Consecutive Overlapping CIC Cycles

Introduction

This topic illustrates how the user has to set the ExposureRecovery and TargetFramePeriod features when ExposureReadoutOverlap = True to properly configure the CIC to avoid trigger overruns and maximize the cycle rate.

The Coaxlink driver calculates the duration of the Camera Cycle value from the user-defined settings ExposureTime, ExposureRecovery and TargetFramePeriod by searching the smallest value satisfying the following conditions:

● Condition 1: The time interval between consecutive Camera Trigger pulses (r – in the drawings) must be greater or equal to the ExposureRecovery settings. This ensures that the Camera Trigger properly flows through the trigger transmission link. It ensures also that a new exposure doesn't begin before the completion of the previous one.

● Condition 2: The CIC Cycle duration (a in the drawings) must be big enough to ensure that a new readout doesn't begin before the completion of the previous one.

●

Condition 3: The CIC Cycle duration must be big enough to include both transitions of the Camera Trigger and the Strobe Signal.

The "readout-limited" use cases illustrate situations where the cycle period is equal to the duration of the readout phase.

The "exposure-limited" use cases illustrate situations where the cycle period is equal to the duration of the exposure phase.

In the following timing diagrams:

e is the Camera Trigger pulse width. This value is defined by ExposureTime.

d is the Strobe delay. This value is defined by StrobeDelay.

Case 1: Readout Limited (Late Strobe)

The camera cycle rate is only limited by the camera readout time

This situation occurs when e (= Exposure Time) is significantly smaller than the readout duration.

In that situation:

● r is likely larger that ExposureRecovery: Condition 1 is fulfilled.

●

The strobe pulse being "inside" the Camera Trigger pulse: Condition 3 becomes irrelevant when Condition 1 is fulfilled.

●

The Condition 2 is the only condition used by the Coaxlink driver to calculate the cycle duration.

The optimal duration of the Cycle is equal to the effective duration of the sensor readout phase. This is obtained when the user sets TargetFramePeriod to a value corresponding to the readout duration.

Note: The readout duration can be derived from the maximum frame rate specification of the camera data sheet or experimentally.

Case 2: Readout Limited (Early Strobe)

The camera cycle rate is only limited by the camera readout time (despite the early strobe)

This situation is similar to the case 1. It shows that despite a early strobe, it is possible to reach the maximum cycle rate of the camera.

This situation occurs when e (= Exposure Time) is significantly smaller than the readout duration.

In that situation:

● r is likely larger that ExposureRecovery: Condition 1 is fulfilled.

● The strobe pulse being terminating before the Camera Trigger pulse: Condition 3 is fulfilled if r is greater than d. This is the case when (d + e < readout duration).

●

The Condition 2 is the only condition used by the Coaxlink driver to calculate the cycle duration.

Note: The readout duration can be derived from the maximum frame rate specification of the camera data sheet or experimentally.

Case 3: Exposure Limited (Late Strobe)

The camera cycle rate is limited by the exposure time settings

This situation occurs when e (= Exposure Time) is significantly larger than the readout duration.

In that situation:

●

All cycles being identical, having the readout duration smaller than the exposure duration, implies that Condition 2 becomes irrelevant.

●

The strobe pulse being "inside" the Camera Trigger pulse: Condition 3 becomes irrelevant when Condition 1 is fulfilled.

●

The Condition 1 is the only condition used by the Coaxlink driver to calculate the cycle duration .

The optimal duration of the Cycle is equal to the effective duration of the exposure phase. This is obtained when the user sets ExposeRecovery to a value corresponding to the minimal time interval allowed by the camera between consecutive Camera Trigger pulses.

Case 4: Exposure Limited with Early-Strobe

The camera cycle rate is limited by the exposure time settings (despite the early strobe)

This situation is similar to the case 3. It shows that despite an early strobe, it is possible to reach the same cycle rate win case of small negative StrobeDelay values.

This situation occurs when e (= Exposure Time) is significantly larger than the readout duration.

In that situation:

●

All cycles being identical, having the readout duration smaller than the exposure duration,implies that Condition 2 becomes irrelevant.

● The strobe pulse terminating before the Camera Trigger pulse: Condition 3 becomes irrelevant when Condition 1 is fulfilled and d < r.

●

Condition 3 and Condition 1 are the only condition used by the Coaxlink driver to calculate the cycle duration.

The user must set ExposeRecovery to a value corresponding to the largest of of the following two values:

●

Minimal time interval allowed by the camera between consecutive Camera Trigger pulses.

● - StrobeDelay

Note: When CycleTriggerSource = Immediate, the cycle rate can be lowered to the desired rate by assigning a greater value to TargetFramePeriod.