# Fraunhofer Tests Digital Holography as a New CMM Measurement Sensor

https://cncoutlook.com/news/fraunhofer-holography-coordinate-measuring-machine/

By CNC Outlook Editorial · 2026-07-31

Integrating digital holography into a coordinate measuring machine broadens optical surface measurement possibilities but needs feature-level uncertainty validation.

[Fraunhofer IPM](<https://metrology.news/world-first-combines-digital-holography-with-coordinate-measuring-machines/>)'s digital-holography experiment places an optical sensor inside a coordinate measuring machine. The research question is precise: can fine surface information be acquired in the same machine coordinate system used for other dimensional checks?

Digital holography uses interference information from coherent light to reconstruct surface shape. Unlike a conventional image, the captured optical phase carries depth-related information that can be processed into geometry. This can be attractive for recording fine surface changes over an area, though practical measurement is affected by surface reflectivity, vibration and the chosen optical configuration.

Digital holography can offer fine vertical sensitivity because depth is reconstructed from optical phase information. At the same time, phase measurements may be affected by environmental disturbance, speckle and limitations associated with particular surfaces. Integrating the method with a CMM could allow a user to position the sensor precisely, but the machine must maintain a stable reference while the optical data is acquired. The achievable result therefore depends on the combined instrument and measurement procedure.

## A sensitive optical measurement inside a moving CMM

Putting such a sensor on a CMM is a system-level change. It means the sensor's local coordinates must be related to the machine's measurement coordinate frame. Errors in that relationship can undermine the apparent precision of the surface data, even when the sensor itself has excellent laboratory performance.

The development is best understood as research rather than an announcement that holography has replaced established tactile measurement. A tactile CMM may remain preferable for certain accessible features, datum definitions or surface conditions. The value of an optical method comes when it provides information that is difficult or slow to acquire with the incumbent process. A factory seeking to adopt the technique would need an uncertainty budget covering sensor calibration, machine positioning, optical reconstruction and the material being measured. A demonstration on a clean reference surface does not establish equivalent performance on a milled steel part with directional texture or on a reflective aluminum component. Research of this kind is valuable because it expands the options available to metrologists, but adoption requires a documented comparison with qualified measurement methods on specific features.

## What industrial qualification would require

For CNC manufacturers, interesting potential applications include assessing local topography and geometric deviations on finished surfaces. But a comparison should use a defined feature and tolerance, not just an image showing a detailed surface reconstruction. Published uncertainty, measurement repeatability and behaviour across relevant material finishes are necessary before the result can support an acceptance decision.

A further requirement is software integration. The CMM's inspection program must coordinate sensor movement, establish a reference system and convert reconstructed geometry into measurable characteristics. If the information cannot be linked to drawings and reports, a high-resolution sensor may produce more data without improving process control.

For CNC metrology teams, the useful outcome of this work will be an uncertainty statement on real machined surfaces and a procedure that links holographic data to the CMM's datum framework. Until those are demonstrated for an application, this remains a promising research integration rather than a production-qualified replacement for established probes.

## Sources & References

- [Fraunhofer Integrates Digital Holographic Sensor into a CMM](<https://metrology.news/world-first-combines-digital-holography-with-coordinate-measuring-machines/>) — Metrology and Quality News (2026-07-31T12:00:00Z)

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