P rof .

R . How e and others to describe an emer ging research field,

w here mechanical elements,

lik e cantilevers or membranes, had been

manuf actured at a scale more ak in to

microelectronics circuit than to lathe

machining. It appears that these devices share the presence of f eatures below 100 _ m that

are not machined using standard machining but using other techniques globall y called

micro-f abrication technolog y . Of course, this simple definition w ould also include

microelectronics, but there is a characteristic that electronic circuits do not share w ith

MEMS. While electronic circuits are inherentl y solid and compact structures, MEMS

have holes, cavit y , channels, cantilevers, membranes, etc, and, in some w a y , imitate

‘mechanical’ parts. The emphasis on MEMS based on silicon is clearl y a result of the

vast k now ledge on silicon material and on silicon based microf abrication gained b y

decades of research in microelectronics. And a gain, even w hen MEMS are based on

silicon, microelectronics process needs to be adapted to cater f or thick er la y er deposition,

deeper etching and to introduce special steps to f ree the mechanical structures. MEMS

needs a completel y diff erent set of mind, w here next to electronics, mechanical and ma-

terial k now ledge pla y s a f undamental role. Then, man y more MEMS are not based on

silicon and can be manuf actured in pol y mer, in glass, in quartz or even in metals.

development of a MEMS component has a cost that should not be misevaluated and the

technolog y has the possibilit y to bring unique benefits. The reasons that prompt the use

of MEMS technolog y are f or example miniaturization of existing devices, development of





new devices based on principles that do not w ork at lar ger scale, development of new

tools to interact w ith the micro-w orld.

Miniaturization reduces cost b y decreasing material consumption. It also increases

applicabilit y b y reducing mass and size allow ing to place the MEMS in places w here a

traditional s y stem doesn’t fit. A t y pical example is brought b y the accelerometer

developed as a replacement f or traditional airba g tri ggering sensor also used in di gital

cameras to help sta-bilize the ima ge or even in the contact-less game controller inte grated

in the latest handphones. Another advanta ge that MEMS can bring relates w ith the s y stem

inte gration. Instead of having a series of external components (sensor, inductor...)

connected b y w ire or soldered to a printed circuit board, the MEMS on silicon can be

inte grated directl y w ith the electronics. These so called smart inte grated MEMS alread y

include data acquisition, filtering, data stora ge, com-munication, interf acing and

netw ork ing [4]. As w e see, MEMS technolog y not onl y mak es the things smaller but

of ten mak es them better.

The MEMS component currentl y on the mark et can be broadl y divided in six

cate gories w here next to the w ell-k now n pressure and inertia sensors produced b y

diff erent manuf acturer lik e Motorola, Analog Devices. The micro-fluidic applications

are best k now n f or the ink jet printer head popularized b y Hew lett Packard.

The MEMS component currentl y on the mark et can be broadl y divided in six cate gories

P ack ard, but the y also include the grow ing bioMEMS mark et w ith micro anal y sis

s y stem lik e the capillary electrophoresis s y stem f rom A gilent or the DNA chips.

Moreover MEMS deals w ith the now rather successf ul optical pro jection s y stem that is

competing w ith the LCD (liquid cry stal displa y) pro jector. R F (radio f requenc y) MEMS is also emer ging as viable MEMS mark et. Next to passive components lik e hi gh-Q

inductors produced on the IC surf ace to replace the h y bridized component as proposed b y

compan y MEMSCAP w e find R F sw itches and soon micromechanical filters. But the

list does not end here and w e can find micro machined rela y s (MMR ) produced f or

example b y Omron, HDD (hard disk drive) read/write head and actuator or even to y s,

lik e the autonomous micro-robot EMR oS produced b y EPSO





MEMS ELEROMETERS

There are man y diff erent w a y s to mak e an accelerometer. Some accelerometers use the

piezo-electric eff ect - the y contain microscopic cry stal structures that get stressed b y

accelerative f orces, w hich cause a volta ge to be generated. Another w a y to do it is b y

sensing changes in capacitance [3]. This seminar is f ocused on the latter.

Capacitive interf aces have several attractive f eatures. In most micromachining

technologies no or minimal additional processing is needed. Capacitors can operate both

as sensors and actuators. The y have excellent sensitivit y and the transduction mechanism is

intrinsicall

y insen

-si

tiv

e

to t

empe

ra

tu

re.

