1 / 21

THE EYE

THE EYE. The Eye. Is an optical instrument that we use to see around us. It acts very much like a camera It uses a converging lens to focus the image on a sensor Lets more or less light in when needed Allows us to view the image. Eye and Camera. Eye Anatomy.

derora
Télécharger la présentation

THE EYE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE EYE

  2. The Eye • Is an optical instrument that we use to see around us. • It acts very much like a camera • It uses a converging lens to focus the image on a sensor • Lets more or less light in when needed • Allows us to view the image

  3. Eye and Camera

  4. Eye Anatomy • Iris  opens or closes to let more or less light in • Cornea and Lens  act to converge light rays to create an image • Retina  screen where image is located. Creates an electrical signal to be interpreted by the brain. • Optic nerve  transmits the electrical signal created by the retina to the brain so that we “see”

  5. Blind Spot – Try It!

  6. Blind Spot • There are no light sensitive areas where the optic nerve connects to the retina • If an image is formed on the blind spot we cannot see it • The reason we normally do not notice our blind spots is because our other eye compensates and “fills in” the gap

  7. Eye vs. Brain • We don’t actually see with our eyes • We use our eyes to create an image on our retina • The eye uses a converging lens so the image produced on the retina is always smaller, inverted and real

  8. Computer Demonstration – Showing smaller inverted image with converging lens • http://www.phy.ntnu.edu.tw/ntnujava/index.php?PHPSESSID=643ae5051e223f1f696d419c040b986d&topic=48.msg297#msg297

  9. These images are sent via electrical signals to the brain to be interpreted • The brain then takes the inverted image and flips it so what we “see” is an upright image

  10. Camera Lens vs. Eye Lens • Both cameras and eyes cannot move their “screen” • Cameras move their lens to focus an image • Eyes cannot move their lens • Eyes instead change the shape of their lens using ciliary muscles which alters the focal length allowing focusing on the retina • This is called Accommodation Computer Simulation to show moving screen, camera lens and Eye

  11. Accommodation

  12. Focusing • Some people cannot focus incoming light rays as well as they should, creating blurred images • This can happen when objects are far away or near

  13. Myopia (Near-sightedness) • The eye can focus light ray from nearby objects but cannot see objects at a distance • Caused by a too-long eye ball or to much converging of light by the lens and cornea • Light is focused in front of the retina

  14. A diverging lens is needed to spread apart the light rays so that they create an image at the retina • The diverging ray is altered slightly and called a negative meniscus so that it looks better Computer Simulation to show Myopia

  15. Hyperopia (Far-sightedness) • Person can see distant objects (a) but cannot see near objects (b) • The eye cannot refract light well enough to create a focused image on the retina • Image is created behind the retina  blurry • Usually caused by the eye ball being too short Computer Demonstration to show Hyperopia

  16. Converging Lens – Positive Meniscus • Since light isn’t refracted well enough (a), far-sighted people can use a converging lens to help out (b) (a) (b)

  17. Positive Meniscus • The converging lens is altered to create a positive meniscus • A positive meniscus is much more appealing shape • It is still a converging lens because it is thicker in the middle then on the edges

  18. Presbyopia • A form of farsightedness (people find it hard to read small print) • Usually comes with age as eye loses its ability to accommodate • Also corrected with converging lenses Demonstration at front

  19. Video • Nearsightedness and Farsightedness Video

  20. Contact Lenses • Have the same function as glasses • Can be shaped to form a positive or negative meniscus • Placed on the cornea of the eye (invisible) • Can also be used to change the eye colour

  21. Laser Eye Surgery • Laser Eye Surgery Video

More Related