Rev. Phys. Appl. (Paris) 14, 569-573 (1979)
DOI: 10.1051/rphysap:01979001404056900

A new investigation of the acoustic imaging with nematic liquid crystals

J.N. Perbet, M. Hareng et S. Le Berre

THOMSON-CSF, Laboratoire Central de Recherches, Domaine de Corbeville, B.P. 10, 91401 Orsay, France

Abstract
Acoustically induced birefringence has been studied in homeotropic cell of nematic liquid crystal in order to obtain an acoustic image detector. The response times and the sensitivity were improved with an electric field always applied on the liquid crystal cell. The improvement of the resolution was obtained by introducing a grid in the cell which divides the sample into a matrix of small liquid crystal cells acting as individual detectors. About the mechanisms, different phenomena occur at the same time, one of them being a mechanism which is not explained within the framework of previous models.

Résumé
Nous avons étudié la biréfringence induite par les ultrasons dans une cellule à cristal liquide nématique en vue d'évaluer les performances d'une rétine sonosensible. Les temps de réponse et la sensibilité ont été améliorés en appliquant continûment un champ électrique sur la cellule. De plus, l'introduction d'une grille dans l'épaisseur de cristal liquide améliore la résolution. D'un point de vue plus fondamental, différents mécanismes apparaissent simultanément et ne peuvent être tous expliqués par les modèles existants.

PACS
4335 - Ultrasonics, quantum acoustics, and physical effects of sound.
4385 - Acoustical measurements and instrumentation.
6130G - Orientational order of liquid crystals in electric and magnetic fields.
7210X - Other instrumentation and measurement systems.
7810 - Sonic and ultrasonic equipment.

Key words
ultrasonic effects -- acoustic imaging -- nematic liquid crystals -- birefringence -- acoustic image detector -- response times -- sensitivity -- ultrasonic induced birefringence