Charge-coupled device based on optical tomography system for monitoring two-phase flow
J. Jamaludin, R. Abdul Rahim
✉, H. Abdul Rahim, M.H. Fazalul Rahiman and J. Mohd Rohani
An application of charge-coupled device (CCD) linear sensor and laser diode in an optical tomography (OPT) system is presented. The measurements are based on thefinal light intensity received by the sensor. The aim is to analyse and demonstrate the capability of laser with a CCD in an OPT system for detecting transparent objects in crystal clear water. The image reconstruction algorithms used were filtered images of linear back projection algorithms. These algorithms were programmed using LabVIEW programming software.
Experiments in detecting transparent hollow straw were conducted.
Based on the results, statistical analysis was performed to verify that the captured data were valid compared with the actual object data. The object’s characteristics such as diameter also are observed. In conclusion, a non-intrusive and non-invasive OPT system that can detect transparent objects in crystal clear water is successfully developed.
Introduction: The gas percentage in the liquid medium, gasflow rate, appearance and disappearance of gases, shape of gases and their diam- eters are imperative information for monitoring and process control.
Petroleum refining systems, textile and fabric industries, oil and gas pipeline systems, geothermal wells, steam generation in boilers and burners and steam condensation all deal with two-phaseflow which is in the form of gas bubbles and liquid [1]. Engineers need to monitor the condensation process or the distribution of steam bubbling to avoid any damage occurring in the high cost and high maintenance of their system.
The optical tomography (OPT) system is considered as a hard-field sensor because the sensingfield is based on the measurement of the attenuation or absorption of radiation [2]. For soft-field sensor, it depends on the changes of conductivity or permittivity of the objects that are being studied. OPT system provides many advantages compared with other soft-field sensors. OPT system gives a good spatial resolution of image reconstruction [3] and this sensor is appropriate for real-time monitoring system because it provides a high-speed data capture.
X-axis movable rod
black box
CCD
square aperture light expansion
system
Fig. 1Diagram of laser diode box system in transparent view
The main objective of this Letter is to develop an OPT system using charge-coupled device (CCD) linear sensors and laser diodes with LabVIEW programming to monitor the two-phase flow. The OPT system developed is a non-intrusive, non-invasive, and it does not require any contrast agents in order to detect foreign objects in the pipe- line system. This system is safe and it does not pollute the environment with any chemicals or hazardous radiation. Since no probes or sensors need to befitted in the liquid medium, this system offers more accurate data due to the absence of any interference of the OPT system in the pipeline processes. LabVIEW programming was developed to recon- struct a cross-sectional pipeline image for real-time data and to measure the object diameter for offline data. Then, the data collected shall be ana- lysed and evaluated using a statistical engineering analysis technique.
Research methodology: This Letter constructs an OPT system using a Sony ILX551A CCD and laser diodes class IIIA oriented in an octag- onal shape to give a wide coverage area of an acrylic pipeline system.
The whole body of the box is black in colour to avoid the effect of light reflection. Fig. 1 illustrates the transparent laser diode box system for a clear view of the arrangement of the optical components.
AnX-axis movable rod allows an adjustable distance between the trans- mitter and receiver to be controlled manually. The light expansion system is a subsystem for the laser diode beam divergent process. The square openings are aligned in parallel with the CCD sensors. Square apertures with dimensions of 40 × 40 mm will limit the area of the beam source that reaches the sensors.
Fig.2shows the detailed construction of the laser diode light expan- sion system. The components involved are a cylindrical rod, laser diode, biconvex lens and sphericalfilter. A 5 dioptre off the shelf lens with 200 mm focal length is used. The laser with the attached lens is covered using a spherical filter. It is used to reduce the laser diode light intensity from 0.7 to 0.5 lx in air and 0.3 lx after passing through crystal clear water. The appearance of a liquid such as crystal clear water helps to absorb the heat that is produced by the laser diode to prevent overheating and damaging the CCD sensors. A greater thickness of water can provide a long passageway that the laser has to undergo. So the heat-affected zone of the laser diode becomes less significant [4].
laser diode
biconvex lens
spherical filter cylindrical rod
Fig. 2Laser diode subsystem
Thefinal design of the mechanical hardware development is shown in Fig.3from the external and internal view.
Fig. 3Mechanical hardware development
There are two software programs involved in this Letter: real-time image reconstruction and offline data measurement. For real-time image reconstruction, linear back projection (LBP) with threshold value andfiltered algorithms are applied. The equation used in this Letter is shown in (1). In (1),Stx,rxrefers to CCD normalised voltage output andMtx,rxrefers to OPT system sensitivity map.
VLBP+Threshold(x,y)=n−1
tx=0
n−1
rx=0
Stx,rxx Mtx,rx(x,y) (1)
Filtered method was applied to enhance the image reconstruction produced by the above equation. Thefiltered image is produced by comparing the current image with an initial image where no objects exist in the pipeline system. Equation (2) shows thefiltered images algorithm involved
Vfilteredx,y
=VLBP+Thresholdx,y
−Vix,y
(2) In (2),VLBP+Thresholdis the image under study using a combination of LBP and threshold methods, andVi is the initial state of LBP and threshold image when no obstacles detected [5].
