Imaging And Signaling Flashcards
Pixel
Picture element
Often comprised of three separate colours RGB
Bit
Basic unit of storage
Either 1 or 0
Byte
Made up of 8 bits
Levels
How many possible arrangements of bits
N=2^b
N= number of levels
Improve contrast
Multiply pixel values by an amount, histogram will be stretched
Edge detection
Subtract neighbouring pixel values
Brightness
Add/subtract a constant value, taller/shorter histogram
Noise reduction
Makes an image smoother, pixels are an average (mean, medium) of surrounding pixels
False colour
Colours assigned to an image to highlight information
Sampling
Turning an analogue signal into a digital one
Data transfer equation
Data transfer rate = number of bits x sampling frequency
Over sampling
Too much data spent sampling noise
Under sampling
Missing main signal
Noise level equation
V total / v noise
Aliasing
Sampling at too low a frequency, these are ‘phantom signals’ of a lower frequency
Avoid aliasing
Sample at double the highest frequency
Quantisation error
Difference between real signal value and sampled value
Resolution
Equipment - smallest scale
Image - distance each pixel represents
Audio signal - voltage between each level
Real image
Can be projected onto a screen, wavefronts lie perpendicular to the direction of the waves motion
Curvature equation
1/ radius
Linear magnification
Image height/ object height, image distance/ object distance
CCDs
Charged coupled devices
A screen covered with pixels that store charge when light is incident upon them.
Analogue signals
- More detailed than digital signals
- cannot be easily amplified due to noise
Digital signals
Noise resistant, easy to send store and receive, faster transmission, easily compressed
- lack of detail easily scrambled
