FIBER OPTIC PRESSURE DETECTOR

• US 3,789,667 A
• Filed: 02/14/1972
• Issued: 02/05/1974
• Est. Priority Date: 02/14/1972
• Status: Expired due to Term

• Current Assignee: David B. Murray, John H. Porter
• Original Assignee: David B. Murray, John H. Porter
• Inventors: Porter, John H., Murray, David B.
• Primary Examiner(s): Woodiel, Donald O.
• Assistant Examiner(s): Shoon, Frederick
• Application Number:
  US05/225,881
• Time in Patent Office: 722 Days
• Field of Search: 73/398R,406 128/2.5D,2.5E,2.5N,2.5R 350/96B
• US Class Current: 73/705
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: G01L 9/0007 using photoelectric means G01L9/0076 takes precedence

Abstract

A differential sensor unit precisely monitors ambient pressure within a confined space, such as intracranial pressure of a human patient, utilizing fiber optic light guides. Three light guides pass within a pneumatic line into a flexible envelope which is implanted in the skull. Of the external ends of the guides, one faces a light source and each of the others faces a light detector. Within the envelope the guide ends are so arranged with respect to light beam modulating mechanism responsive to envelope distortion due to change in relative pressure that motion of the mechanism relative to the internal ends varies the light transmitted from the first light guide internal end to each remaining light guide internal end, and consequently varies the light intensity sensed by each of the detectors. The detectors can be arranged to actuate pressure display means and pneumatic controls acting through the pneumatic line to adjust the internal pressure of the envelope.

Claims

1. For use in apparatus for monitoring ambient pressure within a confined space, said apparatus including a light source, two light detectors, a source of fluid under pressure, control means for controlling the pressure of said fluid in accordance with the difference between the intensities of light sensed by said light detectors, and display means for displaying said pressure, a differential sensor unit comprising an envelope adapted to be placed within the confined space, said envelope having at least one wall movable in response to change in relative pressure between the interior and exterior of said envelope, a fluid conducting line in communication with the envelope interior and adapted to be connected to the fluid source, three light guides each having an internal end within said envelope, and of whose external ends, the first and second each face a light detector, and the third faces the light source, light-modulating mechanism mounted within said envelope in operative relation to the internal ends of said light guides to vary the light transmitted from the internal end of said third light guide to the internal ends of said first and second light guides and correspondingly to vary the intensity of light sensed by each of said light detectors, said light-modulating mechanism being relatively movable with respect to said internal ends responsive to movements of said movable wall, said internal ends and said light-modulating mechanism being so disposed and arranged that in a first position of said lightmodulating mechanism a majority of the light from the light source is transmitted from said third light guide through said first light guide to the first light detector, in a second position of said mechanism a majority of said light is transmitted through said second light guide to the second light detector, and in a third position equal amounts of said light are transmitted to the two light detectors, said light modulating mechanism being movable through a range of positions including said first, second and third positions. so that said control means acting through said pneumatic line will adjust the internal pressure in said envelope in accordance with the difference between the light intensities sensed by the detectors, whereby said internal pressure continually spans said ambient pressure and said display means continually displays said internal pressure.

2. ThE combination of claim 1 wherein said light modulating mechanism comprises a reflector serving in one position primarily to reflect said light from said third to said first internal end, in a second position primarily to reflect said light from said third to said second internal end, and in a third position to reflect light from said third internal end equally to said second and first internal ends.

3. The combination of claim 2 wherein said internal ends are side by side with their faces facing in the same direction and said reflector is arranged to move between a first position adjacent said first internal end, a second position adjacent said second internal end and a third position equidistant from said first and second ends.

4. The combination of claim 1 where said envelope has one rigid wall, said light guides extending within said envelope generally parallel to said rigid wall, said internal ends being generally transverse to said walls, said first internal end being adjacent said rigid wall, said second internal end being adjacent said flexible movable wall, and said third internal end being between the other two, and said reflector being carried on said movable wall and having a face parallel to said internal ends.