Trigger CCD camera at certain frequency

[Jun9]

Hi,

We are trying to trigger a CCD camera for capturing image at certain frequency. Our hardware setting is as follow: we have NI PCI-6281 DAQ card installed on the computer. It connects to BNC-2110 box. The trigger output PFI 12/P2.4 on BNC-2110 was connected to a CCD camera through a 12-Pin Hirose female to BNC cable.

To test whether the triggered image capture works properly. We used Gen Dig Pulse.vi and Triggered Grab.vi. The triggered image capture did work, but it does not work at the desired frequency set by us. I assume the frequency is (1/(high time + low time)). Any suggestion?

Thanks.

[mikeporter]

First of all, what is the frequency of the clock you are generating? And what is the rate at which images are being captured?

It would also be helpful to see the code.

Mike...

[Jun9]

Hi Mike,

Right now I'm just testing whether the image capture is at the frequency I set. For example, when I set high time = 0.5 s and low time = 0.5 s in Gen_Dig_Pulse.vi, I expect the image capture frequency is 1 frame/s, cause 1/(0.5+0.5)=1Hz. But it actually  captures image at 2 frames/s. It appears that the frequency = 1/hight time, since changing the low time value does not affect anything.

Thanks.

Jun

[mikeporter]

This answer doesn't make sense. If what you say is true, the camera isn't really synchronized with the clock.

What happens if you set the off time to a very long time like 20.2 seconds. Do you see a new image every 20.7 seconds, do you see two images captured close together then a long gap before the next 2?

Mike...

[Jun9]

Yeah, it doesn't make sense. I don't think the camera is the problem. I did some test to check the trigger signal generated by Gen_Dig_Pulse.vi by using Acq&Graph Voltage-Int Clk.vi to see the signal. I saw a clear squared periodic signal (which is what's supposed to see) at the frequency decided by only the high time value in Gen_Dig_Pulse.vi settings. I kept the high time value the same and changed the low time value to up to 10s, it didn't affect anyting. The periodic squared signal shows up at constant frequency as set by the high time.

[mikeporter]

Well, I don't know why that is happening, but at least makes sense. Is there any sort of setting for selecting symmetrical vs nonsymetrical clock trains?

Mike...