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6.4. External Trigger Modes
This camera has 3 external asynchronous trigger modes, which can be set by RS-232C commands
or switches.
1. Edge Pre-select Mode. TR=1 Pre-selected exposure. (SM=0, SM=1)
2. Pulse Width Control Mode. TR=2 Pulse width controlled exposure.
3. Frame Delay read out mode. TR=3 Pre-select exp. Read out by trailing trig. edge.
The trigger can be H synchronous (HC=0) or H a-synchronous (HC=1). Refer to fig. 12.
In H synchronous mode, the accumulation will start at the first H (LEN) after the trigger leading
edge. In H a-synchronous mode the trigger leading edge will immediately reset the internal H,
(LEN). After a Xsub pulse the accumulation will start. Shown in fig. 19.
In edge pre-select mode the shutter time can be selected from the normal 10 fixed steps.
(SM=0). Or it can be selected from the 1056 steps programmable (SM=1).
Remark that H is 39.3 µsec. But 43.3 µsec. when vertical binnig is on.
Restart Continuous Trigger RCT mode (RC=1) can be activated in edge pre-select mode (TR=1).
(By RS-232C and CL only)
In pulse width control (PWC) mode the exposure time can be from 2H to ∞. Thermal noise and
dark current noise will increase by accumulation time, therefore the exposure time is not
recommended to exceed 2 seconds.
Vertical binnig mode (BI=1) can be used in all 3 modes. Only with full scan. (SC=0). Binning will
only work on M4
+
and M4CL
+
.
Partial scan (SC=0 through 3) can be used in all 3 modes. Only with binning off. (BI=0).
For all 3 modes smearless read out (SL=1) can be used. At the leading edge of the trigger pulse a
dump read out of the vertical ccd register is performed before the accumulation is started. It
takes 133 H. It means that the trigger pulse width in PWC and frame delay mode should be
>133H. (5.23 msec.)
For frame delay read out (TR=3) the multiple shutter function is available. (ML=1). It can also be
combined with smearless read out.
Xsub
Accum
Int. HD
Trigger
157 clk
3.88µs
3 clk
Xsub
Accum
Int. HD
Trigger
Xsub
Accum
Int. HD
Trigger
157 clk
3.88µs
3 clk
Fig. 19. Accumulation latency time for H a-synchronous trigger.