width and height of ROI

[co2junkie_]

How can I change the Width and Height of ROI ? Im attaching the VI it does the edge detection.. please help

Thankyou

[co2junkie_]

I tried to programattically set the ROI but Attributes are not supported by my camera, is there anyway around it?

Please Help 

[ChristopheC]

For defining image processing region of interest, try the VI IMAQ Convert Rectangle to ROI. The ROI conversion VIs located in the palette Vision and Motion>>Vision Utilities>>Region of Interest>>Region of Interest Conversion are easier to use to build ROIs rather than trying to work directly on the more complex ROI descriptor.

I'm a little confused by your second posting. If you're trying to modify the acquisition area, this can be done by changing the acquisition attributes (width and height), using a property node, if you're using IMAQdx. While some attributes can be changed on the fly (gain, exposure), for some others, like the width and height, you need to stop the acquisition first, change the attribute and restart it again.

Christophe

[alexandresantos]

Hello friend

I would to know if possible get a accuracy of 1mm using NI Vision.

I am taking width measurement from a steel strip under movement which it could be from 750 to 1900mm width.

I am researching a camera from Basler or Ximea. Advices about the best camera will be welcome.

Thanks,

Alexandre

[BruceAmmons]

Yes, you can measure down to 1 mm easily.  The best camera would probably be a line camera, if that is the only measurement you need.

Bruce

[alexandresantos]

Hello Mr. Bruce

Thanks for your message.

Could you suggest a brand or a model camera and lens for our application. Do you have any literature about this subject (explaining how to select a camera, lens and ilumination).

Thanks in advance,

Alexandre.

[BruceAmmons]

I can only point you to the experts I talk to when I need to select equipment.  Talk to Graftek Imaging and they can help you pick out all your equipment.

Bruce

[Emily-C]

Hi Alexandre,

You can absolutely measure down to 1mm with NI Vision! The smallest feature you can see is going to be determined by your camera resolution and lens. You can find more information on choosing a camera on our Camera Network. Under Using Cameras there are links to documents that go over choosing the right camera bus for your application, and calculating camera sensor resolution and lens focal length. You can work back from your "smallest feature" measurement to work out what sort of resolution and lens would be right for your application. 

If this is your first time setting up a vision system, talking to Graftek would also be a great idea for more information. 

I hope this helps!

[alexandresantos]

Hi friend

Thanks for your comment.

Yes it is my first time working with machine vision.

I have some doubts. If there is somebody that can help me:

1-Was recomended by Graftek the line scan camera (raL4096-24gm Basler). I want know how it will work in NI Vision using a measure distance tool, because this camera has only one line horizontal (1 pixel)

2-For GigE camera can I use 100 meter cable between the camera and computer?

3-Why was recommended a red lighting? Is there a reason for the color red?

4-I want to understand better about velocity. Was reccomended a 24kHz camera. For my project the object is under movement in 200m/s. How many meters it can per second?

Thanks in advance.

[BruceAmmons]

The line camera takes pictures of a single line over and over again as the object moves underneath it.  You can build up an image of the object by stacking the lines in a larger image.  If the line of the camera goes straight across the material being measured, you can measure the width with every line.

Yes, you can use a 100 meter cable with a GigE camera.

Red lighting is just the most convenient.  Red is the easiest color to generate, and can easily be filtered to eliminate other light frequencies.  Using colored lighting helps increase the contrast between the lighted areas and the background.

Your image indicates a max speed of 180 m/min, which would be 3 m/sec.  If the camera acquires each line at 24 kHz, that is 24000 lines/sec.  Divide the two to get 8000 lines/m, or 8 lines/mm.  If your computer can keep up, you could make a measurement every 0.125 mm of your material.  That probably isn't practical, but you should be able to make the measurements at the rate you need.

Almost forgot, the width is 1900 mm.  With 4096 pixels wide, you get just over two pixels per mm.  That means your measurements should be accurate to the nearest mm.

Bruce