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International Journal of Science, Engineering and Technology Research (IJSETR), Volume 3, Issue 5, May 2014
1482
ISSN: 2278 – 7798
All Rights Reserved © 2014 IJSETR
Abstract— The infrared (IR) sensor market is developing
rapidly and the microbolometer arrays are available for
different applications. The improvement in the sensitivity and
resolution of the sensor array leads to higher demands on the
IR camera. A new approach for bolometer ROIC has been
designed. This new approach for bolometer is based on high
performance uncooled infrared readout integrated circuit
(ROIC). The noise equivalent temperature difference (NEdT),
the responsivity and power are the important parameters for
uncooled infrared readout integrated circuit. This approach
can reduce the system design complexities and improve the
performance of uncooled bolometer system. This design of
uncooled readout integrated circuit is implemented in
microwind and it provides uniform output over a wide range of
temperature. The performance of the uncooled infrared
readout integrated circuit is higher. The resolution of the
readout integrated circuit is increased and the output power is
reduced.
Index Terms— bolometer, infrared (IR), noise equivalent
temperature difference (NEdT), readout integrated circuit
(ROIC)
I. INTRODUCTION
An infrared imaging system has a wide variety of
technologies, such as infrared sensor manufacturing, image
pattern recognition, analysis and processing algorithms. The
emergence of uncooled detectors has opened new
opportunities for infrared detection for both military and
commercial applications due to their small size, less power
consumption, and are less expensive, making these the ideal
choice for applications.
The infrared radiation is sensed by the infrared detector as
shown in Fig. 1. The readout circuit is an interface between
infrared detectors and signal processing stages.
Manuscript received April , 2014.
V.Yuva Priya, PG Student (M.E. VLSI Design), KPR Institute of
Engineering and Technology, Coimbatore, India, Mobile No.7598329539
M.Vilasini, Assistant Professor, Department of Electronics and
Communication Engineering, KPR Institute of Engineering and Technology,
Coimbatore, India, Mobile No.7639159132
The Readout integrated circuits (ROICs) as shown in Fig.
2 serve as an interface between infrared sensor array and
post- processing stages.
Fig.1 Infrared detector
The block diagram of readout integrated circuit has rows
and columns. The integration controller and the bias circuit
are connected to the array. The pixel array senses the incident
radiation and the infrared detector converts the radiation into
electrical signal and the readout integrated circuit converts
the electrical signal into the signal suitable for the
processing. The detector used for converting the incident
radiation into electrical signal has many cell arrays.
Fig.2 Readout circuit
Design of Low Cost High Performance
Uncooled Infrared Readout Integrated Circuit
V.Yuva Priya¹, M.Vilasini²
¹PG Student (M.E. VLSI Design), KPR Institute of Engineering and Technology, Coimbatore,
India
²Assistant Professor, Department of Electronics and Communication Engineering, KPR Institute of
Engineering and Technology, Coimbatore, India
International Journal of Science, Engineering and Technology Research (IJSETR), Volume 3, Issue 5, May 2014
1483
ISSN: 2278 – 7798
All Rights Reserved © 2014 IJSETR
The readout circuit is composed of a row and column
multiplexers controlled by a timing circuit. The detector
signals are amplified and band limited by the readout circuit.
II. RELATED WORKS
R.K. Bhan et al.,(2009) proposed the uncooled infrared
microbolometer array and the characterization of
microbolometer[2]. A. Rogalski (2009) gave the recent
advances in the developments of the uncooled infrared
detector technologies[8].Sang Joon Hwang et al.,(2010)
proposed the readout integrated circuit for infrared image
sensor application[3]. Joeri De Vos et al., (2011) in their
work compared the different kinds of CMOS imagers and
gave that for high end applications high performance fully
hybrid imagers are the preferred option [7]. Jiawei Friedrich
Xu et al.,(2011) in their work proposed a design which
provided improved performance compared to the
conventional readout integrated circuit (ROIC)[1]. Eun Sik
Jung et al.,(2012) proposed the readout integrated circuit
which applies a fixed current bias sensing method to the
input stage inorder to simplify the circuit structure and the
infrared sensor characteristic control[5]. The image sensors
are designed with different approaches in these works. The
new approach for uncooled infrared readout integrated
circuit (ROIC) is designed to provide high performance.
III. IMPLEMENTATION OF UNIT CELL IN
MICROWIND AND DSCH
The main area of the chip is the identical sensors. The
image data is sent out pixel by pixel to post-processing
component using a row and column select block. Each pixel
sensor is also called a unit cell. The circuit of the pixel sensor
is implemented in DSCH2.
The circuit of the unit cell consists of the integration
capacitance, shutter transistor, sample and hold capacitance
and the column select. The integration capacitor is charged
by the active low reset signal in the unit cell. The integration
starts when the reset is turned off. The readout of the row of
pixels is marked by the reset signal from the column select.
