3. Experimenting with Electromagnetic Waves
Color Investigation of
Digital Image Sensors
Unifying Concepts Module Systems Applications:
Making it Real
Analysis of Wireless
Networks
Image Sensor
Technology
Digital Display
Technology
Reflection
and Absorption
Representing Color in
Digital Devices
Photoelectric Effect
Electromagnetic Waves have
Properties Described by both
Wave and Particle Models
• Reflection
• Absorption
• Refraction
• Polarization
• Diffraction
• Photoelectric effect
Electromagnetic Wave can
Transfer Energy without the
Transfer of Mass
Refraction, Lenses and
Magnification
Measuring
Heartrate using
Reflectance
Spectroscopy
Electromagnetic Waves have
Wavelengths that Span >25
Orders of Magnitude
Resulting in Unique Properties
and Applications
Investigation of Flat Panel
Digital Displays
Color by Addition
Light Emitting Diodes
Polarization
Microwave
Communication
Diffraction
Spectroscopy
Properties of
Microwaves
Network Analysis
Digital Color
Photography
4. Experimenting with Electromagnetic Waves - Unit Overview
Unifying Concepts
• Electromagnetic wave can
transfer energy without the
transfer of mass
• Electromagnetic waves
have properties described
by both wave and particle
models
- Reflection
- Absorption
- Refraction
- Polarization
- Diffraction
- Photoelectric effect
• Electromagnetic waves
have wavelength that span
>25 orders of magnitude
Experiments
• Experiment 1: Absorption
and reflection of light
• Experiment 2: Representing
color in digital devices
• Experiment 3: Exploring
visible light and color by
addition
• Experiment 4: Exploring
colored displays
• Experiment 5: Image
sensors and investigating
infrared light
• Experiment 6: Investigating
illuminance as function of
distance from light source
• Experiment 7: Exploring the
polarization of light
Experiments
• Experiment 8: Investigating
spectral properties using a
transmission diffraction
grating
• Experiment 9: Explore
absorption properties of
your finger: Measure your
pulse using
photoplethysmography
• Experiment 10: Analyzing
wireless networks and the
properties of microwaves
6. Use the link to
observe the live
video from the
Monterey Bay
Aquarium in
California.
Describe the series
of processes that
involve
electromagnetic
waves which enable
you to observe the
jelly fish.
Jelly | Live cam | Monterey Bay Aquarium
29. Experiment 1
Absorption and Reflection of Light
1. Investigate the appearance of “colored” objects or pictures when
illuminated by light sources composed of different wavelengths.
a. Use your phone to create light sources that are white, red, green and
blue (see next page)
b. Illuminate “colorful” pictures and objects with the 4 different light
sources and capture the images for each condition using a second
phone camera
2. Discuss your observations in terms of reflected and absorbed
wavelengths/colors.
30. Your phone can be used as an
illumination source.
• Create white, red, green and
blue colored pictures
• Expand the pictures to full
screen
• Turn brightness up to
maximum
31. The Observed Color is Determined by the Wavelength of
the Light that is Reflected from the Object
Illumination with White, Red, Green and Blue Light
36. A material contains two
molecules that have
absorption properties
described by the graph to the
left. If the object is illuminated
by sunlight, what color will be
observed by the human eye?
1) Blue
2) Green
3) Red
4) White
38. Leaves containing chlorophyll
a and b are illuminated by a
“blue” laser that produces light
at 440 nm. If the experiment is
carried out in a room where
the only light is coming from
the laser, what color will the
leaves appear?
1) Blue
2) Green
3) Red
4) White
39. Blue (440 nm)
Because only blue light is
illuminating the leaves, the
only color that can be
reflected will be blue. The
leaves will appear dark
because much of the 440 nm
light will be absorbed.
41. Experiment 2
Representing Colors in Digital Devices
1. Investigate the use of hexadecimal numbers to represent colors on digital
devices.
a. Make a table comparing decimal, binary and hexadecimal numbers from 0-15 decimal
b. Using information you find on the internet, explain how colors are represented by the
hexadecimal notation such as #1F38AB
2. Investigate creating custom colors in your favorite slide making tool (e.g.,
Google Slides or MS PowerPoint) or go to
https://www.mathsisfun.com/hexadecimal-decimal-colors.html.
