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Fourier Analysis
• Square wave = Sum of sine waves
• Square wave = Fundamental sine wave + harmonics
• Fundamental sine wave is a wave with the same frequency as the square wave
• Third harmonic is a sine wave with 3 times the square wave
• Fifth harmonic is a sine wave with 5 times the frequency of the square wave
Modulation Transfer Function
• Object Contrast-> Lens -> Image contrast
• MTF = Image Contrast/ Object Contrast
• MTF = 1.0 for an ideal lens (or system)
MTF is determined by frequency to obtain a graph.
Modulation Transfer Function (MTF)Frequency Object Contrast Image Contrast MTF
2 10 8 0.80
5 9 7.5 0.83
8 8.7 6.3 0.72
10 7.5 5.2 0.69
15 6.3 3.8 0.60
18 5.2 2.1 0.40
25 4.2 1.5 0.36
30 4 0.9 0.23
40 4 0.7 0.18
50 3.8 0.4 0.11
60 3.6 0.33 0.09
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
2 5 8 10 15 18 25 30 40 50 60
MTF
MTF