Design of Low Cost High Performance Uncooled Infrared...

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


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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.


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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.


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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.


Fig.9.

Fig.9 Characteristics of 16x16 array


Fig.10.



Fig.11.


The output characteristics of the 128x128 array are shown

in Fig.12.


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.


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REFERENCES

[1] Jiawei Friedrich Xu, Glauco Rogerio Cugler Fiorante, Payman

Zarkesh-Ha, and Sanjay Krishna. A Readout Integrated Circuit (ROIC)

with Hybrid Source/Sensor Array, IEEE Trans.2011.

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Infrared Microbolometer Arrays and their Characterization Techniques‖,

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[9] Deniz Sabuncuoglu Tezcan, Selim Eminoglu and Tayfun Akin, ―A

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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.

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