SIGMA LBA-708 - Manual (Page 120)

field rate of 60 Hz can cause a trigger pulse to output at a 30 Hz rate. A non-interlaced camera
running at a frame rate of 60 Hz can produce a trigger output pulse at a 60 Hz rate.
5.1.3.2 Trigger Delay
The LBA-PC will produce trigger output pulses at the programmed frame Interval rate. With the
Trigger Delay check box deselected, the trigger output pulses will occur at vertical sync time.
With the Trigger Delay check box selected, the trigger output pulses will occur in the middle of
the frame of a non-interlaced camera; or in the middle of field 2 of an interlaced camera. The
reason to delay the trigger pulse is discussed in the following sections.
5.1.3.3 CCD Frame Transfer Camera, Interlaced
These camera types can only capture a laser pulse in one field. Therefore 2x is the highest
resolution possible with pulsed lasers. The video output from each laser pulse will occur during
the field outputting immediately after the laser trigger arrives. Since the laser is not
synchronized with the camera, this means that the pulse can occur in either field. As a result you
will observe a field hopping effect in the displayed image.
5.1.3.4 CCD Interline and Full Frame Transfer Camera, Interlaced
These camera types can capture a laser pulse in both fields at the same time. Therefore 1x
high-resolution images are possible with pulsed lasers. The video output from each laser pulse
will occur during the next two fields outputting immediately after the laser trigger arrives.
When the LBA is running, each digitized pixel is being tested for the trigger level pixel value.
When a trigger field is detected, the data is retained in the frame buffer and displayed. The
timing delay to the next frame that can be acquired depends upon the overhead needed to
process the first frame.
As in earlier examples, the Interline camera can display a pulse acquired in both fields while the
Frame transfer camera can only use one field. Because of the asynchronous arrival of the laser
pulse the Frame transfer image will randomly hop fields.
5.1.3.5 CMOS Camera, Interlaced
Most CMOS cameras employ either line or X/Y scanning methods. As a result they are poorly
suited for operation with pulsed lasers. Leave the Trigger Delay box disabled for all of these
camera types.
5.1.3.6 Tube Camera, Interlaced
With pulsed lasers these camera types will yield an image in both the odd and even fields.
Therefore 1x high resolution is possible. Leave the Trigger Delay box disabled for all of these
camera types.
Note many tube style cameras will suffer image degradation in the second field, during the
readout of the first. Tube cameras also suffer from long lag times, which make them poor
devices for any, but the slowest rep rate pulsed lasers.
Operator’s Manual LBA-PC 120