3D Time-of-flight distance measurement with custom - Universität ...

DEMODULATION PIXELS IN CMOS/CCD 125
square wave and evaluation with Equation 2.13, strongly depends on the phase of
the sampled signal. This effect can easily be simulated. The simulation results for a
pure square wave, a sine wave and the first harmonics of a square wave are shown
in Figure 5.13. On the left hand side of the figure the input signals are shown. The
graphs on the right hand side show the calculated amplitude of the corresponding
signal with respect to the signal’s phase.
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
MODULATION SIGNAL: ampitude=0.5
0 50 100 150 200 250 300 350
MODULATION SIGNAL: ampitude=0.5
0 50 100 150 200 250 300 350
0.5
0.4
0.3
0.2
0.1
Square wave
Calculated amplitude vs. phase
Mean = 0.41
Std = 0.04
0
0 50 100 150 200 250 300 350
0.5
0.4
0.3
0.2
0.1
Calculated amplitude vs. phase
Mean = 0.33
Std = 0.04
0
0 50 100 150 200 250 300 350
Basic frequency and first two harmonics of a square wave
MODULATION SIGNAL: ampitude=0.5
0 50 100 150 200 250 300 350
0.5
0.4
0.3
0.2
0.1
Calculated amplitude vs. phase
Mean = 0.33
Std = 0.03
0
0 50 100 150 200 250 300 350
Basic frequency and first harmonic of a square wave
MODULATION SIGNAL: ampitude=0.5
0 50 100 150 200 250 300 350
0.5
0.4
0.3
0.2
0.1
Sine wave
Calculated amplitude vs. phase
Mean = 0.32
Std = 0
0
0 50 100 150 200 250 300 350
Figure 5.13 Measured amplitude versus actual signal phase for different
modulation signals. Left hand side: input signal, right hand side:
calculated amplitude vs. the signal’s phase. The simulation of the
measured amplitude is based on A = 1/2⋅√ [(A0-A2) 2 +(A1-A3) 2 ] where
A0..A3 have been integrated over half the modulation period.