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Object Count & Frame Rate

by oytunkurt » Mon Apr 30, 2018 5:03 am

Hello,

I have a basic application for detecting laser dots with Flex13 camera. I am using it in object mode and getting only the object coordinates. Camera is working at 240 fps which is the maximum value for that camera. Camera looks to the projection screen. Ambient lighting is dimmed to minimum.

I illuminate the projection screen for 40ms with a steady red laser however I get only 2 objects although there must be 9 frames captured within that time period.

Is this because the object mode requires to analyze more than one frame for each object detection? Or is it for something else?

Is object detection runs for every and each frame and detects only the objects within that frame?

Regards,
oytunkurt
 
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by steven.andrews » Mon Apr 30, 2018 10:48 am

Hello oytunkurt,

When running in Object Mode, the cameras should provide data for the light source on each frame. When you say you receive two objects, are these two objects on a single frame? Or two separate frames each with one object?

Typically, you would need to query each frame for the object data or setup a callback.

Cheers,
Steven
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by oytunkurt » Tue May 01, 2018 9:09 pm

Hello Steven,

I get two different frames with a single object. Moreover I am pretty sure that the application empties the frame buffer on the camera (done by getframe() within a while loop).

Since the light source (laser) is constant and the camera determines objects for at least two frames I don't think there is a thresholding problem. But I understand from your explanation that I should receive 9 frames with a single object.

Any ideas?

Regards,
oytunkurt
 
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by steven.andrews » Wed May 02, 2018 12:31 pm

Hi oytunkurt,

Not sure what could be preventing the laser from returning an object on all except for 2 of the frames. Every frame is treated individually and reporting of objects for a given frame does not depend on the previous frame data.

Are we certain the laser is a continuous illumination and does not have some frequency?

It sounds like the laser is visible to the camera, but you can easily check this by putting the camera in a scene mode to view what the camera is actually seeing. The brightest pixels do need to be above the camera Threshold setting for the laser dot location to be returned as a single centroid object. If the light is just on the Threshold, it may have moments where it is and then is not bright enough to result in a centroid object.

You might try increasing the Exposure and decreasing the Threshold on the camera to see if this gives more solid results.

Best,
Steven
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by oytunkurt » Tue May 15, 2018 4:13 am

Hi Steven,

Actually there were some frames lost and after SetSendEmptyFrames(False) method is called no more frame losses. Everything works fine with a steady laser.

However when the laser starts to move rapidly (like a pistol blowback action) the object detection on the camera fails. The laser basically draws a line in this situation and the camera detects objects wandering over this line (start, middle or end of the line). No steady detection can be done. IR filter is activated, exposure is set to 9600 and threshold is set to 60 during the above test (I have tried other values for exposure and threshold but only the extreme ones are noted).

Do you agree that the object mode may fail at a case described above?
If yes do you have any ideas to try? Is it good to try different camera modes? Which one do you suggest? What should be the key parameter to look for in that suggested camera mode to detect a moving laser? First laser hit point is enough for my application, I do not care what shape the laser draws after the first impact point.

Regards,
oytunkurt
 
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by steven.andrews » Tue May 15, 2018 10:57 am

Hi oytunkurt,

If the laser is moving very quickly and the camera is using a high exposure, I suppose it is possible there may be some motion blur on the laser which prevents it from being detected as a circular object. If, indeed, the laser moves fast enough that it is seen as a line rather than a dot, this probably would not come through in Object Mode. You can try using Precision mode to get more information about the light that is being detected to see if the laser is becoming a non-circular object.

I also wonder if, in the movement, perhaps the light from the laser becomes dimmer and is not above the threshold. Though I more suspect the laser is not being seen as just a clean circle during the movement.

Steven
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by oytunkurt » Tue May 15, 2018 10:36 pm

Hello Steven,

I will try the precision mode as soon as possible. In the meantime would you please provide me information about the data structure and available functions for this mode? Do you have a documentation about this information? Even a draft one will help a lot.

Regards,
oytunkurt
 
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