How to do detection of pulsating light (eg torch light)

[SriSwathi]

Hi all,

I am trying a application where i need to do intensity based object detection. The inputs provided for the algorithm are threshold intensity, object size(minimum 3 to 100 pixels) and  pulsating (that is torch light is on in one frame and off in next frame). 

I have already tried imaq threshold, particle filter and particle analysis to perform detection and draw bounding box for the detected object. But my problem is how to extend this algorithm for marking bounding box for only pulsating (blinking) light object.

I have thought of frame differencing but i dont know the way to do it in labview and i am worried of the lag in the output video.

So kindly help me out with better idea to achieve it.

with regards,

Sri

[Klemen]

Hello,

can you explain a little bit more about the problem. Is the camera fixed? Are the lights moving from one frame to another?

If I understand correctly, there are multiple lights, but only one is blinking? Does the blinking light move while blinking and other lights are stationary?

The lag from one iteration to another depends upon camera framerate. So frame subtraction is possible (an variation of background subtraction method). You would probably need to know what is the frequency of the pulses to pick the appropriate framerate. Too slow or too fast and you probably won't be able to detect the intensity change.

Best regards,

K

[SriSwathi]

Hello,

i am using cameralink camera from basler. Actually there are multiple stationary lights  (static in position) and only one light is blinking from frame to frame. The blinking light is not moving  from frame to frame, but it is just on in one frame and off in next frame.

Hope this helps you to understand better.

with regards,

sri

[Klemen]

Hello,

in this case you could try the following:

1. take a reference image when all stationary lights are ON and the blinking light is OFF,

2. in every frame, subtract the reference frame from the current frame,

3. threshold the image,

4. (do some morphological operations to filter out the noisy pixels, e.g. erosion),

5. if the blinking light is on, the thresholded image should show a distinct region that is the result of image subtraction.

Anyway, if your blinking light is stationary, why not thresholding only in the region of the blinking light? You could select the region of interest once at the beginning or is this not a possibility?

Best regards,

K