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

142 CHAPTER 5
modulation frequency: 20 MHz
Integration time per tap: 12.5 ms
Filter
transmit.
No averaging
Optical
power in fW
Average output
voltage swing
in mV
Total
#electrons
in Tint
Frame rate: 20 Hz = 1/(4⋅12.5 ms)
#electr.
in Tmod
#mod. periods
for gen. of 1
electron
STD of
distance
error in cm
100% 9150 fW 941 mV 235200 0.94 1.1 1.6 cm
27% 2500 fW 258 mV 64400 0.26 3.8 1.6 cm
8% 750 fW 77 mV 19300 0.077 13 3.8 cm
2% 200 fW 20 mV 5100 0.02 50 13 cm
0.55% 50 fW 5.2 mV 1300 0.0051 200 55 cm
Average: 16 runs
100% 9150 fW 941 mV 235200 0.94 1.1 0.0 cm
27% 2500 fW 258 mV 64400 0.26 3.8 0.5 cm
8% 750 fW 77 mV 19300 0.077 13 1.5 cm
2% 200 fW 20 mV 5100 0.02 50 4.7 cm
0.55% 50 fW 5.2 mV 1300 0.0051 200 16.5 cm
Table 5.3 Distance accuracy vs. received optical power, total number of
integrated electrons and number of integrated electrons per
modulation cycle.
5.2.7 Noise performance and dynamic range
In this section, we present the measurements of the noise floor, dark noise, “bright
noise”, fixed pattern noise and also the resulting dynamic range D/R and signal-tonoise
ratio SNR. The noise floor is measured in the dark without previous signal
integration (no integration time). It includes thermal noise, reset noise, 1/f-noise and
the additional noise of all amplifiers in the acquisition path. Dark noise is measured
in the dark with a certain integration time, it therefore includes the noise of the dark
current. “Bright noise” is measured with integrated light; it includes photon shot
noise and dark current noise. The dynamic range D/R is the ratio of maximum
voltage swing to the floor noise; the signal-to-noise ratio SNR is the ratio of
maximum voltage swing to the “bright noise”.