1. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Polarization Application of Physical Optics

2. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Previously... E B Direction of Travel –Light is an electromagnetic wave because it requires two interdependent fields to propagate. –Both electrical (E) and magnetic (B) waves must exist for light to propagate. E and B are perpendicular to each other and to the direction of motion. –The electric field has the greater effect on materials, and so we ignore the effect of the magnetic field from this point on.

3. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Polarization Polarized light: Electric fields of waves vary along the same direction. E Unpolarized light: Electric fields vary along many directions. E E E E E

4. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Polarization Representations of light polarized on the x-direction. x x y y z z

5. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Scattering of Light Rayleigh Scattering  BLUE light (400nm) scattered more than RED (700nm) –Light interacts with small air molecules –BLUE sky is seen by Point A when looking toward the horizon (away from the sun). –Light seen by Point B went through more atmosphere, more shorter wavelengths are scattered  RED sky when looking toward the horizon (toward the sun). A B

6. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science “Analyzing” Polarized Light Determine how much light in different components: Light polarized at an angle  x-component & y-component of the light Polarizer; only passes the x- component Output is ONLY the light that is linearly polarized in the x-direction

7. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Analyzing Polarized Light Two Perpendicular (“Crossed”) Polarizers Unpolarized light in Polarizer: Passes ONLY the y-component No light passes through “Crossed” Polarizers Polarizer: Passes ONLY the x-component

8. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Analyzing Polarized Light Add A Third Polarizer BETWEEN First Two Polarizer; only passing the y-component Some light does pass through this system of 3 polarizers, though none passed through 2 Polarizer; only passing the x-component Polarizer; only passing the 45°-component; then split into x and y components

9. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science The Nature of Color Interaction of Light and Matter

10. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Why do objects have a characteristic color? Photons (I.e. light rays or light waves) can interact three ways with materials they encounter: 1. Transmission 2. Reflection 3. Absorption Chester F. Carlson Center for Imaging ScienceImaging Science Fundamentals

11. Chester F. Carlson Center for Imaging Science Transmission Photons pass through an object. Chester F. Carlson Center for Imaging ScienceImaging Science Fundamentals R+G+B

12. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Reflection An object reflects photons of the wavelength that correspond to the color of the object. ONLY RED is reflected. Chester F. Carlson Center for Imaging ScienceImaging Science Fundamentals R+G+B R

13. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Two Types of Reflection Specular: All the energy coming from one direction will reflect in ONE direction. Diffuse: All the energy coming from one direction will reflect in MANY directions. GLOSSY surfacesMATTE surfaces

14. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Absorption An object absorbs photons corresponding to those that do not make up the color of the object. All colors are absorbed EXCEPT RED. Chester F. Carlson Center for Imaging ScienceImaging Science Fundamentals R+G+B R G+B

15. Imaging Science Fundamentals Chester F. Carlson Center for Imaging Science Translucent Objects Some objects reflect, absorb, and transmit light. (examples: Jello, or a semi-transparent plastic balloon) R+G+B R reflected (a little R)+(Some G+B) transmitted (some R)+(a little G+B) absorbed