Accelerometers are being incorporated into more and more personal electronic devices

such as media pla y ers and gaming devices. In particular, more and more smartphones

(such as Apple’s iP hone and the Nok ia N95) are incorporating accelerometers f or step

counters, user interf ace control, and sw itching betw een portrait and landscape modes.

The y use accelerometers as a tilt sensor f or ta gging the orientation to photos tak en w ith

the built-in camera. The Nok ia 5500 sport f eatures a 3D accelerometer that can be used

f or tap gestures, f or example to change to next song b y tapping through clothing

w hen the device is in a pock et. Camcorders use accelerometers f or ima ge stabilization.

Still cameras use accelerometers f or anti-blur capturing. Some di gital cameras, such as

Canon’s P ow erShot and Ixus range contain accelerometers to determine the orientation

of the photo being tak en and also f or rotating the current picture w hen view ing

Accelerometers are also being used in new contactless game controller or mouse. IBM

a

nd Apple

ha

ve

rece

ntl y

s

ta

rte

d usi

ng accele

rome

te

rs

in th

eir la

ptops

to protec

t ha

rd drives f rom dama ge. If y ou accidentall y drop the laptop, the accelerometer detects the

sudden f reef all, and sw itches the hard drive off so the heads don’t crash on the platters

In a similar f ashion, hi gh g accelerometers are the industry standard w a y of

detecting car crashes and deplo y ing airba gs at just the ri ght time. The y are used to

detect the rapid ne gative acceleration of the vehicle to determine w hen a collision has

occurred. The y also have a built-in self -test f eature, w here a micro-actuator w ill

simulate the eff ect of deceleration and allow check ing the inte grit y of the s y stem every time y ou start up the engine. R ecentl y the g yroscopes (the y rel y on a mechanical





structure that is driven into resonance and excites a secondary oscillation in either the

same structure or in a second one, due to the Coriolis f orce [13]) made their apparition f or

anti-sk idding s y stem and also f or navi gation unit. The w idespread use of accelerometers

in the automotive industry has pushed their cost dow n dramaticall y [2, 14].

Accelerometers have also f ound real-time applications in controlling and

monitoring militar y and aerospace s y stems. Smart w eapon s y stems (direct and indirect

fire; aviation-launched and ship-launched missiles, rock ets, pro jectiles and sub

munitions) are among these application. Some MEMS sensors have alread y been used in

satellite. The development of micro (less than 100k g) and nano (about 10k g) satellites is

bringing the mass and volume advanta ge of MEMS to good use.

MEMS B T ON

Micro-f abrication is the set of technologies used to manuf acture structures w ith

micrometric f eatures. This task can unf ortunatel y not rel y on the traditional

f abrication techniques such as milling, drilling, turning, f or ging and casting because

of the scale. The f abrication techniques had thus to come f rom another source. As

MEMS devices have about the same f eature size as inte grated circuits (IC), MEMS f abrication technolog y quick l y took inspiration f rom microelectronics. Techniques

lik e photolithograph y , thin film deposition b y chemical vapor de-position (CVD) or

ph y sical vapor deposition (P VD), thin film grow th b y oxidation and epitaxy , doping b y

ion implantation or diff usion, w et etching, dry etching, etc have all been adopted b y the

MEMS technologists. Moreover, MEMS also grounded man y unique f abrication

techniques that w e w ill describe in this seminar lik e bulk micromachining, surf ace

micromachining, deep reactive ion etching (DR IE), etc .

In general, MEMS f abrication tries to use batch process to benefit f rom the same

econom y of scale that is so successf ul in reducing the cost of ICs. As such, a t y pical

f abrication process starts w ith a w af er (silicon, pol y mer, glass...) that ma y pla y an active

role in the final device or ma y onl y be a substrate on w hich the MEMS is built. This

w af er is processed in a succession of processes that add, modif y or remove materials along

precise patterns.



26 | P a g e

The problem of patterning a material (or mak ing la y out) is generall y split in

tw o distinct steps: first, deposition and patterning of a surrogate la y er that can be

easil y modified locall y . In the most common process called photo-patterning, the

surrogate la y er used is a special pol y mer (called a photoresist) w hich is sensitive to

UV-photon action (F i gure 4.1).

