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Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Cameras and Images
How images are formed in eyes in cameras in xray CAT scans in MRI in holograms Trivia question: Who was Daguerre? Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Simplicity works
A small hole can focus the whole image Still useful in large f/stops for depth of focus Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
A more refined instrument
Reflection of different color light to different sensors and storage sites (natural pixels) “Red” “Yellow” “Blue”^ “Purple” Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
SLR Cameras
Mechanical mirror deflects image to viewfinder Shoot picture with mirror out of the way Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Digital Camera
Silicon instead of plastic Charge-Coupled Devices or CMOS pixels illuminated thru RGB (Bayer) filters Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Fancier CMOS-based “X3” detector
Different colors attenuated at different depths
Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
CCD pictures are inherently blurry
Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
CMOS X3 Puts 3 Colors into Each Pixel
Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
How to Get Particular Colors
Use interference: What is not reflected mst be transmitted Destructive interference cancels reflections Everything goes through Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
CAT scans
Typical one is xray pictures from many directions Computer reconstructs the innards from different shadows cast from different angles of “lighting” Can use any particle (PET, …) Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Holograms
- Interfere reflected and reference beam and store interference pattern
- Illuminate stored pattern to get image Lecture 17, Cameras and Imagers^ Phys 100, How Things Work
Nuclei Are Magnets, Too
Energy levels for magnets: ΔE = hf = γB Energy to flip a magnet depends of field strength (duh!) Transmitted Energy frequency Energy is absorbed only at the frequency that matches γB
