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Digital Input/Output (Trigger/Flash)

uEye Camera Manual Version 3.80

Digital Input/Output (Trigger/Flash)

The majority of models from the uEye series have opto-isolated inputs/outputs that can be used for triggering the camera and for flash control. Some models have general purpose I/Os (GPIOs) instead, or in addition. Use of the GPIOs for flash control is possible to a certain degree. External triggering via the GPIO is not supported.

You can look up which digital inputs and outputs are provided on your camera in the Model Comparison chapter.

Using digital inputs/outputs

Digital input (trigger)

Models with opto-coupler input can use the digital input for externally triggering the image capture, or query the applied signal level.

In trigger mode, a digital signal is applied to the camera's input. You can determine whether the camera will respond to the rising or falling edge of the digital signal. After an internal delay, the sensor is exposed for the defined exposure time. The captured image is then transferred to the PC.

On models with general purpose I/Os (GPIO), you can query a voltage level at these inputs (TTL compatible).

Digital output (flash)

The uEye's digital outputs can be used in both freerun mode and trigger mode. You can synchronize the output level to the exposure time or set it statically.

Models with opto-coupler output allow control of a DC voltage applied to the output. This allows controlling a flash, either directly or via a separate flash controller unit. Models with general purpose I/Os (GPIO) can output a voltage at these outputs (TTL compatible).

Achtung

Note on I/O wiring

Please read the notes on I/O wiring for your camera model in the Electrical Specifications chapter.

Hinweis

Note on the persistence of settings

The settings specified for the digital output will be reset in the following situations:

a GigE uEye camera loses its pairing (i.e. it is closed in the software)
a USB uEye camera is disconnected from the PC or the PC is powered down

Flash timing (trigger mode)

When using the digital output for flash control, you can set the delay and the duration of the flash. The flash timing can be adjusted manually or automatically by the camera driver.

Achtung

Note on sensor latency and delay times

The sensor latency is due to a number of technical factors, including sensor type, image geometry, pixels clock and, with CCD sensors, the exposure time. The latency is constant for a specific combination of parameters.

Trigger delay, flash delay and flash duration are optional and can be set by software.

The following illustrations show a schematic view of the image capture sequence. The sensor exposure and readout times and the transmission times depend on the camera model and the current parameter settings.

Hinweis

Note on the UI-2140 / UI-6140

On the UI-214x / UI-614x models, the start and end of the flash signal are precisely synchronized to the exposure time, also in automatic mode. The flash output is only activated after the sensor latency time has elapsed. With these sensors, the sensor latency is independent of the exposure time.

Automatic flash

If flash delay = 0 and flash duration = 0, the flash signal is automatically synchronized to the exposure time.

The automatic flash feature has the advantage that the flash is synchronized automatically if the settings for image geometry or camera timing are changed.

The disadvantage is that the flash signal is active slightly longer than the exposure time. The flash duration with automatic flash is longer for rolling shutter sensors than for global shutter sensors.

Figure 60: Flash timing with global shutter sensor, automatic flash,<br>
optional trigger delay

Figure 60: Flash timing with global shutter sensor, automatic flash,
optional trigger delay

Figure 61: Flash timing with rolling shutter sensor, automatic flash,<br>
optional trigger delay

Figure 61: Flash timing with rolling shutter sensor, automatic flash,
optional trigger delay

Manual flash synchronization

If one of the flash delay or flash duration parameters is set to a value greater than 0, you can shift the flash signal to any point in the exposure time or change its duration. In this case, the flash delay will be calculated exactly from the start of the exposure time (after the sensor latency time). When manually synchronizing the flash signal to the exposure time, you can use the is_GetGlobalFlashDelays() function to query the data you need.

The advantage of manual flash synchronization is that the flash can be precisely controlled based on the start of exposure. This applies to both rolling and global shutter sensors. You can thus achieve a higher accuracy with the manual flash synchronization than with the automatic flash feature.

The disadvantage is that the flash signal has to be resynchronized whenever any settings for image geometry or camera timing change.

Hinweis

With rolling shutter sensors, you can avoid the rolling shutter effect by selecting suitable delay and duration settings (global flash function). Using is_GetGlobalFlashDelays(), you can query the appropriate values.

Achtung

The flash output is reset with the start of the next image capture. This also applies if you have set a longer flash duration.

Figure 62: Flash timing, user-defined flash duration

Figure 62: Flash timing, user-defined flash duration

Figure 63: Flash timing, user-defined flash duration and delay,<br>
optional trigger delay

Figure 63: Flash timing, user-defined flash duration and delay,
optional trigger delay

Flash timing (freerun mode)

Automatic flash

In freerun mode, the automatic flash feature works in the same way as in trigger mode. As a result, the flash output is continuously or almost continuously active (see illustration below).

Figure 64: Flash timing in freerun mode with rolling shutter sensor, automatic flash

Figure 64: Flash timing in freerun mode with rolling shutter sensor, automatic flash

Manual flash synchronization

Achtung

It is recommended to synchronize the flash manually in freerun mode. This applies to both rolling and global shutter sensors.

In freerun mode, the manual flash synchronization works in the same way as in trigger mode.

Figure 65: Flash timing in freerun mode with global shutter sensor, manual flash

Figure 65: Flash timing in freerun mode with global shutter sensor, manual flash

See also:

Basics: Trigger Mode
uEye Demo: I/O
Specifications: Electrical Specifications

 

Programming:


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