Now w e have to transf er the pattern to the material of interest. There are tw o

main tech-niques that can be used to transf er the pattern: lithograph y and lif t

off. Combination of photo-patterning and lithograph y is k now n as

photolithograph y and is now ada y s the most common techniques f or micro-

f abrication, l y ing at the roots of the IC revolution

This is how the basics of MEMS or at least patterned w af ers that will be used in

further process are made. Technologicall y very important and also quite expensive

step in process is pack a ging. It can present even more than 50% of final product

cost. Let’s now look in detail at some materials and some processes or techniques

that can be used during MEMS process. We alread y mentioned some above.



27 | P a g e

GYROSCOPE SENSOR

A gyroscope plays a significant role in the gaming arena for game consoles as well as

smartphones. Smartphones with gyroscope support are able provide the player a

richer experience in handling the game controls than a smartphone without it. Back

in June 2010, Steve Jobs announced the first iPhone to offer gyroscope support,

which is the Apple iPhone 4 we know today.

A mechanical gyroscope is a device consisting of a small spinning wheel that is

mounted inside two circular metallic rings that are perpendicular to each other. The

spinning wheel would continue spinning on its axis regardless of the alignment of

the outer rings.

it is primarily used in measuring or maintaining orientation. Thus, this nifty device is

able to detect angular movements such as the rotation around the X-axis, rotation

around the Y-axis and the rotation around the Z-axis or also known as roll, yard

and pitch in layman’s terms.



28 | P a g e

On the other hand, an accelerometer is only able to detect three linear axes of

vectors, including left-right (X-axis), top-bottom (Y-axis) and up-down (Z-axis).

Unlike a gyroscope, it measures translation of direction and cannot detect if a devicemade a full spin or is experiencing inertial change. Mechanical and Electronics Engineering today have managed to transform the

mechanical gyroscope into a Microelectromechanical system (MEMS), also known as

vibrating structure gyroscope. So, instead of having a spinning wheel inside the

microchip, a vibrating mass is placed in the center of the chip. The mass will be

vibrated whenever an electrical signal goes through it. Moving the phone will cause

the changes of electrical signals that are picked by the sensors. The sensors will send

instructions to be interpreted by the

software to provide the necessary feedback

to the user.

When combining both the

accelerometer and the gyroscope, you will

have a total of 6-axis motion sensing that is

able to have precise motion detection by

simply moving the phone naturally. This

creates an opportunity for game developers to utilise the motion sensing capability of

the phone to create games that uses motion control instead of on-screen controls.

For example, in a first person shooter game, the player can navigate around

the gameplay by tilting and moving the phone instead of using the on-screen

controls. On the other hand, developers could give player a different perspective on

solving a puzzle, where the player could explore the three dimensional model in a

realistic manner by tilting or twisting the phone



29 | P a g e

.

A number of games from developer Gameloft offer gyroscope controls for both the

iOS and Android platforms including N.O.V.A., Modern Combat: Sandstorm and

Asphalt 6. Other games include Doodle Jump, Temple Run, Gyroblox (iOS) and Zen

Bound 2 Universal (iOS) also supports motion sensing. In addition, augmented

reality apps such as Sky Map (Android) and Wikituide also utilise some aspect of the

gyroscope, allowing discovery and exploration by simply moving the phone around.

BASIC IDEA OF GYROSCOPE

A gyroscope is a device for measuring or maintaining orientation, based on the

principles of angular momentum.In essence, a mechanical gyroscope is a

spinning wheel or disk whose axle is free to take any orientation. Although

this orientation does not remain fixed, it changes in response to an

http://en.wikipedia.org/wiki/Orientation_(rigid_body)

http://en.wikipedia.org/wiki/Angular_momentum


http://en.wikipedia.org/wiki/Orientation_(rigid_body)



30 | P a g e

external torque much less and in a different direction than it would without

the large angular momentum associated with the disk's high rate

of spin andmoment of inertia. Since external torque is minimized by mounting

the device in gimbals, its orientation remains nearly fixed, regardless of anymotion of the platform on which it is mounted.

Gyroscopes based on other operating principles also exist, such as the

electronic, microchip-packaged MEMS gyroscope devices found in consumer

electronic devices, solid-state ring lasers, fibre optic gyroscopes, and the

extremely sensitive quantum gyroscope.

Applications of gyroscopes include inertial navigation systems where magnetic

compasses would not work (as in

the Hubble telescope) or would not be

precise enough (as in ICBMs), or for

the stabilization of flying vehicles like

radio-controlled helicopters

or unmanned aerial vehicles. Due to

their precision, gyroscopes are also

used to maintain direction in tunnel mining.

