Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-11-24
1991-04-23
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25023119, 367141, H01J 516
Patent
active
050102486
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE INVENTION
Hydrophone probes are use for investigating and characterizing water acoustic signals such as ultrasonic pulses or shockwaves as far as their spatial, temporal shape is concerned. Known are particular piezoelectric hydrophone probes under utilization of crystalline ceramic or polymeric piezoelectric material whereby the sensitive element has either planar or spherical shape contours are is situated at the end of a usually coaxial electrical connection. A description of new developments in this particular area is found in the journal Acoustica, volume 54, 1983, page 23.
The aim for developing a hydrophone probe is to replicate acoustic signals with as few errors and as few feedbacks as possible, in a very sensitive fashion and for maximum temporal and spatial resolution. In addition, in the case of shockwave investigations there is a requirement for a high use life in the pressure range of about 1 kbar as arising in the focal point of medical shockwave devices. This is in addition to the requirement for as large as possible a distance or spacing between the actually sensitive tip of the probe and the electronic equipment to be connected thereto such as an amplifier. The last mentioned requirement follows from the point of view of medicine when shockwave pressure is to be determined within the body of the human being.
The presently available piezoelectric hydrophone probes attain a bandwidth of about 10 megaHertz with a sensitivity of about 1 mV per bar. This is described in Acoustica, volume 54, page 23, 1986 and also in volume 64, 1987, page 85. On the other hand shockwave signals have a bandwidth of to 1 gigaHz, see e.g. Acoustica, volume 14, page 187, 1964. In the case of a bandwidth of 10 MHz the effective sampling diameter of the probe is about 1/10 mm. Since the sampling tip is constructed from several layers such as the inner electrode, a piezoelectric layer and an outer electrode further reduction in the dimensions of the device for purposes of increasing the bandwidth encounters considerable difficulties. The sensitivity of the probe goes down with decreasing sampling surface. In addition a large feed length would cause considerable loss in sensitivity owing to the inherent cable capacity. Owing to the aforementioned layer configuration of these probes the use life is quite limited in the case of shockwave investigations. In the pressure range from about 1 kbar and in the case of a fully developed shockwave front the use life is quite frequently below a hundred shockwave exposures.
It is an object of the present invention to provide a hydrophone probe having a very simple configuration and having effective dimensions with diameters below 1/10 mm for purposes of increasing the bandwidth, without loss in sensitivity so that for shockwave exposure in the 1 kbar range one still obtains a high use life, and whereby the feeder length is freely selectable without loss in sensitivity. Moreover these hydrophone probes should be easy to calibrate and have a high degree of reproducibility. This object is attained in accordance with with the invention as per the characterizing feature of claim 1.
Hence instead of a piezoelectric hydrophone probes a light conductor having the configuration of a glass or polymer fiber is introduced into the acoustic wavefield, and the temporal variation of the light reflection at the boundary or interface at the end of the light conductor vis-a-vis the liquid is used as a hydrophone signal during the temporal pressure change. The light reflection at the light conductor end face is tied to the pressure amplitude in the liquid through a relationship between the index of refraction and the density. Upon a pressure increase the density also rises and therefore the index of refraction of the liquid increases accordingly. Such a relationship basically exists also for the light conductor material itself whereby however the lower compressibility of the solid light conductor material as compared with liquid, any pressure dependent changes in the index of ref
REFERENCES:
patent: 3917410 (1975-11-01), Ulrich
patent: 4162397 (1979-07-01), Bucaro
patent: 4235113 (1980-11-01), Carome
patent: 4487206 (1984-12-01), Aagard
patent: 4599711 (1986-07-01), Cuomo
patent: 4691709 (1987-09-01), Cohen
patent: 4907878 (1990-03-01), Arditty
Eisenmenger Wolfgang
Staudenraus Joachim
Nelms David C.
Siegemund Ralf H.
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