<s>
A	O
time-of-flight	B-Device
camera	I-Device
(	O
ToF	B-Device
camera	I-Device
)	O
,	O
also	O
known	O
as	O
time-of-flight	B-Device
sensor	I-Device
(	O
ToF	O
sensor	O
)	O
,	O
is	O
a	O
range	B-Algorithm
imaging	I-Algorithm
camera	O
system	O
for	O
measuring	O
distances	O
between	O
the	O
camera	O
and	O
the	O
subject	O
for	O
each	O
point	O
of	O
the	O
image	O
based	O
on	O
time-of-flight	O
,	O
the	O
round	O
trip	O
time	O
of	O
an	O
artificial	O
light	O
signal	O
,	O
as	O
provided	O
by	O
a	O
laser	O
or	O
an	O
LED	O
.	O
</s>
<s>
Time-of-flight	B-Device
camera	I-Device
products	O
for	O
civil	O
applications	O
began	O
to	O
emerge	O
around	O
2000	O
,	O
as	O
the	O
semiconductor	O
processes	O
allowed	O
the	O
production	O
of	O
components	O
fast	O
enough	O
for	O
such	O
devices	O
.	O
</s>
<s>
The	O
Kinect2	B-Algorithm
for	O
Xbox	B-Device
One	I-Device
was	O
based	O
on	O
ToF	O
technology	O
from	O
Canesta	O
.	O
</s>
<s>
These	O
devices	O
have	O
a	O
built-in	O
shutter	O
in	O
the	O
image	B-Algorithm
sensor	I-Algorithm
that	O
opens	O
and	O
closes	O
at	O
the	O
same	O
rate	O
as	O
the	O
light	O
pulses	O
are	O
sent	O
out	O
.	O
</s>
<s>
The	O
ZCam	B-General_Concept
by	O
3DV	B-General_Concept
Systems	I-General_Concept
is	O
a	O
range-gated	O
system	O
.	O
</s>
<s>
Microsoft	O
purchased	O
3DV	B-General_Concept
in	O
2009	O
.	O
</s>
<s>
Microsoft	O
's	O
second-generation	O
Kinect	B-Algorithm
sensor	O
was	O
developed	O
using	O
knowledge	O
gained	O
from	O
Canesta	O
and	O
3DV	B-General_Concept
Systems	I-General_Concept
.	O
</s>
<s>
Similar	O
principles	O
are	O
used	O
in	O
the	O
ToF	B-Device
camera	I-Device
line	O
developed	O
by	O
the	O
Fraunhofer	O
Institute	O
of	O
Microelectronic	O
Circuits	O
and	O
Systems	O
and	O
TriDiCam	O
.	O
</s>
<s>
The	O
depth	O
resolution	O
of	O
ToF	B-Device
cameras	I-Device
can	O
be	O
improved	O
with	O
ultra-fast	O
gating	O
intensified	O
CCD	O
cameras	O
.	O
</s>
<s>
Range	O
gated	O
imagers	B-Algorithm
can	O
also	O
be	O
used	O
in	O
2D	O
imaging	O
to	O
suppress	O
anything	O
outside	O
a	O
specified	O
distance	O
range	O
,	O
such	O
as	O
to	O
see	O
through	O
fog	O
.	O
</s>
<s>
A	O
pulsed	O
laser	O
provides	O
illumination	O
,	O
and	O
an	O
optical	O
gate	O
allows	O
light	O
to	O
reach	O
the	O
imager	B-Algorithm
only	O
during	O
the	O
desired	O
time	O
period	O
.	O
</s>
<s>
A	O
time-of-flight	B-Device
camera	I-Device
consists	O
of	O
the	O
following	O
components	O
:	O
</s>
<s>
For	O
RF-modulated	O
light	O
sources	O
with	O
phase	O
detector	O
imagers	B-Algorithm
,	O
the	O
light	O
has	O
to	O
be	O
modulated	O
with	O
high	O
speeds	O
up	O
to	O
100MHz	O
,	O
only	O
LEDs	O
or	O
laser	O
diodes	O
are	O
feasible	O
.	O
</s>
<s>
For	O
Direct	O
TOF	O
imagers	B-Algorithm
,	O
a	O
single	O
pulse	O
per	O
frame	O
(	O
e.g.	O
</s>
<s>
Optics	O
:	O
A	O
lens	O
gathers	O
the	O
reflected	O
light	O
and	O
images	O
the	O
environment	O
onto	O
the	O
image	B-Algorithm
sensor	I-Algorithm
(	O
focal	O
plane	O
array	O
)	O
.	O
</s>
<s>
Image	B-Algorithm
sensor	I-Algorithm
:	O
This	O
is	O
the	O
heart	O
