### Step 4 – Position Tool Region of Interest to Surround Target

The next step in the calibration process is to ensure that the dots can be extracted correctly. A blob tool is used for this purpose inside the job.

The parameters that can be set from the left-hand panel are:

- Min Blob – Set this value to be large enough that small objects are ignored;
- Max Blob – Set this value small enough that large objects are ignored;
- Dark Blobs or Light Blobs – The example above shows dark blobs on a light background.

The buttons are:

- Test – Runs the blob step with the current parameters;
- Take Picture – Refreshes the camera image;
- Save Image… – Allows you to save the image to disk for future reference;
- Show Advanced… – Shows the blob step datums to the right of the image. Can be useful if there is other clutter in the image.

Note that you can zoom in on the image using the mouse scroll wheel if you need to verify that the correct objects are being recognized. In the image below you can clearly see the blob outlines being correctly identified.

The number of parts shown below the buffer is also useful. In this case we know that we are looking at a 15 x 15-dot grid. That means that there should be 225 objects found, and that is confirmed by the data for NumParts. (NumBlobs also includes holes, so in the example below there is one extra blob counted for the light hole inside the central dot).

If the lighting is uneven, it may not be possible to adjust the blob tool correctly and you will need to fix the illumination.

Proceed to the next step.