Allied Vision Technologies MF-145B2 Instruction Manual download pdf (Page 63)

Controlling image capture

MARLIN Technical Manua

Page 55

9 Controlling image capture

The cameras support the SHUTTER_MODES specified in IIDC V1.3. For all CCD-models this shutter

is a global shutter; meaning that all pixels are exposed to the light at the same moment and for

the same time span.

In continuous modes the shutter is opened shortly before the vertical reset happens, thus acting

in a frame-synchronous way.

Combined with an external trigger, it becomes asynchronous in the sense that it occurs whenever

the external trigger occurs. Individual images are recorded when an external trigger impulse is

present. This ensures that even fast moving objects can be grabbed with minimal image blur.

The external trigger is fed as a TTL signal through Pin 4 of the HiRose connector.

For CMOS sensors, a global shutter is not common. Therefore a rolling curtain shutter is used to

shorten the exposure or integration time. The curtain’s width defines the integration time and

the curtain sweeps with the frame readout time over the image. Although this is appropriate for

still images, image distortion will be created with moving objects, because the upper image part

is scanned earlier than the lower image part.

The MF-131 features both rolling curtain and global shutter. By default, global shutter is used.

A side effect of global shutter is that the integration or shutter time is added to the readout

time, thus affecting the frame rates to be achieved.

The cameras support Trigger_Mode_0 and Trigger_Mode_1.

Trigger_Mode_0 sets the shutter time according to the value set in the shutter (or extended

shutter) register. Trigger_Mode_1 sets the shutter time according to the active low time of the

pulse applied (or active high time in the case of an inverting input).

Figure 36: Trigger_modes

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Allied Vision Technologies MF-145B2 Instruction Manual Page 63