How to acheive repeatability in measurement accurately using pattern matching

[VPM]

Hi, I am working on project where i want to measure dimensions of some parts within 40 micron accuracy.

I used 8 mega pixel camera and my area of image is 60 mm x 60 mm.

I have devloped software in which i am searching template in area and locating object and doing my measurements.but the problem is

when i am measuring dimension of any object repetadely i am not getting same dimension.i am getting error of 2 to 3 pixels for the same measurement.

Can somebody help me?

[BruceAmmons]

When you set up pattern matching, did you use sub-pixel accuracy?  That can frequently improve the accuracy.

Bruce

[VPM]

Thanks but i tried it still i am getting 2 to 3 pixel error when i am shifting my object in my inspection area.

[BruceAmmons]

Can you post a picture so we can see what you are trying to locate?  That may help.

Bruce