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Night Vision

Night Vision

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Night Vision

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  1. Night Vision Shin-Ying Lu April 26, 2006 Liquid Crystal Institute Kent State University

  2. Outline • Night vision: the ability to see at night. • Biological night vision. • Night vision devices can be • Enhanced intensity range. • Enhanced spectral range. • Equipment • Applications

  3. Biological night vision • http://en.wikipedia.org/wiki/Rod_%28eye%29

  4. Night Vision of Humans • Molecules of rhodopsin in the rods of the eye undergo a change in shape as light is absorbed. cones rods 2. http://en.wikipedia.org/wiki/Night-vision

  5. Tarsier owl Night Vision of Animals • Big eyes: • Wider pupil. • Increased retinal surface.

  6. Night Vision of Animals • Big eyes: • Wider pupil. • Increased retinal surface. • Packed With Rods Fruit Bat

  7. Helmet gecko Human Cat Cat Night Vision of Animals • Big eyes: • Wider pupil. • Increased retinal surface. • Packed With Rods • Circular vs. slit pupils

  8. Night Vision of Animals • Big eyes: • Wider pupil. • Increased retinal surface. • Packed With Rods • Circular vs. slit pupils • Tapetum lucidum (Bright carpet) Cat

  9. Night Vision of Animals • Big eyes: • Wider pupil. • Increased retinal surface. • Packed With Rods • Circular vs. slit pupils • Tapetum lucidum • (Bright carpet) • Heat detecting Pit-viper Heat-sensing Pit

  10. Natural Illumination Levels 10,000 Lux = lm/m2

  11. Image-intensifier Tube - Generation 1 - • Objective Lens  Photocathode  Phosphor screen. • Single stage devices offer gains of between 50 and 100. • For star light levels, gains of >50,000 are required. 3. http://www.physics.ohio-state.edu/~wilkins/writing/Samples/shortmed/johnmedium/index.html

  12. Image-intensifier Tube - Generation 2 - • Objective lens  Image intensifier  Microchannel plate Phosphors  Ocular lens 3. http://www.physics.ohio-state.edu/~wilkins/writing/Samples/shortmed/johnmedium/index.html

  13. Image-intensifier Tube - Generation 2 - • Contain between 2 to 6 million holes. • These tubes are 10um in diamter and 1mm long. • A single stage tube can produce gains of up to 50,000. Microchannel tube Photocathod Luminescent screen 4. http://www.proxitronic.de/prod/bv/eein.htm 5. http://www.sciam.com.tw/circus/circusshow.asp?FDocNo=284&CL=9

  14. Image-intensifier Tube - Generation 3 - • Gallium-Arsenide. • The high infrared sensitivity. 6. http://www.acfr.usyd.edu.au/teaching/4th-year/mech4721-Signals/material/lecture%20notes/05%20Visible%20Imaging.pdf

  15. Image Intensifier Image

  16. It is quite easy to see everything during the day... ...but at night, you can see very little. Thermal imaging lets you see again. Thermal Imaging 7. http://science.howstuffworks.com/nightvision.htm

  17. Black Body Radiation • Every object not at 0K emits EM radiation. • 6000K0.45- 1um. • 300K IR wavelengths between 3 and 14 um.

  18. Thermal Imaging • A lens which focuses the infrared light emitted by all of the objects in view. • The infrared-detector elements create a thermogram. • Translate the thermogram into electric impulses. • Processing signals and create the image. 7. http://science.howstuffworks.com/nightvision.htm

  19. Detector Types • Photoconductive: absorb photons to elevate an electron from the valence band to the conduction band of the material, changing the conductivity of the detector. • Photovoltaic: absorb photons to create an electron hole pair across a p-n junction which can produce a small current.

  20. Temperature Noise • Johnson Noise: Random thermal motion of carries. • Shot Noise: Flunctuations in the rates of thermal generation and recombination of carriers. • Cooling system is needed.

  21. Thermal Images www.x20.org/thermal/

  22. Color Night Vision • Judging distance? http://www.newscientisttech.com/article/mg18524865.900.html

  23. Color Night Vision • Sample color pictures of a similar type of landscape are taken in daylight.

  24. Color Night Vision • Superimposing colors associated with the shades of grey onto the greyscales in a target image gives the viewer better depth perception.

  25. Equipment • Scopes • are normally handheld or mounted on a weapon, scopes are monocular (one eye-piece). • get a better look at a specific object and then return to normal viewing conditions. • Goggles • are most often worn on the head. Goggles are binocular (two eye-pieces). • are excellent for constant viewing, such as moving around in a dark building. • Cameras • send the image to a monitor for display or to a VCR for recording. • are used when night-vision capability is desired in a permanent location 7. http://science.howstuffworks.com/nightvision.htm

  26. Applications • Military • to locate enemy targets at night. • navigation, surveillance and targeting. • Law enforcement • to discover items that have been hidden by criminals, including money, drugs and bodies • Entertainment • hunting 8. http://www.acfr.usyd.edu.au/teaching/4th-year/mech4721-Signals/material/lecture%20notes/04%20Imaging%20Infrared.pdf 9. http://www.electrophysics.com/Browse/Brw_ProductLineCategory.asp?Area=NV&CategoryId=27

  27. Applications • BMW 10. http://www.germancarfans.com/print.cfm/ID/2050712.008/lang/eng

  28. Conclusions • Biological night vision. • Night Vision equipment. • Reduced size of surrounding halos. • Lighter and smaller equipment.

  29. Thank You!

  30. References 1. http://en.wikipedia.org/wiki/Rod_%28eye%29 2. http://en.wikipedia.org/wiki/Night-vision 3. http://www.physics.ohio-state.edu/~wilkins/writing/Samples/shortmed/johnmedium/index.html 4. http://www.proxitronic.de/prod/bv/eein.htm 5. http://www.sciam.com.tw/circus/circusshow.asp?FDocNo=284&CL=9 6. http://www.acfr.usyd.edu.au/teaching/4th-year/mech4721-Signals/material/lecture%20notes/05%20Visible%20Imaging.pdf 7. http://science.howstuffworks.com/nightvision.htm 8. http://www.acfr.usyd.edu.au/teaching/4th-year/mech4721-Signals/material/lecture%20notes/04%20Imaging%20Infrared.pdf 9.http://www.electrophysics.com/Browse/Brw_ProductLineCategory.asp?Area=NV&CategoryId=27 10. http://www.germancarfans.com/print.cfm/ID/2050712.008/lang/eng