Basler raL2048-48gm User Manual download pdf (Page 124)

Acquisition Control AW00118302000

114 Basler racer GigE

Determining whether your camera is operating with overlapped or non-overlapped exposure and

readout is not a matter of issuing a command or switching a setting on or off. Rather the way that

you operate the camera will determine whether the exposures and readouts are overlapped or not.

If we define the “line period” as the time from the start of exposure for one line acquisition to the

start of exposure for the next line acquisition, then:

 Exposure will not overlap when: Line Period > Exposure Time + Readout Time

 Exposure will overlap when: Line Period  Exposure Time + Readout Time

You can determine the readout time by reading the value of the Readout Time Abs parameter. The

parameter indicates what the readout time will be in microseconds given the camera’s current

settings. You can read the Readout Time Abs parameter value from within your application software

by using the Basler pylon API. The following code snippet illustrates using the API to get the

parameter value:

double ReadoutTime = Camera.ReadoutTimeAbs.GetValue( );

You can also use the Basler pylon Viewer application to easily get the parameter value.

For more information about the pylon API and the pylon Viewer, see Section 3 on page 23.

8.2.7.1 Guidelines for Overlapped Operation

To ensure smooth line acquisition and avoid overtriggering, you may only apply a line acquisition-

related trigger when the camera is waiting for it. If the trigger is nonetheless applied, the trigger will

be ignored and considered an overtrigger.

The risk of overtriggering exists particularly for overlapped operation where the sequence of line

start triggers must be carefully coordinated both with the camera’s exposure time and the sensor

readout time.

The following examples use a non-inverted, rising edge external line start trigger signal (ExLSTrig).

llegal Line Acquisition by Overtriggering

Certain attempts of triggering overlapped line acquisition are illegal and do not result in line

acquisitions: When a line start trigger signal attempts an illegal line acquisition the trigger signal will

be ignored and, accordingly, no line acquisition will be performed. In addition, the trigger signal will

be reported as an overtrigger (see also Section 10.10 on page 185). Illegal triggering and

impossible overlaps are shown in Fig. 39 on page 115 and Fig. 40 on page 116.

Illegal triggering when overlapping line acquisitions:

 The line start trigger goes high to start the exposure for line acquisition N+1 before the

exposure or the exposure overhead for line acquisition N has ended (see Fig. 39 on page 115).

This would result in the illegal overlap of exposures or of exposure and exposure overhead.

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Basler raL2048-48gm User Manual Page 124