3. Use the Color Detection tool in the Physics Toolbox application to detect
colors around your house.
a. Compare the colors you detect to colors generated by your device using the
hexadecimal representations for color in either Google Slides for MS PowerPoint
42. Representing Colors in Digital Devices
The primary colors – Red, Green, & Blue – are
represented in the three number systems:
Binary: 8 bits or a byte
Range of values: 0000 0000 1111 1111
Decimal: 256 values are represented by one byte
Range of values: 0 255
Hexadecimal: 2 digits can represent all values of one byte
Range of values: 00 FF
43. Hexadecimal
Number
Decimal Value of
First Digit
Decimal Value of
Second Digit
Decimal Value
02 0 x 161 = 0 2 x 160 = 2 0 + 2 = 2
0B 0 x 161 = 0 11 x 160 = 11 0 + 11 = 11
A5 10 x 161 = 160 5 x 160 = 5 160 + 5 = 165
FF 15 x 161 = 240 15 x 160 = 15 240 + 15 = 255
Example Conversion
Hexadecimal to Decimal Number
44. Representing Colors in Digital Devices
A combination of Red, Green and Blue can be
used to represent a wide range of colors using
two hexadecimal digits for each primary color.
#RRGGBB
10 / 255 Red 0A
80 / 255 Green 50
255 / 255 Blue FF
Hexadecimal representation: #0A50FF
Total # of Colors Possible: 256x256x256 = 16,777,216
Example
Color
60. Experiment 3
Exploring Visible Light and Color by Addition
1. Explore Shadows with White Light.
a. Look at different objects
b. Explore distance between object and source
c. Explore distance between object and image plane
d. Explore the angles between light source, object and image plane
2. Explore Shadows from Primary Colors.
a. Single colors – blue, green and red
b. Pairs of colors – red & blue, red & green, green and blue
c. All three colors
3. Explore Shadows from Secondary Colors.
a. All three colors – yellow, magenta and cyan
4. Explore Shadows from Mixing of Complimentary Colors.
a. Pairs of colors – red & cyan, yellow & blue, magenta & green
Capture
Images
of
Your
Shadows
with
a
Second
Phone
Camera
68. Light Source
Image using Phone Camera
The shadow of white light appears
“black” which is what we perceive
when there is a lower level of white
light.
Light Travels in Straight Lines – Result is a Shadow
72. Light Source
Image using Phone Camera
The shadow of blue light appears
“black” which is what we perceive
when there is a lower level of blue
light.
Shadow with Blue Light Source
73. Image using Phone Camera
The Shadow is Less Blue
Increase
Brightness
75. Light Source
Image using Phone Camera
The shadow of red light appears
“black” which is what we perceive
when there is a lower level of red
light.
Shadow with Red Light Source
77. Light Source
Image using Phone Camera
The shadow of green light appears
“black” which is what we perceive
when there is a lower level of green
light.
Shadow with Green Light Source
78. Light Source
Image using Phone Camera
The combination of green and blue
light create cyan. The “shadow”
locations are observed where one of
the colors is blocked so they are only
illuminated by a single color of light.
Shadow with both Green and Blue Light
79. Light Source
Image using Phone Camera
Shadow with Red and Blue Light
The combination of red and blue light
create magenta. The “shadow”
locations are observed where one of
the colors is blocked so they are only
illuminated by a single color of light.
80. Light Source
Image using Phone Camera
Shadow with Red and Green Light
Source
The combination of red and green
light create yellow. The “shadow”
locations are observed where one of
the colors is blocked so they are only
illuminated by a single color of light.
81. Light Source
Image using Phone Camera
Green + Blue Cyan
Red + Blue Magenta
Red + Green Yellow
Red + Green + Blue White
Shadow with Red, Green and Blue Light Source
84. Light Source
Image using Phone Camera
Complimentary Color Light Source
Magenta and Cyan Blue
Yellow and Cyan Green
Yellow and Magenta Red
Yellow + Magenta + Cyan White
101. Cathode Ray Tubes – CRTs
CRTs were the dominate electronic display technology for decades
Today’s personal electronics would have not been possible
using cathode ray tubes because of the large size required for
the vacuum tube which was central to their operating principle.
