HFR Acquisition Mode

The HFR acquisition mode is intended for the acquisition of snapshot images from high frame rate cameras.

In HFR acquisition mode, the unique sequence is divided into phases, each phase acquiring PhaseLength_Fr frames into a single destination surface.

The HFR acquisition mode is applicable to area-scan cameras with a frame rate not exceeding 1,275,000 frames per second.

The HFR acquisition mode is explicitly invoked by assigning value HFR to AcquisitionMode.

The first action is to define all MultiCam Channel parameters before channel activation.

More specifically the following acquisition control parameters need to be configured:

Parameter Value range
AcquisitionMode HFR
TrigMode IMMEDIATE, HARD, SOFT and COMBINED
NextTrigMode SAME, REPEAT, HARD, SOFT and COMBINED
SeqLength_Fr MC_INDETERMINATE, 1 ~ (PhaseLength_Fr × 65,534)
PhaseLength_Fr 1 ~ 255

When invoking the HFR acquisition mode:

● The ActivityLength parameter is enforced to 1. The channel goes inactive at the completion of the sequence.
● The number of frames per acquisition phase is specified by PhaseLength_Fr. The minimal applicable value is the camera frame rate divided by 5000.
● The TrigMode parameter establishes the starting condition of the sequence and consequently the starting condition of the first slice of the first phase —the first frame— of the sequence. Possible values are IMMEDIATE, HARD, SOFT and COMBINED. The default MultiCam setting is IMMEDIATE.
● The NextTrigMode parameter establishes the starting condition of the subsequent slices —frames— within the sequence. Possible values are SAME, REPEAT, HARD, SOFT and COMBINED. The default value is SAME.
● The sequence length is specified by SeqLength_Fr. Assigning a value MC_INDETERMINATE enforces an indefinite acquisition sequence.

The trigger source is determined by the Start Trigger condition. Usually, the start trigger event is a hard trigger; however a soft trigger signal can also be selected. Usually, the trigger is derived from a position detector. The trigger condition is defined by parameter TrigMode.

A programmable time delay can optionally be specified with parameter TrigDelay_us. It compensates a trigger advance delivered by a position detector placed away from the camera field of view.

To summarize the usage of trigger parameters, see Hardware Trigger.

At first trigger event, the image capture starts effectively; a "Start of Sequence" signal is reported to the user.

The trigger source for all subsequent acquisition slices is determined by the Next Start Trigger condition. Usually, the Next start trigger event is the same as the Start Trigger condition. The next trigger condition is defined by parameter NextTrigMode.

To summarize the usage of trigger parameters, see Hardware Trigger.

A programmable time delay can optionally be specified with parameter TrigDelay_us. It compensates a trigger advance delivered by a position detector placed away from the camera field of view.

At subsequent trigger events, the image capture starts effectively; however no "Start of Sequence" signal is reported to the user.

The HFR acquisition mode allows two methods to stop the sequence: Manual stop and Automatic stop.

If the number of frames to capture is known before starting the sequence and is not higher than (PhaseLength_Fr × 65,534), the automatic stop method can be used to automatically stop the sequence after a predefined number of frames. This variant of HFR acquisition is named Finite HFR acquisition. In this case, the number of frames to be acquired needs to be specified before Channel activation.

If the number of frames is unknown or higher than (PhaseLength_Fr × 65,534), the manual stop method is required. In this case, the parameter SeqLength_Fr should be set to MC_INDETERMINATE, in order to define an infinite HFR acquisition sequence.

The HFR acquisition sequence stops by setting ChannelState=IDLE.

In case of a user break event, the BreakEffect parameter value is irrelevant. The acquisition terminates ALWAYS at a phase —frame— boundary ensuring the integrity of the frame.

The sequence terminates automatically after the acquisition of the specified number of frames. An indefinite acquisition sequence stops when the channel is forced to its inactive state.

Use parameter SeqLength_Fr to specify the total number of frames to be acquired. The sequence will automatically stop after the last acquired frame.

Setting ChannelState parameter to ACTIVE activates the channel and arms the trigger circuit.

The HFR acquisition sequence will effectively start after the first trigger event occurring after channel activation when the first acquisition phase is triggered.

Once the HFR acquisition phase is started, the frame grabber acquires PhaseLength_Fr image frames and stores images data into one surface.

This means that each phase is divided in slices. The interruption rate of the operating system is then divided by the number of slice in a phase.

The HFR acquisition mode allows two methods to stop the sequence: Manual stop and Automatic stop.

If the number of frames to capture is known before starting the sequence and is not higher than 65,535, the automatic stop method can be used to automatically stop the sequence after a predefined number of frames. This variant of HFR acquisition is named Finite HFR acquisition. In this case, the number of frames to be acquired needs to be specified before Channel activation.

If the number of frames is unknown or higher than 65,535, the manual stop method is required. In this case, the parameter SeqLength_Fr should be set to MC_INDETERMINATE, in order to define an infinite SNAPSHOT acquisition sequence.

The HFR acquisition sequence stops by setting ChannelState=IDLE.

In case of a user break event, the BreakEffect parameter value is irrelevant. The acquisition terminates ALWAYS at a phase —frame— boundary ensuring the integrity of the frame.

The sequence terminates automatically after the acquisition of the specified number of frames. An indefinite acquisition sequence stops when the channel is forced to its inactive state.

Use parameter SeqLength_Fr to specify the total number of frames to be acquired. The sequence will automatically stop after the last acquired frame.

● The Elapsed_Fr parameter reports the number of acquired frames in the sequence.
● When the sequence length is defined (SeqLength_Fr≠MC_INDETERMINATE), Remaining_Fr reports the number of remaining frames in the sequence.
● When the sequence contains more than 1 frame (SeqLength_Fr>1), PerSecond_Fr reports the measured average frame rate.