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GigE Line Scan Use Case Descriptions and Diagrams#

The following topic describes common use cases for Basler line scan GigE and 5GigE cameras and how to configure these cameras for these use cases. The use cases in this topic are intended to help you in developing an initial understanding of how triggers and parameters interact.

Notes

Note that the camera provides multiple trigger functions, e.g., LineStartTrigger or FrameActiveTrigger, that can be set by the TriggerSelector parameter. Where applicable in the following use case descriptions, the necessary trigger selector setting is indicated under To set the parameters. All parameters related to the trigger configuration that aren't indicated in the To set the parameters section of the respective use case examples, are assumed to remain at their factory default values.
For further triggering background information, see the Triggered Image Acquisition and Aquisition Timing Information topics.
If an acquisition stop command is issued when not all lines of the current frame are acquired yet, a partial frame will be transmitted.
See the Features section and its sub-sections (e.g., Line Timeout and Spatial Correction topics), for detailed information about the features and how to configure them.
GigE Vision line scan cameras combine multiple lines to a larger frame. This can greatly reduce the processing load for the recipient (e.g., host computer, transport layer).

Info

For the sake of simplicity, the frame height in the following use case examples are set to only a few lines (e.g., 2 or 3). However, for real-world applications a frame height of at least 100 to 1000 lines per frame is highly recommended.

Use Case 1: Endless Stream of Objects or Material#

This is the most basic way of using a GigE line scan camera. The camera transmits a continuous stream of image frames. The host computer can combine multiple frames to build a larger image or process each frame on its own.
The objects or the endless material are or is moved through the camera’s field of view. The camera acquires the first line; afterwards, the object or the material is moved by one line and the camera acquires the next line, and so on.

In the following, two variants of use case 1 are shown:

Use case 1a: Objects moving at a constant speed
Use case 1b: Endless material moved by rollers at a varying speed

Case 1 a: Objects Moving at a Constant Speed#

When objects are free-falling, e.g., when sorting rice, cotton, or material for recycling, these objects move at a predictable speed and the camera can be set to a fixed line rate. No triggers are necessary to acquire geometrically correct images.

To set the parameters:

Set the frame height to the example value of 3, i.e., 3 lines per frame:
In the Image Format Control category, set the Height parameter to 3.

In the Acquisition Control category:
Enable the acquisition line rate control to slow down the line rate to the desired speed:
1. Set the AcquisitionLineRateEnable to True.
2. Set the acquisition line rate to 10 kHz:
  Set the AcquisitionLineRate parameter to 10.0.
Enable the Continuous frame mode:
Set the AcquisitionMode to ContinuousFrame.
This feature is not available via the pylon Viewer feature tree. Instead, use the Continuous Shot button in the toolbar of the pylon Viewer.

Line Scan Use Case 1a Timing

Case 1 b: Endless Material Moved by Rollers at Variable Speed#

Endless material is often moved by and over rollers. Load changes and vibrations cause the transport speed to vary. This fluctuation in speed can be compensated when a shaft encoder is used to generate a line trigger each time the material moves forward by a certain distance.
In the following example, the shaft encoder signal is connected to input line 2. The shaft encoder is set up to generate one encoder pulse per line. For further information about how an encoder works, see the Encoder Control feature topic.

To set the parameters:

Set the frame height to the example value of 3, i.e., 3 lines per frame:
In the Image Format Control category, set the Height parameter to 3.

In the Acquisition Control category:
Enable the line start trigger:
Set the Trigger Selector parameter to Line Start and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 2 as the signal source for the line start trigger: Set the TriggerSource parameter to Line2.
Enable the Continuous frame mode:
Set the AcquisitionMode to ContinuousFrame.
This feature is not available via the pylon Viewer feature tree. Instead, use the Continuous Shot button in the toolbar of the pylon Viewer.

Line Scan Use Case 1b Timing

Use Case 2: Individual Objects on a Conveyor Belt#

When inspecting objects on a moving conveyor belt, it is often desirable to receive one image per object. This facilitates image processing and avoids the waste of processing resources. In this setup, the system usually provides an object trigger that indicates the arrival of the next object. The object trigger can be generated for example by a light barrier or by a PLC (programmable logic control) unit.

