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A Seminar Report
(IMAGE SENSOR SYSTEM)
Jayesh Mangroliya (120330131033)
Miral Modi (120330131039)
Jaydeep Bhayani (120330131042)
B.E. III Year (Sem-5th
Ms. Rozmin Mansur
Asst. Prof, E.C. Dept.
Mahatma Gandhi Institute of Technical Education and Research
A Seminar Report
(IMAGE SENSOR SYSTEM)
For the partial fulfillment of degree Of Bachelor of Engineering for
Gujarat technical University
Jayesh Mangroliya (120330131033)
Miral Modi (120330131039)
Jaydeep Bhayani (120330131042)
B.E. III Year (Sem-5th
Ms. Rozmin Mansur
Asst. Prof, EC Dept.
Mahatma Gandhi Institute of Technical Education
and Research Center, Navsari
INSTITUTE OF TECHNICAL EDUCATION AND
This is to certify that Jayesh Mangroliya
ID: 120330131033, Miral Modi ID: 120330131039
Jaydeep Bhayani ID: 120330131042, in Third Year
Computer science and Engineering has satisfactorily
completed their SEMINAR for the term June-2014 to
Seminar Title: SENSOR SYSTEM
Rozmin Mansur Himanshu Rana
Faculty Guide Head of Department
Knowledge, in itself is a continuous process. Research is hard but involves Great Joy as well.
For achieving success, a person is not an individual identity. It is the guidance and the support
of his colleagues, peer and teachers which help him to find the way of success. It is good to
have knowledge about something and to have a perfect knowledge there is always a
requirement of a correct source and a helpful guide.
First of all, I am thankful and grateful to my Guide, Ms. Rozmin Mansur, and the Lecturer of
E.C Engineering Dept. for her immense support and providing her deep Knowledge to me
about my seminar layout and work. I would like to thank my Head of Department, Mr.
Hemanshu Rana, for providing us such a wonderful platform to work upon.
Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor)
and lamps which dim or brighten by touching the base. There are also innumerable
applications for sensors of which most people are never aware. The most widely used sensors
measure temperature, pressure or flow. Applications include manufacturing and machinery,
airplanes and aerospace, cars, medicine and robotics. A sensor is a device, which responds to
an input quantity by generating a functionally related output usually in the form of an electrical
or optical signal. A sensor's sensitivity indicates how much the sensor's output changes when
the measured quantity changes. After seeing this overview of the sensor system, we discuss
about the image sensor which is the important context of this technology. An image sensor is
a device that converts an optical image into an electronic signal. Image sensors are
everywhere. They are present in single shot digital cameras, digital video cameras, embedded
in cellular phones, and many more places. When many people purchase a digital imager, the
primary metric they use as a comparison is the pixel array size, expressed in megapixels. The
higher the megapixel count, the better the imager is the prevailing wisdom to most consumers.
There are many more metrics with which to compare imagers that may give a better indication
of performance than raw pixel counts. Further, many of these metrics may be based on the type
of imaging technology, CCD (charge coupled device) or CMOS (complementary metal oxide
semiconductor). This paper will explain the fundamentals of how a digital image sensor works,
focusing on how photons are converted into electrical signals, and thus images. It will detail
the difference between the functionality of CCD and CMOS sensors, the two chief architectures
for image sensor design. It will also discuss various metrics which are commonly used in
analyzing the performance of image sensors. It will include a statistical comparison of recent
CCD and CMOS imaging systems from the literature using these metrics, and compare them
to some commercially available sensors. It will also develop a model for how two of these
metrics, well capacity and conversion gain, are related.
LIST OF FIGURES
Figure Page No.