The circuit is implemented in DSCH. The verilog file is
compiled in the microwind and the layout is obtained. The
simulation provides the characteristics of voltage and time as
default. The characteristics of voltage, current and time,
static voltage and voltage, frequency and time are obtained.
This method is used for the design of the readout
integrated circuit. The unit cell is first formed and using the
unit cell the array of readout integrated circuit is formed.
Then the resolution of the array is increased and the power is
analyzed for the readout integrated circuit.
The implementation of unit cell in DSCH2 is given in
Fig.3.
Fig.3 Implementation of unit cell
The unit cell is implemented in DSCH2 and the layout of
the unit cell is obtained and the characteristics of voltage,
current and time are obtained.
The characteristics of the unit cell are shown in Fig.4.
Fig.4 Characteristics of unit cell
IV. IMPLEMENTATION OF ROIC ARRAY IN
MICROWIND AND DSCH
The readout integrated circuit has pixel array made of
rows and columns. For implementing the array, the unit cell
is first implemented in the DSCH2. The pixel sensor array is
then formed by connecting the unit cells in the form of array.
The circuit of 4x4 pixel sensor array is implemented in
DSCH2 and is shown in Fig.5.
International Journal of Science, Engineering and Technology Research (IJSETR), Volume 3, Issue 5, May 2014
1484
ISSN: 2278 – 7798
All Rights Reserved © 2014 IJSETR
Fig.5 Implementation of 4x4 pixel sensor array
The layout and output characteristics of 4x4 pixel sensor
array are obtained.
The characteristics of 4x4 pixel sensor array are shown in
Fig.6.
Fig.6 Characteristics of 4x4 pixel sensor array
The characteristics are simulated and the power is
obtained for the temperature. The simulation parameters are
output voltage, input voltage and temperature.
When the temperature value is changed and the power gets
altered. As the temperature is increased, the power decreases.
The power at various conditions is observed based on the
substrate temperature. The output characteristics are uniform
over wide range of temperature.
The 4x4 pixel sensor array is now formed. The 4x4 array is
now converted to a block. The block is shown in Fig.7.
The resolution can be increased by connecting this
structure and the output characteristics are obtained and high
performance is achieved.
Fig.7 Block of 4x4 pixel sensor array
When the array formed by connecting the structure is
simulated the output characteristics are obtained.
The block of the 4x4 array are connected so that the 8x8,
16x16, 32x32, 64x64 and 128x128 array are formed. The
resolution of the array is thus increased and the pixel sensor
arrays are implemented.
The output characteristics of the 8x8 array are shown in
Fig.8.
Fig.8 Characteristics of 8x8 pixel sensor array
In this way the 16x16 array, 32x32 array, 64x64 array and
128x128 array are formed and the output characteristics are
obtained.
International Journal of Science, Engineering and Technology Research (IJSETR), Volume 3, Issue 5, May 2014
1485
ISSN: 2278 – 7798
All Rights Reserved © 2014 IJSETR
V. RESUTS AND DISCUSSION
The 4x4 array block is connected and the 16x16 array,
32x32 array, 64x64 array and 128x128 array are formed.
They are simulated in microwind and their output
characteristics and the output power of the array are
obtained.
The output power of the 128x128 array is 90.79µW. Thus
the power is less.
The output characteristics of the 16x16 array are shown in
Fig.9.
Fig.9 Characteristics of 16x16 array
The output characteristics of the 32x32 array are shown in
Fig.10.
Fig.10 Characteristics of 32x32 array
The output characteristics of the 64x64 array are shown in
Fig.11.
Fig.11 Characteristics of 64x64 array
The output characteristics of the 128x128 array are shown
in Fig.12.
Fig.12 Characteristics of 128x128 array
VI. CONCLUSION
The new approach for bolometer ROIC is designed. This
improves the performance of the uncooled bolometer system.
The new design provides output characteristics over a wide
range of substrate temperature for infrared detector array.
When compared to the other approaches, this approach
provides improved performance and the reduction in power.
When the resolution of the array is increased, even though
the size of the circuit increases, the power is reduced. In
future, the element can be added suitably in the circuit of the
pixel sensor array, so that the power is further reduced.
International Journal of Science, Engineering and Technology Research (IJSETR), Volume 3, Issue 5, May 2014
1486
ISSN: 2278 – 7798
All Rights Reserved © 2014 IJSETR
REFERENCES
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V.Yuva Priya pursued B.E Electrical and Electronics Engineering in
P.A.College of Engineering and Technology in 2012. She is currently doing
M.E. VLSI Design in KPR Institute of Engineering and Technology.
M.Vilasini pursued B.E Electronics and Communication Engineering in
1999 and M.E in Government College of Technology in 2004. She is currently
doing Ph.D in Anna University. Her research interests are image processing,
satellite images and communication.