7.6 Acquisition Monitoring Tools
7.6.2 Trigger Wait Signals
7.6.2.2 Frame Trigger Wait Signal
Overview
As you are acquiring frames, the camera automatically monitors the frame start trigger status and supplies a signal that indicates the current status. The Frame Trigger Wait signal will go high whenever the camera enters a "waiting for frame start trigger" status. The signal will go low when an external frame start trigger (ExFSTrig) signal is applied to the camera and the camera exits the
"waiting for frame start trigger status". The signal will go high again when the camera again enters a "waiting for frame trigger" status and it is safe to apply the next frame start trigger signal.
If you base your use of the ExFSTrig signal on the state of the frame trigger wait signal, you can avoid "frame start overtriggering", i.e., applying a frame start trigger signal to the camera when it is not in a "waiting for frame start trigger" acquisition status. If you do apply a frame start trigger signal to the camera when it is not ready to receive the signal, it will be ignored and a frame start overtrigger error will be declared.
Figure 30 illustrates the Frame Trigger Wait signal. The camera is set for the trigger width exposure mode with rising edge triggering and with exposure and readout overlapped.
For more information about the overtrigger error, see Section 10.13 on page 243.
The frame trigger wait signal will only be available when hardware frame start triggering is enabled.
Frame Acquisition N
Exposure Readout
Time Frame Trigger
Wait Signal
Frame Acquisition N+1
Exposure Readout
Frame Acquisition N+2
Exposure Readout
ExFSTrig Signal
= Camera is in a "waiting for frame start trigger" status
Fig. 30: Frame Trigger Wait Signal
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Frame Trigger Wait Signal Details
When the camera is set for the timed exposure mode, the rise of the Frame Trigger Wait signal is based on the current exposure time parameter setting and on when readout of the current frame will end. This functionality is illustrated in Figure 31.
If you are operating the camera in the timed exposure mode, you can avoid overtriggering by always making sure that the Frame Trigger Wait signal is high before you trigger the start of frame capture.
Frame Acquisition N
Exposure Readout
Time Frame Trig
Wait Signal
Frame Acquisition N+1
Exposure Readout
Frame Acquisition N+2
Exposure Readout
ExFSTrig Signal
Exp. Time Setting
Exp. Time Setting
The rise of the Frame Trigger Wait signal is based on the end of frame readout and on the current exposure time parameter setting
= Camera is in a "waiting for frame start trigger" status
Fig. 31: Frame Trigger Wait Signal with the Timed Exposure Mode
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When the camera is set for the trigger width exposure mode, the rise of the Frame Trigger Wait signal is based on the Exposure Overlap Time Max parameter setting and on when readout of the current frame will end. This functionality is illustrated in Figure 32.
If you are operating the camera in the trigger width exposure mode, you can avoid overtriggering the camera by always doing the following:
Setting the camera’s Exposure Overlap Time Max parameter so that it represents the smallest exposure time you intend to use.
Making sure that your exposure time is always equal to or greater than the setting for the Exposure Overlap Time Max Abs parameter.
Monitoring the camera’s Frame Trigger Wait signal and only using the ExFSTrig signal to start exposure when the Frame Trigger Wait signal is high.
You should set the Exposure Overlap Time Max parameter value to represent the shortest exposure time you intend to use. For example, assume that you will be using trigger width exposure mode and that you intend to use the ExFSTrig signal to vary the exposure time in a range from 3000 µs to 5500 µs. In this case you would set the camera’s Exposure Overlap Time Max parameter to 3000 µs.
Frame Acquisition N
Exposure Readout
Time Frame Trig
Wait Signal
Frame Acquisition N+1
Exposure Readout
Frame Acquisition N+2
Exposure Readout
ExFSTrig Signal
Exp. Overlap Time Max Abs Setting
Exp. Overlap Time Max Abs Setting
The rise of the Frame Trigger Wait signal is based on the end of frame readout and on the current Exposure Overlap Time Max parameter setting
= Camera is in a "waiting for frame start trigger" status
Fig. 32: Frame Trigger Wait Signal with the Trigger Width Exposure Mode
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Setting the Exposure Overlap Time Max Using Basler pylon
You can use the Basler pylon API to set the Exposure Overlap Time Max Abs parameter value from within your application software by using the Basler pylon API. The following code snippet illustrates using the API to set the parameter value:
// Set the Exposure Overlap Time Max to 3000 µs Camera.ExposureOverlapTimeMaxAbs.SetValue(3000);
You can also use the Basler pylon Viewer application to easily set the parameters.
Setting the Exposure Overlap Time Max Using Direct Register Access
If you are parameterizing the camera via direct register access, the Exposure Overlap Time Max Raw register sets the exposure overlap time max.
1. Set the value of the Exposure Overlap Time Max Raw register.
A value in a raw register is simply an integer value with no units. To determine what the actual exposure time will be, you must multiply the value in the raw register by the camera’s time base.
The time base on ace cameras is 1 µs.
For example, if you set the Exposure Overlap Time Max Raw register to 3000, the exposure overlap time max would be 3000 µs (3000 x 1 µs = 3000 µs).
Selecting the Frame Trigger Wait Signal as the Source Signal for an Output Line Using Basler pylon
You can select the frame trigger wait signal as the source signal for the camera’s GPIO line (assuming it is set as an output) or the CL Spare output line.
1. Configure the GPIO line as an output (if you want to use the GPIO line).
2. Use the Line Selector to select the desired line.
3. Set the value of the Line Source parameter to the frame trigger wait signal.
You can set the Line Selector and the Line Source parameter value from within your application software by using the Basler pylon API. The following code snippet illustrates using the API to set the selector and the parameter value:
// Configure the GPIO line as an output
Camera.LineSelector.SetValue(LineSelector_Line1);
Camera.LineMode.SetValue(LineMode_Output);
//Select the GPIO line
Camera.LineSelector.SetValue(LineSelector_Line1);
//Set the source for the selected line
Camera.LineSource.SetValue(LineSource_FrameTriggerWait);
//Select the CL Spare line
Camera.LineSelector.SetValue(LineSelector_ClSpare);
To set the exposure overlap time max:
To select a source signal for an output line:
AW00098506000 Image Acquisition Control
//Set the source for the selected line
Camera.LineSource.SetValue(LineSource_FrameTriggerWait);
You can also use the Basler pylon Viewer application to easily set the parameters.
For more information about the pylon API and the pylon Viewer, see Section 3.1 on page 21.
Selecting the Frame Trigger Wait Signal as the Source Signal for an Output Line Using Direct Register Access
You can select the frame trigger wait signal as the source signal for the camera’s GPIO line (assuming it is set as an output) or the CL Spare output line.
1. Set the GPIO line to operate as an output by setting the value of the Line Mode Line 1 register to Output.
2. Set the value of the Line Source Line 1 register to Frame Trigger Wait.
1. Set the value of the Line Source CL Spare register to Frame Trigger Wait.
For more information about direct register access, see Section 3.2 on page 23.
For more detailed information about the camera’s GPIO line, see Section 5.6 on page 36.
To select the frame trigger wait signal as the source signal for the GPIO line:
To select the frame trigger wait signal as the source signal for the CL Spare line:
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