Temperature measurement of a candle flame using a CCD camera

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EL600
-

Interim Report


Temperature measurement
of a candle flame using a CCD
camera


Arpit Patel (ap378)


Supervisor: Dr. G Lu













12/17/2008




Temperature measurement of a candle flame using a CCD camera


Interim Report

Page
1

1

INTRODUCTION

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2

2

SPECIFICATION

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2

3

TECHNICAL AP
PROACH

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2

3.1

T
HEORY

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2

3.2

S
YSTEM
S
ETUP

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3



M
AIN
C
OMPO
NENTS
U
SED

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..

3



D
ESIGN OF THE
C
AMERA
H
OUSE

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...........................

4

F
IGURE
2

SHOWS THE DESIGN OF
THE CAMERA HOUSE AND

THE FILTER HOLDER
.

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4

3.3

S
OFTWARE

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4



C
LASS
S
TRUCTUR
E

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5

G
RAPHICS
I
NTERFACE

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6

4

PROJECT PROGRESS

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7

4.1

U
PDATED
P
ROJECT
P
LAN

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7

4.2

P
ROGRESS

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7



Temperature measurement of a candle flame using a CCD camera


Interim Report

Page
2

1

Introduction

Flame temperature distribution is one of the key requirements for efficiency of
a
combustion
process.
The f
lame temperature is needed to measure in a combustion system for evaluating the
combustion efficiency and emission formation process, which is diffic
ult to measure as the
temperature is very high.
Most existing f
lame monitoring devices monitor only the indication
of the flame ignition.


Research work was m
ade to measure the temperature distribution by using a film portrait and
analysing the image accordingly but these
techniques for flame temperature measurement are
mostly local and offline. For similar cases a
r
emote and online flame temperature measuremen
t
is desirable.

With the recent technological advances in imaging, remote and online temperature
measurement could be brought into a new dimension using a CCD camera.


A CCD camera can present two dimensional information of the target flame in form of real

time image transfer and is therefore suitable for online and remote monitoring of the
temperature distribution. The project carried out is the prototype of an imaging system
consisting of a CCD camera and signal processing software for candle flame. The s
ystem
operates on two
-
colour method to calculate the temperature distribution.

2

Specification

The project aims to develop a prototype imaging system for the temperature measurement of a
candle flame. The imaging system is to be designed and implemented, to
consist a CCD
camera, optical filters and signal processing software. The system software is to be developed
to process the flame images captured by the camera and calculate the temperature of the flame.

3

Technical Approach

3.1

Theory

In order to calculate th
e temperature distribution of a flame from its gray scale images using
two
-
colo
u
r method, it is necessary to reconstruct the image to only region of interest i.e., only
the flame part of the image, for the two different spectral bands.

The temperature
measurements are based on the measurements of the emission and absorption
of radiation by soot particles

at two different wavelengths
, and thus represent average particle
temperatures.


The radiation of an object is governed by Planck's radiation law:


M(
𝜆
,T) = C
1
/
𝜆
5

(e
C
2
/
𝜆
T



1)
-
1



(1)


Where,
M(λ,T) is the monochromatic radiance, λ is the wavelength of the radiation, T is
the absolute temperature of the blackbody, C
1

& C
2

are Planck’s constants


The temperature distribution of each section can be calculated from the ratio of gray levels of
corresponding pixels in the two band
-
limited section reconstructions using the two
-
colour
method. The two
-
colour method is a well
-
established technique for dete
rmining temperature
Temperature measurement of a candle flame using a CCD camera


Interim Report

Page
3

from radiation emitted by an object and can be adapted to utilize gray scale images as captured
by a monochromatic CCD camera. The expression for flame temperature using the two
-
colour
method can be written as








(








)


























(




)



(




)




(2)


Where, T = temperature in Kelvin, C
2

= Planck’s constant = 1.4388 x 104 [µm.K],
λ
1 &
λ
2 are wavelength of respective optical filters,















is the ratio gray
-
level ratio,










are spectral sensitivities of the imaging system at
λ
1 &
λ
2, and







are bandwidths of
λ
1 &
λ
2.


3.2

System Setup


A schematic of the prototype is shown in Figure 1. The system consists of a monochrome CCD
camera, stepper motor mounted with a custom
optical filters holder and motor controller
circuitry, a PC equipped with USB port/Serial port and signal processing software. The optical
setup lets the light pass through two optical filters and are projected onto the CCD camera, thus
every image capture
d by the camera contains a flame image. The software produces an average
image of the captured gray level frames, using this information provided by average image, the
temperature distribution of the flame is derived from the gray scale representation base
d on
two
-
colour method.