For offline programming, data on the object diameter are collected for evaluation. Fifty numbers of data are observed to investigate the capa- bility of this OPT system in detecting and capturing images of transpar- ent objects. The data collected were analysed and evaluated with the help of Minitab software.
Fig.4shows an example of normalised CCD voltage output results versus time. When an object intercepts the system projection, the nor- malised voltage will increase in a certain period of time. The time ranges of this voltage increment represent the object diameter.T1 is the effective pixel starting time and T2 equals to effective pixel ending time. For this example, the effected pixel time occurred
ELECTRONICS LETTERS 2nd March 2017 Vol. 53 No. 5 pp. 331–333
1350911x, 2017, 5, Downloaded from https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/el.2016.3084 by Cochrane Malaysia, Wiley Online Library on [19/11/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
between the times of 0.460 s to the time of 0.478 s. Equations (3) and (4) were used to convert the time range into pixel number [6]
Time range=T2−T1 (3)
Total pixel numbers= Time range(s)
Time clock per cycle(s) (4)
2.0
1.5
seconds, s
voltage, v
time range T1
1.0
0.5
0
0.458 0.460 0.462 0.464 0.466 0.468 0.470 0.472 0.474 0.476 0.478 0.480 0.482 0.484 T2
Fig. 4Normalised CCD voltage output against time
The time range is divided by the CCD clock cycle (8.8 µs). The diam- eter of the object will be obtained by multiplying the total pixel numbers by 0.014 mm, per pixel length as shown in the following equation:
Diameter mm( ) =Total pixel×0.014 mm (5)
Results and discussions: These experiments were conducted not only for evaluating the OPT system capability in capturing images of trans- parent objects in crystal clear water, but also for analysing the diameter of these objects. First, the objects were measured by a Vernier calliper to get targeted diameter value before proceeding witht-test analysis.
individual value plot of transparent hollow straw (upper plane) (with Ho and 95% t-confidence interval for the mean)
6.45 6.50 6.55 6.60 6.65 6.70
diameter, mm Ho
X-
one-sample T: transparent hollow straw
Fig. 5 T-test graph result for transparent hollow straw diameter measurement using OPT system
3D view method
LBP+thresholdfiltered
sideview
Fig. 6Real-time image reconstruction of transparent hollow straw Thet-test analysis was conducted to verify the capability of this OPT system to determine the diameter of transparent objects detected in crystal clear water. The main focus oft-test analysis is to compare the diameter of transparent hollow straw measured by this proposed system with the actual diameter measured by a Vernier calliper. The two hypotheses involved in this analysis are:
H0: Mean of experiment diameter data = Calliper measured diameter data H1: Mean of experiment diameter data≠Calliper measured diameter data In Fig.5, a statistical chart known as individual value plot graphs was gen- erated using Minitab software. This chart consists of a few statistical symbols where, the red dotted lines present the data samples’distribution, xbars are the sample mean, blue line is the mean range and light red circles are the targeted diameter value of the transparent hollow straw.
From the statistical results, it shows thatP-value for the OPT system of the transparent hollow straw is more than 0.05, thus we fail to reject the null hypothesis. It also proved that the mean value of the OPT system transparent hollow straw diameter measurements is statistically the same as the transparent hollow straw diameter value measured by the Vernier calliper. Meanwhile, Fig.6shows the real-time image recon- struction for transparent hollow straw using LPB andfiltered methods.
Conclusion: Based on thet-test results, it is proved that the OPT hard- ware and software development is reliable in measuring low opacity object diameters exists in crystal clear water. The statistical test results concluded that the OPT system measures the same object diameter as that measured by a Vernier calliper. For the image reconstructions of transparent hollow straw in crystal clear water, it is proven that the com- bination of LBP with threshold value andfiltered algorithms are capable of reconstructing a cross-sectional image of a transparent object that exist in multiphase pipeline system.
Acknowledgments: The authors thank Universiti Teknologi Malaysia for supporting this research project and PROTOM research group for their cooperation in this Letter.
© The Institution of Engineering and Technology 2017 Submitted:25 August 2016 E-first:6 February 2017 doi: 10.1049/el.2016.3084
One or more of the Figures in this Letter are available in colour online.
J. Jamaludin (Faculty of Engineering and Built Environment, Universiti Sains Islam Malaysia, 71800 Bandar Baru Nilai, Negeri Sembilan, Malaysia)
R. Abdul Rahim (Faculty of Electrical and Electronic Engineering, UniversitI Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia)
✉E-mail: [email protected]
H. Abdul Rahim (Process Tomography and Instrumentation Engineering Research Group (PROTOM-i), Infocomm Research Alliance, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia)
M.H. Fazalul Rahiman (School of Mechatronic Engineering, Universiti Malaysia Perlis, Arau, Perlis, Malaysia)
J. Mohd Rohani (Sondotech Sdn. Bhd, 31, Jalan Mutiara Emas5/1, Taman Mount Austin, 81100 Johor, Malaysia)
R. Abdul Rahim: Also with Process Tomography and Instrumentation Engineering Research Group (PROTOM-i), Infocomm Research Alliance, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia
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ELECTRONICS LETTERS 2nd March 2017 Vol. 53 No. 5 pp. 331–333
1350911x, 2017, 5, Downloaded from https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/el.2016.3084 by Cochrane Malaysia, Wiley Online Library on [19/11/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License