# Calibrate Functions

Calibration is the process of converting pixel measurements into meaningful, real-world values. In this process, a two-dimensional (2D) transformation mathematically maps points from pixel coordinates of an image to real-world coordinates. Once an image has been calibrated, other vision tools can then reference the calibration as an input, and report the results in the calibrated (real-world) units.

Note:

- When using a Calibrate function Functions are tools that are available in Spreadsheet for processing and analyzing acquisitions or other results. You can add functions to your Spreadsheet job to create tool chains and produce results for specific applications., the physical and optical set-up (the lens, sensor and the physical relationship between the sensor and the scene being acquired) must be the same for both the calibration and run-time operation. If any of these items is altered, the system must be re-calibrated. Therefore, it is recommended that the same sensor and lens be used to both calibrate and process the run-time images. The sensor and lens must also retain their original set-up and calibration settings. For example, changing the acquisition Acquisition is the process or result of the vision system acquiring a new image. format (by altering the resolution) or moving the sensor invalidates the computed 2D transformation that maps pixel to real-world coordinates.
- The output of any vision tool that reports in real-world coordinates cannot be used as a fixture A fixture is a coordinate location on the image that keeps the tool in the place determined by the fixture. or region input to another vision tool.