CVS-1456 Image Distortion

[S_RAGHURAMAN]

Hi,

I am using CVS-1456 to acquire image from a FLIR A20M Infrared camera. I am using the latest IMAQ-1394 drivers, MAX, and LabVIEW 8.2.

I am using the raw-data mode (16-bit) for the FLIR camera which is also called "Format 7, Mode 0. 320x240, 60/50 Hz, 16-bit monochrome".

The 16-bit image represents temperature data at each pixel. I then scale the 16-bit temperature data to 8-bit data so that i can create an 8-bit image that i can use with the Vision processing functions.

What i find is that during several periods of time the images are corrupted, but are still collected and displayed. In these cases, the image appears to be shifted to the right and the far right part of the picture is wrapped around to the left side, or in some cases, the image appears shifted to the left. There appears to be a part of the image with vertical lines.  I have attached two images demonstrating this phenomenon below.

In some cases, the problem has corrected itself and I have only discovered it when reviewing the data. In one case, it was still displaying the corrupt image. I then restarted the CVS without restarting the camera. The image then returned to normal. This problem appears to occur about every 2 to 4 days. It then continues for several hours or up to 24 hours before correcting itself or until the CVS is restarted.

Can you please help with this issue?

Thanks

--Sundaram Raghuraman

[Jasper S]

Hello Sundaram,

This definately sounds like a strange issue, especially because the images return to an uncorrupted state after an uncertain amount of time. 

You said that you are using the latest version of the IMAQ 1394 driver.  Are you referring to the latest version of the legacy 1394 driver or the IMAQdx driver?

And would it be possible for you to post an uncorrupted image that you are acquiring on the CVS?

Regards,

Jasper S

[S_RAGHURAMAN]

Yes, I am using the Legacy IMAQ driver, not the IMAQdx.

Enclosed is a "good" reference image when there is no distortion.

[Jasper S]

Hello Sundaram,

It seems that you may be experiencing some packet loss.  This could be due to a number of issues, most notably a poor connection.  Have you verified that the cabling is good?  Are you using a shielded cable?

Also, does this happen at other resolutions as well?  In MAX, try setting the packet size to twice the image width (since you are using two bytes per pixel).

After you have explored these options, we can also look at the driver.  I would recommend trying this application with the IMAQdx driver instead of legacy 1394.  It is our currently supported driver for firewire connections. 

Regards,

Jasper S

[S_RAGHURAMAN]

Hi Jasper

Thanks for your response.

I am using a standard firewire cable (about 4 ft) long along with a 14ft Firewire repeater cable.  I need the cable length to be atleast 17 feet long, so just a 14ft cable won't be enough. Could this be the problem?

Having said that, I remember seeing the distorted image even when i was using just the 4ft cable. It is hard to reproduce the problem -- it could appear in 5 minutes or it might take 3 days.

Will re-initializing the IMAQ acquisition periodically help? (for example, re-initialize every hour).

Regarding IMAQdx, i tried that but could not use it because the Format 7, Mode 0 options were not configurable the way I wanted (the controls were disabled/grayed out) -- iI was only able to set these options correctly in the Traditional IMAQ driver. Without these options set correctly, i was not getting the data from FLIR camera correctly.

[BlueCheese]

Hi Sundaram,

Sorry to change the topic from your original problem, but would you mind elaborating on the problems configuring the Format 7 Mode 0 options (maybe a screenshot) with IMAQdx? The new driver should support everything the legacy driver did (and more), so if there's some capability that appears to be missing we would like to know about it.

Thanks,
Eric G

[S_RAGHURAMAN]

Eric

In IMAQdx, the fields "Actual Bit Depth", "Bit Alignment" and "Byte Order" were disabled. I remember that i had to set either the "Bit Alignment " or the "Byte Order" to a non-default value in Traditional IMAQ, so since these fields were disabled, i could not use IMAQdx.

Raghu

[BlueCheese]

Hi Raghu,

I believe the issue you saw with the 16-bit fields being disabled in MAX on an RT target is a known issue in 3.0 (assigned an internal ID of 44K8TNG1). It is actually just a problem with that particular panel in MAX, but you can still easily access it in the "Camera Attributes" tab if you select the "Show All Attributes" button above the tree view. The ones you are looking for are under "Acquisition Attributes" and are "BitsPerPixel", "ShiftPixelBytes", and "SwapPixelBytes". This issue with the other tab will be fixed in our next release.

I'd encourage you to try going back to IMAXdx for your development so you can take advantage of new features and continued support in the future. That said, I do not believe this will solve your original problem of corrupted images. There is not much on the driver's side that would cause random corruption of the image in that manner, so it is much more likely a hardware problem. Most likely you are losing packets on the bus and this causes the frames to get distorted. My initial suspicion would be the repeater, but you said you still saw the problem with just a single cable. Have you tried replacing your firewire cables? I suppose another easy idea could be to try swapping out firewire cards on your host PC and see if that helps.

Please let us know if you continue having troubles.
-Eric G

[JohannS]

Sundaram

I understand that you need your CVS 17 ft away from the camera, but in my experience the 14ft repeaters can cause intermittent and inexplicable problems. My recommendation to you problem is to find a way to move the camera and CVS closer together and use a single direct cable connection.

If it is not possible to move your camera and CVS closer, then you should consider a single direct cable connection with good shielding. Although the FireWire standard recommends 4.5m cables as the maximum length for a single cable, AVT sells a good 10m cable for industrial applications.

As a final recommendation, make sure your CVS is properly grounded. If you have sporadic voltages coming through the CVS housing, it could cause problems.

Hope this helps,

Johann