Manual

Programming Basics and Setup 5-21

Size

The maximum size of the Model Window in FmNT is 256 x 256 pixels (approx. 120 x 120 mils on the

part). Fiducials must be smaller than that in order to be used, unless a portion of the fiducial element can

be used to represent the whole fiducial. Large fiducials take longer to find. However, if the fiducial is

too small, other artifacts or contamination in the Search Window on the workpiece might be

misinterpreted as a fiducial.

Uniqueness

While a fiducial must be a unique feature on the workpiece, it must appear the same on all similar

workpieces. The fiducial includes the feature and the background. This means that the same shape on

two workpieces with different backgrounds will not be identified as the same.

Contrast

The ability to enhance the contrast of the fiducial can be optimized by Vision System parameters.

However, you should choose a fiducial that has good natural contrast from the background.

Figure 5-11 shows good fiducial shape, background, size, and contrast for various model fiducials.

Figure 5-11 Model Fiducials

Metal Dot Fiducial on

Dark Background

Donut Fiducial with

High Contract

Background

Shaped Fiducial

Pattern

Search Windo

Outer Contrast

Ring

Metal Dot Fiducia

Model Window