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Night Vision

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Night Vision Shin-Ying Lu April 26, 2006 Liquid Crystal Institute Kent State University Outline Night vision: the ability to see at night. Biological night vision. – PowerPoint PPT presentation

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Title: 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

3
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

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
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
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 gt50,000 are
    required.

3. http//www.physics.ohio-state.edu/wilkins/writ
ing/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/writ
ing/Samples/shortmed/johnmedium/index.html
13
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
14
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
15
Image Intensifier Image
16
Thermal Imaging
7. http//science.howstuffworks.com/nightvision.ht
m
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.ht
m
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.ht
m
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/m
ech4721-Signals/material/lecture20notes/0420Imag
ing20Infrared.pdf 9. http//www.electrophysics.co
m/Browse/Brw_ProductLineCategory.asp?AreaNVCateg
oryId27
27
Applications
  • BMW

10. http//www.germancarfans.com/print.cfm/ID/2050
712.008/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_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
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