Fig. 1.1 Imaging System Pipeline 1
Fig 3.1 Pixel 4
Fig 3.2 Fill Factor 4
Fig. 3.3 Image Sensor Architectures for Digital Cinematography 5
Fig. 3.4 Readout architectures of interline transfer CCD 6
Fig. 3.5 CMOS image sensor 7
Fig. 3.6 Conventional and Exmor CMOS Sensor 8
Fig. 4.1 CCD Sensor Structure 9
Fig. 4.2 Interline Image Sensor 10
Fig. 4.3 Full Frame Image Sensor 11
Fig. 4.4 Modern Frame Transfer Image Sensor 12
Fig. 4.5 Frame Transfer CCD Operational Principle 12
Fig. 4.6 CMOS Image Sensor 13
Fig. 4.7 A typical CMOS chip design 14
Fig. 4.8 Active Pixel Image Sensor 14
Fig. 4.9 Passive Pixel Image Sensor 15
Fig. 4.10 Creatin Colour using Beam Splitter 15
Fig. 5.1 Fill-Factor limit in layout 17
Fig. 6.1 Image sensors applications in medicine 19
Fig. 6.2 Application in different field 20
Fig. 6.3 Analysis of growth 20
TABLE OF CONTENTS
CHAPTER PAGE NO.
Title Page I
Certificate Page II
List of Figures V
Table of Content VI
Chapter 1. INTRODUCTION 1
1.1 The Physics of Silicon Image Sensors 1
1.2 Performance Metrics for Image Sensors 1
1.3 Performance Comparison of Image Sensors 2
Chapter 2. HISTORY 3
2.1 Image Sensor History 3
2.1.1 CCD History 3
2.1.2 CMOS History 3
Chapter 3. ARCHITECTURE 4
3.1 What is a Pixel? 4
3.2 What is Fill Factor? 4
3.3 Architecture of CCD 6
3.4 Architecture of CMOS 7
Chapter 4. WORKING 9
4.1 Basic Operation of CCD 9
4.1.1 Interline Transfer CCD Image Sensor 10
4.1.2 Frame Transfer Image Sensor 12
4.2 Basic Operation of CMOS 13
4.2.1 Active Pixel Image Sensor 14
4.2.2 Passive Pixel Image Sensor 15
4.3 How Can We Creating Colour in Image Sensor? 15
Chapter 5. ADVANTAGE AND DISADAVANTAGE 16
5.1 Advantages and Disadvantages of CCD 16
5.1.1 Advantages of CCD Image Sensor System 16
5.1.2 Disadavantages of CCD 16
5.2 Advantages and Disadvantages of CMOS Image Sensor 16
5.2.1 Advantages of CMOS 16
5.2.2 Disadvantages of CMOS 17
5.3 Comparision between CCD vs CMOS 17
5.4 CMOS vs CCD today 18
Chapter 6. APPLICATION 19
Image sensors are being used in many areas today, in cell phone cameras, digital video
recorders, still cameras, and many more devices. The issue is how to evaluate each sensor,
to see if significant differences exist among the designs. Megapixels seem to be the largest
used barometer of sensor performance, with the idea that the more pixels an imager has, the
better its output. This may not always be the case. Many other metrics are important for
sensor design, and may give a better indication of performance than raw pixel count.
Furthermore, specific applications may require the optimization of one aspect of the sensor's
performance. As silicon process technology improves, some of these metrics may get better,
while others might become worse.
Fig. 1.1 Imaging System Pipeline
1.1 The Physics of Silicon Image Sensors The first thing to explain is how a modern digital
image sensor works. Nearly every modern image sensor today is produced using silicon.
The chief reason is that silicon, being a semiconductor, has an energy gap in between its
valence band and conduction band, referred to as the band gap, which is perfect for capturing
light in the visible and near infrared spectrum.
1.2 Performance Metrics for Image Sensors When comparing image sensors, either CCD
or CMOS, the system is essentially a box where the input is light, and the output is an image
based on the light that is seen. The service provided by the sensor is the conversion of light
to a digital image. There are a number of common metrics that are used for image sensors.
These categories are not hard and fast categories, as there will be some overlap amongst
1.3 A Performance Comparison of Image Sensors This section will look at a sample of
the state-of-the-art in image sensors culled from the literature over the last five years. A
discussion of the results will follow the analyses.
This paper described how modern image sensors work. It showed the difference in how
CCD and CMOS image sensors function. It also gave a description of many of the common
metrics used when comparing the performance of different image sensors. An analysis was
performed using a sample of state of the art image sensors. The analysis showed that for
dark current and dynamic range, no significant difference could be seen, although the
sample size was small for both CCD and CMOS populations. The model predicts that
smaller well capacities lead to large conversion gains, while larger capacities lead to smaller
Mobile imaging, digital still and video cameras, Internet-based video conferencing,
surveillance, and biometrics. Over 860 million parts shipped in 2013. Estimated annual
growth rate of over 28%.
