JAI AT-140GE - Manual (Page 33)

AT-140GE
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 Exposure Time Abs (GenICam Standard)
This is a function specified in the GenICam standard.
The shutter speed can be entered as an absolute exposure time in microseconds (μs) in
register address 0xA018. The entered absolute time (Time Abs) is then converted to a
programmable exposure (PE) value inside the camera.
The calculating formula below shows the relationship between the PE value used by the
camera for the different readout modes and the value entered in register 0xA018.
Due to rounding (decimals rounded down), some discrepancies may occur.
The relation between PE value and Time Abs
Normal readout PE= INT (Exposure time – 64.13) µs / (1958/42954000)
Vertical Binning PE= INT (Exposure time – 84.13) µs / (2462/42954000)
(Note: INT means round down.)
Note :The minimum value in normal readout is 22.8µs.
 GPIO in combination with Pulse Width trigger
More precise exposure time can be obtained by using GPIO in combination with Pulse Width
mode. The clock generator and counter can be programmed in very fine increments.
For an example, refer to
7.5.1 GPIO Plus PWC shutter
 Auto shutter
The AT-140GE has an automatic shutter function which sets the video at an appropriate level
depending on illumination.
Auto shutter range : 1/25 sec to 1/250 sec
9.3.6 Auto-detect LVAL-sync / async accumulation
This function replaces the manual setting found in older JAI cameras. Whether accumulation
is synchronous or asynchronous in relation to LVAL depends on the timing of the trigger input.
When a trigger is received while FVAL is high (during readout), the camera works in LVAL-
synchronous mode, preventing reset feed-through in the video signal. There is a maximum
jitter of one LVAL period from issuing a trigger and accumulation start.
When a trigger is received during FVAL low, the camera works in LVAL-asynchronous mode (no
delay) mode.
This applies to both Edge Pre-select (EPS) trigger mode and Pulse Width Control (PWC) trigger
mode.
Fig.25 Auto-detect LVAL sync/async accumulation
FVAL
(1) (3)
(1) In this period camera executes trigger at next LVAL (prevents feed-through noise)
(2) Avoid trigger at FVAL transition (+/- LVAL period), as the function may randomly
switch between “ next LVAL ” and “ immediate ”.
(2)
External Trigger
+/- 1 LVAL
(3) In this period, camera executes trigger immediately ( no delay).