A NOVEL METHOD OF IMAGING THE IRRADIANCE PROFILE OF DENTAL LIGHT CURING UNITS

By

ANTHONY DULAL

A THESIS PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2018

© 2018 Anthony Dulal

To my sister (Christina Dulal) and my parents (Mr. Nandalall Dulal and Mrs. Carolyn Dulal), for always believing in me

4

ACKNOWLEDGMENTS

I would like to thank my family for their unwavering support and many years of

loving encouragement. I am also grateful to my advisor, Dr. Huikai Xie, because this

research work would not have been possible without his guidance. I would like to thank

Dr. Ant Ural and Dr. Sanjeev Koppal for being a part of my committee. I would like to

thank Kaushik Ragam and Dr. Jean-Francois Roulet for giving me access to their data,

research papers, laboratory, and light curing units. I would like to thank Liang Zhou and

Dingkang Wang for assisting me with any questions I had in Dr. Xie’s laboratory. I would

also like to express my gratitude to Andrew Reath for his helpful comments and for

being a great friend. I also want to thank Shaun Green and Alexander Martinez for

always being there for me when I needed them.

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TABLE OF CONTENTS page

ACKNOWLEDGMENTS .................................................................................................. 4

LIST OF TABLES ............................................................................................................ 6

LIST OF FIGURES .......................................................................................................... 7

ABSTRACT ..................................................................................................................... 8

CHAPTER

1 INTRODUCTION .................................................................................................... 10

Motivation ............................................................................................................... 10

Related Work .......................................................................................................... 13

2 METHODS .............................................................................................................. 15

Choosing the Neutral Density Filter ........................................................................ 15

Irradiance Measurement and Linear Regression Analysis ...................................... 15

Using MATLAB for Image Processing .................................................................... 17

3 RESULTS ............................................................................................................... 22

LCU Irradiance Profiles with Irradiance Scales ....................................................... 22

Qualitative Comparison of Spectrometer-Based Study ........................................... 22

Comparison to MARC Resin Calibrator Irradiance Imaging .................................... 23

Discussion .............................................................................................................. 24

LIST OF REFERENCES ............................................................................................... 31

BIOGRAPHICAL SKETCH ............................................................................................ 33

6

LIST OF TABLES

Table page 2-1 Converted and predicted data from photodetector measurements ............................. 20

7

LIST OF FIGURES

Figure page 2-1 Overexposed irradiance profile of Valo Cordless ................................................ 18

2-2 Irradiance profiles of Valo Cordless (left) and Ascent OL5 (right) after ND filters ................................................................................................................... 19

2-3 Irradiance measurement process illustration ...................................................... 19

2-4 Linear regression fitted line of LCU’s (Valo on left, Ascent on right) ................... 20

2-5 Grayscale images of LCU irradiance profile (Valo on left, Ascent on right) ........ 21

2-6 False color images of LCU irradiance profile (Valo on the left, Ascent on the right). .................................................................................................................. 21

3-1 Valo Cordless irradiance profile .......................................................................... 26

3-2 Ascent OL5 irradiance profile ............................................................................. 26

3-3 Spectrometer-based LCU irradiance profile ....................................................... 27

3-4 MARC Resin Calibrator data collection process ................................................. 27

3-5 MATLAB approximated 2D irradiance profile of Valo Cordless .......................... 28

3-6 MATLAB generated 3D irradiance profile of Valo Cordless ................................ 28

3-7 MATLAB generated 3D irradiance profile of Ascent OL5 ................................... 29

3-8 MATLAB approximated 2D irradiance profile of Ascent OL5 .............................. 29

3-9 Sectioning LCU for point-by-point analysis ......................................................... 30

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science

A NOVEL METHOD OF IMAGING THE IRRADIANCE PROFILE OF DENTAL LIGHT

CURING UNITS

By

Anthony Dulal

May 2018

Chair: Huikai Xie Major: Electrical and Computer Engineering

Traditional spectrometer-based methods of imaging the irradiance profile of an

LCU (Light Curing Unit) are accurate but they are often very costly. Many dentists and

researchers around the world pay thousands of dollars to purchase spectrometer-based

devices or have others image LCU’s for them off-site. In some cases, an irradiance

profile that approximates the relative irradiance values across the surface of an LCU is

all that is required to better understand an LCU’s capabilities. In those cases, an

irradiance profile generated through the use of a spectrometer may not be necessary.

