Endoscopes: The Light at the End of the Tunnel

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EndoscopesThe Light at the End of the Tunnel

• Scott Morris
• Opti 422
• 19 Sept 03

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The What/Why of Endoscopes

• Comes from Greek endom (within) and skopein
  (view)
• Endoscopes are used to image/work within a
  confined cavity not otherwise accessible
• Three usage categories medical, veterinary,
  and industrial
• Trend towards least-invasive surgeries during
  last few decades has accelerated use and
  research
• Includes advantages of improved and early
  detection of medical conditions

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How?

• Endoscopes transmit object image to operator
  using three distinct subsystems
• Objective lens system
• Relay (lenses, fibers, electronic)
• Eyepiece
• Three main categories of endoscopes
  presented
• Rigid Relay
• Gradient-index (GRIN)
• Fiber optic

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Rigid Relay

• Alternating field/relay lenses direct chief ray
  down tube
• Field/relay lenses coupled (Hopkins) into rods
• Trade-off between increasing light throughput and
  reducing vignetting in small OD systems
• Advantage able to continually control
  aberrations this type typically has best
  resolution and image quality

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GRIN

• Gradient index elements with index a function of
  radius (n-higher at periphery)
• Objective images onto long relay lens that
  re-images every half-period
• Advantage lack of glass-air interfaces
  increases maximum throughput (brightness)

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Fiber Optic

• Objective images onto coherent fiber bundle
• Each fiber approx 10µm bundle has 104 fibers
• Each fiber relays 1 pixel to ocular for
  magnification
• Advantages flexible, smallest ODs
• Disadvantages aberrations, lower resolution

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Video Gastroscope
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What Else?

• Engineered to withstand manipulation/sterilization
  
• Additional channels for light, water, scalpel,
  etc.
• Future technology
• Capsule Endoscopy
• In-vivo spectroscopy
• Typical stats
• Up to 170 cm working length OD from 3mm to 14mm
• 120 FOV with rotation/angulation up to 180

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Questions???

• Reach me at gsmorris_at_email.arizona.edu