unit 3 – topic 4 eyes & cameras
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Unit 3 – Topic 4Eyes & Cameras
Eyes vs. Camera
• You can think of the eye & camera as an “image producing” technologies– 1 is natural – 1 is artificial
• Cameras are built on the principles of human sight – Their components are very
comparable!
Light Entering
Eye Camera
Pupil Aperture
Allows light in
Light Entering
Eye Camera
Pupil Aperture
Allows light in
How much light depends on how much light is needed
Lots = big
Little = small
Light Entering
• How is this all controlled? • Eye = tiny muscles around the
eye called the iris• Colour
of irisis youreye colour
Light Entering
• How is this all controlled? • Camera = cylinder or dial around
the aperture that when turned increases or decreases the size of the aperture
Inside The Eye
• Light enters eye through pupil
• Light goes into the retina
• Retina is covered with photoreceptors
Inside The Eye
Two Types
Photoreceptors
Rods
Cones
Sensitive to Light
Operate in Low light
DetectColour
In low lightonly detect shades
3 Types- Green- Red- Blue
Inside The Eye
Inside The Eye
• Photoreceptors send messages to optic nerve
• Optic nerve sends messages to the brain
• Brain creates an image film on camera
Focusing Light
• Eyes & Cameras have transparent lenses
• Lens must be in right position to sharpen image (double convex)
• Muscles attached to lens (ciliary muscles) contract to lengthen & relax to shorten
Focusing Light
Focusing Light
• Changing the shape of lens focuses the image on the retina
• Cameras do this automatically when they have the auto-focus feature & can be done manually
Correcting Vision Issues
Most eye problems fall into two categories
Nearsightedness Farsightedness
Cannot see objectsfar away
Cannot see objectsclose up
Correcting Vision Issues
Lens not fat enough
Lens not thin enough
Laser Eye Surgery
Used to replace the need for glasses/contacts
Reshapes corneaCuts flap in tissue Covering the eye
Which acts as thenew correctivelens
Folded back so corneais exposed
Reshaped with UV light pulses
Laser Eye Surgery
Night Vision Goggles
2 Lenses and 1 Viewing Screen
In general they intensify an image and project it on to a screen
Which is why the image is green
Screen is covered in phosphor
Phosphor glows green when hit with light (particles)
Night Vision Goggles
Camera Eyes
We like to compare eyes vs. cameras
If they have …
RetinaCornea
LensRoughly round in shape
We call them camera eyes
Camera Eyes
They can vary
Fish
Large lens (goes through pupil) Allows them
to see all directions
Birds
Ultra sharp vision
More cones than humans
Can see different wavelengths
Bees see UV light
Camera Eyes
Nocturnal
Awake at night
Large pupils (Capture more light) Extra layer in
eye
Tapetum Lucidum
Acts like a mirror which reflects light
Have more rods
Camera Eyes
Compound EyesMade up of
many individual
“eyes”Each unit ommatidium
Long Tube
Lens on
outer surfac
e
Focusing cone
Light sensitive cell
Compound EyesThese eyes tend to be convex
Makes them excellent at detecting motion
Compound EyesThere are some drawbacks Difficult to form a single image
Works like a TV / Pixels
More ommatidium better image
Digital/Stadium Images
Stadium Image
Each card contains a coordinate
When pieced together they form an image
Digital ImagesDigital Images
The process of creating an image using a computer
The image is made up of
pixels
From the term
Picture Elements
Pic Ele
Colouring Digital Images
Digital Images
Each pixel is given a value
Each value corresponds to a colour
That pixel then displays that colour
Image QualitySize of Pixel
Large
Many smallsquares
Small
Many more small squares
Low resolution High resolution
Capturing A Digital Image
Light Enters through aperture
Converted to digital information
Reaches a CCD(Charged-CoupleDisplay) Like grid-paper
Small electrical current chargessquares
This can be stored and transmitted
TransmittingDigital Transmission
Information can be coded, transmitted coded, reassemble by a computerWithout this we would
not be able to transmit information anywhere
Can also see different light spectrums
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