Calibrate Optics

This option calibrates the optics on the system. PC-DMIS supports five separate calibrations (depending on hardware and the available calibration artifact):

If your zoom cell automatically calibrates, then you won't need to perform a specific magnification calibration. Instead, PC-DMIS displays a message when it completes the calibration process.

To calibrate the optics, follow these steps:

  1. From the list on the Calibrate Probe dialog box, select Calibrate Optics.

  2. Click Calibrate to open the Calibrate Optics dialog box.


Calibrate Optics dialog box

When the calibration procedure starts, DO NOT move the calibration standard.

  1. From the Calibrate area, select the needed options.

Accuracy - There are two methods for calibrating parcentrality/parfocality:

  1. From the Settings area, select the calibration settings:

  1. Click the Calibrate button. The software displays a message box stating that your calibration standard must be clean and aligned with the X axis. You must also ensure that the standard is face up.

Although the calibration processing employs noise and dirt rejection techniques, a dirty calibration standard may trigger calibration failures or yield less accurate measurement values. Be sure to clean any dust, dirt, fingerprints, or other material from the calibration standard's glass portion. Use a mild non-depositing cleaning solution, such as rubbing alcohol, and a soft, lint-free cloth. Be sure to also clean the stage glass where the calibration standard is positioned. For proper cleaning techniques, refer to your hardware documentation. If the stage carrying the glass standard might move during the calibration sequence, hold the standard to the stage with clay or putty.

  1. Place the calibration artifact on the stage so the length of the standard runs along the X axis of the machine. For the ROI slides, ensure that the larger targets are on the left (-X direction) and the smaller targets on the right (+X direction). Verify the alignment with the X axis by watching the horizontal line on the standard while traversing the stage X axis. The line should remain in the field of view and ideally very near center.

  2. Click the OK button. Additional messages appear, requesting that you center the target.

  3. Place a target so that it completely fits within the camera's view. This target should be roughly centered within the FOV and focused. The focus does not need to be optimal, just a good starting place for the software focus process.

  4. Click the OK button. If you have a DCC machine, it automatically focuses on the target. If you have a manual machine, the software displays a prompt for you to focus on the target.

  5. Use the manual controls to move the optical measuring system and roughly center the rectangle or square calibration standard in the FOV. PC-DMIS determines the target size based on your optics.

Do not change the Z position or the focus during the rest of the calibration procedure.

  1. Click OK after you have centered the target. The calibration routine automatically proceeds based on the calibration options you selected:

Pixel Size Calibration

2D lens distortion

Focus Calibration

Camera Rotation Calibration

Target centered on Concentric Circles of HexagonMI Standard

The Calibration Process continues. It focuses and takes a series of measurements at different magnification levels. This process establishes that the optical center and focal depth coincide through the focal range. This means if you focus and measure a circle at one magnification, it gives the same XYZ position at another magnification.

  1. Near the end of calibration, PC-DMIS generates and runs a series of dynamic measurement routines in the background. It does this to perform a basic verification that measures a subset of the calibration data. As the software measures each target in these measurement routines, the Status area on the Calibrate Optics dialog box updates its message to show the step number.

Status Message Showing Pixel Size and Error

  1. There is a pixel size verification which is turned off by default and is controlled by the ProbeQualVisionOpticsCalPixelSizeVerifyEnabled registry entry in the PC-DMIS Settings Editor. If this registry is enabled, then at the end of calibration, PC-DMIS performs a basic verification that measures a subset of the calibration data. As the software measures each target in these measurement routines, the Status area on the Calibrate Optics dialog box updates its message to show the step number.

Verification Complete dialog box

If the Pixel Size Verification dialog box appears, you can click Run Again to re-run the verification. This helps determine if any errors were simply anomalies in the verification. If the verification fails multiple times, try and re-run the entire pixel size calibration. If both the calibration and the verification fail repeatedly, contact Hexagon Technical Support.

Click Continue to accept the results of the verification.

The ProbeCal section of the PC-DMIS Settings Editor contains registry entries that affect the pixel size calibration.

  1. Click the Close button to close the Calibrate Optics dialog box. The software also writes the calibration results to the Calibration Results dialog box so that you can view the results of the calibration later. To view the results, click the Results button on the Probe Utilities dialog box:

Calibration Results dialog box

You have now calibrated the field of view. Repeat this process for each lens you wish to use on the machine.

On a CMM-V camera, you only need to calibrate the FOV for the A0B0 wrist angle. You may wish to place some reflective white paper on the CMM table under the "Calibration Artifact Holder" (Part Num. CALB-0001). The "Calibration Artifact Holder" includes a glass slide (CALB-0002) and a ring gage (CALB-0003). The artifact holder is used for calibration of the CMM-V camera.