imaging + signalling Flashcards
number of alternatives for a b number of bits?
N = 2^b
where:
• N = number of alternatives
• b = number of bits
number of bits needed for N number of alternatives?
b = log{2}(N)
where:
• b = number of bits
• N = number of alternatives [aka alternative quantisation levels]
how to figure out the number of useful levels?
number of useful levels = V total/V noise
where:
• V total = total voltage range used by signal (INCLUDING NOISE) (max + min of y-axis)
• V noise = range of voltage on signal used by noise (max + min on y-axis for noise)
how to calculate out [max] number of bits you should use to sample signal?
b max = log{2}(V total max/V noise max)
where:
• b max = max number of bits you can use to sample signal
• V total max = max range of voltage used by signal
• V noise max = max range of voltage used by noise
what is the equation for the refractive index (n) for light travelling from a vacuum into a medium? (v,c)
refractive index = speed of light in vacuum/speed of light in medium
n = c/v
equation for refractive index (n) for light travelling from a vacuum into a medium? (c, v, θi and θr)
n = speed of light in vacuum/wavelength of light in medium = sinθi/sinθr
what is snell’s law? (n1, n2, sinθi, sinθr)
n1sinθi = n2sinθr
equation for curvature? (using r)
curvature = 1/r
where radius (r) of curvature is focal length (f) of lens (for plane wavefronts entering convex lens)
equation for lens power? (using f)
lens power = 1/f
where f = focal length
lens equation? (v, u, f)
1/v = 1/u + 1/f
(u is ALWAYS negative)
equation for magnification (m)? (v, u)
m = v/u
where v = image distance and u = object distance
equation for magnification (m)? (object height, image height)
m = image height/object height
equation for resolution? (length of object, no. pixels across object)
resolution = true length of object/no. of pixels across object
equation for amount of information[/data] in image?
amount of information in image = number of pixels x bits per pixel
wave equation? (v, f, λ)
wave speed = frequency x wavelength
v = fλ
nyquist’s theorem?
sampling f > 2 x f of smallest important change
OR
sampling f > 2 x highest f
equation to work out number of quantisation levels needed per sample?
no. of quantisation levels needed per sample = Vtotal/Vnoise
equation to work out number of bits (b) needed to sample signal?
b = log(2)[Vtotal/Vnoise]
^also known as shannon’s criteria
equation for resolution of sampled signal?
resolution = range of variation of signal/number of quantisation levels
remember no. of quantisation levels = 2^b
equation for transmission rate?
transmission rate of info = f of sample x bits or bytes per sample
OR
transmission rate of info = total info sent [in bits, bytes, etc]/time taken
rule for θi and θr?
when light moving from less optically dense material to more optically dense material:
θi > θr