In recent years, with growing interest in small HD-resolution camcorders, there has been
significant development of CMOS sensors which are low power consumption devices with
high-speed image readout capabilities. In the field of security surveillance, this development
is accompanied by the increasing prevalence of IP networking, which in turn builds demand
for HD resolution, as the digital of the network surveillance camera signal does not depend
on a conventional TV format.
Because of these growing need, Sony has amassed its image quality knowledge accumulated
in CCDs, and dedicated this to creating new, more advantageous high speed, high-resolution
CMOS sensors. The result is a CMOS sensor with an entirely new structure: the “Exmor”.
1930 First high-temperature thermostat metals introduced.
2.1 Image Sensor History:
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.
2.1.1 CCD History: Invented in 1970 by Bell Labs. Honeywell developed this into an X-Y
scanner and taken further by IBM. Originally for data storage! Taken up by research and
astronomy areas. 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
2.1.2 CMOS History: Complementary metal–oxide–semiconductor (CMOS), is a major
class of integrated circuits. CMOS technology is used in microprocessors, microcontrollers,
static RAM, and other digital logic circuits. CMOS technology is also used for a wide
variety of analogue circuits such as image sensors, data converters, and highly integrated
transceivers for many types of communication. Frank Wanlass successfully patented CMOS
Now used in security cameras, digital cameras and virtually all digital video applications.
Before we see the architecture of an image sensor, we describe two concepts: 1) Pixel
2) Fill Factor
3.1 What is a Pixel?
The smallest discrete component of an image or picture on a CRT screen is known as a
“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.
3.2 What is Fill Factor?
Fill factor refers to the percentage of a photo site that is sensitive to light.
If circuits cover 25% of each photo site, the sensor is said to have a fill factor of 75%. The
higher the fill factor, the more sensitive the sensor.
Fig.3.2 Fill Factor
In this chapter we will see the architecture of different types of image sensor and what
parameter need to build the image sensor.
An image sensor is typically of two types:
1. Charged Coupled Device (CCD)
1) Full Frame CCD Image Sensor
2) Interline Transfer Image Sensor
2. Complementary Metal Oxide Semiconductor (CMOS)
1) Active Pixel CMOS Image Sensor
2) Passive Pixel CMOS Image Sensor
Following fig. shows that the different type of Image sensor in this fig. the full frame
and frame transfer image sensor both are same there is little difference between them.
Fig.3.3 Image Sensor Architectures for Digital Cinematography
3.3 Architecture of CCD:
CCD is silicon-based integrated circuits consisting of a dense matrix of photodiodes. A CCD
has photo sites, arranged in a matrix. Each comprises a photodiode which converts light into
charge and a charge holding region. The charges are shifted out of the sensor as a bucket
Fig.3.4 Readout architectures of interline transfer CCD
3.2 Architecture of CMOS:
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.
“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).
Fig.3.5 CMOS image sensor
Another major element that determines image quality is noise reduction. In “Exmor”
CMOS sensor, noise on the analog part is eliminated by the built-in Correlated
Double Sampling (CDS) circuit. Other new structural element drastically also decrease the
Here below figure shows that these structures.
The A/D conversion conventionally done just before signal readout is now performed
immediately after the light-to-electricity conversion, and is performed for each column.
This helps to reduce noise because the analog circuit is made shorter, and the frequency
Noise-elimination circuits (CDS circuit) are equipped in the digital domain in addition to
in the analog domain.
Fig.3.6 Conventional and Exmor CMOS Sensor
4.1 Basic Operation of CCD:
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. The A/D conversion is done at the edge of the circuit.
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.