Figure 1. Schematic Diagram of the System





Main Components Used

The main component used

in the system design is shown Table 1

Temperature measurement of a candle flame using a CCD camera


Interim Report

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4


Table

1
. Main Component
u
sed

Stepper Motor

Model

Mclean

7.5° Unipolar with 25:2 Gearbox

CCD Camera

Model

Hitachi KP
-
M1E/K
-
S10

Effective Pixels

752(H) x 582 (V)

Iris

Manual, 0.5 Inch Diameter, 6mm focus

Optical Filters

3 x Filters

550nm, 650nm & 700nm wavelengths

Serial Interface
Board


Processor

PicAxe 281X Series from microchip

Port

Serial RS
-
232 Connector

Software


OS

Windows XP

Main Application

Qt 4.4.3 Compiler(Open Source)

PIC Programming

PicAxe Programmer




Design of the Camera House

Figure 2 shows the d
esign of the
c
amera
h
ouse

and the filter holder.



Figure 2. Camera House & Filters Holder



3.3

Software


The software is designed to capture set of images from
a
monochrome CCD camera at two
different filters and average the set of images for a filter to reduce the background noise,
the
similar process is run for
an
other filter. Average
d

images are run through noise elimination
system to reduce any other noise. Ima
ges are converted to a gray
-
level matrix
, with values
from 0 to 255,

to reduce complication in temperature distribution calculation. Results are
displayed on screen through graphics interface as in Fig
ure

5,
after successful completion of
the temperature c
alculations.

A software aspect of the theory is implemented as flow chart in
Figure 3.

Temperature measurement of a candle flame using a CCD camera


Interim Report

Page
5


Figure
3.

Flow chart
of Software



Class Structure



Figure 4. Class Structure of Software

The software uses the class structure as shown in Figure 4. Description for
each class used in
the software is as follows:



eGraphics


Important g
raphic
s

class for interface display
&

conn
ections to different
processes.



eMotorControl


This
sends commands to the

motor
for
rotation as guided from the
eCapture or eGraphics

classes
.



eCapture


All the image capture processes are controlled using this class. Captured data is
stored in eData.



eDiagnose


Independent class to diagnose connection between motor
& camera



eAverageNoise


Averages images and removes noise from the captured im
ages and stores
the resultant average image in eData.



eCalculate


Implements the algorithm as stated in the theory to calculate the results which
are again stored in eData.



eSave


S
ave process to convert the resultant data into required

format
.



eData


M
ain storage class which also acts as memory for the application. Average images
and calculation results are stored in eData. Captured images and intermediate data is

eData

e
Diagnose

e
MotorControl

e
Graphics

e
Calculate

e
AverageNoise

e
Capture

e
Save

Temperature measurement of a candle flame using a CCD camera


Interim Report

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6

cleaned and/or deleted with completion of calculations to save memory and optimise the
wo
rking of software.

Graphics Interface


The GUI for the signal processing software is as in Figure
5.

The interface is divided into
two

sections, the
top

section displays the
live camera input and averaged
images at filter 1 & 2,
while the
bottom part displ
ays

the calculations results like temperature histogram, distribution
and mean values
.


Figure 5. Graphics Interface of the System

Auto capture button is programmed to capture the images at both filters 1 & 2, and send for
processing, while with Manual ca
pture, one can select which filter to use for the temperature
calculations. Also extra options as to how many frames to capture at a filter and the time
difference between capture from filter 1 to 2 can be specified.

Menu bar contains specific diagnostic t
ools for checking connections, manually connecti
ng

to
motor and camera. It also has save options to PDF/CSV/XML and help on how to use
advanced options like changing intensity values and lighting parameters.



Temperature measurement of a candle flame using a CCD camera


Interim Report

Page
7

4

Project Progress

4.1

Updated Project Plan


Table
2.

Updated Project Plan



4.2

Progress


As seen in the project plan in Table 2, most of the tasks were finished on time, there were
irregularities like the ordering of components didn’t take place until week 9, due to problems
deciding the specifications with

the computer, The hardware design was completed, but due to
irregularity and instability of USB port the design was scrapped and option of using Serial (RS
-
232) port is to be used. Circuit diagrams need to be redrawn which is set to be completed in
week 1
3/14. Also certain tasks like
Optical Setup and Power Supply

and
USB/Serial Driver
Configuration

were completed before time as resources were available and also to make space
for the unfinished tasks to be completed on time. Even though certain tasks were
not finished
in order, the task set in the original plan is being completed in the scheduled time.