Measuring the Diameter of a Circle

Circle Fitting

Objective

Following this tutorial, you will learn how to use EasyGauge to measure the diameter of a circle in an image.

You'll first load an image for calibration —a dot grid— (step 1), and calibrate the field of view (step 2). Then you'll load the source image for inspection (step 3), and attach a circle fitting gauge (step 4). The inspection is automatically performed (step 5). All measurement results are expressed in physical units..

Measuring the diameter of a circle

Step 1: Load the calibration image

1.

From the main menu, click EasyGauge, then New World Shape.

2.

Keep the default variable name, and click OK.

3.

In the Dot Grid Calibration tab, click the Open icon, and load the image file EasyGauge\Dot Grid 1.tif.

4.

Keep the default variable name for the new image object, and click OK.

Step 2: Calibrate the field of view

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Click Calibrate. From now on, the field of view is calibrated, and all results will be expressed in physical units.

Step 3: Load the source image

1.

From the Gauges tab, click the Open icon, and load the image file EasyGauge\Bracket 6.tif.

2.

Keep the default variable name, and click OK.

Step 4: Attach a circle gauge to the image

1.

In the Gauges tab of the world shape dialog box, right-click the frame shape icon, select New > Circle Gauge from the contextual menu.

2.

Keep the default variable name, and click OK.

3.

The circle location gauge appears on the image. It consists of the following elements:

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A blue ring in which the circle is searched for.

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A blue nominal circle.

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Six white handles, allowing the user to move and rotate the segment.

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A gray arrow, indicating in which direction the segment is traversed.

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Black and white rectangles, indicating which kind of transition are searched for.

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A green arc of circle, indicating the circle found (if any).

4.

Using the handles, drag the circle fitting gauge around the upper bracket hole. Adjust the nominal circle on the hole edge and extend the searching area if necessary.

5.

In the Measurement tab of the circle gauge dialog box, select 'From Begin' from the Choice dropdown list.

Step 5: Perform the inspection

1.

The image is automatically inspected. However, clicking Process in the world shape dialog box will insert the corresponding code into the script window.

2.

Click the Results tab to retrieve the measured diameter. All measurement results are expressed in physical units.