This work attempts to find an alternative to spectrometer-based imaging that may not be

as accurate, but can still generate useful irradiance profiles for thousands of dollars

less.

This study employs a three stage approach to generate a relative irradiance

profile of an LCU. An inexpensive Arducam 5 camera module is used to determine the

required light attenuation of the image it captures so that adequate resolution is

achieved. This is done through the use of successive, stacked, ND (Neutral Density)

filters through which the camera images the LCU. The incident power is then measured

9

over a 13 cm range using a photodetector connected to a power meter. These values

are converted to radiance values so that linear regression can be done to determine the

radiance value at a distance of 1cm from the surface of the LCU. Once this is

determined, the radiance value is converted to irradiance and used as the maximum

irradiance threshold of the LCU in the next stage of the process.

The final stage of this method involves the use of MATLAB (version R2017a) to

process the images taken by the camera. The original image of the LCU is converted to

a monochromatic, grayscale image of varying pixel intensity. This grayscale image is

subsequently converted to a false color image complete with irradiance value scale. It is

shown that the generated irradiance profiles are visually comparable to irradiance

profiles from spectrometer-based imagers. It is also shown that the generated irradiance

profile possesses similar irradiance values to spectrometer-based profiles.

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CHAPTER 1 INTRODUCTION

Motivation

Effective photo-polymerization is essential to the long term clinical success and

effectiveness of resin composite dental restorations [1]. To achieve the required curing

polymerization, a dental Light Curing Unit (LCU) is utilized to activate the photo-initiators

within the resin. Most photo-initiators consist of the photo-initiator, which directly

absorbs light directly, and the co-initiator, which interacts with the photo-initiator to

produce a reactive free radical that will initiate the polymerization process [2]. The

curing process utilizes a layering technique in which a layer of resin, no thicker than

2mm, is cured with an LCU; incremental layers are subsequently added and cured until

the desired thickness and shape of the restoration has been met [3]. It has been shown

that an LCU of source intensity between 400 mW/cm2 and 578 mW/cm2 will provide an

adequate cure, based upon the results of cure at the 2mm depth [3]. Exceeding this

intensity range or increasing the exposure time past the adequate, 60 second, duration

will not yield significantly better resin curing [3]. When the polymerization of the resin

composite in the dental restoration is inadequate, deleterious effects occur on the

mechanical properties and dimensional stability of the restoration [4]. A decrease in light

intensity of as little as 10% at the surface of the resin may lead to ineffective curing of

the resin at 2 mm beneath the restoration surface [4]. Thus, there is a need to examine

the radiant flux (incident power) arriving at the resin surface per unit area, otherwise

known as irradiance, synonymous with irradiance intensity [5].

The current methods employed to determine the irradiance profile of an LCU are

effective, but they tend to be expensive due to the cost of purchasing specialized

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sensing devices or sending LCU’s to offsite locations to be imaged. Imaging an LCU

through the use of a spectrometer with an integrating sphere that adheres to the ISO

10650 code for testing is highly effective especially when a diffuser is not employed that

would introduce homogeneity to the beam profile [6]. Unlike a dental radiometer, a

laboratory grade spectrometer connected to an integrating sphere can measure all the

light output from an LCU as well as the LCU’s emission spectrum [7]. However, the cost

of the spectrometer/spectrophotometer sometimes deters researchers from receiving

the benefits of utilizing them, even outside of LCU irradiance profile imaging [8]. Another

spectrometer-based instrument imaging device widely marketed to the dentistry field is

the MARC®-Resin Calibrator (Blue-light Analytics Inc., Halifax, NS) test device. This

device can measure radiant emittance over a wavelength range and, after integrating

the irradiance, the radiant exposure can be shown [9]. Despite its usefulness, the

MARC®-Resin Calibrator cannot provide an image of an LCU’s irradiance profile without

aid from other external software and costs thousands of dollars. Unlike spectrometer-

based imagers, dental radiometers are inexpensive, but cannot generate an irradiance

profile on their own and are only effectively used for periodical monitoring of intensity of

a point on the LCU surface [1].

