Optical Instruments

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Optical Instruments
Eye Camera Magnifier Telescope Microscope Eyepiece
Illuminator
Eye
Cornea The crystal clear dome that covers the
front of the eye. Bends 70 of refraction.
Lens The crystalline lens finishes the focusing
of light. "fine tuning"
Iris The part of the eye with color
Pupil The opening in the middle of the iris.
Retina Thin layer of nerve tissue that senses
light.
Fovea This is the center of the retina.
Nerve cells are more densely packed in this
area, so images that are focused on
the fovea can be seen better
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macular (?? yellow spot) 2.53 mm. ???? ????
?? Forvea Centralis 0.3 mm, Cones are thinner
and denser
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Rods ???? Cones ????
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Rods 0.002 mm, 1? 2??? high speed BW Cones
0.006 mm, 650?? Low Speed Color
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?? ??? ?? ?? ASA (American Standard Association)
        ASA 32     ???              ??, ??? ??
??         ASA 64         ASA 100    ????
        ASA 200         ASA 400         ASA
800     ???            ??? ??? ??? ?
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In the central fovea, there are approximately
150,000 cones/ sq. mm. The distance between cone
centers in the hexagonal packing of the cones is
about 0.003 mm. To convert this to degrees of
visual angle you need to know that there are
0.29 mm/deg so that the spacing is 0.003/0.29
0.013 between cone centers
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