Lens Technologies & the Human Eye

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Presentation transcript:

Lens Technologies & the Human Eye 12.3 Image: http://cdna.allaboutvision.com/i/news/asian-lady-applying-cls-280x179.jpg

Refracting Telescopes: Galileo and Kepler

Reflecting Telescope - Newton Image: http://www.bro.lsu.edu/telescope/Classroom/2.How%20Telescopes%20Work/Reflecting.gif Reduces chromatic aberration

Binoculars 2 refracting telescopes Reflection through prisms lengthens the light path, increasing magnification Image: https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Binocularp.svg/300px-Binocularp.svg.png

Microscopes Image: http://bolvan.ph.utexas.edu/~vadim/Classes/10f/Microscope2.jpg

Structure – Human Eye

Focussing – Human Eye Ciliary muscles make the lens shorter and thicker to focus a nearby object Relaxed eye lens focusses on a distant object

Eye vs. Camera

Correcting Vision Using Lenses Image: http://www.visionexcellence.com.au/WP1/wp-content/uploads/2013/05/myopia-verses-myopia-corrected.png Near-sightedness; eyeball too long, so image forms in front of retina.

Hyperopia Image from: http://www.visionexcellence.com.au/common-eye-conditions/hypermetropia-hyperopia-long-sightedness-reading-glasses/ Far-sightedness; eyeball too short, so rays reach retina before they meet.

Presbyopia Lenses become stiff with age, cannot change shape Can’t focus on nearby objects.

Astigmatism Blurred or distorted vision caused by incorrectly shaped cornea. Part of an image may be in focus, but the rest is blurry. Image: http://www.visionexcellence.com.au/WP1/wp-content/uploads/2013/05/astigmatism.jpg