Photon Focus MV1-D2048-3D06 series, Руководство пользователя

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5.4 Trigger and Strobe
5.4.3 Exposure Time Control
The exposure time is defined by the camera. For an active high trigger signal, the camera starts
the exposure with a positive trigger edge and stops it when the programmed exposure time
has elapsed.
External Trigger
In the external trigger mode with camera controlled exposure time the rising edge of the
trigger pulse starts the camera states machine, which controls the sensor and optional an
external strobe output. Fig. 5.21 shows the detailed timing diagram for the external trigger
mode with camera controlled exposure time.
e
x t e r n a l t r i g g e r p u l s e i n p u t
t r i g g e r a f t e r i s o l a t o r
t r i g g e r p u l s e i n t e r n a l c a m e r a c o n t r o l
d e l a y e d t r i g g e r f o r s h u t t e r c o n t r o l
i n t e r n a l s h u t t e r c o n t r o l
d e l a y e d t r i g g e r f o r s t r o b e c o n t r o l
i n t e r n a l s t r o b e c o n t r o l
e x t e r n a l s t r o b e p u l s e o u t p u t
t
d - i s o - i n p u t
t
j i t t e r
t
t r i g g e r - d e l a y
t
e x p o s u r e
t
s t r o b e - d e l a y
t
d - i s o - o u t p u t
t
s t r o b e - d u r a t i o n
t
t r i g g e r - o f f s e t
t
s t r o b e - o f f s e t
Figure 5.21: Timing diagram for the camera controlled exposure time
The rising edge of the trigger signal is detected in the camera control electronic which is
implemented in an FPGA. Before the trigger signal reaches the FPGA it is isolated from the
camera environment to allow robust integration of the camera into the vision system. In the
signal isolator the trigger signal is delayed by time t
d
−
iso
−
input
. This signal is clocked into the
FPGA which leads to a jitter of t
jitter
. The pulse can be delayed by the time t
trigger
−
delay
which
can be configured by a user defined value via camera software. The trigger offset delay
t
trigger
−
offset
results then from the synchronous design of the FPGA state machines. The
exposure time t
exposure
is controlled with an internal exposure time controller.
The trigger pulse from the internal camera control starts also the strobe control state machines.
The strobe can be delayed by t
strobe
−
delay
with an internal counter which can be controlled by
the customer via software settings. The strobe offset delay t
strobe
−
delay
results then from the
synchronous design of the FPGA state machines. A second counter determines the strobe
duration t
strobe
−
duration
(strobe-duration). For a robust system design the strobe output is also
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