With the prevalence of LCU’s in dentistry around the world, it is valuable to

determine an alternative approach to irradiance profiling that is both cost-effective and

accurate. Our system, which is an alternative to spectrometer and dental radiometer

based imaging, would be a low-cost relative irradiance profiling technique that produces

an irradiance profile of an LCU that is comparable to current imaging techniques. The

method that we have developed to image the irradiance profile of the two LCU’s in this

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study, the Valo® Cordless (Ultradent Products Inc., South Jordan, UT) and the Ascent®

OL5 (Cao Group Inc., West Jordan, UT), starts with utilizing a camera module, an

Arducam 5 camera module compatible with the Raspberry Pi platform, inside of a dark

room. Neutral Density (ND) filters are placed between the camera and the LCU so that

overexposure is reduced and the features of the LCU surface recorded by the camera

are resolved.

The next stage of the process involves utilizing a power meter and photodetector

combination to measure the irradiance profile of the LCU. In this study, the Model 815

Series Digital Power Meter (Newport Corp., Irvine, CA) and the Model 818-SL

Photodetector (Newport Corp., Irvine, CA) are used. First, an irradiance measurement

from the closest possible distance, 3 cm in our case, to the ND filter surface is taken.

Then, an irradiance measurement is taken at 1 cm intervals moving away from the LCU.

These iterative measurements are collected to estimate the irradiance from a distance

of 1 cm because a measurement from that distance is not physically possible to obtain

due to the thickness of the ND filters used. The estimate of the irradiance from 1 cm is

done through a conversion of irradiance values to radiance values followed by linear

regression analysis performed on a personal computer using the Minitab software

(version 18). The result yields a radiance value that, when converted back to an

irradiance value, serves as the threshold for the maximum possible irradiance at any

point in the irradiance profile.

The final stage of the method employs the use of MATLAB (version R2017a) for

image processing: to convert the image of the LCU irradiance profile originally taken to

a grayscale version. This conversion is done in order to change the original image to a

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monochromatic image that varies only by pixel color intensity. This grayscale image is

then converted to a false color image and the maximum irradiance value previously

found is assigned as the maximum value in the false color image colormap. The

resulting image of the LCU irradiance profile is comparable to the profile produced by a

spectrometer-based imaging device, but for thousands of dollars less.

Related Work

Today’s irradiance profiling of LCU’s is usually done with spectrometer-based

imagers. However, there is research being conducted into other methods of LCU

imaging as well. One example is performing irradiance beam profiling on dental LCU’s

using low-budget cameras to correlate it to a “gold standard” beam profiler camera [10].

In this case, the spectral radiant power of the LCU’s are measured using a

spectrophotometer with a 16 mm diameter collection area [10]. The light from the LCU

under test is projected onto a glass diffuser and recorded using two low-budget

cameras, a DSLR camera (NEX-F3, Sony) and a smartphone camera (iPhone® 7Plus,

Apple) [10]. These low-budget camera images were compared to a CCD (Charge-

Coupled Device) Beam Profiler camera (OPHIR-SP503U, Ophir-Spiricon) image [10].

Although this technique is effective, it still employs the use of a spectrometer for

irradiance profile imaging. This method also uses a glass diffuser during the image

capturing process which serves to homogenize and distort the true irradiance profile

because a diffuser inherently possesses light scattering properties [11,12].

In another study, irradiance or power density of the LCU is measured so that it

could be related to a rise in temperature of the LCU measured by a thermocouple

embedded in the resin composite [13]. It was found that for most lights there was a

14

linear relation between temperature rise over time and power density [13]. However, the

study also includes that a different radiometer of the same make, under the same

conditions, gave power density readings 1.5 times higher than the other radiometer [13].

Utilizing radiometers for purely power density measurements can be done but still

remains unreliable.

15

CHAPTER 2 METHODS

Choosing the Neutral Density Filter

After the initialization of the camera module and the setup of the Raspberry Pi

remote connection, an ND filter had to be selected to reduce the exposure of the

camera module. We chose absorptive ND filters in order to reduce back reflections,

since in this case the excess heat generated by such filters was not significant [14]. It is

assumed for this application that the neutral density filters used have an approximately

constant degree of light attenuation over the desired wavelength range, approximately

350nm to 550nm [15,1]. The ND filter selection process was an iterative approach to

find the filter combinations that would attenuate enough light to resolve the LCU

irradiance features but not completely attenuate the light. First, the ND filters that

attenuate more light, 12.5% and 25% total light transmission, are stacked and 50% or

62.2% total light transmission ND filters are added if more attenuation is needed due to

an overexposed camera image, as shown in Figure 2-1. It is determined that a series of

6 filters stacked upon each other creating an equivalent filter that transmitted about

0.302% of the total light is adequate. The resulting images using the proper equivalent

ND filter for the two LCU’s studied in this thesis are shown in Figure 2-2. The features of

each LED within each LCU surface can be seen and, although it is not easy to discern

now, visible differences in irradiance may be observed.

