Relationship between liquid crystal layer thickness and variable-focusing characteristics of an ultrasound liquid crystal lens

Scanning airborne ultrasound source technique has been developed as a safe and simple non-contact non-destructive inspection method. This method enables non-contact excitation of guided waves by using high-intensity airborne ultrasonic waves. However, the airborne ultrasound source that can generate high intensity airborne ultrasounds use resonance drive, so the sound waves are emitted for a long time. As a result, the inspection results become complicated, and the inspection accuracy decreases. To solve this problem, we proposed a pulse compression using chirp signals of guided waves generated by airborne ultrasound. In this paper, we investigated the pulse compression of guided waves generated in mortar samples using an airborne ultrasound source driven by a chirp signal. As a result, it was confirmed that the visualization accuracy of defects was improved by pulse compression.

Section: Introductionmentioning

confidence: 99%

Pulse compression of guided wave by airborne ultrasound excitation for improving defect detection accuracy in concrete

Shimizu

Osumi

Ito

2023

“…14) Our group has developed a technique to control the spatial refractive index distributions of LC materials using ultrasound resonant standing waves, 15) and varifocal optical ultrasound LC lenses have also been developed. 16) We have investigated the optical characteristics of these ultrasound LC lenses, including studies of the relationships between their focusing characteristics, the LC layer thicknesses, and the birefringence, 17) and the use of multilayering of the LC layer to expand the varifocal function. 18,19) Switching of the resonant standing and traveling waves generated using quadrantal ultrasound transducers enables control of the lens aperture 20) and focusing control in three dimensions.…”

mentioning

confidence: 99%

Acousto-thermal birefringence of iron(III) chloride using ultrasound flexural standing wave

Kuroda,

Emoto,

Koyama

2024

Self Cite

Small, thin devices that can realize high-speed light modulation are important in the imaging and sensing technology fields. In this paper, a combination of iron(III) chloride and ultrasound was proposed to modulate the spatial distribution of the iron(III) chloride layer’s refractive index. An ultrasound cell containing an iron(III) chloride layer and two ultrasound transducers was fabricated to investigate the variations in the refractive index under ultrasonication. The maximum change in the material’s birefringence was observed at the center of the cell, indicating that thermal generation caused by the ultrasound vibration induced this phenomenon.

“…The two glass discs (diameter: 19 and 22 mm; thickness: 500 μm) were combined coaxially via a polyethylene terephthalate film spacer in order that a 200 μm thick LC layer with vertical alignment forms between the two glass discs; this thickness was optimum for the focus controlling function in our previous study. 17) Nematic LC, 4-Cyano-4′-pentylbiphenyl (C1550, Tokyo Chemical Industry-TCI, Japan), was infused into the thin gaps, and the surrounding parts were sealed entirely with epoxy. An annular piezoelectric lead zirconate titanate (PZT) transducer (thickness: 1 mm; outer diameter: 16 mm; inner diameter: 10 mm; C-213; Fuji Ceramics Corporation, Japan) was glued to the 19 mm diameter glass disc with epoxy.…”

mentioning

confidence: 99%

How to fix an ultrasonic variable-focus liquid crystal lens for substrate-mountable applications

Kuroda¹,

Harada²,

Onaka³

et al. 2023

Self Cite

This paper proposed a board-mounted ultrasonic variable-focus liquid crystal (LC) lens. The lens controls the focus using the acoustic radiation force generated by the resonant flexural vibration mode. The LC lens was fixed to an aluminum substrate with a hole whose aperture corresponded to the inner diameter of the transducer. The part of the LC lens attached to the substrates functioned as a fixed condition, and the flexural vibration mode was successfully generated. The fixed lens exhibited a gradual focal change with current, confirming that fixing the condition affected the rate of focal change.