Imaging

Imaging

1. Binary

   • Binary consists of 2 numbers: 1 & 0
   • On: 1 Off: 2
     • "One on or off" = 1 bit
   • 00010100 00000101 01100011 = 20/05/97
   • One Byte = 8bits
   • 0=0, 1=1, 2=01, 3=11, 4=100, 5=101
   • 2⁴= 16 (0-15) 16 Numbers
     • 2⁵ = 32 (0-31) 32 Numbers
     • 2⁸ = 8 bits = 1 byte

2. Resolution

   • Resolution is the size of the smallest thing you can see.
   • A higher frequency means that there will be a shorter wavelength making it more easy to see smaller images.

3. Charged Coupled Devices (CCDs)

   • Uses Of CCDs
     • Used to capture and share image data in telescopes, scanners, bar code readers and digital still and video camera
     • CCDs can be made that are sensitive to a wide range of the electromagnetic spectrum e.g. Ultra violet ot Ifrared.
   • Integrated circuit etched onto a silicon surface, forming light sensitive elements called pixels.

4. Pixels

   • A photon in a packet of energy.
   • Each is an electrical component which produces the number for a pixel
   • Reads each individual number in order and then sends it off to a computer

5. Digital Processing

   • Smoothing Edges
     • Replace each pixel by the mean of its value and those of its neighbours.
   • Removing Noise
     • Replace each pixel by the median (middle value when written in order) of its value and those of its neighbours.
   • Finding Edges
     • Subtract the N,S,E and W neighour pixels from 4 times the value of the pixel.
   • Contrast: Multiply each pixel by a constant number.
   • Brightness: Add or subtract a constant number.

6. Imaging with lenses

   • Ray Diagrams
     • Direction - arrows
     • Straight lines for rays
     • Focal Points etc.
     • Labels
     • Distance between wavefronts need to be equal
   • Types of Lenses
     • Convex Lens (Converging) - Comes together
     • Concave Lens (Diverging) - Goes away together
       • Anti-curvature: -1 + 1 = 0
   • The focal length starts at the centre of the lens and finishes and the focal point.
   • The focal length is the point when the rays come in parralel to a focus point.
   • POV
     • Ray Point of view: Light travels out in straight lines from a small source.
     • Wave point of view: Light spreads out in spherical wave fronts from a small source.
   • Equations
     • Power of lens = 1 / Focal Length/m (P=1/F) - Measured in dioptnes (D).
     • Curvature Before + Change of curvature by lens = Curvature after lens
       • 1/u + 1/f = 1/v
         • Carlesson Conversion: 1/v = 1/u +1/f
         • When u is equal to ∞, 1/u is equal to 0. Therefore, 1/f = 1/v and f = v.
           • When v = ∞, 1/u + 1/f = 0 and 1/u = -1/f
       • Values to the left of the lens are negative and values to the right are positive.
     • Linear Magnification: -v/u
   • The Iris
     • When eyes are closed, iris contract and causes increase in pupil size because there is a larger gap. Iris contracts to keep similar amounts of light in different situations. When opening eyes there is a sudden change of light and therefore iris expands and pupil increases in size to keep amount of light coming in similar (allows less light in). Too much light coming in will burn retina.

Imagens e arquivos do mapa