Why I cannot reach the maximum frame rate

[Haifei]

Hi, All,

I am doing visual servo real-time control now. My Camera is Photonfocus MV-D640-66. The maximum frame rate is 200Hz, this is in free running mode; in external trigger mode, the maximum frame rate can reach 100Hz. Now I use the PCI-7831R to generate the trigger signal, which is sent to PCIe-1429 by RTSI Cable. I modified a example to realise this function, the vi is attached. However, the maximum frame rate can only be about 70Hz. Why 100Hz cannot be achieved by this vi? Thank you in advance.

Camera: Photonfocus MV-D640-66
http://www.photonfocus.com/html/eng/products/products.php?prodId=11

Image Grabber: PCIe-1429
Data Acquisition Board: PCI-7831R
Operation System: ETS-RTOS

Regards,
Haifei

[VuD]

Hello Haifei,

I found a KnowledgeBase document that should help explain the behavior you are reporting.  By going to http://www.ni.com and typing in the keywords “expected frame rate”, the following link pops up: Why Am I Not Acquiring Images at the Expected Frame Rate of my Camera?

Under the Triggered Acquisition section, it explains that

“…When the IMAQ board receives an external trigger, it will capture the next valid frame available. In other words, if the camera is in the process of sending an image when the trigger is received, the IMAQ board must wait until the next full frame is available before it can be acquired…unless the IMAQ board receives each trigger at the exact instant when the current acquired frame is complete and immediately before the camera begins to output a new frame, you will only be able to acquire externally triggered images at roughly 1/2 the rate the camera is outputting frames.”

There is more useful information which is given in the KB, specifically regarding asynchronous reset mode settings.  After looking at the manual for the camera, you might also want to examine your exposure time and ROI as both of these features affect your frame rate (page 17 of the user manual from the link you posted).  CPRE and RESET (explained on page 27) are other attributes you might also look at.  Please let us know if you would like further clarification or assistance regarding this issue.

Regards,

Vu D
Applications Engineer

[Haifei]

Thank you very much. That's link does help a lot.

Regards,
Haifei