Peak detection of a surface - laser spot tracking

[kamal1987]

Hey I’m doing the same project here …. I did acquire the image and all I know that I should make it in gray scale so it could be easier in processing and then I should transform the image into a matrix and then bring the centroid of the matrix and when the spot of the laser is not in the center of the camera’s view the labview should send a signal to my stepper motors to make it in the center again. Any suggestions how I can continue or from where shell I start and if someone has any document about this project could he send it urgently. 
Thanks

[OliviaC]

Hi,

If you search NI you'll find this KnowledgeBase the explains how to convert a colored image to a grayscale. Depending on how accurate you want it to be, to find where the laser spot is, you can use Root Canal's suggestion earlier in the post. 

[Peter Johns]

Root Canal,

 can you please upload a sample VI. I am using the IMAQdx Grab.vi example to obtain video from firewire CCD camera. I tried to follow the steps above but didnt succeed. I would like to read the peak position on the fly.

 Many Thanks

[Joe D.]

Hi Peter,

This forum is rather old what exactly are you looking for? What appears to be the issue?

[Peter Johns]

I would like to have a VI which uses IMAQdx FireWire cameras aquisition which alows me to define the ROI and lets me track a laser beam which is pointed at a CCD. And most importantly  with integrating(exposure) time scroll.

 If I can get one this will be great help for me.

[Joe D.]

Hi Peter,

You should just be able to use Vision Assistant to threshold and calculate the centroid of the laser.As for the time integrating time scroll you can place the data in an array and use that.

Please let me know if there is anything else I can do to help.

[A.Low]

---

@root Canal wrote:

You may want to try using a more conventional approach:

Use an automatic threshold function like IMAQ AutoBThreshold 2 to find a good threshold value.

Generate an image mask using this threshold value; you could use IMAQ Threshold for this purpose.

Find the pixel value weighted centroid of the non-masked portion of the image; you can use IMAQ Centroid for this.

as long as the threshold is calculated properly, the energy weighted centroid of the non-masked portion of the image should give you the center coordinates of the beam, even with a non-symmetric beam distribution.

---

Sorry to bump an old thread, but I'm trying to do peak detection of a bright spot in an image.

I managed to use Vision Assistant to do this by grabbing an image, setting the threshold and finding the centroid.

However, what if i have multiple bright spots and i need the centroids of all of them? What technique should i use?

I have tried adding an additional centroid in the Vision Assistant but both output are the same.

Thanks in advance.

[Greg-H]

Hi,

Here I just created a black image with 4 white circles in Paint (I think this simulates the hot spots you are talking about).

In Vision Assistant I used the following steps:

Acquire the Image

Color Threshold (min: 0, max: 50 for RGB)

Binary Image Inversion

Circle Detection 1

This found all 4 "hot spots" and returned the x,y coordinates of the centroids.  

Hope this helps.

Regards,

Greg H.

[A.Low]

---

@Greg-H wrote:

Hi,

Here I just created a black image with 4 white circles in Paint (I think this simulates the hot spots you are talking about).

In Vision Assistant I used the following steps:

Acquire the Image

Color Threshold (min: 0, max: 50 for RGB)

Binary Image Inversion

Circle Detection 1

This found all 4 "hot spots" and returned the x,y coordinates of the centroids.  

Hope this helps.

Regards,

Greg H.

---

Hi,

I am unable to find "Binary Image Inversion". Where can this VI be found?

I have Vision Development Module by the way.

[Greg-H]

Hi,

Oh sorry I thought from your original post you were using Vision Assistant.

Try the attached example.

Regards,

Greg H.