Electronic Magnification CCTV - PowerPoint PPT Presentation

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Electronic Magnification CCTV

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Movement is exaggerated through the telescope ... microscope and telescope. Usually spectacle mounted. Generally a microscope cap is placed on a telescope lens ... – PowerPoint PPT presentation

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Title: Electronic Magnification CCTV


1
Electronic Magnification (CCTV)
Mouse Unit EVS Max
Stand alone unit Telesensory
2
Flipper port EVS
Videoeye Swing Arm
Max port Head Worn
3
Electronic Magnification
  • Advantages
  • Can significantly increase size
  • Controls for contrast and glare
  • Portable depending on model
  • Versatile
  • Permits binocular use of eyes
  • Preserves field of view

4
Electronic Magnification
  • Disadvantages
  • Expensive
  • 350 and up
  • Cheaper models are not portable
  • Can be difficult to wear and to position
  • Higher cognitive demand
  • Sometimes difficult to tolerate motion
  • Perceived as high tech by older users

5
Patients should always wear their eyeglasses when
using any magnifier
  • Eyeglasses correct for refractive errors
  • Hand held magnifier should be viewed through
    DISTANCE CORRECTION
  • Stand magnifier should be viewed through READING
    ADD

6
Telescopes
  • Used to view objects at a distance
  • Have different focusing ranges
  • Afocal
  • Focuses beyond 20 feet
  • Reading cap
  • Permits focusing distance of 16-18 inches

7
Telescope Design
Objective lens
Ocular lens
8
Exit pupil is the optical window the patient
views through
Exit pupil
Higher the magnification, the smaller the exit
pupil
9
Telescopes Come in Two Basic Styles
  • Galilean
  • Used for most low vision
  • Smaller and lighter weight
  • Keplerian
  • Astronomical telescope
  • Has a larger exit pupil
  • But weighs more

10
Strength of Telescopes
  • Label indicates power and field of view
  • Example
  • 6 x 30 telescope
  • 6x power and a 30mm objective lens

11
Challenges Using Telescopes
  • Motion Parallax
  • Movement is exaggerated through the telescope
  • Creates a speed smear (described as bouncing)
    when used in dynamic situation
  • Difficult to adjust to, reduces accuracy

12
Challenges cont.
  • Objects appear closer than they really are
  • Generally the field of view is very small unless
    the magnifier is really bulky
  • Lose light- images appear darker

13
For maximum image brightness, the exit pupil
should match the patients pupil
  • To determine the size of the exit pupil
  • Divide the diameter of the objective lens by the
    power of the magnifier
  • Example
  • 6 x 30 magnifier
  • 30 5 mm
  • 6

14
  • Measure the width of the patients pupil using a
    metric ruler and compare
  • If the exit pupil is smaller than the patients
    pupil, the image will be dark
  • To correct-try a telescope with a larger exit
    pupil

15
Clip-on Monocular
  • For short term or periodic telescopic needs

16
Bioptic (for continuous use)
  • Used in combination with carrier lens
  • Carrier is used for most activities-bioptic for
    detail
  • Dip head to view through biotic
  • Limited field, motion parallax

17
Full Field Binocular
  • Covers entire lens in frame
  • often used to view sporting events /TV
  • sportscopes
  • Doesnt allow viewer to look around
  • Can only use when stationary
  • Heavy-can be hard on nose bridge and ears

18
Clip on monocular
Head worn binocular
19
Automatic Focusing Telescopes
Monocular
Binocular
from Ocutech
20
Some persons can be fitted with a contact lens
system
  • High minus power serves as the ocular lens
  • Plus spectacle worn as the objective lens
  • Provides a 50 degree visual field with 2x
    magnification

21
Miscellaneous stuff.
  • Monocular telescope powers
  • 2.5x, 2.8x, 3x, 4x, 6x, 8x, 10x
  • Spectacle powers
  • 2x, 2.2x, 3x, 4x, 6x, 8x
  • For monoculars, person should always wear glasses
    unless instructed not to
  • Correct for astigmatism

22
Telemicroscope
  • Combination microscope and telescope
  • Usually spectacle mounted
  • Generally a microscope cap is placed on a
    telescope lens
  • Gives advantage of microscope magnification at a
    longer focal distance

23
Telemicroscope
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