camera selection for screw thread analysis

[Geen]

Hi,

Could you please help me to suggest some cameras, which helps to do the following.

I need to take the image of a screw and compare it with bad screw image, taken using the same Camera. The screw will be presented infront of the Camera using the robot

More specifically I need to analyse the screw threads. The screw length ranges between 1 inch to 4 inch, and the diameter will be 1/4 inch.

Please suggest, what all the things I need to take care before deciding the Camera?

[muks]

Ok here goes my list

1. Consider what is the dimensional tolerance that are permissible to be accepted.

2. What is the resolution of the image required?

 3. Always see how to minimize the wastage of pixels.

4. See how much is the working distance that you can keep. Detemine a suitable lens

5. What is the lighting that you have used? is it uniform? Can it be made uniform? Can it be made consistent?

6. What is the cost you are looking at?

7. How are you planning to trigger the camera?

8. What is the acceptable shutter speed for this application?

9. What is the positional accuracy the robot can offer?

[Geen]

 Thanks for the reply. I am a beginner in the machine Vision world. So please be patient, if I am giving some silly answers. I just started the learning. If I am wrong in something please correct me.

1. Consider what is the dimensional tolerance that are permissible to be accepted.

         I am not sure, of the tolerance level..Please hold this question for a while, I will answer it later

2. What is the resolution of the image required?

           5MP ideally, if could suggest me the best resolution for analysing screw threads, it will be great

3. Always see how to minimize the wastage of pixels.

          Could you please tell me, what does it means. How can I make sure this

4. See how much is the working distance that you can keep. Detemine a suitable lens

              I can ask the robot to place where ever I need, So I am behind cheaper price and high resolution

5. What is the lighting that you have used? is it uniform? Can it be made uniform? Can it be made consistent?

              I can make it uniform  

6. What is the cost you are looking at?

              From cheaper to 1000 USD

7. How are you planning to trigger the camera?

              A software trigger from my program, which controls the robot and the Camera. For the Camera control for the image processing and trigger, I can use  NI Vision build

8. What is the acceptable shutter speed for this application?

            I understood, even that won't be a matter, once the image is taken at one shot, then once it is done,then I will be positioning the screw holder for the next picture, moving to 90 degree, then take the second.then 90 degree, thus I will complete the 360  degree angle. SO i will have 4 pictures of the same screw at these angles.

9. What is the positional accuracy the robot can offer?

 Robot will be placing in a screw holder, and screw holder will be always in same position. If you could forsee some wrong thing then please tell

[Robert_Eastlund]

If the screw will be stationary when the image is acquired, and if you want a 5 MP camera for less than $1000 USD, I would suggest looking at AVT's Guppy F-503B, see

http://www.alliedvisiontec.com/us/products/cameras/firewire/guppy/f-503bc.html

A Guppy F-F03B is approximately $900.00 USD and includes with it a firewire cable.

For lighting, I would suggest a telecentric backlight or collimated backlight, see

http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productid=3026 (select the technical images tab).

and

http://www.advill.com/uploads/products/CBXXYY.pdf

Since the bolts are four inches long, the Advanced Illumination light source is probably more practical for your application.   You will want to mask off any portion of the collimated backlight that is not in use.  You can also use the camera's area of interest function (AOI) to mask off portions of the image that are not in use.

If the presentation of the screw relative to the camera is repeatedly.  You will also to use either a fairly high focal length lens, appropriate for a 5 MP camera.

Best Regards,

Robert Eastlund

www.graftek.com

[muks]

Have a look here too.

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Always see how to minimize the wastage of pixels.

          Could you please tell me, what does it means. How can I make sure this

---

Focusing on the required area alone. If the thread is what is required to be inspected dont focus on the head as well.

 My first and 9th point will determine your repeatability and minimum resolution that can be measured by your system...

[Geen]

Thanks for the reply,

yes, that was a good suggestion, Guppy Camera of AVT.

as an alternative, If I am just moving the screw infront of the camera using Robot and taking the pictures, which camera will be good.

Between,

If I am using Camera's AOI, Can I avaoid the use of the lighting. I felt it is expensive.

[Geen]

The dimensional tolerance is between 0.1mm to 0.2mm

Robot accuracy, there is a chance that, when it picks the screw from the tray, it might not be in a same position(Not always Vertical as expected, it can tilt, because of the gripper action)

I hope, if we identify the good screw image , then we can search for that particular pattern in the bad image, so evenif it tilt, that won't matter.

Please correct if I am wrong.

Please let me know your thought

[muks]

You have to use a uniform illumination for consistency. Did you check the imaging source. AVT is costly (My personal thought).

[Geen]

Could you please tell some other suggestions in your mind for the camera

Imaging source, I though tht will be the screw on top of the gripper, please correct me

[muks]

I meant this

Imaging source