Irradiance Measurement and Linear Regression Analysis

After an equivalent ND filter has been chosen, incident power measurements

should be taken by the photodetector to determine the irradiance of the image at 1 cm

away from the LCU. As stated in the “Motivation” section, the thickness of the ND filters

16

stacked together makes it impossible to measure the irradiance at 1 cm from the LCU.

In this case, we place the photodetector as close to the first ND filter of the stack without

touching it, which is 3 cm away from the LCU. Then we take our first measurements of

the LCU’s incident power. More measurements are iteratively taken from 3 cm to 16 cm

away from the LCU in 1 cm increments, as illustrated in Figure 2-3. All of the ND filters

are stacked together and taped onto the inside surface of the purple viewing apparatus

for measurement replicability.

After all of the power values incident on the photodetector have been collected,

over five trials per measuring point, the values must be converted to the proper

irradiance units based on active area of the photodetector because the optical power

meter outputs values in mW. This is done through the use of Equation 2-1, where

NDeq ≈ 1/331 and Aphotodetector = 1.003 cm2.

Irradiance = Power DensityNDeq×Aphotodetector

(2-1)

Once the incident power values are converted to irradiance (mW/cm2), the

irradiance values can be converted into radiance values based on the solid angle. The

solid angle is a ratio of the area irradiated to the squared distance from the source [16].

Radiance values should remain constant over distance because radiance does not

depend upon distance due to the area irradiated increasing at the same rate distance

increases, but this is not the case [16]. The size-of-source effect can be neglected in

this case because we are not changing the irradiation area of the photodetector or

source [16]. The distance effect, however, cannot be ignored and is responsible for the

varying radiance observed over increasing distance [16]. The distance effect is a linear

ratio of the output signal at a given distance from the source to the output signal at a

17

reference distance [16]. This effect makes radiance approximately vary linearly with

distance. The irradiance values follow an approximate inverse square law trend of

nonlinear regression that makes data more problematic to approximate [17,18]. For

these reasons, data conversion to radiance values is done using equation 2-2.

Radiance=Irradiance× 𝑖 𝑎𝑛 2Aphotodetector

(2-2)

Linear regression is then performed using Minitab (version18) for both LCU

datasets, as shown in Figure 2-4. Table 2-1 shows all of the averaged values found

through the data collected from the photodetector and optical power meter. Also shown

is the predicted radiance values at 1 cm and 2 cm for both LCU’s. Converting radiance

at a distance of 1 cm from the LCU into an irradiance value for each LCU yields

maximums of 2125 mW/cm2 for the Valo Cordless and 654.2 mW/cm2 for the Ascent

OL5. These maximum irradiance values will serve as the maximum threshold for the

false color colormap irradiance profile discussed in the next section, using MATLAB for

the image processing.

Using MATLAB for Image Processing

Grayscale images assign only intensity information from the amount of light

captured in the image per pixel [19]. This intensity information is useful because the

intensity of the pixel in the image of the LCU irradiance profile is proportional to the

irradiance level at that can be measured spatially through use of a radiometer or by

sectioning the LCU surface and measuring irradiance incrementally over the surface

from a distance of 1 cm [19]. This irradiance information is found in Figure 2-5. It is

notable that the grayscale image works sufficiently as an image of the irradiance profile

of the LCU because it contains all of the intensity information; conversion to a false

18

color image only aids in information visualization and is more comparable to irradiance

profiles found by spectrometer-based profilers.

Once the irradiance profile of the LCU has been converted to grayscale, the next

step is a conversion to a false colormap so that the irradiance peaks may be discerned

more easily. Figure 2-6 displays these converted false color images with a jet(255)

colormap from the MATLAB software package.

Figure 2-1. Overexposed image of Valo Cordless, January 18, 2018. Photo courtesy of author.

19

Figure 2-2. Images of Valo Cordless (left) and Ascent OL5 (right) after ND filters, January 27, 2018. Photo courtesy of author.

Figure 2-3. Irradiance measurement process illustration, January 17, 2018. Photo courtesy of author.

20

Figure 2-4. Linear regression fitted line of LCU’s (Valo on left, Ascent on right). Table 2-1. Converted and predicted data from photodetector measurements.

