CHAPTER-1
INTRODUCTION
The market for image sensors explored in the last few years shows an
enormous increase in sales and developments of cameras. Imaging sensors are
mainly classified into two types: complementary metal oxide semiconductor
(CMOS)
image sensors and charge couple device (CCD) sensors. Active pixel
sensors (APS) are the emerging sensors for the replacement of existing and
widely used charged couple device (CCD) sensors. Now a days, APS are extensively
used in webcams, robotics, X-rays, computer based videos, smart toys, both
still and video digital cameras, mobile phones cameras, automobiles, cinematography,
spectrography,radiography, photogrammetric, and in many scientific
applications. The above applications of APS are driving researchers to
concentrate on achieving low power consumption, reduced size, increasing
resolution, more sensitivity, marginal noise and more importantly fast operation.
This work explores state-of-the-art research on APS by reviewing the concepts behind
existing designs and new designs as well. Imaging sensors of different varieties are widely used in
commercial and scientific applications. CMOS active pixel sensor (APS) imagers
are fabricated in standard CMOS processes, which make it possible to integrate
the timing and control electronics, sensor array, signal processing
electronics, analog-to-digital converter (ADC) and full digital interface on
one chip.
llus helps to achieve a cost effectivehghly integrated and highly
compact imaging system, i.e. camera-on-a-chip, by utilizing the same design
techniques that have been developed over the years for lowpowerCMOS digital and
analog circuits.
1.1 CMOS ACTIVE PIXEL SENSOR
APS Technology: The
image sensor is photodiode-type CMOS active pixel sensor
imaging system on chip,designed by Jet Propulsion
Laboratory and manufactured by a standard commercial CMOS production line. The
imager is a 512 by 512
photodiode pixel array, which can randomly access any window in the array from
1 pixel by 1 pixel allthe way to 512 pixels by 512 pixels in any rectangular shape.
The minimum interface consists of five wires: Vdd, Ground, Serial Data Input,
Serial Data Output and Clock.The
imager size is approximately 10 mm by 15.5 mm with
CHAPTER-2
THEME: ACTIVE PIXEL SENSOR
2.1 CCD IMAGE SENSOR
CCD Image Sensors were invented in 1969 by Bell Laboratories. At the time digital photography was the major field of application. Upon exposure of the sensor, the charge on the first row (row of pixels) is transferred to the read out register. The read out register signals are fed to an amplifier and then on to an analog-to-digital converter. Once the row has been read, the charges on the readout register row are deleted, the next row is transferred to the first row and this procedure is carried on till last row is read out.
CCD Image Sensors were invented in 1969 by Bell Laboratories. At the time digital photography was the major field of application. Upon exposure of the sensor, the charge on the first row (row of pixels) is transferred to the read out register. The read out register signals are fed to an amplifier and then on to an analog-to-digital converter. Once the row has been read, the charges on the readout register row are deleted, the next row is transferred to the first row and this procedure is carried on till last row is read out.
CHAPTER-3
CONCLUSION
CMOS sensors found their first applications in the detection of visible light
and became widely spread in consumer
applications. We are now developing this
technology
to meet the stringent requirements of scientific applications. CMOS sensors can be efficiently
used to detect a broad spectrum of
electromagnetic radiation and charged particles. The dominant source of noise, the reset noise,
can be reduced and, at low illumination
levels, noise in the range of 10 rms can
be obtained,
without any
correlated double sampling. Different types of analogue to digital converter architectures allow to
trade off between
speed and resolution
required. We anticipate that the use of CMOS sensors for scientific applications will expand in the
next few years
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