Conventional Metrology Research Articles

Pseudophase information from the complex analytic signal of speckle fields and its applications Part I: Microdisplacement observation based on phase-only correlation in the signal domain

As an alternative to the intensity correlation used in conventional speckle metrology, we propose a new technique for displacement observation that is based on spatial-signal-domain phase-only correlation and that makes use of the pseudophase of the complex analytic signal generated from a Hilbert-filtered speckle pattern. Experimental results are presented that demonstrate the validity and the advantage of the proposed signal-domain phase-only correlation technique over both the conventional intensity correlation technique and the spatial-frequency-domain phase-only correlation technique.

Phase singularities in analytic signal of white-light speckle pattern with application to micro-displacement measurement

Rather than regarding the phase singularities as obstacles or nuisances in phase unwrapping, we explore new possibilities of making use of the phase singularities in optical metrology. Instead of intensity correlation techniques used in conventional speckle metrology, we propose a new technique of displacement measurement that makes use of the density of phase singularities in the complex analytic signal of the speckle pattern, which is generated by Hilbert filtering. Experimental results and theoretical analysis are presented that demonstrate the validity of the proposed technique.

Analytical chemistry at the interface between metrology and problem solving

The constant need to harmonize theory and practice in analytical chemistry requires the continued evolution of metrology in chemistry. In this contribution, we highlight conflicts that arise from the diverging foci of conventional metrology and analytical problem solving and put them into context with the role of analytical chemistry as a scientific discipline that is embedded in society and is producing (bio)chemical information. We suggest strategies that allow harmonization of the intrinsic and the extrinsic aspects of analytical chemistry that are seen in metrology and analytical problem solving, respectively. Facing the constraints of analytical measurements, which may result from limitation in time, financial or instrumental resources among others, we propose to define quality compromises in each situation where analytical information is required. Based on the adapted quality compromises, there is a need to adopt intrinsic and extrinsic aspects of the analytical process under investigation. This undertaking aims to assure high integral quality of analytical results in a given context.

In-process drilled hole inspection for aerospace applications

The principles of operation and comprehensive testing of a prototype system for high speed in-process inspection of drilled holes in aerospace applications are described. The system measures both the general geometry of the hole (diameter, roundness, taper etc.) and the profile of the surface finish. The proposed system, based on the use of fringe-field capacitive sensors, is rapid and sufficiently rugged for in-process monitoring. Principles of analysis and design of the sensor system are presented within the context of aerospace inspection requirements. Experimental results include the direct comparison of the system with conventional metrology techniques.