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

IMAGING TOF RANGE CAMERAS 163
pixel 1-tap lock-in CCD line, we have interrupted the RC string after every 27 th
modulation gate in order to insert metallic connections to the polysilicon strips, in
addition to connecting the modulation gates from two sides. This means that the
load one has to drive consists of four 27-pixel RC-strings in parallel instead of a
non-terminated 108 pixel RC string. According to our SPICE simulations
(Figure 6.9) this results in a 30 times higher electrical cut-off frequency for the
slowest gate.
Gate voltage in volts
10
8
6
4
2
0
1st CCD gate 14th CCD gate
0 20 40
Time in ns
Relative amplitude
1
0.8
0.6
0.4
0.2
0
1st CCD gate 14th CCD gate
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
Frequency in Hz
Figure 6.9 Five-site connected modulation gates: after every 27 th pixel the RC
chain is broken for a metal connection of the modulation gates: Time
response and amplitude spectrum. The cut-off frequencies are now,
for the 1 st gate: 230 MHz and for the 14 th gate: 150 MHz
(improvement by a factor of 30). This realization has been chosen for
the 108-pixel TOF-sensor.
6.2.2 System architecture
The 2D-camera
Photographs of the TOF line camera are in Figure 6.10. In the middle of the
camera one can see the objective (f=4 mm, F/#=1.2) mounted to the driver board,
which is connected to the sequencer board. The modulated illumination module
consists of a line arrangement of 64 HPWT-DH00 LEDs.