This slide share presentation will help you to know the comparison of our natural eye with artificial optical system (Camera).

1. Eye as an optical system
Presenter: Amrit jha
Subject code:MO101

2. EYE AS AN OPTICAL SYSTEM

3. Introduction :
What is an eye?
As we all know eye is specialized sense organ capable of receiving light for images
visual, which are then carried to the brain for final execution.
What is Optical system?
An optical system is a combination of succession of optical elements, which may
include frame body and cover, lenses, mirrors, light, light detectors,screen,
dispersing devices, Fibre-optics and many more elements.
So, when talking about our biological functional eye we can say that our eye is also
a compound optical system composed of Tear film, cornea, Aqueous, Iris, pupil,
Lens, cilliary, vitreous, retina, Optic-nerve and many more components.

4. Similarities in between eye and optical system.
 In every optical system there exists some major properties of light optics and
light propagation. Ex: reflection, refraction, colour capturing, convergence,
divergence of light and many more.
 Lets, take a camera as an optical system to illustrate similarities of it with eye.
 The Eye is an adaptive compound optical system composed of a main two
optical part known as cornea and crystaline lens.
 The anatomy of the camera bears more similarities to the biological eyeball and
it’s optics. So, we can take camera as robotic eye model.

5. SIMILAR PARTS OF OPTICAL SYSTEM CAMERA AND EYE
HUMAN EYE
 Eyelids
 Cornea
 Sclera/Choroid
 Iris
 Pupil
 Lens
 Retina
 Rod and cones of photoreceptor
retina.
CAMERA
 Plastic body cap
 Glass lens mount
 Black body paint
 Diaphragm / Shutter
 Aperture
 Lens
 Photo-film
 Phosphor and silver compound
coated film

6. Diagramatic illustration of Camera Vs. Eye

7. FUNCTION OF THE OPTICAL SYSTEM BELONGINGS :
 EYELIDS & BODY CAP : In human eye system, eyelids protects the eye from
foreign body and dust. Same as of eyelid, body cap of camera protects glass
mount as well as lens from dust and foreign body.
 CORNEA & GLASS LENS MOUNT : Work of cornea in a human eye is one of
most important. As, cornea is first transparent reflecting as well as refracting part
of eye. It plays major role in refraction of light passing into eye. So, in camera
glass lens mount play role as first transparent medium which allows light to pass
through it. If it gets damaged image can’t be clear although all parts are working
well.
 SCLERA/CHOROID & BLACK BODY PAINT : Function of sclera is to maintain
proper rigid-elastic shape where as function of choroid is to protect eye from
internal infection. So as of sclera and chorid, the black body of camera gives it’s
camera a shape and also protects camera from getting physical damage.

8. Continuation....
 PUPIL & APERTURE: When light gets pass through cornea it reaches to small
black hole area of eye called pupil. Pupil regulates the amount of light which
needs to enter upto retina by changing it’s size. Whereas, in camera same work
is done by aperture of camera.
 IRIS & DIAPHRAGM : As the amount of light entering eye is controlled by pupil
alike of that pupil size is controlled by iris of eye. When there is high intensity of
light exposure iris makes pupil size small/narrow and if there is low light
intensity iris makes pupil size wider. Whereas, same work is executed by
shutter diaphragm In camera

9. Continuation.....
 CRYSTALLINE LENS & CAMERA LENS : lens is second most important
refracting part of optical system. It focuses object light on photoreceptor.
Focusing mechanism of eye and camera lenses are different.
1/F = 1/do + 1/di
1.) Crystalline lens focusing :-
In the human eye, the image distance is fixed. If the object distance changes, the
focal length is adjusted to create a sharp image. This is done by changing the
shape/curvature of the lens using cilliary muscle and zonules(accommodation).
2.) Camera lens focusing :-
In camera, basic camera lens has a fixed focal length. If the object distance is
changed, the image distance ( the distance between the lens and the film) is
adjusted by moving the lens.

10.  RETINA & PHOTO-FILM : When light gets passed through lens it focuses light
on Photoreceptors. Both eye as well as camera have photoreceptors.
1.) Human retina: Retinal layer have cone and rod cells which are responsible for
image formation in day and night timing conditions. Cone cells are responsible for
image formation in light condition and Rod cells are responsible for image
formation in dim light conditions.
2.) Camera Film: Camera film are having few chemical coatings which are
responsible for image formation. Normally, camera have flash light which is used
for both day and night image capturing. In that bright light condition those film
have silver compond coating as photoreceptor. But, if no flash light is used to
capture image at night then phosphor coating film is used for night vision
camera photography.
Continuation.....

11. Image formation on Retina and in camera:
Human eye: If thinking optical way about biological eye and robotic camera eye
then we get conclusion that both optical system are having one convex lens and
one cancave mirror like surface. Due to which real and inverted image is formed.
So, to make it erect image retinal photoreceptors send information to brain via
opticnerve. After that brains‘ occipital lobe helps to decode it and gives erect
image sensation to eye.
While in a case of camera there is two possibilities:
Analog camera is totally based on our eye technique. So, it also forms real and
inverted negative image on 35mm film band.
Digital camera now a days do not use chemical as photoreceptor rather they form
image by CCD array. Charged-coupled device works like sensor. It senses photon
light signal and makes it electric signal to form image as Human opticnerve do.
Continuation.....

12. Conclusion:
 After all that discussion it’s clear that biological human eye is
similar to optical device.
 There in eye happens reflection, refraction, Colour sensation, signal/impulse
transfer, optics of lens and focal point changes while accommodation and many
more which occurs in any of optical system.
 So, there is no doubt that if any of componet gets altered all optics in an optical
system or eye gets altered.

13. Three optical defect in optical system of eye :-
1.) Myopia : Myopia or nearsightedness means you can see better up close than
you can at far distances as image gets focused in front of retina. This defect arises
because the power of the eye is too great due to the decrease in focal length of the
crystalline lens.
This may arise due to either
a) excessive curvature of the cornea, or
b) elongation of the eyeball.
This defect can be corrected by using a concave (diverging) lens. A concave lens
of appropriate power or focal length is able to
bring the image of the object back on the retina itself

14. 2.) Hypermetropia : Farsightedness, also called hypermetropia, common name for
a defect in vision in which a person sees near objects with blurred vision, while
distant objects appear in sharp focus. In this case, the image is formed behind the
retina.
This defect arises because either
a) the focal length of the eyelens is too great, or
b) the eyeball becomes too short.
This defect can be corrected by using a convex (converging) lens of appropriate
focal length. Eyeglasses with converging lenses supply the additional focussing
power required for forming the image on the retina.

15. 3) Astigmatism : It is a defect in the outer curvature on the surface of the eye that
causes distorted vision. In astigmatism, a person cannot simultaneously focus on
both horizontal and vertical lines.
This defect is usually due to the cornea that is not perfectly spherical. Consequently,
it has different curvatures in different directions in vertical and horizontal planes.
This results in objects in onedirection being well-focussed,
while those in a perpendicular direction not wellfocussed.
This defect can be corrected by using eyeglasses with cylindrical lenses oriented to
compensate for the irregularities in the cornea.

16. So, with all these topic we finally came at a point that, eye is really an
optical system with different aspects of optical components.
References:
 http://eugeneeyecare.com/conditions/What_is_Nearsightedness,_Farsig
htedness,_and_AstigmatismQQ.html
 www.sciencewithme.com
 http://hyperphysics.phy-astr.gsu.edu/hbase/vision/eyedef.html#c1
 http://www.pasadenaeye.c
 Wikipedia

17. Thank you All !!!