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Abstract

An optical device for measuring slight pressure differences by means of a light intensity change characterized by a membrane extending across a recess of a housing part to form a first chamber of a first volume which is isolated from a second chamber on the opposite side of the membrane, a right angle isosceles glass prism mounted in the recess with a hypotenuse surface facing said membrane and extending parallel thereto, an input optical waveguide coupled to one short side surface of the prism extending to the light source of a given light intensity for coupling light from said source into the prism and an output optical waveguide being coupled to the other short side surface of the prism for output coupling light from the prism to a measuring device. The surface of the membrane opposite the hypotenuse surface is a light receiving surface such as either by absorbing light or being permeable to light and the membrane surface with the membrane in an idle condition is spaced at an interval such as not greater than the wavelength of the light being used so that approximately 50% of the coupled in light intensity is totally reflected by the hypotenuse surface. Changes in the position of the membrane will cause changes in the intensity which can be measured to determine the pressure differences.

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