EPC660 Datasheet, PDF (67/116 Pages) Espros Photonics corp – 3D TOF Imager 320 x 240 Pixel

7.4. Operating and unambiguity range versus time base setting
The epc660 3D TOF imager uses the time-of-flight principle. It is implemented with a repeating, continuous-mode modulation signal (sine
or PN) during the integration phase (refer to chapter 6., Measurement Modes). Consequently, only signals returning within the maximum
time slots can be detected at all (PN mode) or unambiguously (sine or PN mode).
The operating range is the maximum distance which corresponds to the maximum time-of-flight inside of one period of the used modula -
tion: for sine, it is one period of fLED and for PN mode, it is the chip period tc. Objects inside this area are detected unambiguously. For PN
mode it means also, that objects above this distance and below the unambiguity distance are suppressed and cannot be detected (see
Figure 59).
The unambiguity range defines the repetition distance, where objects outside of the targeted operating range can still be detected as far
they are of very high reflectivity (remission). Strongly reflected signals outside of this range may therefore interfere with the measurement.
The operating range, the unambiguity distance, the time base for the integration time and the resolution of the distance signal are defined
by the modulation clock mod_clk. This corresponds for the epc660 to a maximum default operating range of 7.5m @ mod_clk = 80MHz. It
may be necessary depending on the application to adapt this parameters to other values. It can be done by a change of the mod_clk. Ta-
ble 29 lists as an example some values of the modulation clock mod_clk in function of the operating range, the unambiguity distance, of
the distance resolution and of the multiplier of the integration time base.
TOF sine & PN
TOF sine
Operating
Int. time
Distance
range
multiplied by resolution ²
Modulator
clock
mod_clk
_div
LED/LD mod. Unambiguity
freq.
range
mod_clk
(0x85)
fLED
[m]
[#]
[cm]
[MHz]
[#]
[MHz]
[m]
7.50
1
0.250
80.0
0
20.000
7.50
15.00 ¹
2
0.500
40.0
1¹
10.000
15.00
30.00
4
1.000
20.0
3
5.000
30.00
60.00
8
2.000
10.0
7
2.500
60.00
120.00
16
4.000
5.0
15
1.250
120.00
240.00
32
8.000
2.5
31
0.625
240.00
Table 29: Operating range versus mod_clk
Notes:
1 _{Default values}
2 _{The distance resolution is given for an operating range corresponding to 3'000 LSB.}
TOF PN
Chip period
tC
[ns]
50.0
100.0
200.0
400.0
800.0
1'600.0
Unambiguity
range
e.g. LSFR 8
[m]
1'912
3'825
7'650
15'300
30'600
61'200
© 2017 ESPROS Photonics Corporation
Characteristics subject to change without notice
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Datasheet_epc660-V1.09
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