Fig.4.1 CCD Sensor Structure
1) The photodiode within the pixel receives light which is then converted to
electrical charges and accumulated. 2) The electrical charges accumulated in all the
receiving sections are simultaneously transferred to the vertical CCD shift registers. 3) The
charges that have passed through the vertical CCD shift registers are transferred to the
horizontal CCD shift registers. 4) The charges sent from the horizontal CCD shift registers
are converted to a voltage and amplified in the amplifier, then sent to camera signal
There are two types of CCD image sensor. 1) Interline Transfer CCD Image Sensor
2) Frame Transfer CCD Image Sensor
4.1.1 Interline Transfer CCD Image Sensor:
In the interline transfer design the charge holding region is shielded from light. Light
is collected over the entire imager simultaneously and then transferred to the next, adjacent
charge transfer cells within the columns. This implies a low fill factor, which on modern
designs usually is compensated for by micro lenses.
Next, the charge is read out: each row of data is moved to a separate horizontal
charge transfer register. Charge packets for each row are read out serially and sensed by a
charge-to-voltage conversion and amplifier section.
Here, the following fig. Shows that an interline image sensor has a light shielded
VCCD adjacent to each photodiode photo sensor. Charge is transferred from the photo sites
to the vertical CCD in one cycle. Then charge is transferred into the horizontal CCD, one
raw at a time.
Fig.4.2 Interline Image Sensor
The next image can be integrated while the previous image is safely transferred out
of the imager. Interline imager sensor, unlike full-frame device, do not require an external
Here, Full frame means in the full frame design the charge holding region is
integrated with the light sensing region. Light is collected over the entire imager
simultaneously. Then the light has to be shut off so that the charge can be transferred down
Finally, each row of data is moved to a separate horizontal charge transfer register.
Charge packets for each row are read out serially and sensed by a charge-to-voltage
conversion and amplifier section.
This design features a high, almost 100% fill factor but external shuttering is
required and light cannot be collected during readout.
Here, Fig. Shows that the pixels are both photo sites and the VCCD. Charge os
transported down the columns from pixel to pixel. Charge in the first VCCD row is
transferred into the HCCD. The HCCD clocks out one row at a time.
Fig.4.3 Full Frame Image Sensor
Fig.4.4 Modern Frame Transfer Image Sensor
4.1.2 Frame Transfer Image Sensor:
In frame transfer CCD has photo sites, arranged in an X-Y matrix. (Almost) the
entire photo site is light sensitive, i.e. a good fill factor.
When light has been collected over the entire imager simultaneously it is rapidly
shifted into an equal size rectangular array of charge holding regions which is shielded from
Fig.4.5 Frame Transfer CCD Operational Principle
4.2 Basic Operation of CMOS:
The CMOS sensor’s architecture is arranged more like a memory cell or flat-panel
display. Each photosite contains a photodiode that converts light to electrons, a charge-to-
voltage conversion section, a reset and select transistor and an amplifier section. This
additional electronics limits the fill factor.
Fig.4.6 CMOS Image Sensor
1) The photodiode within the pixel receives light which is then converted to
electrical charges and accumulated. 2) The accumulated charges are converted to a voltage
by an amplifier within the pixel. 3) The converted voltage is transferred to the vertical signal
line depentding on the selexted transistor. 4) Various random noise and fixed pattern noise
are eliminated by correlated double sampling at a column ciucuit. 5) After CDS, the image
signal voltage is output through the horizontal signal line.
Overlaying the entire sensor is a grid of metal interconnects to apply timing and
readout signals, and an array of column output signal interconnects. The column lines
connect to a set of decode and readout (multiplexing) electronics that are arranged by
column outside of the pixel array.
This architecture allows the signals from the entire array, from subsections, or even
from a single pixel to be readout by a simple X-Y addressing technique— something a CCD
Fig.4.7 A typical CMOS chip design
There are two types of CMOS sensor: 1) Active Pixel Image Sensor
2) Passive Pixel Image Sensor
4.2.1 Active Pixel Image Sensor:
3-4 transistors per pixel. Fast, higher SNR, but Larger pixel, lower fill factor. Lower voltage
and lower power.