103. Experiment 4
Exploring Colored Displays
1. Investigate electronic displays using the zoom features of your phone’s
camera.
a. Take pictures using the zoom feature on your phone camera of several electronic
displays. If you have an older television or computer monitor, make sure you
investigate those older devices as the pixels may be larger and easier to visualize.
b. Are your able to see individual pixels? Describe what you observe.
2. Use a method of magnification (laser diode collimating lens or water
droplet) in combination with your phone camera to investigate various
electronic displays.
a. Capture images of a wide range of electronic displays. You should be able to fully
resolve the individual red, green, and blue subpixels.
b. See if you can identify displays that use different technologies such as liquid crystal
displays and organic light emitting diodes.
c. Research the different display technologies and discuss the physics that enables
the different display types.
104. Collimating lens for a laser diode
• Attach edges with double stick tape
• Allows use of any of the phone’s cameras
• Allows different orientations for capturing images
• Costs <$1
Magnification: Option #1
105. Image using Back Facing Camera with x7 Digital Zoom
Google Pixel 3
No Additional Optics With Laser Diode Collimating Lens
106. Simple Design of a “Microscope Stand”
Allows course and fine adjustment of working distance
Course adjustment of
the working distance
can be made with solid
objects, like books.
Fine adjustment can
be made by
incorporating a layer of
“elastic” material under
the phone and applying
a variable force on the
phone to move it up and
down. In this case a
padded envelope and
some magazines were
used as the elastic
material.
107. A small drop of water
placed above the
front facing camera
can be used to
magnify images.
Magnification: Option #2
Water drop lens
108. Water Drop as Convex Lens for Magnification
Pencil Tip Magnification
Standard Image from Front
Facing Camera
Magnification using water
drop lens.
Focal length <1 cm
109. ~1.2 mm ~2.2 mm ~3.5 mm ~4.5 mm
Observation of Water Drop Lens Shape as Function of Drop Size
The Shape of Lens will Determine the Refraction and the Magnification of the Image
Competing Forces:
• Cohesive Forces of Water
• Adhesive Forces of Water and Glass Surface
• Gravity on Mass of Water
110. Center Water Drop Over Front Camera Aperture
Uniform Blur of Far Field Image
Normal Image
No water droplet
Water droplet centered
Water droplet not
centered
111. • Focal length is < 1 cm so the display to be inspected must be held just above
the phone camera taking the image
• It is difficult to hold the display steady with an unsupported hand
• Creating a microscope stand similar to that illustrated earlier to adjust the distance of
the display to be imaged is recommended.
• The depth of field is very limited so you will have to take multiple pictures as
you move through the focal point to capture an image with the optimal focus.
Most front facing cameras do not allow digital zoom while viewing so this
becomes an iterative process to determine when the focus is ideal.
• Inspect your images by zooming in on each picture to see the detail.
Hints for Capturing a High-Quality Image
using the Water Drop Lens
112. Water drop is on the front facing camera of the bottom phone
and is observing the display of the top phone
113. Image taken with front facing camera of an iPad.
Image of a white portion of an iPhone 12 display.
• Water drop was about 4.5 mm which is a little
larger than ideal
Full image from camera
that turns out to not be in
focus after zooming in on
the photo.
Expanded view from
upper left-hand corner
Not in focus.
It is possible to
see some
structure in
this “white”
image,
however the
focus is not
perfect so the
individual red,
green and blue
diodes are not
resolved.
114. Same large image as on last slide, but the
expanding region was chosen from the top middle
which was in better focus. More distinct colors are
visible, but the individual RGB elements can not be
resolved. This was the best I could do with the
larger water droplet.
Full image from camera
that turns out to not be in
focus after zooming in on
the photo.
Expanded view from
upper center.
Still not in focus.
115. The size of the water droplet used was ~3 mm.
Individual RGB diodes are fully resolved.
