US 4,902,137 AGranted

Method and apparatus for the determination of foreign bodies in fluids

AssigneeHarro Hofliger Verpackungsmasghinen GmbH

InventorsGunther Krieg, Gerhard Barth, Eberhard Vaas, Manfred Reiser

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Abstract

A method is proposed for detecting foreign bodies in fluids to investigate the fluids such as infusion liquids for foreign bodies which can lead to the plugging of infusion needles or other dangers for a patient. In the method light is directed onto the fluid and the light departing from this fluid is detected. The fluid is illuminated evenly with polarized light, and the light penetrating through the fluid is further dimmed by further polarization. The light intensity of individual measuring regions is measured through photo-electric sensing and the measured intensity is compared with an adjustable threshold so that when the threshold is exceeded at any given time during a measuring interval, corresponding signals are produced.

Claims16

Dependent claims

The method for detecting particles in a moving fluid provided in a stationary containment vessel and comprising the following steps:

providing light transparent windows in the fluid containment vessel one of which windows is an entry window and has a generally convex external surface and the other window being an exit window and oriented on an optical axis through said windows,
directing a polarized beam along the optical inspection axis and through the entry and exit windows provided on this axis,
masking the window in an area where the light beam is generally perpendicular said convex window surface so that all of the polarized light entering the moving fluid is refracted at least slightly by the stationary convex entry window,
cross polarizing the light exiting the exit window so that the light beam consists only in that part of the polarized light beam that has been unpolarized by particles in the fluid or by defects in or on the transparent windows,
providing a video camera for the cross polarized light beam,
comparing the video output from successive video frames to provide an indication of the particles in the moving fluid.

3 more elements

Apparatus for detecting articles in a moving fluid, said apparatus comprising, means for directing a light beam along an optical axis oriented generally perpendicular to inspection station axis, polarizing means for said light beam, means defining an inspection station and defining entry and exit windows in a fluid containment vessel one of which windows has a generally convex external shape and the other window being oriented in spaced relationship relative to the entry window on said optical inspection axis, means for blocking the polarized light beam along a line oriented generally perpendicular to said optical inspection axis so that the polarized light beam entering the moving fluid is refracted slightly by the convex stationary entry window, means for moving the fluid while holding the containment vessel in a stationary condition during an inspection sequence, a cross polarizing device on said optical inspection axis outside the exit window for cross polarizing the light exiting the window to pass only that part of the polarized light that has been "unpolarized" by particles in the fluid or by defects in the windows, video camera means for detecting cross polarized light and means for comparing the video output from successive video frames from said camera to provide indication of the particles in the moving fluid.

Dependencies are inferred from the claim text.