Fig.4.8 Active Pixel Image Sensor
4.2.2 Passive Pixel Image Sensor
One transistor per pixel. Small pixel, large fill factor, but Slow, low signal to noise ratio
Fig.4.9 Passive Pixel Image Sensor
4.3 How Can We Creating Colour in Image Sensor?
Here we discuss some little information about creating colour in digital camera image
One- or three-chip camera -Three-chip is usually at least 3 times as expensive. The color
filter matrix for one- chip, usually ”Bayer mosaic”.
Reduces color resolution to about half. Also reduces light collection efficiency.
Anisotropic in x and y. A new method invented by Foveon uses.
“vertical filters” with less resolution loss.
Fig.4.10 Creatin Colour using Beam Splitter
ADVANTAGE AND DISADAVANTAGE
There is always some good and bad possiblities of every technology because no device can
give the 100% facility of their feature.
In this chepter we will also discuss the comparision between CCD and CMOS image sensor.
5.1 Advantages and Disadvantages of CCD:
Here we will discuss the some of the advantages and disadvantages of CCD image sensor
5.1.1 Advantages of CCD Image Sensor System:
CCD’s started developing in early 70-ies, optimized for optical properties and image quality,
continues to improve. It is high quality.
The optimized photodetectors in architecture produces – high QE, low dark current.
very low noise – no noise introduce during shifting
very low fixed pattern noise (nonuniformity) – no FPN introduced by shifting
That is why CCD is high-performance imager.
More light sensitive than CMOS (1 lux vs 5-10 lux).
5.1.2 Disadavantages of CCD
The optimization makes integrating other electronics onto the silicon impractical.
In addition, operating the CCD requires application of several clock signals, clock levels,
and bias voltages, complicating system integration and increasing power consumption,
overall system size, and cost.
5.2 Advantages and Disadvantages of CMOS Image Sensor
5.2.1 Advantages of CMOS
Lower system cost. In high-volume foundries. Support electronics easier integrate. Benefit
from process and material improvements made in mainstream semiconductor technology.
Lower power usage. Easy integration of additional circuitry on-chip. Can read out
subsections for variable resolution/speed.
5.2.2 Disadvantages of CMOS:
There only one disadvantages of CMOS which is fill factor limit.
Image quality a longer development and more optimized designs.
Fig.5.1 Fill-Factor limit in layout
5.3 Comparision between CCD vs CMOS
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
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.
5.4 CMOS vs CCD today
Today there is no clear line dividing the types of applications each can serve.
CMOS designers have devoted intense effort to achieving high image quality, while CCD
designers have lowered their power requirements and pixel sizes.
As a result, you can find CCDs in low-cost low- power cellphone cameras and CMOS
sensors in high-performance professional and industrial cameras, directly contradicting the
Latest Nikon has CCD while Canon has CMOS both high end in the 10-20 megapixel range.
The image sensor used in many devices like mobile video phone, Finger Print Scanner,
Virtual Key Board, Self-Parking Car, Aerospace, Auto Pilot Technology etc.
Samsung CMOS image sensors (CIS) enable bright, crisp images and smooth-motion video
for a broad range of applications, from smartphones and cameras to notebooks and smart
Almost all medical and near medical areas benefit from image sensors utilization. These
sensors are used for patients’ observation and drug production, inside the dentists offices
and during surgeries. In most cases the sensor itself represents only a small fraction (in size
and cost) of the larger system, but its functionality plays a major role in the whole system.
Figure 12 shows examples of medical applications where CMOS image sensors are used. In
this section of the paper we mostly concentrate on applications that push current image
sensor technology to the edge of the possibilities. These applications are wireless capsule
endoscopy and retinal implants. Both of these applications will play an important role in
millions of patients’ lives in the near future.
Fig. 6.1 Image sensors applications in medicine
The following figure shows that the application of an image sensor are used in different
area or field.
Fig. 6.2 Application in different field
Here the following figure shows that the analysis of growth of an image sensor.
Fig. 6.3 Analysis of growth
Image sensors are an emergent solution for practically every automation-focused machine-
vision application. New electronic fabrication processes, software implementations, and
new application fields will dictate the growth of image-sensor technology in the future. The
two major segments—CCD and CMOS—of the world image sensors market offer a range
of image sensors for multiple end uses. The world image sensors market is poised for
growth, with certain factors likely to aid its growth during the period 2011–2015.