Freeform non-contact surface metrology with UltraSurf

The flow of a liquid through a tube deformed by a piezoelectric cell under a harmonic law is studied in this paper. Linear deformations are compared for the Dirichlet and Neumann boundary conditions on the contact surface of the tube and piezoelectric element. The flow of fluid through a deformed channel for two flow regimes is investigated: in a tube with one closed end due to deformation of the tube; for a tube with two open ends due to deformation of the tube and the differential pressure applied to the channel. The flow rate of the liquid is calculated as a function of the frequency of the deformations, the pressure drop and the physical parameters of the liquid.

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Nano-imprinted subwavelength gratings as polarizing beamsplitters

Journal of the European Optical Society Rapid Publications ◽

10.1186/s41476-021-00149-8 ◽

2021 ◽

Vol 17 (1) ◽

Author(s):

Julian Wüster ◽

Yannick Bourgin ◽

Patrick Feßer ◽

Arne Behrens ◽

Stefan Sinzinger

Keyword(s):

Nanoimprint Lithography ◽

Optical Measurement ◽

Design Method ◽

Optical Systems ◽

Surface Metrology ◽

Measurement Systems ◽

Common Path ◽

Dielectric Coatings ◽

Subwavelength Gratings ◽

Wide Range

AbstractPolarizing beamsplitters have numerous applications in optical systems, such as systems for freeform surface metrology. They are classically manufactured from birefringent materials or with stacks of dielectric coatings. We present a binary subwavelength-structured form-birefringent diffraction grating, which acts as a polarizing beamsplitter for a wide range of incidence angles −30∘…+30∘. We refine the general design method for such hybrid gratings. We furthermore demonstrate the manufacturing steps with Soft-UV-Nanoimprint-Lithography, as well as the experimental verification, that the structure reliably acts as a polarizing beamsplitter. The experimental results show a contrast in efficiency for TE- and TM-polarization of up to 1:18 in the first order, and 34:1 in the zeroth order. The grating potentially enables us to realize integrated compact optical measurement systems, such as common-path interferometers.

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Temporal coherency of mechanical stimuli modulates tactile form perception

Scientific Reports ◽

10.1038/s41598-021-90661-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Masashi Nakatani ◽

Yasuaki Kobayashi ◽

Kota Ohno ◽

Masaaki Uesaka ◽

Sayako Mogami ◽

...

Keyword(s):

Sensory Neuron ◽

Sensory Neurons ◽

Contact Surface ◽

Relative Magnitude ◽

Form Perception ◽

Tangential Displacement ◽

Surface Geometry ◽

Tactile Stimuli ◽

Surface Patterns ◽

Temporal Coherency

AbstractThe human hand can detect both form and texture information of a contact surface. The detection of skin displacement (sustained stimulus) and changes in skin displacement (transient stimulus) are thought to be mediated in different tactile channels; however, tactile form perception may use both types of information. Here, we studied whether both the temporal frequency and the temporal coherency information of tactile stimuli encoded in sensory neurons could be used to recognize the form of contact surfaces. We used the fishbone tactile illusion (FTI), a known tactile phenomenon, as a probe for tactile form perception in humans. This illusion typically occurs with a surface geometry that has a smooth bar and coarse textures in its adjacent areas. When stroking the central bar back and forth with a fingertip, a human observer perceives a hollow surface geometry even though the bar is physically flat. We used a passive high-density pin matrix to extract only the vertical information of the contact surface, suppressing tangential displacement from surface rubbing. Participants in the psychological experiment reported indented surface geometry by tracing over the FTI textures with pin matrices of the different spatial densities (1.0 and 2.0 mm pin intervals). Human participants reported that the relative magnitude of perceived surface indentation steeply decreased when pins in the adjacent areas vibrated in synchrony. To address possible mechanisms for tactile form perception in the FTI, we developed a computational model of sensory neurons to estimate temporal patterns of action potentials from tactile receptive fields. Our computational data suggest that (1) the temporal asynchrony of sensory neuron responses is correlated with the relative magnitude of perceived surface indentation and (2) the spatiotemporal change of displacements in tactile stimuli are correlated with the asynchrony of simulated sensory neuron responses for the fishbone surface patterns. Based on these results, we propose that both the frequency and the asynchrony of temporal activity in sensory neurons could produce tactile form perception.

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