Dist. (cm)

Valo Power (mW)

Valo Irrad. (mW/cm2)

Valo Rad. (mW/str/cm2)

Ascent Power (mW)

Ascent Irrad. (mW/cm2)

Ascent Rad. (mW/str/cm2)

1 N/A 2125.0 2119 N/A 654.204 652.2 2 N/A 545.7 2176 N/A 161.412 643.5 3 0.620 204.6 1836 0.192 63.362 568.5 4 0.423 139.6 2227 0.120 39.673 632.8 5 0.280 92.4 2303 0.079 25.940 646.6 6 0.207 68.3 2459 0.054 17.822 639.6 7 0.158 52.1 2547 0.038 12.542 612.6 8 0.125 41.3 2632 0.029 9.504 606.4 9 0.103 34.0 2745 0.022 7.194 581.0

10 0.087 28.7 2862 0.018 5.874 585.6 11 0.076 25.1 3026 0.014 4.620 557.3 12 0.062 20.5 2937 0.012 3.828 549.6 13 0.048 15.8 2669 0.010 3.168 533.8 14 0.042 13.9 2708 0.008 2.772 541.7 15 0.038 12.5 2813 0.007 2.244 503.4 16 0.032 10.6 2695 0.006 2.112 539.1

21

Figure 2-5. Grayscale images of LCU irradiance profile (Valo on left, Ascent on right).

Figure 2-6. False color images of LCU irradiance profile (Valo on the left, Ascent on the right).

22

CHAPTER 3 RESULTS

LCU Irradiance Profiles with Irradiance Scales

The final LCU irradiance profiles are scaled based on the maximum irradiance

value determined in the previous chapter. This value serves as a threshold to assign to

the maximum intensity of the false color image as shown in the Valo Cordless of Figure

3-1 and the Ascent OL5 of Figure 3-2. From Figure 3-1 and Figure 3-2, it is can be seen

that there exists definite hot areas, “hot-spots,” and cold areas that irradiate the image

surface significantly more or less than the surrounding LCU surface. The shape of the

LCU’s LED array determines where these hot spots occur as shown by the Valo

Cordless and the Ascent OL5.

Qualitative Comparison to Spectrometer-Based Study

The irradiance profile of the Valo Cordless is seen in a study characterizing

radiant exitance of dental LCU’s [1]. Figure 3-3 borrows the spectrometer irradiance

profile image taken in the study using an integrating sphere and a spectrometer to

image the irradiance profile of the Valo Cordless, among other LCU’s [1]. There are

many similarities between the Valo Cordless irradiance profile imaged with the

spectrometer as compared to the irradiance profile generated in this thesis. Both

images have two distinct hotspots diagonally oriented on the along the surface of the

LCU. Both images are approximately symmetrical along an imaginary diagonal axis

dividing the Valo Cordless LCU surface in half. Also, both irradiance profiles experience

a decrease in irradiance as distance from one of a hot spot increases. Although the

study claims there is a 0 mm distance from sensor to LCU during the irradiation

measurement and profile capture, the sensor has a glass screen of non-negligible

23

thickness before the sensor and the Valo Cordless lens does not directly touch the

screen [1]. In this thesis, the distance of 1 cm from LCU to photodetector/camera is the

true distance from internal photodetector sensor to LCU; thus, the maximum irradiance

value in the study of 2027 mW/cm2 for the Valo Cordless is relatively comparable to the

maximum irradiance value for the Valo Cordless in this thesis, 2125 mW/cm2. These

two irradiance values are less than 5% different from each other, signifying that the

method introduced in this thesis may be a viable one for capturing the irradiance profile

of the Valo Cordless.

Comparison to MARC Resin Calibrator Irradiance Imaging

Another irradiance measurement technique was concurrently conducted with the

technique introduced in this thesis for the purpose of drawing a comparison between

them. The MARC Resin Calibrator utilizes spectrometry-based measurement to deliver

irradiance measurements [20]. These irradiance measurements require additional

software to piece together the collected data points and that is where MATLAB’s

contour3() and surf() functions proved useful. The data is collected according to a

Cartesian coordinate system where the origin, (0,0), corresponds to a point 0 mm from

the origin in the x-direction and 0 mm from the origin in the y-direction. The LCU under

test is placed into an arm and measured in 1 mm increments along x and y directions

until no irradiance can be observed in the Cartesian plot that is mapped out by the data

collection. This process is partially illustrated in Figure 3-4. It is important to note that for

the measurement process, the bottom sensor (left sensor) and corresponding

calibration is utilized and the bottom sensor is about 5 mm inside of the bottom sensor

well [21]. During measurement, the LCU never truly touches the surface of the MARC

Resin Calibrator so the distance from sensor to LCU surface is approximately 1 cm

24

total, just as the distance from sensor to LCU in this thesis is 1 cm. This makes

comparison of LCU irradiance profiles possible.