The conveyor belt speed may fluctuate. It is therefore often advisable to use a shaft encoder to synchronize the line trigger to the mechanical movement of the belt. The following examples assume that a line trigger is used.

In the following, three variants of use case 2 are shown:

Use case 2a: One frame per object
Use case 2b: Multiple frames per object
Use case 2c: Varying number of frames per object

Case 2 a: One Frame per Object#

When the objects are small enough so that each fits in one frame, the object trigger can be used as a direct frame trigger.

To set the parameters:

Set the frame height to the example value of 3, i.e., 3 lines per frame:
In the Image Format Control category, set the Height parameter to 3.

In the Acquisition Control category:
Enable the frame start trigger:
Set the Trigger Selector parameter to Frame Start and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 1 as the signal source for the frame start trigger:
Set the TriggerSource parameter to Line1.
Enable the line start trigger:
Set the Trigger Selector parameter to Line Start and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 2 as the signal source for the line start trigger:
Set the TriggerSource parameter to Line2.
Enable the Continuous frame mode:
Set the AcquisitionMode to ContinuousFrame.
This feature is not available via the pylon Viewer feature tree. Instead, use the Continuous Shot button in the toolbar of the pylon Viewer.

Line Scan Use Case 2a Timing

Case 2 b: Multiple Frames per Object#

When the objects are too large to fit in one frame, a frame burst trigger can be used to trigger multiple frames for each individual object trigger. The image processing application may combine all frames of a frame burst into one image.

To set the parameters:

Set the frame height to the example value of 3, i.e., 3 lines per frame:
In the Image Format Control category, set the Height parameter to 3.

In the Acquisition Control category:
Set the number of frames for each frame burst to the example value of 2:
Set the AcquisitionFrameCount parameter to 2.
Enable the frame burst start trigger:
Set the Trigger Selector parameter to AcquisitionStart and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 1 as the signal source for the line start trigger:
Set the TriggerSource parameter to Line1.
Enable the line start trigger:
Set the Trigger Selector parameter to Line Start and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 2 as the signal source for the line start trigger:
Set the TriggerSource parameter to Line2.
Enable the Continuous frame mode:
Set the AcquisitionMode to ContinuousFrame.
This feature is not available via the pylon Viewer feature tree. Instead, use the Continuous Shot button in the toolbar of the pylon Viewer.

Line Scan Use Case 2b Timing

Case 2 c: Varying Number of Frames per Object#

When a mix of objects of varying sizes is inspected on the same conveyor belt, the frame start trigger can be used to acquire exactly the required number of frames for each object. The frame trigger signal should be generated by a presence detector, e.g., a light barrier, to ensure the signal is active whenever the object is in the camera’s field of view.

To set the parameters:

Set the frame height to the example value of 3, i.e., 3 lines per frame:
In the Image Format Control category, set the Height parameter to 3.

In the Acquisition Control category:
Enable the frame start trigger:
Set the Trigger Selector parameter to FrameStart and the TriggerMode parameter to On.
Set the trigger to act on a high level of the presence detector's output signal:
Set the TriggerActivation parameter to LevelHigh.
This results in a sequence of frame triggers issued while the trigger signal is active.
Select line 1 as the signal source for the frame start trigger:
Set the TriggerSource parameter to Line1.
Enable the line start trigger:
Set the Trigger Selector parameter to Line Start and the TriggerMode parameter to On.
Set the trigger to act on the rising edge of the trigger signal:
Set the TriggerActivation parameter to RisingEdge.
Select line 2 as the signal source for the line start trigger:
Set the TriggerSource parameter to Line2.
Enable the Continuous frame mode:
Set the AcquisitionMode to ContinuousFrame.
This feature is not available via the pylon Viewer feature tree. Instead, use the Continuous Shot button in the toolbar of the pylon Viewer.

Line Scan Use Case 2c Timing