Night Vision

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

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Biological night vision
Rods Cones
used for night vision used for day vision
have more pigment than cones, so can detect less light have less pigment than rods, require more light to detect images
one type of photosensitive pigment three types of photosensitive pigment in humans
confer achromatic vision confer color vision

1. http//en.wikipedia.org/wiki/Rod_28eye29

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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
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Night Vision of Animals

• Big eyes
• Wider pupil.
• Increased retinal surface.

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Night Vision of Animals

• Big eyes
• Wider pupil.
• Increased retinal surface.
• Packed With Rods

Fruit Bat
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Night Vision of Animals

• Big eyes
• Wider pupil.
• Increased retinal surface.
• Packed With Rods
• Circular vs. slit pupils

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Night Vision of Animals

• Big eyes
• Wider pupil.
• Increased retinal surface.
• Packed With Rods
• Circular vs. slit pupils
• Tapetum lucidum
• (Bright carpet)

Cat
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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
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Natural Illumination Levels
10,000
Lux lm/m2
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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 gt50,000 are
  required.

3. http//www.physics.ohio-state.edu/wilkins/writ
ing/Samples/shortmed/johnmedium/index.html
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Image-intensifier Tube - Generation 2 -

• Objective lens ? Image intensifier ?
  Microchannel plate? Phosphors ? Ocular lens

3. http//www.physics.ohio-state.edu/wilkins/writ
ing/Samples/shortmed/johnmedium/index.html
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Image-intensifier Tube - Generation 2 -
Microchannel tube
Photocathod
Luminescent screen

• 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.

4. http//www.proxitronic.de/prod/bv/eein.htm 5.
http//www.sciam.com.tw/circus/circusshow.asp?FDoc
No284CL9
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Image-intensifier Tube - Generation 3 -

• Gallium-Arsenide.
• The high infrared sensitivity.

6. http//www.acfr.usyd.edu.au/teaching/4th-year/m
ech4721-Signals/material/lecture20notes/0520Visi
ble20Imaging.pdf
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Image Intensifier Image
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Thermal Imaging
7. http//science.howstuffworks.com/nightvision.ht
m
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Black Body Radiation

• Every object not at 0K emits EM radiation.
• 6000K?0.45- 1um.
• 300K ?IR wavelengths between 3 and 14 um.

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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.ht
m
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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.

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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.

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Thermal Images
www.x20.org/thermal/
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Color Night Vision

• Judging distance?

http//www.newscientisttech.com/article/mg18524865
.900.html
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Color Night Vision

• Sample color pictures of a similar type of
  landscape are taken in daylight.

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Color Night Vision

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

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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.ht
m
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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/m
ech4721-Signals/material/lecture20notes/0420Imag
ing20Infrared.pdf 9. http//www.electrophysics.co
m/Browse/Brw_ProductLineCategory.asp?AreaNVCateg
oryId27
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Applications

• BMW

10. http//www.germancarfans.com/print.cfm/ID/2050
712.008/lang/eng
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Conclusions

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

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Thank You!
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References

• 1. http//en.wikipedia.org/wiki/Rod_28eye29
• 2. http//en.wikipedia.org/wiki/Night-vision
• 3. http//www.physics.ohio-state.edu/wilkins/writ
  ing/Samples/shortmed/johnmedium/index.html
• 4. http//www.proxitronic.de/prod/bv/eein.htm
• 5. http//www.sciam.com.tw/circus/circusshow.asp?F
  DocNo284CL9
• 6. http//www.acfr.usyd.edu.au/teaching/4th-year/m
  ech4721-Signals/material/lecture20notes/0520Visi
  ble20Imaging.pdf
• 7. http//science.howstuffworks.com/nightvision.ht
  m
• 8. http//www.acfr.usyd.edu.au/teaching/4th-year/m
  ech4721-Signals/material/lecture20notes/0420Imag
  ing20Infrared.pdf
• 9.http//www.electrophysics.com/Browse/Brw_Product
  LineCategory.asp?AreaNVCategoryId27
• 10. http//www.germancarfans.com/print.cfm/ID/2050
  712.008/lang/eng