It is of note that the MARC Resin Calibrator contains a diffuser that homogenizes

the irradiance profile and, much unlike the previously observed spectrometer-based

irradiance profile and the irradiance profile from this thesis, generally has one

centralized hot spot. For the Valo Cordless, Figure 3-5 illustrates the 2D (2 dimensional)

irradiance profile homogeneity caused by the diffuser in the system. The Valo Cordless’

irradiance profile appears to be different than the corresponding irradiance profile from

this thesis; however, the irradiance values are similar for both irradiance profiles. An

additional 3D irradiance profile of the Valo Cordless, found in Figure 3-6, better

illustrates that despite the presence of the diffuser in the MARC Resin Calibrator-based

image, the profiles are similar in irradiance value over the LCU surface area.

A similar comparison can be drawn between the irradiance profile of the Ascent

OL5 from this thesis and the corresponding irradiance profile as collected by the MARC

Resin Calibrator and pieced together in MATLAB. Figure 3-7 depicts the 3D irradiance

profile of the Ascent OL5; although the irradiance profiles appear different, again, their

irradiance values are similar. The 2D irradiance profile in Figure 3-8 shows the effects of

the diffuser on the irradiance profile of the Ascent OL5 as well.

Discussion

An alternative to more expensive LCU irradiance profile imaging was presented

through the systematic method detailed in this thesis. We have shown that by using a

simple camera, easily accessible ND filters, along with a photodetector and power

meter that it is possible to create irradiance profiles of LCU’s that resemble profiles

25

made by spectrometers. While a spectrometer with integrating sphere will remain a

highly accurate and reliable way to measure irradiance profiles, the novel method

presented here can be useful for imaging irradiance profiles when the utmost accuracy

is not necessary. The method introduced here can generate a highly accurate

approximation of what the irradiance profile of an LCU should resemble without a

diffuser.

The method’s dependence on linear regression of radiance over distance proves

to be the factor that can make it inaccurate. Future work should be aimed at modeling

the irradiance or radiance over distance more accurately in order to develop a better

approximation for the maximum value at a 1 cm distance from the LCU. If this hurdle is

overcome, then another great advancement in this method would be to introduce point-

by-point analysis of the LCU surface, as illustrated in Figure 3-9, to study the effect

each point of the LCU has on the irradiance profile, as a whole. Software such as

Zemax® (Kirkland, WA) can also be used in future work to introduce nonlinear effects as

a result of light emission from the LCU’s LED’s.

26

Figure 3-1. Valo Cordless irradiance profile.

Figure 3-2. Ascent OL5 irradiance profile.

27

Figure 3-3. Spectrometer-based LCU irradiance profile [1].

Figure 3-4. MARC Resin Calibrator data collection process, February 2, 2018. Photo courtesy of author.

28

.

Figure 3-5. MATLAB approximated 2D irradiance profile of Valo Cordless.

Figure 3-6. MATLAB generated 3D irradiance profile of Valo Cordless.

29

Figure 3-7. MATLAB generated 3D irradiance profile of Ascent OL5.

Figure 3-8. MATLAB approximated 2D irradiance profile of Ascent OL5.

30

Figure 3-9. Sectioning LCU for point-by-point analysis, March 1, 2018. Photo courtesy of author.

31

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BIOGRAPHICAL SKETCH

Anthony Dulal was born in Toronto, ON in 1994. He moved to Florida and

received his Bachelor of Science in electrical engineering degree with honors from the

University of South Florida in May of 2016. While pursuing his degree at the University

of South Florida, he worked on his honors thesis under the supervision of his thesis

chair, Dr. Arash Takshi. Anthony received his Master of Science in electrical

engineering degree from the University of Florida in May of 2018. While pursuing his

graduate degree at the University of Florida, he worked on his master’s thesis under the

supervision of his committee thesis chair, Dr. Huikai Xie. His research interests include

optical imaging systems, light curing unit irradiance profile imaging, carbon nanotube

supercapacitors, gel electrolytes, electronic circuits, and welding technologies.