Multiple pictures were required to achieve the
best focus. It is not always possible to
determine optimum focus without zooming in on
the picture afterwards.
A portion of this image
is in focus.
117. “White” region of image.
Red, green, and blue pixels all “on” to produce white light.
HD TV - Liquid Crystal Display
Direct observation with Phone Camera without Additional Magnifying Lens
153. Using you understanding of how displays create “white”, what can you
say about the relative intensities of the RGB AMOLEDs in the “Mono”
image as you move from light to dark regions?
154. The mono image is comprised of regions where there is more or less
“white” light. This is achieved by adjusting the relative intensity of the
red, green and blue OLEDs to produce light which appears white to
our eyes and then reducing the collective RGB intensity to create
lighter and darker regions that define the image.
155. Original Mono
An Oil Drop was Used to Magnify the Nose of the Snake in both
Images Displayed on an iPhone 12 AMOLED Display
157. Original
Mono
Apply Filter
Discuss how you might
design a mathematical filter
to convert a colored image to
a “mono” image composed of
“white” and progressively
“less white” regions?
160. Experiment 5
Image Sensors and Investigating Infrared Light
1. Investigate how human vision works and how humans are able to
differentiate colors (not experiment).
2. Investigate how digital image sensors work and how they are able to
differentiate colors (not experiment).
3. Replicate the process used by a digital color camera by creating a color
image from 3 images capture through red, green, and blue filters.
a. Capture 3 photos of a colored image using the 3 filters
b. Combine the three images using JS9 software to create a full color image
162. Link to video where an iPhone is taken apart to show the camera lens and sensor:
iPhone 12 Pro Max Teardown! - I've NEVER seen this before... - Bing video
Complimentary Metal-Oxide-Semiconductor (CMOS) Image Sensors
Advances in CMOS fabrication have revolutionized digital photography
167. Spectral Response of Image Sensors in Selected Phones
Includes Filter to Remove Infrared Light
168. Original
scene.
Output of
120x80 pixel
sensor with
Bayer filter
Output with
Bayer filter
colors
Reconstruction
of image after
interpolation of
color
information -
“Demosaicing”
Process for Using Bayer Filter and CMOS
Image Sensor to Create Color Image
170. Color Image to be Used in
Demonstrating the Concepts of
Digital Color Photography
171. Experimental Design
Geometry for Capturing Images using Red, Green, and Blue Filters with Minimal Movement
This design used the front
facing camera to take the
digital images. Setting the
camera on the table allowed
for multiple images to be
taken without movement of
the camera. The filters could
be sequentially slid into
position over the camera
lens. The object to be
photographed was a picture
from a book that was held in
position above the camera.
The design was adjusted to
achieve uniform lighting.
173. Color Image
Monochrome Image
Image Captured using iPhone 12 Pro Max
Comparison of
monochrome image and
the color image that
results from digital
processing of images
taken through red, green,
and blue filters integrated
into the phone’s camera
system.
The experiment which
follows will demonstrate this
digital image processing
using external filters to
generate a color image.
174. Capture Images Using Red, Green, and Blue Filters
Export to computer and name files appropriately for each filter
Potential methods for capturing images:
1) Using “mono” filter in camera mode that captures gray scale
image
or
2) Use post processing the photo with a “mono” filter that also
produces a gray scale image
In both cases the gray scale image represents the light that reached
the image sensors through either the red, green, or blue filter.
182. Combine Images Using Color Menu to Select “rgb mode”
This can be done while displaying any of the three single-color images
183. Standard Color Image using Bayer Filter and
Internal Image Processing on Smartphone
Color Image from Images Captured Through
External Red, Green, and Blue Filters
Comparison of Digital Color Images
184. To continue lesson, be
sure to download
Experimenting with
Electromagnetic Waves
(Part 2)
185. 185
Prepared by:
David Rakestraw
Senior Scientist
Lawrence Livermore National Laboratory
rakestraw1@llnl.gov • 925-216-8106 • st.llnl.gov
I welcome any
feedback on errors
you might find or ideas
on how to improve this
for students and
teachers.
186. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
