Non-destructive testing system employing a liquid crystal detect

Details Non-destructive testing system employing a liquid crystal detect Non-destructive testing system employing a liquid crystal detect

1982-07-20

1985-03-26

Kreitman, Stephen A.

Measuring and testing

Vibration

By mechanical waves

350330, G01N 2900, G02F 111

Patent

active

045065500

ABSTRACT:
There is disclosed herein an ultrasonic imaging system for use in non-destructively testing objects, which system includes a source of ultrasonic energy, a liquid crystal detector cell and an optical viewing system. The liquid crystal detector cell includes a pair of acoustically transmissive covers which encase a nematic liquid crystal material. The material exhibits an acousto-optic effect, and in particular, exhibits birefringence in response to ultrasonic energy. The cell construction, geometry, and material are acoustically matched to the frequencies of the insonifying ultrasonic transducer so as to optimize the performance of the cell. The covers are substantially acoustically transparent to ultrasonic energy incident on the cover at both normal and oblique attitudes. The acoustic impedance of the covers match as closely as possible to that of the coupling medium. The average alignment of the liquid crystal molecules, as indicated by the director, is selectively aligned to be oblique to the ultrasonic beam, and by reason thereof the cell exhibits high sensitivity and high image resolution in the "non-streaming" region. Electric field enhancement may be used to cooperate in aligning the liquid crystal molecules and to enhance the resolution and sensitivity of the image.

REFERENCES:
patent: 3831434 (1974-08-01), Greguss
patent: 3991606 (1976-11-01), Dreyer
patent: 4338821 (1982-07-01), Dion

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