of	O
the	O
TOF	B-Device
camera	I-Device
.	O
</s>
<s>
Driver	O
electronics	O
:	O
Both	O
the	O
illumination	O
unit	O
and	O
the	O
image	B-Algorithm
sensor	I-Algorithm
have	O
to	O
be	O
controlled	O
by	O
high	O
speed	O
signals	O
and	O
synchronized	O
.	O
</s>
<s>
For	O
comparison	O
:	O
current	O
CPUs	B-Device
reach	O
frequencies	O
of	O
up	O
to	O
3GHz	O
,	O
corresponding	O
to	O
clock	O
cycles	O
of	O
about	O
300ps	O
-	O
the	O
corresponding	O
'	O
resolution	O
 '	O
is	O
only	O
45mm	O
.	O
</s>
<s>
The	O
camera	O
then	O
provides	O
a	O
distance	O
image	O
over	O
some	O
interface	O
,	O
for	O
example	O
USB	B-Protocol
or	O
Ethernet	O
.	O
</s>
<s>
The	O
simplest	O
version	O
of	O
a	O
time-of-flight	B-Device
camera	I-Device
uses	O
light	O
pulses	O
or	O
a	O
single	O
light	O
pulse	O
.	O
</s>
<s>
In	O
analog	O
timing	O
imagers	B-Algorithm
,	O
connected	O
to	O
the	O
photo	O
diode	O
are	O
fast	O
switches	O
,	O
which	O
direct	O
the	O
current	O
to	O
one	O
of	O
two	O
(	O
or	O
several	O
)	O
memory	O
elements	O
(	O
e.g.	O
</s>
<s>
In	O
digital	O
timing	O
imagers	B-Algorithm
,	O
a	O
time	O
counter	O
,	O
that	O
can	O
be	O
running	O
at	O
several	O
gigahertz	O
,	O
is	O
connected	O
to	O
each	O
photodetector	O
pixel	O
and	O
stops	O
counting	O
when	O
light	O
is	O
sensed	O
.	O
</s>
<s>
For	O
direct	O
TOF	O
imagers	B-Algorithm
,	O
such	O
as	O
3D	O
Flash	O
LIDAR	O
,	O
a	O
single	O
short	O
pulse	O
from	O
5	O
to	O
10	O
ns	O
is	O
emitted	O
by	O
the	O
laser	O
.	O
</s>
<s>
In	O
contrast	O
to	O
stereo	B-Algorithm
vision	I-Algorithm
or	O
triangulation	B-Algorithm
systems	I-Algorithm
,	O
the	O
whole	O
system	O
is	O
very	O
compact	O
:	O
the	O
illumination	O
is	O
placed	O
just	O
next	O
to	O
the	O
lens	O
,	O
whereas	O
the	O
other	O
systems	O
need	O
a	O
certain	O
minimum	O
base	O
line	O
.	O
</s>
<s>
In	O
contrast	O
to	O
laser	B-Algorithm
scanning	I-Algorithm
systems	I-Algorithm
,	O
no	O
mechanical	O
moving	O
parts	O
are	O
needed	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
this	O
task	O
uses	O
only	O
a	O
small	O
amount	O
of	O
processing	O
power	O
,	O
again	O
in	O
contrast	O
to	O
stereo	B-Algorithm
vision	I-Algorithm
,	O
where	O
complex	O
correlation	O
algorithms	O
are	O
implemented	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
illumination	O
units	O
in	O
many	O
of	O
today	O
's	O
TOF	B-Device
cameras	I-Device
can	O
provide	O
an	O
illumination	O
level	O
of	O
about	O
1	O
watt	O
.	O
</s>
<s>
In	O
certain	O
types	O
of	O
TOF	O
devices	O
(	O
but	O
not	O
all	O
of	O
them	O
)	O
,	O
if	O
several	O
time-of-flight	O
cameras	O
are	O
running	O
at	O
the	O
same	O
time	O
,	O
the	O
TOF	B-Device
cameras	I-Device
may	O
disturb	O
each	O
other	O
's	O
measurements	O
.	O
</s>
<s>
For	O
an	O
imager	B-Algorithm
capturing	O
at	O
30Hz	O
,	O
the	O
probability	O
of	O
an	O
interfering	O
interaction	O
is	O
the	O
time	O
that	O
the	O
camera	O
acquisition	O
gate	O
is	O
open	O
divided	O
by	O
the	O
time	O
between	O
laser	O
pulses	O
or	O
approximately	O
1	O
in	O
50,000	O
(	O
0.66	O
s	O
divided	O
by	O
33	O
ms	O
)	O
.	O
