Camera Trigger Input Modes and Output Signals

Introduction to Camera Trigger Input Modes

Scientific cameras typically offer several different triggering modes, allowing researchers to select the behavior that best suits their experimental ?requirements. It is important to note that there is no industry-wide naming convention for these modes, so the exact terms used may vary between camera manufacturers. Nevertheless, the fundamental behaviors described below are widely supported across different camera models, including the Tucsen Dhyana 400BSI v3. Understanding the rolling shutter in camera systems is particularly relevant when selecting trigger modes, as different modes may be better suited to different sensor architectures.

Common Trigger Input Modes

Mode NameBehaviorTypical Use Case

No TriggeringCamera runs on internal timing; triggers in are ignoredStandard operation when external synchronization is not required

Frame TriggerEach frame is initiated by an individual digital trigger pulse or edgeApplications requiring precise control over frame timing

Level Exposure TriggerFrame triggered by a pulse; exposure duration determined by pulse level durationApplications requiring variable exposure time controlled by external hardware

Triggered SequenceCamera acquires a sequence of frames on internal timing, but start is delayed until a trigger is receivedApplications where the start of acquisition must be synchronized with an external event

The rolling shutter mechanism introduces additional complexity in triggering modes, as the row-by-row exposure pattern means that the timing of trigger signals must be carefully managed to achieve optimal results. Understanding the rolling shutter in camera systems is therefore essential when selecting and configuring trigger modes. Cameras such as the Tucsen Dhyana 400BSI v3 provide multiple triggering options to accommodate different experimental needs. The rolling shutter in camera architectures often determines the specific timing relationships that must be maintained for reliable triggering.

Avoiding Missed Triggers

When operating cameras according to external triggers, situations can arise where a trigger for a subsequent frame is sent before the camera has finished acquiring the previous frame. This results in a "missed trigger" event, where the camera fails to respond to a valid trigger signal. There are several approaches to avoiding this common issue:

Control trigger timing relative to camera exposure:?When the camera is operating on a software-set exposure time, ensure that the duration between triggers is at least approximately two camera line times longer than the exposure time. The precise delay required varies between different camera models.

Send multiple triggers:?Another approach is to send multiple trigger pulses at a rate significantly higher than the frame rate—for example, at tens or hundreds of kilohertz. As soon as the camera becomes ready to acquire the next frame, the next trigger in the sequence will initiate the acquisition. This approach can introduce slight timing variations depending on the trigger frequency.

Monitor the camera's ready trigger:?If the hardware supports this capability, ensure that a trigger is only sent to the camera once the camera indicates that it is ready to begin a new frame. This is achieved by monitoring the camera's ready trigger output signal. For cameras with a rolling shutter in camera design,the ready trigger timing may vary depending on the current position of the rolling shutter scan.

Typical Camera Trigger Output Signals

Cameras can output a variety of trigger signals to indicate their internal state to other hardware components. For global shutter cameras, a single digital trigger can indicate when the camera is exposing to light or when it is not exposing. For rolling shutter cameras, multiple trigger signals may be available to correspond to different events within the exposure of each frame.



Typical rolling shutter exposure triggers might indicate the exposure of any row or pixel, the exposure of the first row of the camera, or the simultaneous exposure of every row—the latter being the basis for pseudo-global shutter operation. Some rolling shutter cameras also include advanced modes that produce a trigger pulse each time the rolling shutter advances by one row, enabling extremely precise synchronization with other hardware components. These advanced features are available on cameras like the Tucsen Dhyana 400BSI v3. which offers comprehensive trigger output options. The rolling shutter in camera systems can thus be leveraged to provide detailed timing information for complex experimental setups.Both sensor types can also output signals indicating that readout is ongoing or has ended, and that the camera is ready to acquire a new frame. The specific trigger output capabilities vary between camera models, and the Tucsen Dhyana 400BSI v3 offers a comprehensive set of output options that can be configured to meet the demands of various experimental setups.

Multi-Camera Setups and Synchronization

Many scientific applications benefit from or require the use of multiple cameras acquiring images simultaneously. This is common in experiments involving simultaneous acquisition of multiple wavelength channels, multiple z-planes, multiple polarizations, or multiple angles of view.While software can offer sufficiently fast and precise timing control for some applications, many experiments require the increased speed and precision of hardware triggering to ensure that all cameras acquire at exactly the same time. Inter-camera delay can typically be kept within 10 to 20 microseconds or lower when hardware triggering is used.There are two common scenarios for multi-camera synchronization. In the first scenario, external hardware is used to control camera timing. A trigger splitter or multiple output pins can be used to connect all cameras' trigger inputs to the same signal, offering the highest degree of simultaneity.In the second, simpler scenario, the trigger output portof one camera is connected to the trigger input port of another camera or cameras. The sending camera is configured to output a signal as soon as the first row begins exposing, which starts the acquisition of the other cameras with a latency typically on the order of the camera line time—usually 5 to 20 microseconds. When using cameras with a rolling shutter in camera design, it is important to account for the rolling shutter timing when configuring sender/receiver relationships.

Avoiding Missed Frames in Multi-Camera Setups

The considerations for avoiding missed triggers apply even more significantly in multi-camera setups. It is essential to ensure that each camera is ready before sending fresh signals. In a sender/receiver configuration, if the sender camera is operating on its own internal timing, the exposure time for receiver cameras must be at most slightly shorter than the sender camera's exposure time. This accommodates the delay between the starts of the sender and receiver frame acquisitions, which is typically one to two camera line times. Using different exposure times for each camera is common, though the sender camera should be given the longest exposure to ensure reliable triggering.