Within mechanical systems or devices, a conventional gyroscope is a

mechanism comprising a rotor journaled to spin about one axis,

the journals of the rotor being mounted in an inner gimbal or ring; the inner

gimbal is journaled for oscillation in an outer gimbal for a total of two

gimbals.

The outer gimbal or ring, which is the gyroscope frame, is mounted so as to

pivot about an axis in its own plane determined by the support. This outer

gimbal possesses one degree of rotational freedom and its axis possesses none.

The next inner gimbal is mounted in the gyroscope frame (outer gimbal) so as

to pivot about an axis in its own plane that is always perpendicular to the

pivotal axis of the gyroscope frame (outer gimbal). This inner gimbal has two

degrees of rotational freedom.

http://en.wikipedia.org/wiki/Torque

http://en.wikipedia.org/wiki/Rotation

http://en.wikipedia.org/wiki/Moment_of_inertia

http://en.wikipedia.org/wiki/Gimbal

http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope#MEMS_gyroscope

http://en.wikipedia.org/wiki/Ring_laser_gyroscope

http://en.wikipedia.org/wiki/Fibre_optic_gyroscope

http://en.wikipedia.org/wiki/Quantum_gyroscope

http://en.wikipedia.org/wiki/Inertial_navigation_system

http://en.wikipedia.org/wiki/Hubble_telescope

http://en.wikipedia.org/wiki/ICBM

http://en.wikipedia.org/wiki/Unmanned_aerial_vehicle

http://en.wiktionary.org/wiki/rotor

http://en.wikipedia.org/wiki/Coordinate_axis

http://en.wikipedia.org/wiki/Journal_(mechanics)



http://en.wikipedia.org/wiki/Journal_(mechanics)

http://en.wikipedia.org/wiki/Coordinate_axis

http://en.wiktionary.org/wiki/rotor

http://en.wikipedia.org/wiki/Unmanned_aerial_vehicle

http://en.wikipedia.org/wiki/ICBM

http://en.wikipedia.org/wiki/Hubble_telescope

http://en.wikipedia.org/wiki/Inertial_navigation_system

http://en.wikipedia.org/wiki/Quantum_gyroscope

http://en.wikipedia.org/wiki/Fibre_optic_gyroscope

http://en.wikipedia.org/wiki/Ring_laser_gyroscope

http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope#MEMS_gyroscope



http://en.wikipedia.org/wiki/Rotation




31 | P a g e

The axle of the spinning wheel defines the spin axis. The rotor is journaled to

spin about an axis, which is always perpendicular to the axis of the inner

gimbal. So the rotor possesses three degrees of rotational freedom and its axis

possesses two. The wheel responds to a force applied about the input axis by areaction force about the output axis.

The behaviour of a gyroscope can be most easily appreciated by consideration

of the front wheel of a bicycle. If the wheel is leaned away from the vertical so

that the top of the wheel moves to the left, the forward rim of the wheel also

turns to the left. In other words, rotation on one axis of the turning wheel

produces rotation of the third axis.

A gyroscope flywheel will roll or resist about the output axis depending upon

whether the output gimbals are

of a free- or fixed- configuration.

Examples of some free-output-

gimbal devices would be the

attitude reference gyroscopes

used to sense or measure

the pitch, roll and yaw attitude

angles in a spacecraft or aircraft.

The centre of gravity of the rotor

can be in a fixed position. The rotor simultaneously spins about one axis and is

capable of oscillating about the two other axes, and, thus, except for its

inherent resistance due to rotor spin, it is free to turn in any direction about

the fixed point. Some gyroscopes have mechanical equivalents substituted forone or more of the elements. For example, the spinning rotor may be

suspended in a fluid, instead of being pivotally mounted in gimbals. A control

moment gyroscope (CMG) is an example of a fixed-output-gimbal device that

is used on spacecraft to hold or maintain a desired attitude angle or pointing

direction using the gyroscopic resistance force.

In some special cases, the outer gimbal (or its equivalent) may be omitted so

that the rotor has only two degrees of freedom. In other cases, the centre of

http://en.wikipedia.org/wiki/Flight_dynamics


http://en.wikipedia.org/wiki/Control_moment_gyroscope









32 | P a g e

gravity of the rotor may be offset from the axis of oscillation, and, thus, the

centre of gravity of the rotor and the centre of suspension of the rotor may not

coincide.