</s>
<s>
In	O
contrast	O
to	O
laser	B-Algorithm
scanning	I-Algorithm
systems	I-Algorithm
where	O
a	O
single	O
point	O
is	O
illuminated	O
,	O
the	O
time-of-flight	O
cameras	O
illuminate	O
a	O
whole	O
scene	O
.	O
</s>
<s>
Direct	O
TOF	O
imagers	B-Algorithm
are	O
vulnerable	O
if	O
the	O
light	O
is	O
reflecting	O
from	O
a	O
specular	O
surface	O
.	O
</s>
<s>
The	O
second-generation	O
Kinect	B-Algorithm
sensor	O
originally	O
included	O
with	O
the	B-Device
Xbox	I-Device
One	I-Device
console	O
used	O
a	O
time-of-flight	B-Device
camera	I-Device
for	O
its	O
range	B-Algorithm
imaging	I-Algorithm
,	O
enabling	O
natural	B-Application
user	I-Application
interfaces	I-Application
and	O
gaming	O
applications	O
using	O
computer	B-Application
vision	I-Application
and	O
gesture	B-General_Concept
recognition	I-General_Concept
techniques	O
.	O
</s>
<s>
Creative	O
and	O
Intel	O
also	O
provide	O
a	O
similar	O
type	O
of	O
interactive	O
gesture	O
time-of-flight	B-Device
camera	I-Device
for	O
gaming	O
,	O
the	O
Senz3D	O
based	O
on	O
the	O
DepthSense	B-General_Concept
325	O
camera	O
of	O
Softkinetic	B-General_Concept
.	O
</s>
<s>
Infineon	O
and	O
PMD	O
Technologies	O
enable	O
tiny	O
integrated	O
3D	B-Algorithm
depth	I-Algorithm
cameras	I-Algorithm
for	O
close-range	O
gesture	B-General_Concept
control	I-General_Concept
of	O
consumer	O
devices	O
like	O
all-in-one	O
PCs	O
and	O
laptops	O
(	O
Picco	O
flexx	O
and	O
Picco	O
monstar	O
cameras	O
)	O
.	O
</s>
<s>
Several	O
smartphones	B-Application
include	O
time-of-flight	O
cameras	O
.	O
</s>
<s>
The	O
first	O
mobile	O
phone	O
to	O
employ	O
such	O
technology	O
was	O
the	O
LG	B-Application
G3	I-Application
,	O
released	O
in	O
early	O
2014	O
.	O
</s>
<s>
In	O
industrial	O
machine	B-General_Concept
vision	I-General_Concept
,	O
the	O
time-of-flight	B-Device
camera	I-Device
helps	O
to	O
classify	O
and	O
locate	O
objects	O
for	O
use	O
by	O
robots	O
,	O
such	O
as	O
items	O
passing	O
by	O
on	O
a	O
conveyor	O
.	O
</s>
<s>
ToF	B-Device
cameras	I-Device
have	O
been	O
used	O
to	O
obtain	O
digital	B-Application
elevation	I-Application
models	I-Application
of	O
the	O
Earth	O
's	O
surface	O
topography	O
,	O
for	O
studies	O
in	O
geomorphology	O
.	O
</s>
<s>
Kinect	B-Algorithm
-	O
hands-free	O
user	O
interface	O
platform	O
by	O
Microsoft	O
for	O
video	O
game	O
consoles	O
and	O
PCs	O
,	O
using	O
time-of-flight	O
cameras	O
in	O
its	O
second	O
generation	O
of	O
sensor	O
devices	O
.	O
</s>
<s>
2+3D	O
-	O
High-resolution	O
SXGA	O
(	O
1280×1024	O
)	O
TOF	B-Device
camera	I-Device
developed	O
by	O
startup	O
company	O
odos	O
imaging	O
,	O
integrating	O
conventional	O
image	O
capture	O
with	O
TOF	O
ranging	O
in	O
the	O
same	O
sensor	O
.	O
</s>
<s>
Senz3D	O
-	O
TOF	B-Device
camera	I-Device
by	O
Creative	O
and	O
Intel	O
based	O
on	O
DepthSense	B-General_Concept
325	O
camera	O
of	O
Softkinetic	B-General_Concept
,	O
used	O
for	O
gaming	O
.	O
</s>
<s>
Cube	O
eye	O
-	O
ToF	B-Device
Camera	I-Device
and	O
Modules	O
,	O
VGA	O
Resolution	O
,	O
website	O
:	O
</s>
