This section describes how to calibrate an imaging setup so that you can convert pixel coordinates to real-world coordinates. Converting pixel coordinates to real-world coordinates is useful when you need to make accurate measurements from inspection images using real-world units.

Introduction

Spatial calibration is the process of computing pixel to real-world unit transformations while accounting for many errors inherent to the imaging setup. Calibrating your imaging setup is important when you need to make accurate measurements in real-world units.

An image contains information in the form of pixels. Spatial calibration allows you to translate a measurement from pixel units into another unit, such as inches or centimeters. This conversion is easy if you know a conversion ratio between pixels and real-world units. For example, if one pixel equals one inch, a length measurement of 10 pixels equals 10 inches.

This conversion may not be straightforward because perspective projection and lens distortion affect the measurement in pixels. Calibration accounts for possible errors by constructing mappings that you can use to convert between pixel and real world units. You also can use the calibration information to correct perspective or nonlinear distortion errors for image display and shape measurements.

Vision calibration software supports area scan cameras using rectilinear or telecentric lenses. Vision calibration software may not accurately calibrate true fisheye or curvilinear lenses.