PROPERTIES OF A GYROSCOPE

Gyroscopes can be used to construct gyrocompasses, which complement or

replace magnetic compasses (in ships, aircraft and spacecraft, vehicles in

general), to assist in stability (Hubble Space Telescope, bicycles, motorcycles,

and ships) or be used as part of an inertial guidance system. Gyroscopic effects

are used in tops, boomerangs, yo-yos, and Powerballs. Many other rotating

devices, such as flywheels, behave in the manner of a gyroscope, although the

gyroscopic effect is not being used.

The fundamental equation describing the behavior of the gyroscope is:

where the pseudovectors τ and L are, respectively, the torque on the

gyroscope and its angular momentum, the scalarI is its moment of inertia, the vector ω is its angular velocity, and the vector α is its angular

acceleration.

It follows from this that a torque τ applied perpendicular to the axis of

rotation, and therefore perpendicular to L, results in a rotation about an

axis perpendicular to both τ and L. This motion is called precession . The

angular velocity of precession ΩP is given by the cross product:

Precession can be demonstrated by placing a spinning gyroscope with its axis

horizontal and supported loosely (frictionless toward precession) at one end.

Instead of falling, as might be expected, the gyroscope appears to defy gravity

by remaining with its axis horizontal, when the other end of the axis is left

unsupported and the free end of the axis slowly describes a circle in a

horizontal plane, the resulting precession turning. This effect is explained by

http://en.wikipedia.org/wiki/Gyrocompass

http://en.wikipedia.org/wiki/Hubble_Space_Telescope

http://en.wikipedia.org/wiki/Powerball_(toy)

http://en.wikipedia.org/wiki/Flywheel

http://en.wikipedia.org/wiki/Pseudovector




http://en.wikipedia.org/wiki/Precession



http://en.wikipedia.org/wiki/Cross_product

http://en.wikipedia.org/wiki/Cross_product





http://en.wikipedia.org/wiki/Pseudovector

http://en.wikipedia.org/wiki/Flywheel

http://en.wikipedia.org/wiki/Powerball_(toy)

http://en.wikipedia.org/wiki/Hubble_Space_Telescope

http://en.wikipedia.org/wiki/Gyrocompass



33 | P a g e

the above equations. The torque on the gyroscope is supplied by a couple of

forces: gravity acting downward on the device's centre of mass, and an equal

force acting upward to support one end of the device. The rotation resulting

from this torque is not downward, as might be intuitively expected, causingthe device to fall, but perpendicular to both the gravitational torque

(horizontal and perpendicular to the axis of rotation) and the axis of rotation

(horizontal and outwards from the point of support), i.e., about a vertical axis,

causing the device to rotate slowly about the supporting point.

Under a constant torque of magnitude τ , the gyroscope's speed of

precession ΩP is inversely proportional to L , the magnitude of its angular

momentum:

where θ is the angle between the vectors ΩP and L. Thus, if the gyroscope's

spin slows down (for example, due to friction), its angular momentum

decreases and so the rate of precession increases. This continues until the

device is unable to rotate fast enough to support its own weight, when it stops

precessing and falls off its support, mostly because friction against precessioncause another precession that goes to cause the fall.

By convention, these three vectors - torque, spin, and precession - are all

oriented with respect to each other according to the right-hand rule.

To easily ascertain the direction of gyro effect, simply remember that a rolling

wheel tends, when it leans to the side, to turn in the direction of the lean.

GYROST T

A gyrostat is a variant of the gyroscope. It consists of a massive flywheel

concealed in a solid casing. Its behaviour on a table, or with various modes of

suspension or support, serves to illustrate the curious reversal of the ordinary

laws of static equilibrium due to the gyrostatic behaviour of the interior

invisible flywheel when rotated rapidly. The first gyrostat was designed

by Lord Kelvin to illustrate the more complicated state of motion of a spinning

http://en.wikipedia.org/wiki/Right-hand_rule

http://en.wikipedia.org/wiki/Lord_Kelvin

http://en.wikipedia.org/wiki/Lord_Kelvin

http://en.wikipedia.org/wiki/Right-hand_rule



34 | P a g e

body when free to wander about on a horizontal plane, like a top spun on the

pavement, or a hoop or bicycle on the road.

MEMS GYROSCOPE

A MEMS gyroscope takes the idea of the Foucault pendulum and uses a

vibrating element, known as a MEMS (Micro Electro-Mechanical System). The

MEMS-based gyro was initially made practical and producible by Systron

Donner Inertial (SDI). Today, SDI is a large manufacturer of MEMS

gyroscopes.

