Results of the application of wavelet transform for signal processing in white-light interferometry are reported. The mother wavelet frequency is chosen to be the light-source correlogram 1’s, and accurate phase measurements are obtained from simple correlation computations. The fringe envelope is also addressed and permits a complete analysis of coherence-limited fringe patterns. Miscalibrations of phase shift and mean wavelength are also considered.

We report a simple method for generating microaxicons at the extremity of commercial optical fibers. The proposed solution, based on a polishing technique, can readily produce any desired microaxicon cone angle and is independent of the nature of the fiber. An optical study of microaxicon performance, in terms of confinement ability and length of the generated Bessel-like beams, is presented as a function of the microaxicon angle. This study, made possible by the experimental acquisition of the 3D light distribution of the Bessel-like beams, reveals the relationship between the Bessel-like beam confinement zone and the beam length. Finally, the effect of diffraction of the Bessel-like beams, induced by the limited lateral extent of the incident fiber mode, is studied and discussed.

At the nanoscale, accurate control and position sensing are recurrent issues conditioning advances of technologies and instruments in diverse fields of application. Recent advances were reported that combine optical microscopy and computer vision for non-contact and multi-axis position sensing of end-effectors with a high accuracy. This paper contributes to this domain by introducing a micro-encoded target aimed to high accurate (x,y,θ) measurements over an extended range. The micro-encoded target is designed to allow linear phase measurements, leading to high accuracy in position sensing, and unambiguous binary encoding leading to absolute position determination. In this way, ultimate performances and allowed measurement ranges are independent of each other and a current zone of observation can be registered with respect to the whole encoded area with an extra-large range-to-resolution ratio. Experiments reported in this paper demonstrate a precision below one nanometer in lateral position and of ${4\cdot10^{-6}}$ rad. in rotation with an encoded target of more than ${11\times11\ \rm{cm^{2}}}$ . The device demonstrated can be either inserted into experimental setups to allow accurate position control or used to calibrate in-plane displacements of one to three degrees of freedom actuators.

In white light interferometry, the visibility of the fringes is directly related to the optical path difference between the two interfering beams. With a very short coherence length light source, the zero-order interference fringe may be detected by a simple maximum intensity location while the reference mirror is shifted by a piezoelectric transducer. We use this possibility for high-resolution profilometry. We discuss the maximum sampling distance, which guarantees a correct detection, as a function of the self coherence function of the light source. A practical configuration based on Mirau interferometric microscope objective was built. The experimental results show the nanometric resolution of this technique and its ability to profile surfaces with sharp slopes and deep holes. The application field of either heterodyne or confocal profilometers may be extended by associating them with the proposed method.

In many cases, soft and continuum robots represent an interesting alternative to articulated robots because they have the advantages of miniaturization capability, safer interactions with humans and often simpler fabricating and integration. However, these benefits are usually considered to arise at the expense of accuracy and precision because of the soft or flexible limbs. This paper demonstrates that, with a proper design, a planar parallel continuum robot is capable of great precision. Indeed, the proposed 3-Degrees-of-Freedom planar parallel continuum robot exhibits a precision of 9.13 nm in position and 1.2 μrad in orientation. In addition, the novel robotic design leverages the effect of the actuators' defects, making the robot more precise than its own actuators. Finally, the workspace of the proposed robot (62.3 mm2, 36.97 deg) is significantly larger than most compliant mechanisms, which is particularly interesting when both very high precision and relatively large displacements are required.