Indirect optical geometry measurement

Introduction

Optical metrology is driving our society forward and has strong impacts on manufacturing, mobility, medicine, and fundamental science. This is highlighted by the SI revision in 2019 and the Nobel Prize-winning microscopy with visible light in the nanometre range in 2014.

Importance of Optical Techniques

Optical techniques allow fast and precise geometry measurements, but only if sufficient light energy is reflected from the object’s surface to the photo detection unit. For this reason, specific measurement approaches for each surface type had to be developed, such as deflectometry for highly reflective surfaces.

Paradigm Shift in Measurement Approach

To provide one single measurement approach applicable to any surface and with the potential of sub-micrometre resolution, InOGeM will initiate a paradigm shift:

1. Instead of measuring the object’s surface, the geometry of the surrounding gas is measured.
2. The surrounding gas is detected optically by using tiny, well-controlled, fluorescent particles or molecules, a confocal microscope, and model-based signal processing, which enables sub-micrometre resolution.

This will break new ground for assessing additively manufactured parts and lightweight components made of fibre-reinforced composites, because the indirect measurement is less sensitive regarding the varying optical properties of the measurement object’s surface and material.

Capabilities of Indirect Measurements

Furthermore, indirect optical geometry measurements are possible at strongly curved or translucent objects, even through limited access, which is currently considered impossible. Such challenging conditions occur, for example, for gears and additively manufactured parts.

As a result, InOGeM has a large potential for:

• Low-noise gears (e-mobility)
• Fuel cells (hydrogen)

Conclusion

As a result, fast geometry measurements with a currently unachievable precision below classical limits are achieved in the nanometre range for a wide range of applications. By developing the framework of a new class of measuring instruments, InOGeM takes the field of optical geometry measurements to the next level.