reading text from plastic using vision builder OCR

[lightgoal]

Hello, I'm just trying  to read some text from a red color plastic using OCR of vision buider ai 3.6. the text is made by a hot metal. I'm using a 640*480 camera for a field of view of about 8*6cm with a distance of about10cm, so I think the resolution is good enough. but the problem is that the recieved data from each character is not very well the same in picture to picture and also sometimes it's more like another character in the text. for example the text 'E' maybe read as '8'. also the machine which makes these character in these plastic is flexible, we can make it push harder. but any way it makes a little of bad effects arround each character when it pushes too hard, and it's normal working is not very well clean at character edges. for more detail I attach a picture of it to this message.

so I think I need some advices, maybe about the illumination which I'm not so good at it in this case or any thing else,Thank you.

http://w15.easy-share.com/1903341066.html

[Kristen_K.]

Hi lightgoal,

Thanks for posting to the National Instruments discussion forums!  There is a really extensive and helpful Developer Zone Tutorial about illumination titled A Practical Guide to Machine Vision Lighting.  Here’s is the link: http://zone.ni.com/devzone/cda/tut/p/id/6901

Also, you may consider using the OCR VIs in the Vision Development Module. Here’s a link to an example program that is available in the NI Developer Zone: http://zone.ni.com/devzone/cda/epd/p/id/5575 
The OCR Training Interface has training capabilities that would help with your ‘E’ and ‘8’ confusion issue.  I hope this helps!

Kristen H.

[Robert_Eastlund]

I would suggest either a collimated on axis (coaxial) or darkfield (a low angle ring) illumination see http://www.ccs-inc.co.jp/cgi-bin/hp.cgi?menu=104-105e.  Since the dimensions of the part are 8x6 cm and the camera is only 10 cm distance, I would probably try the low angle ring first.  Are there any constraints on how close the light source can be to the part?

If you would like, send a few samples of the part to me for testing.  My address can be located at http://www.graftek.com/contact.htm.

-Robert