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
1
INTRODUCTION .......................................................................................................................................... 2
2
SPECIFICATION ........................................................................................................................................... 2
3
TECHNICAL APPROACH ............................................................................................................................... 2
3.1
THEORY ....................................................................................................................................................... 2
3.2
SYSTEM SETUP .............................................................................................................................................. 3

MAIN COMPONENTS USED .................................................................................................................................. 3

DESIGN OF THE CAMERA HOUSE ........................................................................................................................... 4
FIGURE 2 SHOWS THE DESIGN OF THE CAMERA HOUSE AND THE FILTER HOLDER. .................................................. 4
3.3
SOFTWARE ................................................................................................................................................... 4

CLASS STRUCTURE ............................................................................................................................................. 5
GRAPHICS INTERFACE .................................................................................................................................................. 6
4
PROJECT PROGRESS .................................................................................................................................... 7
4.1
4.2
UPDATED PROJECT PLAN ................................................................................................................................ 7
PROGRESS.................................................................................................................................................... 7
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Temperature measurement of a candle flame using a CCD camera
1 Introduction
Flame temperature distribution is one of the key requirements for efficiency of a combustion
process. The flame temperature is needed to measure in a combustion system for evaluating the
combustion efficiency and emission formation process, which is difficult to measure as the
temperature is very high. Most existing flame monitoring devices monitor only the indication
of the flame ignition.
Research work was made 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 remote and online flame temperature measurement
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
time image transfer and is therefore suitable for online and remote monitoring
temperature distribution. The project carried out is the prototype of an imaging
consisting of a CCD camera and signal processing software for candle flame. The
operates on two-colour method to calculate the temperature distribution.
of real
of the
system
system
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 the temperature distribution of a flame from its gray scale images using
two-colour 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) = C1/𝜆5 (e C2/𝜆T – 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, C1 & C2 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 determining temperature
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Temperature measurement of a candle flame using a CCD camera
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
𝑇=
1
1
− )
λ2 λ1
S
𝐺(λ ,T)
λ 6
Δλ
ln 1 + ln λ2+ ln( 1 ) +ln( 2 )
𝐺(λ2 ,T)
Sλ1
λ2
Δλ1
𝐶2 (
(2)
Where, T = temperature in Kelvin, C2 = Planck’s constant = 1.4388 x 104 [µm.K], λ1 &
λ2 are wavelength of respective optical filters,
𝐺(λ1 ,T)
𝐺(λ2 ,T)
is the ratio gray-level ratio,
Sλ2 & Sλ1 are spectral sensitivities of the imaging system at λ1 & λ2, and Δλ1 & Δλ2
are bandwidths of λ1 & λ2.
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 captured 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 based 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
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Temperature measurement of a candle flame using a CCD camera
Stepper Motor
CCD Camera
Optical Filters
Serial Interface
Board
Software

Table 1. Main Component used
Model
Mclean 7.5° Unipolar with 25:2 Gearbox
Model
Hitachi KP-M1E/K-S10
Effective Pixels
752(H) x 582 (V)
Iris
Manual, 0.5 Inch Diameter, 6mm focus
3 x Filters
550nm, 650nm & 700nm wavelengths
Processor
PicAxe 281X Series from microchip
Port
Serial RS-232 Connector
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 design of the camera house 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 another filter. Averaged images are run through noise elimination
system to reduce any other noise. Images 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 Figure 5, after successful completion of
the temperature calculations. A software aspect of the theory is implemented as flow chart in
Figure 3.
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Temperature measurement of a candle flame using a CCD camera
Figure 3. Flow chart of Software
 Class Structure
eData
eCalculate
eAverageNoise
eMotorControl
eSave eCapture
eDiagnose
eGraphics
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 graphics class for interface display & connections 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 images 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 – Save process to convert the resultant data into required format.
 eData – Main 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
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Temperature measurement of a candle flame using a CCD camera
cleaned and/or deleted with completion of calculations to save memory and optimise the
working 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 displays 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 capture, 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 tools for checking connections, manually connecting 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.
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Temperature measurement of a candle flame using a CCD camera
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 (RS232) port is to be used. Circuit diagrams need to be redrawn which is set to be completed in
week 13/14. 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.
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