FOG

A fiber optic gyroscope (FOG) is a gyroscope that uses the interference of light

to detect mechanical rotation. The sensor is a coil of as much as 5 km of

optical fiber. The development of low-loss single-mode optical fiber in the

early 1970s for the telecommunications industry enabled the development

of Sagnac effect fiber optic gyros.

VSG or CVG

A vibrating structure gyroscope (VSG), also called a Coriolis Vibratory

Gyroscope (CVG), uses a resonator made of different metallic alloys. It takes a

position between the low-accuracy, low-cost MEMS gyroscope and the

higher-accuracy and higher-cost FOG. Accuracy parameters are increased by

using low-intrinsic damping materials, resonator vacuumization, and digital

electronics to reduce temperature dependent drift and instability of control

signals.

High-Q Wine-Glass Resonators for precise sensors like HRG or CRG are based

on Bryan's "wave inertia effect". They are made from high-purity quartz

glass or from single-crystalline sapphire.

USES

http://en.wikipedia.org/wiki/MEMS_gyroscope

http://en.wikipedia.org/wiki/Foucault_pendulum

http://en.wikipedia.org/wiki/Microelectromechanical_systems

http://en.wikipedia.org/w/index.php?title=Systron_Donner_Inertial&action=edit&redlink=1


http://en.wikipedia.org/wiki/Fiber_optic_gyroscope

http://en.wikipedia.org/wiki/Sagnac_effect

http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope

http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope#Coriolis_Vibratory_Gyroscope_.28CVG.29


http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope#Wine_glass_resonator

http://en.wikipedia.org/wiki/George_H._Bryan

http://en.wikipedia.org/wiki/Quartz_glass


http://en.wikipedia.org/wiki/Sapphire

http://en.wikipedia.org/wiki/Sapphire



http://en.wikipedia.org/wiki/George_H._Bryan

http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope#Wine_glass_resonator



http://en.wikipedia.org/wiki/Vibrating_structure_gyroscope

http://en.wikipedia.org/wiki/Sagnac_effect

http://en.wikipedia.org/wiki/Fiber_optic_gyroscope



http://en.wikipedia.org/wiki/Microelectromechanical_systems

http://en.wikipedia.org/wiki/Foucault_pendulum

http://en.wikipedia.org/wiki/MEMS_gyroscope



35 | P a g e

In addition to being used in compasses, aircraft, computer pointing devices,

etc., gyroscopes have been introduced into consumer electronics. Since the

gyroscope allows the calculation of orientation and rotation, designers have

incorporated them into modern technology. The integration of the gyroscopehas allowed for more accurate recognition of movement within a 3D space

than the previous lone accelerometer within a number of smartphones. Scott

Steinberg, known for his critiques on newly released technology, says that the

new addition of the gyroscope in the iPhone 4 may "completely redefine the

way we interact with downloadable apps".

Nintendo has integrated a gyroscope into the Wii console's Wii

Remote controller by an additional piece of hardware called "Wii

MotionPlus". It is also included in the 3DS, which detects movement when

turning.

Cruise ships use gyroscopes to level motion sensitive devices like gyroscopic

self-levelling pool tables.

http://en.wikipedia.org/wiki/IPhone_4

http://en.wikipedia.org/wiki/Nintendo

http://en.wikipedia.org/wiki/Wii

http://en.wikipedia.org/wiki/Wii_Remote


http://en.wikipedia.org/wiki/Wii_MotionPlus


http://www.funham.com/gyroscopic-self-leveling-pool-table-on-a-cruise-ship/








http://en.wikipedia.org/wiki/Wii

http://en.wikipedia.org/wiki/Nintendo

http://en.wikipedia.org/wiki/IPhone_4



PROXIMITY SENSOR

The main function of this proximity sensor is to detect how close your smart

phone's screen is to your body. When you use your smart phone, it detects the

position of ear with respect to screen and turns off the light of screen and

saves battery. Also proximity sensor stops the accidental touch, unwanted

input during talk. This sensor also detects the signal strength, interference

sources and amplifies or filters by use of Beam Forming Technique. Thus, in a

nutshell, proximity sensor detect the presence of body like cheek, face or ear

and stops the web surfing, music or video during talk/calling and save thebattery. After the conversation, it resumes the same function which was

stopped earlier during talk.

modern sensors

Documents